Patent Description:
The invention relates to a system as defined in claim <NUM> and a storage medium as defined in claim <NUM>. Systems for use of one or more evoked response signals to determine an insertion state of an electrode lead during an electrode lead insertion procedure are described herein. For example, a diagnostic system may direct an acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulus frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. The diagnostic system may direct the cochlear implant to use an electrode disposed on the electrode lead to record a plurality of evoked response signals during the insertion procedure. Each evoked response signal included in the plurality of evoked response signals may correspond to a different stimulus frequency included in the plurality of stimulus frequencies and may be representative of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient. The evoked responses may each be an electrocochleographic ("ECoG") potential (e.g., a cochlear microphonic potential, an action potential, a summating potential, etc.), an auditory nerve response, a brainstem response, a compound action potential, a stapedius reflex, and/or any other type of neural or physiological response that may occur within a recipient in response to application of acoustic stimulation to the recipient. Evoked responses may originate from neural tissues, hair cell to neural synapses, inner or outer hair cells, or other sources.

As will be described herein, attributes associated with the evoked response signals recorded by the electrode may be indicative of an insertion state of the electrode lead within the cochlea of the recipient. For example, an amplitude and/or a phase of one or more evoked response signals may be indicative of a particular insertion state. As used herein, "an insertion state" may correspond to any of a plurality of different insertion states that may be associated with insertion of the electrode lead into the cochlea of the recipient. For example, one or more insertion states may be associated with passing a characteristic frequency location of the cochlea, passing a cluster of hair cells or neurons, contacting a structure of the cochlea (e.g., the basilar membrane), causing trauma to the cochlea (e.g., passing through the basilar membrane), etc. Accordingly, the diagnostic system may determine an insertion state of the electrode lead within the cochlea of the recipient based on an amplitude and a phase of each of one or more evoked response signals included in the plurality of evoked response signals.

By using acoustic stimulation having a plurality of stimulus frequencies to facilitate determining an insertion state, the systems and methods described herein may optimize determination of an insertion state and/or facilitate determination of additional or alternative insertion states as compared to conventional methods. In addition, the systems and methods described herein may be used to provide real time feedback to a user (e.g., a surgeon) performing an insertion procedure to ensure proper placement of an electrode lead within a cochlea of a recipient. These and other benefits and advantages of the systems and methods described herein will be made apparent herein.

<FIG> illustrates an exemplary cochlear implant system <NUM> configured to be used by a recipient. As shown, cochlear implant system <NUM> includes a cochlear implant <NUM>, an electrode lead <NUM> physically coupled to cochlear implant <NUM> and having an array of electrodes <NUM>, and a controller <NUM> configured to be communicatively coupled to cochlear implant <NUM> by way of a communication link <NUM>.

The cochlear implant system <NUM> shown in <FIG> is unilateral (i.e., associated with only one ear of the recipient). Alternatively, a bilateral configuration of cochlear implant system <NUM> may include separate cochlear implants and electrode leads for each ear of the recipient. In the bilateral configuration, controller <NUM> may be implemented by a single controller configured to interface with both cochlear implants or by two separate controllers each configured to interface with a different one of the cochlear implants.

Cochlear implant <NUM> may be implemented by any suitable type of implantable stimulator. For example, cochlear implant <NUM> may be implemented by an implantable cochlear stimulator. Additionally or alternatively, cochlear implant <NUM> may be implemented by a brainstem implant and/or any other type of device that may be implanted within the recipient and configured to apply electrical stimulation to one or more stimulation sites located along an auditory pathway of the recipient.

In some examples, cochlear implant <NUM> may be configured to generate electrical stimulation representative of an audio signal processed by controller <NUM> in accordance with one or more stimulation parameters transmitted to cochlear implant <NUM> by controller <NUM>. Cochlear implant <NUM> may be further configured to apply the electrical stimulation to one or more stimulation sites (e.g., one or more intracochlear locations) within the recipient by way of one or more electrodes <NUM> on electrode lead <NUM>. In some examples, cochlear implant <NUM> may include a plurality of independent current sources each associated with a channel defined by one or more of electrodes <NUM>. In this manner, different stimulation current levels may be applied to multiple stimulation sites simultaneously by way of multiple electrodes <NUM>.

Cochlear implant <NUM> may additionally or alternatively be configured to generate, store, and/or transmit data. For example, cochlear implant may use one or more electrodes <NUM> to record one or more signals (e.g., one or more voltages, impedances, evoked responses within the recipient, and/or other measurements) and transmit, by way of communication link <NUM>, data representative of the one or more signals to controller <NUM>. In some examples, this data is referred to as back telemetry data.

Electrode lead <NUM> may be implemented in any suitable manner. For example, a distal portion of electrode lead <NUM> may be pre-curved such that electrode lead <NUM> conforms with the helical shape of the cochlea after being implanted. Electrode lead <NUM> may alternatively be naturally straight or of any other suitable configuration.

In some examples, electrode lead <NUM> includes a plurality of wires (e.g., within an outer sheath) that conductively couple electrodes <NUM> to one or more current sources within cochlear implant <NUM>. For example, if there are n electrodes <NUM> on electrode lead <NUM> and n current sources within cochlear implant <NUM>, there may be n separate wires within electrode lead <NUM> that are configured to conductively connect each electrode <NUM> to a different one of the n current sources. Exemplary values for n are <NUM>, <NUM>, <NUM>, or any other suitable number.

Electrodes <NUM> are located on at least a distal portion of electrode lead <NUM>. In this configuration, after the distal portion of electrode lead <NUM> is inserted into the cochlea, electrical stimulation may be applied by way of one or more of electrodes <NUM> to one or more intracochlear locations. One or more other electrodes (e.g., including a ground electrode, not explicitly shown) may also be disposed on other parts of electrode lead <NUM> (e.g., on a proximal portion of electrode lead <NUM>) to, for example, provide a current return path for stimulation current applied by electrodes <NUM> and to remain external to the cochlea after the distal portion of electrode lead <NUM> is inserted into the cochlea. Additionally or alternatively, a housing of cochlear implant <NUM> may serve as a ground electrode for stimulation current applied by electrodes <NUM>.

