Abstract:
A cortical stimulator system is provided. The system may include; a stimulation device having a switch configured to selectively control various electrodes; and a user interface device operatively connected to the stimulation device for controlling the electronic switch and stimulation device, the cortical stimulator system configured to provide a report of provided stimulation. A method of operating a cortical stimulator may be provided. The method may include: connecting a set of probes to the cortical stimulator, selecting parameters regarding a signal to be sent to the set of probes, sending a signal to the set of probes; observing the response of a subject having the set of probes contacting the subjects brain when the signal is sent to the probes, entering the observed response into the cortical stimulator, associating the response to a specific set of probes, and generating a report describing the response and associated probes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to provisional U.S. patent application entitled, Cortical Stimulator Method and Apparatus, filed Apr. 24, 2009, having Ser. No. 61/172,372, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to cortical stimulators and the like. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cortical stimulation has been performed as part of a pre-surgical work up for decades, and has been well documented and clinically accepted. Cortical stimulation is typically achieved by means of direct stimulation of the cortex with biphasic constant current pulses being delivered by means of a bipolar probe, typically during brain surgery of a patient, or through intracranial electrodes during long-term monitoring. Functional brain mapping identifies critical functional regions of the brain including the motor area, which controls movement; somatosensory area, which controls sensation; and expressive and receptive language areas, which control speech and comprehension. By mapping the brain, the neurosurgeon can find a balance between tumor or epileptogenic foci resection and potential damage to critical brain areas that would affect patient quality of life. 
         [0004]    Stimulation through a grid electrode is typically awkward, as the electrodes must be switched from the amplifier to the stimulator and back, either through a switchboard or manually, which is labor intensive and extremely error prone. In addition, brain maps which display the results of the stimulation, in terms of ictal, inter-ictal and functional responses, are typically hand-drawn. 
         [0005]    Accordingly, there is a need and desire for a cortical stimulator having electronic electrode switching, stimulation capability, software integration and/or report generation. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of the present invention advantageously provide a cortical stimulator having electronic electrode switching, stimulation capability, and software integration and/or report generation. 
         [0007]    In accordance with some embodiments of the invention, a cortical stimulator system is provided. The system may include; a stimulation device having a switch configured to selectively control various electrodes; and a user interface device operatively connected to the stimulation device for controlling the electronic switch and stimulation device, the cortical stimulator system configured to provide a report of provided stimulation. 
         [0008]    In accordance with some embodiments of the invention, a method operating a cortical stimulator may be provided. The method may include: connecting a set of probes to the cortical stimulator, selecting parameters regarding a signal to be sent to the set of probes, sending a signal to the set of probes; observing the response of a subject having the set of probes contacting the subjects brain when the signal is sent to the probes, entering the observed response into the cortical stimulator, associating the response to a specific set of probes, and generating a report describing the response and associated probes 
         [0009]    Before explaining at least one embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0010]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective schematic view of a cortical stimulator in accordance with an embodiment of the present invention. 
           [0012]      FIG. 2  is a perspective schematic view of a stimulus control unit in accordance with an embodiment of the present invention. 
           [0013]      FIG. 3  is a bottom schematic view of the  FIG. 2  stimulus control unit. 
           [0014]      FIG. 4  is a block diagram of electronics associated with a stimulus control unit in accordance with an embodiment of the present invention. 
           [0015]      FIG. 5  is a perspective schematic view of a portion of a cortical stimulator in accordance with an embodiment of the present invention. 
           [0016]      FIG. 6  is a perspective bottom view of the portion of the cortical stimulator shown in  FIG. 5 . 
           [0017]      FIG. 7  is a block diagram of a stimulus switching unit in accordance with an embodiment of the present invention. 
           [0018]      FIG. 8  is a graph showing a biphasic waveform in accordance with an embodiment of the present invention. 
           [0019]      FIG. 9  is a schematic diagram of one embodiment of cortical stimulator system in an OR probe biphasic mode. 
           [0020]      FIG. 10  is a schematic diagram of one embodiment of cortical stimulator system in an electrode biphasic mode. 
           [0021]      FIG. 11  is a schematic diagram of an embodiment of cortical stimulator system in an electrode biphasic mode. 
           [0022]      FIG. 12  is a schematic diagram of an embodiment of cortical stimulator system in an electrode biphasic mode. 