Controller <NUM> may be configured to interface with (e.g., control and/or receive data from) cochlear implant <NUM>. For example, controller <NUM> may transmit commands (e.g., stimulation parameters and/or other types of operating parameters in the form of data words included in a forward telemetry sequence) to cochlear implant <NUM> by way of communication link <NUM>. Controller <NUM> may additionally or alternatively provide operating power to cochlear implant <NUM> by transmitting one or more power signals to cochlear implant <NUM> by way of communication link <NUM>. Controller <NUM> may additionally or alternatively receive data from cochlear implant <NUM> by way of communication link <NUM>. Communication link <NUM> may be implemented by any suitable number of wired and/or wireless bidirectional and/or unidirectional links.

As shown, controller <NUM> includes a memory <NUM> and a processor <NUM> configured to be selectively and communicatively coupled to one another. In some examples, memory <NUM> and processor <NUM> may be distributed between multiple devices and/or multiple locations as may serve a particular implementation.

Memory <NUM> may be implemented by any suitable non-transitory computer-readable medium and/or non-transitory processor-readable medium, such as any combination of non-volatile storage media and/or volatile storage media. Exemplary non-volatile storage media include, but are not limited to, read-only memory, flash memory, a solid-state drive, a magnetic storage device (e.g., a hard drive), ferroelectric random-access memory ("RAM"), and an optical disc.

Memory <NUM> may maintain (e.g., store) executable data used by processor <NUM> to perform one or more of the operations described herein. For example, memory <NUM> may store instructions <NUM> that may be executed by processor <NUM> to perform any of the operations described herein. Instructions <NUM> may be implemented by any suitable application, program (e.g., sound processing program), software, code, and/or other executable data instance. Memory <NUM> may also maintain any data received, generated, managed, used, and/or transmitted by processor <NUM>.

Processor <NUM> may be configured to perform (e.g., execute instructions <NUM> stored in memory <NUM> to perform) various operations with respect to cochlear implant <NUM>.

To illustrate, processor <NUM> may be configured to control an operation of cochlear implant <NUM>. For example, processor <NUM> may receive an audio signal (e.g., by way of a microphone communicatively coupled to controller <NUM>, a wireless interface (e.g., a Bluetooth interface), and/or a wired interface (e.g., an auxiliary input port)). Processor <NUM> may process the audio signal in accordance with a sound processing program (e.g., a sound processing program stored in memory <NUM>) to generate appropriate stimulation parameters. Processor <NUM> may then transmit the stimulation parameters to cochlear implant <NUM> to direct cochlear implant <NUM> to apply electrical stimulation representative of the audio signal to the recipient.

In some implementations, processor <NUM> may also be configured to apply acoustic stimulation to the recipient. For example, a receiver (also referred to as a loudspeaker) may be optionally coupled to controller <NUM>. In this configuration, processor <NUM> may deliver acoustic stimulation to the recipient by way of the receiver. The acoustic stimulation may be representative of an audio signal (e.g., an amplified version of the audio signal), configured to elicit an evoked response within the recipient, and/or otherwise configured. In configurations in which processor <NUM> is configured to both deliver acoustic stimulation to the recipient and direct cochlear implant <NUM> to apply electrical stimulation to the recipient, cochlear implant system <NUM> may be referred to as a bimodal hearing system and/or any other suitable term.

Processor <NUM> may be additionally or alternatively configured to receive and process data generated by cochlear implant <NUM>. For example, processor <NUM> may receive data representative of a signal recorded by cochlear implant <NUM> using one or more electrodes <NUM> and, based on the data, adjust one or more operating parameters of controller <NUM>. Additionally or alternatively, processor <NUM> may use the data to perform one or more diagnostic operations with respect to cochlear implant <NUM> and/or the recipient.

Other operations may be performed by processor <NUM> as may serve a particular implementation. In the description provided herein, any references to operations performed by controller <NUM> and/or any implementation thereof may be understood to be performed by processor <NUM> based on instructions <NUM> stored in memory <NUM>.

Controller <NUM> may be implemented by one or more devices configured to interface with cochlear implant <NUM>. To illustrate, <FIG> shows an exemplary configuration <NUM> of cochlear implant system <NUM> in which controller <NUM> is implemented by a sound processor <NUM> configured to be located external to the recipient. In configuration <NUM>, sound processor <NUM> is communicatively coupled to a microphone <NUM> and to a headpiece <NUM> that are both configured to be located external to the recipient.

Sound processor <NUM> may be implemented by any suitable device that may be worn or carried by the recipient. For example, sound processor <NUM> may be implemented by a behind-the-ear ("BTE") unit configured to be worn behind and/or on top of an ear of the recipient. Additionally or alternatively, sound processor <NUM> may be implemented by an off-the-ear unit (also referred to as a body worn device) configured to be worn or carried by the recipient away from the ear. Additionally or alternatively, at least a portion of sound processor <NUM> is implemented by circuitry within headpiece <NUM>.

Microphone <NUM> is configured to detect one or more audio signals (e.g., that include speech and/or any other type of sound) in an environment of the recipient. Microphone <NUM> may be implemented in any suitable manner. For example, microphone <NUM> may be implemented by a microphone that is configured to be placed within the concha of the ear near the entrance to the ear canal, such as a T-MIC™ microphone from Advanced Bionics. Such a microphone may be held within the concha of the ear near the entrance of the ear canal during normal operation by a boom or stalk that is attached to an ear hook configured to be selectively attached to sound processor <NUM>. Additionally or alternatively, microphone <NUM> may be implemented by one or more microphones in or on headpiece <NUM>, one or more microphones in or on a housing of sound processor <NUM>, one or more beam-forming microphones, and/or any other suitable microphone as may serve a particular implementation.

Headpiece <NUM> may be selectively and communicatively coupled to sound processor <NUM> by way of a communication link <NUM> (e.g., a cable or any other suitable wired or wireless communication link), which may be implemented in any suitable manner. Headpiece <NUM> may include an external antenna (e.g., a coil and/or one or more wireless communication components) configured to facilitate selective wireless coupling of sound processor <NUM> to cochlear implant <NUM>. Headpiece <NUM> may additionally or alternatively be used to selectively and wirelessly couple any other external device to cochlear implant <NUM>. To this end, headpiece <NUM> may be configured to be affixed to the recipient's head and positioned such that the external antenna housed within headpiece <NUM> is communicatively coupled to a corresponding implantable antenna (which may also be implemented by a coil and/or one or more wireless communication components) included within or otherwise connected to cochlear implant <NUM>. In this manner, stimulation parameters and/or power signals may be wirelessly and transcutaneously transmitted between sound processor <NUM> and cochlear implant <NUM> by way of a wireless communication link <NUM>.

In configuration <NUM>, sound processor <NUM> may receive an audio signal detected by microphone <NUM> by receiving a signal (e.g., an electrical signal) representative of the audio signal from microphone <NUM>. Sound processor <NUM> may additionally or alternatively receive the audio signal by way of any other suitable interface as described herein. Sound processor <NUM> may process the audio signal in any of the ways described herein and transmit, by way of headpiece <NUM>, stimulation parameters to cochlear implant <NUM> to direct cochlear implant <NUM> to apply electrical stimulation representative of the audio signal to the recipient.

In an alternative configuration, sound processor <NUM> may be implanted within the recipient instead of being located external to the recipient. In this alternative configuration, which may be referred to as a fully implantable configuration of cochlear implant system <NUM>, sound processor <NUM> and cochlear implant <NUM> may be combined into a single device or implemented as separate devices configured to communicate one with another by way of a wired and/or wireless communication link. In a fully implantable implementation of cochlear implant system <NUM>, headpiece <NUM> may not be included and microphone <NUM> may be implemented by one or more microphones implanted within the recipient, located within an ear canal of the recipient, and/or external to the recipient.

<FIG> illustrates an exemplary diagnostic system <NUM> that may be configured to perform any of the operations described herein. As shown, diagnostic system <NUM> may include, without limitation, a storage facility <NUM> and a processing facility <NUM> selectively and communicatively coupled to one another. Facilities <NUM> and <NUM> may each include or be implemented by hardware and/or software components (e.g., processors, memories, communication interfaces, instructions stored in memory for execution by the processors, etc.). In some examples, facilities <NUM> and <NUM> may be distributed between multiple devices and/or multiple locations as may serve a particular implementation.

Storage facility <NUM> may maintain (e.g., store) executable data used by processing facility <NUM> to perform any of the operations described herein. For example, storage facility <NUM> may store instructions <NUM> that may be executed by processing facility <NUM> to perform any of the operations described herein. Instructions <NUM> may be implemented by any suitable application, software, code, and/or other executable data instance. Storage facility <NUM> may also maintain any data received, generated, managed, used, and/or transmitted by processing facility <NUM>.

Processing facility <NUM> may be configured to perform (e.g., execute instructions <NUM> stored in storage facility <NUM> to perform) various operations. For example, processing facility <NUM> may direct an acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulus frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient, direct the cochlear implant to use an electrode disposed on the electrode lead to record a plurality of evoked response signals during the insertion procedure, each evoked response signal included in the plurality of evoked response signals corresponding to a different stimulus frequency included in the plurality of stimulus frequencies and representative of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient, and determine, based on an amplitude and a phase of each of one or more evoked response signals included in the plurality of evoked response signals, an insertion state of the electrode lead within the cochlea of the recipient. These and other operations that may be performed by processing facility <NUM> are described in more detail herein.

Diagnostic system <NUM> may be implemented in any suitable manner. For example, <FIG> shows an exemplary configuration <NUM> in which diagnostic system <NUM> is implemented by a computing system <NUM> configured to communicatively couple to sound processor <NUM>. As shown, computing system <NUM> may include an acoustic stimulation generator <NUM> communicatively coupled to a speaker <NUM>. Computing system <NUM> is also communicatively coupled to a display device <NUM>. While computing system <NUM> is described herein as being be coupled to sound processor <NUM>, computing system <NUM> may be alternatively coupled to any other implementation of controller <NUM> as may serve a particular implementation.

Computing system <NUM> may be implemented by any suitable combination of hardware (e.g., one or more computing devices) and software. For example, computing system <NUM> may be implemented by a computing device programmed to perform one or more fitting operations with respect to a recipient of a cochlear implant. To illustrate, computing system <NUM> may be implemented by a desktop computer, a mobile device (e.g., a laptop, a smartphone, a tablet computer, etc.), and/or any other suitable computing device as may serve a particular implementation. As an example, computing system <NUM> may be implemented by a mobile device configured to execute an application (e.g., a "mobile app") that may be used by a user (e.g., the recipient, a clinician, and/or any other user) to control one or more settings of sound processor <NUM> and/or cochlear implant <NUM> and/or perform one or more operations (e.g., diagnostic operations) with respect to data generated by sound processor <NUM> and/or cochlear implant <NUM>.

Acoustic stimulation generator <NUM> may be implemented by any suitable combination of components configured to generate acoustic stimulation. In some examples, the acoustic stimulation may include one or more tones having one or more stimulus frequencies. Additionally or alternatively, the acoustic stimulation may include any other type of acoustic content that has at least a particular stimulus frequency of interest. Speaker <NUM> may be configured to deliver the acoustic stimulation generated by acoustic stimulation generator <NUM> to the recipient. For example, speaker <NUM> may be implemented by an ear mold configured to be placed in or near an entrance to an ear canal of the recipient.

Display device <NUM> may be implemented by any suitable device configured to display graphical content generated by computing system <NUM>. For example, display device <NUM> may display one or more graphs of evoked responses recorded by an electrode disposed on electrode lead <NUM>. Display device <NUM> is shown in <FIG> as an external device configured to display content generated by computing system <NUM>. Additionally or alternatively, computing system <NUM> may include display device <NUM> as an integrated display in certain implementations.