           [0023]      FIG. 13  is a schematic diagram of an embodiment of cortical stimulator system in a stand alone configuration. 
           [0024]      FIG. 14  is a schematic diagram of an embodiment of cortical stimulator system including a computer. 
           [0025]      FIG. 15  is a schematic diagram of an embodiment of cortical stimulator system including a laptop type computer. 
           [0026]      FIG. 16  shows a table of error codes and the meaning of the error codes. 
           [0027]      FIG. 17  is a perspective schematic view of a amplifier for a cortical stimulator system in accordance with an embodiment of the present invention and shows an enlargement of part of the amplifier. 
           [0028]      FIG. 18 . shows various settings for a channel selector for the amplifier shown in  FIG. 17 . 
           [0029]      FIG. 19 . is a table showing an LED light configuration indicating which LED lights are illuminated when which channels for the amplifier of  FIG. 17  are active. 
           [0030]      FIG. 20  is a flow chart illustrating steps in a method of operating a cortical stimulator. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and show by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other embodiments may be utilized, and that structural, logical, processing, and electrical changes may be made. The progression of processing steps described is an example; however, the sequence of steps is not limited to that set forth herein and may be changed as is known in the art, with the exception of steps necessarily occurring in a certain order. 
         [0032]    Embodiments of a cortical stimulator of the present invention include a complete system of hardware and software integrated to provide comprehensive biphasic constant current stimulation with trains of stimulation pulses while monitoring patient electroencephalogram (EEG) for real-time electrophysiological responses. This complete system may be combined with the ability to electronically select any pair of, for example, up to 128 grid and/or strip electrodes. Stimulation initiation and other parameters can be controlled from either the hardware or software control panel. 
         [0033]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout.  FIG. 1  is a perspective schematic view of a cortical stimulator in accordance with an embodiment of the present invention. A cortical stimulator  100  may include a stimulus control unit  110 , a first amplifier  120 , a stimulus switching unit (SSU)  130 , and a second amplifier  140 . 
         [0034]      FIG. 2  is a perspective schematic view of a stimulus control unit in accordance with an embodiment of the present invention. The stimulus control unit (SCU)  110  may include a status indicator  202  for showing a current status of the stimulator  100 . The various status conditions may include a set-up mode, a ready mode and a Stim-on (where stimulation may be actually occurring) mode. A setup selector  204  on the stimulus control unit  110  may be for allowing a user to change parameters of the stimulus control unit  110 . For example, some changes to the SCU  110  may include changing between a probe biphasic and a electrode biphasic mode (these modes will be discussed later below). Selecting between a numeric and montage label sets, and a list of languages messages from the SCU  110  will appear. The SCU  110  may include a pulse frequency selector  206  for viewing and/or setting a rate at which pulses are delivered. A typical rate is 50 Hz but other rates may also be used. 
         [0035]    The SCU  110  may include a pulse duration selector  208  for viewing and/or setting a length of time for each pulse. The actual pulse length may be twice the pulse duration. Example pulse durations may range from 100-1000 uSec, however other durations may be used. A train duration selector  210  may be used for viewing and/or setting a maximum stimulus duration. A train duration of 5 seconds is typical, however other durations my be used. A single train duration or an externally controlled trigger (such as by a computer connected to the SCU  110 ) may be selected. 
         [0036]    The stimulus control unit  110  may further include electrode channel selectors  212 ,  214 . The channel selectors  212 ,  214  may used to switch a probe or electrode from anode to cathode or vise versa. In some embodiments the channel selectors  212 ,  214  may select between 1-64 channels or 1-128 channels if a second SSU (explained further below) is connected to the SCU  110 . Selecting a channel will select which electrodes will received the stimulus. Rotation of the selector knob  228  may select a channel once the channel selectors  212  and/or  214  are actuated. The SCU  110  is equipped with a set stimulus selector  216  for setting a current level to be applied to a patient. A base line up to about 8 mAmps or less is typical although other levels may be used. The selector knob  228  may be used to adjust the value of the current after the stimulus selector  216  is actuated. A delivered stimulus indicator  218  displays the stimulation level being delivered to a patient. An LED may illuminate to indicate when stimulation is being delivered. A stimulus check selector  220  can apply a selected stimulus to an internal load (not shown) to verify correct operation. In some optional embodiments LED lights may illuminate when this feature is enabled. The actual current that is delivered is displayed to a delivered stim display field. 