<FIG> shows another exemplary configuration <NUM> in which diagnostic system <NUM> is implemented by computing system <NUM>. In configuration <NUM>, acoustic stimulation generator <NUM> is included in sound processor <NUM>. For example, sound processor <NUM> may be implemented by a bimodal sound processor (i.e., a sound processor configured to direct cochlear implant <NUM> to apply electrical stimulation to a recipient and acoustic stimulation generator <NUM> to apply acoustic stimulation to the recipient). In some examples, speaker <NUM> may be implemented by an audio ear hook that connects to sound processor <NUM>.

<FIG> illustrate an exemplary insertion procedure in which an electrode lead <NUM> is inserted into a cochlea <NUM> of a recipient. For illustrative purposes, cochlea <NUM> is depicted in <FIG> as being "unrolled" instead of its actual curved, spiral shape. Electrode lead <NUM> may be similar to electrode lead <NUM> and may include a plurality of electrodes (e.g., electrodes <NUM>-<NUM> through electrode <NUM>-<NUM>) disposed thereon. Electrode <NUM>-<NUM> is a distal-most electrode on electrode lead <NUM> and electrode <NUM>-<NUM> is a proximal-most electrode on electrode lead <NUM>.

Various characteristic frequency locations within cochlea <NUM> are depicted by vertical dashed lines in each of <FIG>. As shown, a first characteristic frequency location is associated with <NUM>. Hence, electrical stimulation applied by an electrode positioned at this characteristic frequency location may result in the recipient perceiving sound having <NUM> or the hair cell and neural structures there respond to <NUM> acoustic stimulus. <FIG> also depict characteristic frequency locations associated with <NUM>, <NUM>, <NUM>, and <NUM>. As shown, the frequencies associated with the characteristic frequency locations are tonotopically arranged, with relatively higher frequencies being located towards the entrance (or base) of cochlea <NUM> and relatively lower frequencies being located towards the distal end (or apex) of cochlea <NUM>.

<FIG> shows electrode lead <NUM> entering cochlea <NUM>. In this figure, electrode <NUM>-<NUM> is barely within cochlea <NUM>. <FIG> shows electrode lead <NUM> after electrode lead <NUM> has been advanced further into cochlea <NUM> such that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM>. <FIG> show electrode lead <NUM> after electrode lead <NUM> has been advanced further into cochlea <NUM> such that electrode <NUM>-<NUM> is positioned at the characteristic frequency location corresponding to <NUM> (<FIG>), then <NUM> (<FIG>), then <NUM> (<FIG>), and then <NUM> (<FIG>).

As mentioned, it is desirable to monitor an insertion state of an electrode lead as the electrode lead is inserted within a cochlea to ensure that the electrode lead is inserted properly. To that end, diagnostic system <NUM> may direct an acoustic stimulation generator (e.g., acoustic stimulation generator <NUM>) to apply acoustic stimulation having a plurality of stimulus frequencies (i.e., concurrently) to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. Diagnostic system <NUM> may direct the acoustic stimulation generator to apply the acoustic stimulation having the plurality of stimulus frequencies in any suitable manner. For example, diagnostic system <NUM> may direct the acoustic stimulation generator to continuously apply the acoustic stimulation during an insertion procedure, intermittently apply the acoustic stimulation during the insertion procedure, simultaneously apply different stimulus frequencies of the acoustic stimulation during the insertion procedure, sequentially apply the different stimulus frequencies of the acoustic stimulation during the insertion procedure, or apply the acoustic stimulation in any other suitable manner as may serve a particular implementation.

The acoustic stimulation may have any suitable plurality of stimulus frequencies as may serve a particular implementation. In certain examples, the acoustic stimulation may have four different stimulus frequencies that are concurrently applied during an insertion procedure. For example, in certain implementations the acoustic stimulation may include a first stimulus frequency corresponding to <NUM>, a second stimulus frequency corresponding to <NUM>, a third stimulus frequency corresponding to <NUM>, and a fourth stimulus frequency corresponding to <NUM>. In certain alternative implementations, the acoustic stimulation may have less than or more than four stimulus frequencies.

The acoustic stimulation is configured to produce a plurality of evoked responses during an insertion procedure that are useful in determining an insertion state. Accordingly, diagnostic system <NUM> may direct cochlear implant <NUM> to use an electrode to record a plurality of evoked response signals during an insertion procedure. Diagnostic system <NUM> may direct cochlear implant <NUM> to use any suitable electrode or combination of electrodes on an electrode lead to record the plurality of evoked response signals. For example, in certain implementations, diagnostic system <NUM> may direct the cochlear implant to use a distal-most electrode (e.g., electrode <NUM>-<NUM>) to record the plurality of evoked response signals. Each evoked response signal included in the plurality of evoked response signals may correspond to a different stimulus frequency included in the plurality of stimulus frequencies. In addition, each evoked response signal included in the plurality of evoked response signals may be representative of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient.

In certain examples, the plurality of evoked response signals may be considered as being included as part of a single evoked response detected by diagnostic system <NUM> in response to the acoustic stimulation applied to the recipient.

Attributes of the plurality of evoked response signals may be indicative of an insertion state of the electrode lead as the electrode lead is inserted within the cochlea. For example, as the electrode lead is inserted within the cochlea, an amplitude and/or a phase of one or more evoked response signals included in the plurality of evoked response signals may change in a manner that is indicative of a particular insertion state of the electrode lead. Accordingly, based on an amplitude and a phase of each of one or more evoked response signal included in the plurality of evoked response signals, diagnostic system <NUM> may determine an insertion state of the electrode lead within the cochlea of the recipient.

Diagnostic system <NUM> may determine any suitable number and/or type of insertion states as may serve a particular implementation. In certain examples, an insertion state may correspond to the electrode lead passing a particular characteristic frequency location within the cochlea. In such examples, diagnostic system <NUM> may determine that the electrode lead passes the particular characteristic frequency location when, within a predetermined amount of time, both an amplitude of a particular evoked response signal included in the plurality of evoked response signals decreases by at least an amplitude threshold amount and a phase of the particular evoked response signal changes by at least a phase threshold amount. The particular characteristic frequency location may correspond to a particular stimulus frequency that corresponds to the particular evoked response signal and that is included in the plurality of stimulus frequencies. Accordingly, diagnostic system <NUM> may determine an insertion state as passing a certain characteristic frequency location based on which evoked response signal has both a decrease in amplitude by at least an amplitude threshold amount and a phase change by at least a phase threshold amount.

To illustrate, <FIG> shows an exemplary lead insertion procedure in which electrode lead <NUM> is advanced into cochlea <NUM>. Reference numbers P1 through P3 indicate positions of electrode lead <NUM>. For example, at position P1, electrode lead <NUM> is at a first position in which electrode <NUM>-<NUM> is at the characteristic frequency location that corresponds to <NUM>. At position P2, electrode lead <NUM> is at a second position in which electrode <NUM>-<NUM> is at the characteristic frequency location that corresponds to <NUM>. At position P3, electrode lead <NUM> is at a third position in which electrode <NUM>-<NUM> is at the characteristic frequency location that corresponds to <NUM>.

<FIG> also shows a graph <NUM> of amplitudes <NUM> (e.g., amplitudes <NUM>-<NUM> through <NUM>-<NUM>) of evoked response signals recorded by electrode <NUM>-<NUM> at different insertion times T (e.g., T1 through T3) during the lead insertion procedure. In addition, <FIG> shows a graph <NUM> of phases <NUM> (e.g., phases <NUM>-<NUM> through <NUM>-<NUM>) of the evoked response signals recorded by electrode <NUM>-<NUM> at different insertion times T during the lead insertion procedure. In this example, first, second, and third evoked response signals are generated in response to acoustic stimulation having stimulus frequencies of <NUM>, <NUM>, and <NUM>, respectively. Hence, as shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the amplitude <NUM>-<NUM> of a first evoked response signal, which is generated in response to acoustic stimulation having a stimulus frequencies of <NUM>, increases and peaks at insertion time T1 when electrode lead <NUM> is positioned at position P1. As electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, the first evoked response amplitude <NUM>-<NUM> decreases until it settles at a steady state value. As shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the phase <NUM>-<NUM> of the first evoked response signal remains at a relatively high level. However, the phase <NUM>-<NUM> suddenly changes to a relatively low level at insertion time T1 as electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>.

As shown in <FIG>, the decreasing of the first evoked response amplitude <NUM>-<NUM> and the changing of the phase <NUM>-<NUM> from the high level to the low level occur at substantially the same insertion time T1, and both occur as electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM>. Hence, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM> by detecting, within a predetermined time period, that both an amplitude <NUM>-<NUM> of the first evoked response signal recorded by electrode <NUM>-<NUM> decreases by at least an amplitude threshold amount and a phase <NUM>-<NUM> of the first evoked response signal recorded by electrode <NUM>-<NUM> changes by at least a phase threshold amount. The predetermined time period, the amplitude threshold amount, and/or the phase threshold amount may each be set by diagnostic system <NUM> to be any suitable value. For example, the predetermined time period may be set to be a relatively short time period (e.g., less than a few milliseconds) to ensure that the change in amplitude and in phase correspond to one another. In some examples, diagnostic system <NUM> may set the predetermined time period, the amplitude threshold amount, and/or the phase threshold in response to user input (e.g., by way of a graphical user interface). Additionally or alternatively, diagnostic system <NUM> may set the predetermined time period, the amplitude threshold amount, and/or the phase threshold automatically based on one or more factors, such as hearing loss, the stimulus frequency, recipient characteristics (e.g., age, gender, etc.), etc..

As is further shown in <FIG>, after electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>. As electrode lead <NUM> advances toward the characteristic frequency location that corresponds to <NUM>, the amplitude <NUM>-<NUM> of the second evoked response signal, which is generated in response to acoustic stimulation having a stimulus frequencies of <NUM>, increases and peaks at insertion time T2 when electrode lead <NUM> is positioned at position P2. As electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, the second evoked response amplitude <NUM>-<NUM> decreases until it settles at a steady state value. As shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the phase <NUM>-<NUM> of the second evoked response signal remains at a relatively high level. However, the phase <NUM>-<NUM> suddenly changes to a relatively low level at insertion time T2 as electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>.

The decreasing of the second evoked response amplitude <NUM>-<NUM> and the changing of phase <NUM>-<NUM> from the high level to the low level in <FIG> occur at substantially the same insertion time T2, and both occur as electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM>. Hence, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM> by detecting, within an additional predetermined time period, that both an amplitude <NUM>-<NUM> of the second evoked response signal recorded by electrode <NUM>-<NUM> decreases by at least an amplitude threshold amount and a phase <NUM>-<NUM> of the second evoked response signal recorded by electrode <NUM>-<NUM> changes by at least a phase threshold amount. The additional predetermined time period, the amplitude threshold amount, and/or the phase threshold amount may each be set by diagnostic system <NUM> to be any suitable value, such as described herein.

As is further shown in <FIG>, after electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>. As electrode lead <NUM> advances toward the characteristic frequency location that corresponds to <NUM>, the amplitude <NUM>-<NUM> of the third evoked response signal, which is generated in response to acoustic stimulation having a stimulus frequencies of <NUM>, increases and peaks at insertion time T3 when electrode lead <NUM> is positioned at position P3. As electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>, the third evoked response amplitude <NUM>-<NUM> decreases until it settles at a steady state value. As shown in graph <NUM>, as electrode lead <NUM> advances towards the characteristic frequency location that corresponds to <NUM>, the phase <NUM>-<NUM> of the third evoked response signal remains at a relatively high level. However, the phase <NUM>-<NUM> suddenly changes to a relatively low level at insertion time T3 as electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM>.

The decreasing of the third evoked response amplitude <NUM>-<NUM> and the changing of phase <NUM>-<NUM> from the high level to the low level in <FIG> occur at substantially the same insertion time T3, and both occur as electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM>. Hence, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> passes the characteristic frequency location that corresponds to <NUM> by detecting, within an additional predetermined time period, that both an amplitude <NUM>-<NUM> of the third evoked response signal recorded by electrode <NUM>-<NUM> decreases by at least an amplitude threshold amount and a phase <NUM>-<NUM> of the third evoked response signal recorded by electrode <NUM>-<NUM> changes by at least a phase threshold amount. The additional predetermined time period, the amplitude threshold amount, and/or the phase threshold amount may each be set by diagnostic system <NUM> to be any suitable value, such as described herein.

In certain examples, diagnostic system <NUM> may perform similar operations such as those described herein to determine when electrode lead passes other characteristic frequency locations that correspond to other frequencies (e.g., <NUM>, <NUM>, etc.).

In certain examples, diagnostic system <NUM> may determine that electrode lead <NUM> passes a characteristic frequency based on at least one of an amplitude of an additional evoked response signal included in the plurality of evoked response signals not decreasing by at least the amplitude threshold amount and a phase of the additional evoked response signal not changing by at least the phase threshold amount. For example, diagnostic system <NUM> may determine that electrode lead <NUM> passes the characteristic frequency location that corresponds to <NUM> based on amplitude <NUM>-<NUM> of the third evoked response signal not decreasing by an amplitude threshold amount and/or phase <NUM>-<NUM> not changing by at least a phase threshold amount at insertion time T2 in addition to amplitude <NUM>-<NUM> and phase <NUM>-<NUM> of the second evoked response signal changing by an amplitude threshold amount and a phase threshold amount at insertion time T2.

In <FIG>, various aspects of electrode lead <NUM> and the illustrated anatomical features of the recipient are simplified for clarity of illustration. For instance, while cochlea <NUM> has been "unrolled" in <FIG>, it will be understood that cochlea <NUM> has a curved, spiral-shaped structure and that electrode lead <NUM> curves to follow the spiral-shaped structure. Similarly, the anatomy of cochlea <NUM> omit many details and are not drawn to scale.

<FIG> does, however, illustrate at least one additional structure that may be associated with an insertion state that may be determined by diagnostic system <NUM>. In particular, <FIG> also shows a basilar membrane <NUM> that extends along a length of cochlea <NUM>. As electrode lead <NUM> is inserted along cochlea <NUM>, electrode lead <NUM> may contact a structure of cochlea <NUM> such as basilar membrane <NUM>. In such examples, diagnostic system <NUM> may determine that electrode lead <NUM> is in contact with the structure of cochlea <NUM> when amplitudes of at least two of the evoked response signals included in the plurality of evoked response signals have decreased by at least an amplitude threshold amount and phases of the at least two of the evoked response signals have changed by at least a phase threshold amount.

In certain alternative examples, diagnostic system <NUM> may determine that electrode lead <NUM> is in contact with the structure of cochlea <NUM> when amplitudes of each of the evoked response signals included in the plurality of evoked response signals have decreased by at least an amplitude threshold amount and phases of each of the evoked response signals have changed by at least a phase threshold amount.

To illustrate, <FIG> shows an exemplary electrode lead insertion procedure in which electrode lead <NUM> is advanced into cochlea <NUM>. <FIG> also shows graph <NUM> of amplitudes <NUM> (e.g., amplitudes <NUM>-<NUM> through <NUM>-<NUM>) of evoked response signals recorded by electrode <NUM>-<NUM> during the lead insertion procedure. In addition, <FIG> shows graph <NUM> of phases <NUM> (e.g., phases <NUM>-<NUM> through <NUM>-<NUM>) of the evoked response signals recorded by electrode <NUM>-<NUM> during the lead insertion procedure. In this example, first, second, third, and fourth evoked response signals are generated in response to acoustic stimulation having stimulus frequencies of <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

As shown in <FIG>, electrode lead <NUM> has come into contact with basilar membrane <NUM> at a position <NUM> along the length of basilar membrane <NUM>. Hence, as shown in graph <NUM>, amplitudes <NUM> of each of the first, second, third, and fourth evoked response signals increase and peak as a result of electrode lead <NUM> contacting basilar membrane <NUM> at position <NUM>. In addition, as shown in graph <NUM>, phase <NUM> of each of the first, second, third, and fourth evoked response signals change from a relatively high level to a relatively low level as a result of electrode lead <NUM> contacting basilar membrane <NUM> at position <NUM>.

As shown in <FIG>, the decreasing of the first, second, third, and fourth evoked response amplitudes <NUM> and the changing of each of phases <NUM> from the high level to the low level occur at substantially the same time (e.g., within a predetermined time period), and each occur as electrode lead <NUM> contacts basilar membrane <NUM> and changes mechanical stiffness of basilar membrane <NUM>. Hence, diagnostic system <NUM> may determine that electrode lead <NUM> contacts a structure such as basilar membrane <NUM> by determining, within a predetermined time period, that the amplitudes of each of the evoked response signals included in the plurality of evoked response signals have decreased by at least the amplitude threshold amount and the phases of each of the evoked response signals have changed by at least the phase threshold amount. The predetermined time period, the amplitude threshold amount, and/or the phase threshold amount may each be set by diagnostic system <NUM> to be any suitable value, such as described herein.

In certain examples, diagnostic system <NUM> may be configured to determine a location and/or an amount of contact with respect to the structure of cochlea <NUM> based on amplitudes and phases of each of the evoked response signals. The location of the contact may be determined in any suitable manner. In addition, the amount of contact may be determined in any suitable manner. For example, amplitudes <NUM> of each of the first, second, third, and fourth evoked response signals shown in <FIG> may be indicative of a first amount of contact with respect to basilar membrane <NUM> at position <NUM>. Relatively larger amplitudes <NUM> of each of the first, second, third, and fourth evoked response signals may be indicative of a second amount of contact with respect to basilar membrane <NUM> at position <NUM> that is relatively greater than the first amount of contact. Additionally or alternatively, an amount of phase change may be indicative of an amount of contact with respect to basilar membrane <NUM> at position <NUM>. For example, the amount of phase change shown in <FIG> may be indicative of electrode lead <NUM> contacting basilar membrane <NUM> at a first amount of contact. The amount of phase change may increase with greater contact and/or in response to electrode lead <NUM> translocating basilar membrane <NUM>.

In certain examples, an insertion state of an electrode lead may be associated with an electrode lead passing a cluster of a particular type of cells (e.g., hair cells, neuron cells, etc.) within the cochlea. In such examples, diagnostic system <NUM> may determine that an electrode lead passes a cluster of a particular type of cells such as hair cells when amplitudes of one or more evoked response signals included in the plurality of evoked response signals have decreased by at least an amplitude threshold amount and phases of the one or more evoked response signals have not changed by at least a phase threshold amount. For example, diagnostic system <NUM> may determine that the electrode lead passes a cluster of hair cells when the amplitudes of the second, third, and fourth evoked response signals decrease by at least an amplitude threshold amount and the phases of the second, third, and fourth evoked response signals do not change by at least a phase threshold amount.

In certain alternative examples, diagnostic system <NUM> may determine that an electrode lead passes a cluster of a particular type of cells such as hair cells when amplitudes of each of the evoked response signals included in the plurality of evoked response signals have decreased by at least an amplitude threshold amount and phases of each of the evoked response signals have not changed by at least a phase threshold amount. To illustrate an example, <FIG> shows an exemplary electrode lead insertion procedure in which electrode lead <NUM> is advanced into cochlea <NUM>. <FIG> also shows graph <NUM> of amplitudes <NUM> (e.g., amplitudes <NUM>-<NUM> through <NUM>-<NUM>) of evoked response signals recorded by electrode <NUM>-<NUM> during the lead insertion procedure. In addition, <FIG> shows graph <NUM> of phases <NUM> (e.g., phases <NUM>-<NUM> through <NUM>-<NUM>) of the evoked response signals recorded by electrode <NUM>-<NUM> during the lead insertion procedure. In this example, first, second, third, and fourth evoked response signals are generated in response to acoustic stimulation having stimulus frequencies of <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

As shown in <FIG>, electrode lead <NUM> passes a cluster of hair cells <NUM> along the length of cochlea <NUM>. As a result of passing cluster of hair cells <NUM>, an amplitude <NUM> of each of first, second, third, and fourth evoked response signals has peaked and dropped at an insertion time associated with passing cluster of hair cells <NUM>. However, as shown in graph <NUM>, phases <NUM> of each of the first, second, third, and fourth evoked response signals have not changed by at least a phase threshold amount as a result of passing cluster of hair cells <NUM>. Hence, diagnostic system <NUM> may determine that electrode lead <NUM> passes cluster of hair cells <NUM> when, within a predetermined time period, amplitudes of one or more evoked response signals included in the plurality of evoked response signals have decreased by at least an amplitude threshold amount and that phases of the one or more evoked response signals have not changed by at least a phase threshold amount.

In certain examples, an insertion state of an electrode lead may be associated with a possible occurrence of trauma (e.g., translocation from the scala tympani to the scala vestibuli (i.e., by penetrating through the basilar membrane)) to a structure of a cochlea of a recipient. Such trauma may be caused by the electrode lead penetrating the basilar membrane of the cochlea, inadvertently being placed within a wrong duct of the cochlea, and/or in any other suitable manner. In such examples, diagnostic system <NUM> may determine that the electrode lead has caused trauma to the cochlea based on a determination that amplitudes of evoked response signals included in a plurality of evoked response signals have decreased by at least an amplitude threshold amount and phases of the evoked response signals have changed by at least a phase threshold amount that is relatively larger than an additional phase threshold amount indicative of the electrode lead merely contacting a structure of the cochlea. In this regard, diagnostic system <NUM> may use different phase threshold amounts to determine different insertion states of electrode lead <NUM> in certain implementations.

As shown in <FIG>, electrode lead <NUM> has come into contact with and has punctured basilar membrane <NUM> at a position <NUM> along the length of basilar membrane <NUM>. Hence, as shown in graph <NUM>, amplitudes <NUM> of each of the first, second, third, and fourth evoked response signals increase and peak decrease by at least an amplitude threshold amount with respect to each other as a result of electrode lead <NUM> puncturing basilar membrane <NUM> at position <NUM>. As shown in graph <NUM>, phase <NUM> of each of the first, second, third, and fourth evoked response signals change from a relatively high level to a relatively low level as a result of electrode lead <NUM> puncturing basilar membrane <NUM>. The amount of phase change shown in <FIG> is relatively larger than the amount of phase change shown in <FIG>. This is because there is a relatively higher phase change threshold associated with electrode lead <NUM> causing trauma to cochlea <NUM> as compared to electrode lead <NUM> merely contacting basilar membrane <NUM>, as shown in <FIG>.

As shown in <FIG>, the decreasing of the first, second, third, and fourth evoked response amplitudes <NUM> by at least the amplitude threshold amount and the changing of each of phases <NUM> from the high level to the low level occur at substantially the same time, and each occur as electrode <NUM>-<NUM> punctures basilar membrane <NUM>. Hence, diagnostic system <NUM> may determine that electrode <NUM>-<NUM> has caused trauma to cochlea <NUM> based on diagnostic system <NUM> determining, within a predetermined time period, that the amplitudes of the evoked response signals included in the plurality of evoked response signals have decreased by at least the amplitude threshold amount and the phases of the evoked response signals changing have changed by at least a phase threshold amount that is relatively larger than an additional phase threshold amount indicative of the electrode lead contacting a structure of the cochlea. The phase threshold amount associated with causing trauma to cochlea <NUM> may be set by diagnostic system <NUM> to be any suitable value, such as described herein.

In certain examples, evoked response amplitudes (e.g., evoked response amplitudes <NUM>) decreasing by different amounts with respect to each other may additionally or alternatively be indicative of an electrode lead causing trauma to the cochlea. Any suitable amount difference in the decrease of the amplitudes of the evoked response signals may be indicative of trauma to the cochlea.

In certain examples, diagnostic system <NUM> may be configured to provide a notification regarding an insertion state while an electrode lead is inserted into a cochlea. Such a notification may be provided in any suitable manner. For example, diagnostic system <NUM> may be configured to provide an audible notification, a text notification, and/or a graphical notification configured to inform a user (e.g., a surgeon) of the insertion state. In certain examples, the notification may include providing a graph of the evoked response signals for display in one or more graphs displayed by way of a display device (e.g., display device <NUM>) associated with diagnostic system <NUM>. For example, diagnostic system <NUM> may direct a display device to display a graph of the evoked response signals in substantially real time as an insertion procedure is being performed by displaying each evoked response signal included in the plurality of evoked response signals such that, at any given time, multiple evoked response signals included in the plurality of evoked response signals are concurrently displayed by the display device. By displaying one or more graphs of the evoked response signals recorded by an electrode during the insertion procedure, diagnostic system <NUM> may provide real-time feedback to a user (e.g., a surgeon) performing the insertion procedure. This feedback may be used by the user to ensure proper placement of the electrode lead <NUM> within cochlea <NUM> and/or for any other purpose as may serve a particular implementation.

To illustrate, in the exemplary insertion procedure shown in <FIG>, system <NUM> may be configured to provide a textual notification in a graphical user interface on a display screen to indicate that electrode lead <NUM> has punctured basilar membrane <NUM>. In response to seeing such a notification appear within the graphical user interface, a user may stop the insertion procedure and/or take other remedial action (e.g., by pulling back the electrode lead outside the cochlea, changing electrode insertion angle, etc.). Any other type of notification (e.g., audible or visible notification) may additionally or alternatively be presented to the user as may serve a particular implementation.

In certain examples, diagnostic system <NUM> may direct a display device to display a first graph representative of the amplitudes of the evoked response signals and a second graph representative of the phases of the evoked response signals. For example, diagnostic system <NUM> may direct a display device to display graph <NUM> as a first graph and graph <NUM> as a second graph shown, for example, in <FIG> in any suitable manner. In certain examples, diagnostic system <NUM> may direct a display device to concurrently display graphs <NUM> and <NUM> in a single graphical user interface.

Additionally or alternatively, a single graphical user interface that displays graphs <NUM> and <NUM> may also display a graphical representation of cochlea <NUM> and a graphical representation of electrode lead <NUM> being inserted within cochlea <NUM> during the insertion procedure similar to what is shown, for example, in <FIG>. In such examples, the graphical representation of electrode lead <NUM> may be animated to facilitate depicting electrode lead <NUM> being inserted in real time into cochlea <NUM>. In addition, such a graphical representation of electrode lead <NUM> be animated to depict certain insertion states. For example, the graphical representation of electrode lead may be depicted as contacting a wall of cochlea <NUM> if diagnostic system <NUM> determines that an insertion state corresponding to contact of electrode lead <NUM> with a structure of cochlea <NUM> occurs.

In certain alternative implementations, diagnostic system <NUM> may direct a display device to display amplitudes and phases of evoked response signals for display in a single graph. To illustrate, <FIG> shows an alternative implementation in which a single graph <NUM> includes both amplitudes <NUM> and phases <NUM> of first, second, third, and fourth evoked response signals that may be generated in response to an insertion procedure in which electrode lead <NUM> passes cluster of hairs <NUM>. Graph <NUM> may be provided for display to a user in any suitable graphical user interface to facilitate the user performing an insertion procedure.

<FIG> illustrates an exemplary method <NUM>. The operations shown in <FIG> may be performed by diagnostic system <NUM> and/or any implementation thereof. While <FIG> illustrates exemplary operations according to one embodiment, other embodiments may omit, add to, reorder, and/or modify any of the operations shown in <FIG>.

In operation <NUM>, a diagnostic system directs an acoustic stimulation generator to apply acoustic stimulation having a plurality of stimulus frequencies to a recipient of a cochlear implant during an insertion procedure in which an electrode lead communicatively coupled to the cochlear implant is inserted into a cochlea of the recipient. Operation <NUM> may be performed in any of the ways described herein.

In operation <NUM>, the diagnostic system directs the cochlear implant to use an electrode disposed on the electrode lead to record a plurality of evoked response signals during the insertion procedure, each evoked response signal included in the plurality of evoked response signals corresponding to a different stimulus frequency included in the plurality of stimulus frequencies and representative of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient. Operation <NUM> may be performed in any of the ways described herein.

In operation <NUM>, the diagnostic system determines, based on an amplitude and a phase of each of one or more evoked response signals included in the plurality of evoked response signals, an insertion state of the electrode lead within the cochlea of the recipient. Operation <NUM> may be performed in any of the ways described herein.

<FIG> illustrates an exemplary computing device <NUM> that may be specifically configured to perform one or more of the processes described herein. As shown in <FIG>, computing device <NUM> may include a communication interface <NUM>, a processor <NUM>, a storage device <NUM>, and an input/output ("I/O") module <NUM> communicatively connected one to another via a communication infrastructure <NUM>. While an exemplary computing device <NUM> is shown in <FIG>, the components illustrated in <FIG> are not intended to be limiting. Additional or alternative components may be used in other embodiments. Components of computing device <NUM> shown in <FIG> will now be described in additional detail.

In some examples, any of the systems, computing devices, and/or other components described herein may be implemented by computing device <NUM>. For example, storage facility <NUM> may be implemented by storage device <NUM>, and processing facility <NUM> may be implemented by processor <NUM>.

Claim 1:
A system comprising:
a memory (<NUM>) storing instructions (<NUM>); and
a processor (<NUM>) communicatively coupled to the memory and configured to execute the instructions to:
direct an acoustic stimulation generator (<NUM>) to apply acoustic stimulation having a plurality of stimulus frequencies to a recipient of a cochlear implant (<NUM>) during an insertion procedure in which an electrode lead (<NUM>, <NUM>) communicatively coupled to the cochlear implant is inserted into a cochlea (<NUM>, <NUM>) of the recipient, wherein the plurality of stimulus frequencies are concurrently applied to the recipient during the insertion procedure;
direct the cochlear implant to use an electrode (<NUM>, <NUM>) disposed on the electrode lead to record a plurality of evoked response signals during the insertion procedure, each evoked response signal included in the plurality of evoked response signals corresponding to a different stimulus frequency included in the plurality of stimulus frequencies and representative of evoked responses that occur within the recipient in response to the acoustic stimulation applied to the recipient; and
determine, based on an amplitude and a phase of each of one or more evoked response signals included in the plurality of evoked response signals, an insertion state of the electrode lead within the cochlea of the recipient.