         [0037]    The stimulus control unit  110  may further include a mark channel selector  222  for indicating which channel or channels are selected. The mark channel selector  222  may be depressed by a user when the channel is selected. The SCU  110  has a start selector  224  for delivery of the stimulation pulse (train, single or single). In one embodiment, the start selector  224  may function only when the cortical stimulator  100  is in a “ready state,” i.e., ready to provide cortical stimulation and the external trigger function is not being used. The SCU  110  may include an ictal disrupt selector  226 . When actuated the ictal disrupt selector  226  may repeat a first pulse in a pulse train. The selector input  228  may allow a user to scroll through various options accessed by any of the various selectors and indicators, for example, the electrode channel selectors  212 ,  214  and set stimulus selector  216 . A stop selector  230  may interrupt stimulation. Trigger in, trigger out, and synchronization connector inputs  232 ,  234 ,  236  may allow external control of the stimulus control unit  110 . A serial port  238  may allow a serial connection for an external interface to other devices or a computer. A USB port  240  may allow a USB connection for an external interface, for example, for service diagnostics and optionally for a computer interface. A remote start/stop port  242  may allow remote control of starting and/or stopping the cortical stimulator  100 . 
         [0038]    The stimulus control unit  110  may further include a display  244  for displaying any information and/or parameters pertinent to operation to the user including any information generated by any of the above-described indicators and selectors. The display  244  may be, for example, a liquid crystal display (LCD). 
         [0039]      FIG. 3  is a bottom schematic view of the  FIG. 2  stimulus control unit. The stimulus control unit  110  may further include a power switch  250  and a power supply connection  252 . It should be appreciated that any of the  FIGS. 2 and 3  elements may be located at any appropriate location. The illustrated elements are not limited to the locations, sizes, or geometries shown. For example, although the selector input  228  is shown as a knob, it may be a joystick, scroll wheel, arrow buttons, or any input device suitable for the desired function. 
         [0040]      FIG. 4  is a block diagram of a stimulus control unit  110  in accordance with an embodiment of the present invention. The stimulus control unit  110  may include a front panel membrane  301  on which the selectors  202 - 230  may be located. It should be appreciated that the markings on the membrane may be graphical or text in any appropriate language. In one embodiment of the present invention, both text and graphics are provided such that a user who is not familiar with the language in which the text is written may understand and operate the cortical stimulator  100 . Inputs made to the front panel membrane  301  may feed into at least one debounce circuit  302  for debouncing and stabilizing user inputs. A programmable logic device (PLD)  303 , for example, a complex programmable logic device (CPLD) or a field-programmable gate array (FPGA), may receive inputs from the indicators and selectors described above via the debounce circuit  302  or directly from the front panel membrane  301 . 
         [0041]    Address, data, and control information may be passed between the PLD  303  and a processor (uP)  304  for controlling operations of the stimulus control unit  110 . The processor  304  may also control the display  244 . The selector input  228  may provide an input directly to the processor  304 . The processor  304  may provide outputs to a positive stim AND logic  307  and to a negative stim AND logic  308 , which provide a respective positive and negative input to a biphasic stimulator  309 . 
         [0042]    The PLD  303  may be electrically connected to the trigger in and trigger out connector inputs  232 ,  234 . 
         [0043]    When the power switch  250  is set to an “ON” position, power is provided via the power supply connection  252 , which may be passed through other circuitry to a direct current to direct current (DC/DC) converter  313 . The DC/DC converter converts a voltage level received, e.g., +15 V, into a voltage level required by the biphasic stimulator  309 , e.g., +150 V. The biphasic stimulator  309  provides stimulation to the patient based on controls sent from the PLD  303  and processor  304 . 
         [0044]    As shown in  FIG. 4 , a PSU sync  420  may be attached to the CPLD  303 . An ADC  422  is located between the Current sense  424  and the uP  304 . Some embodiments in accordance with the invention may include an isolation circuit  426  to reduce the likelihood of current leaking from the SCU  110  to the subject. In some embodiments of the invention, the isolation circuit (sometimes referred to as a blocking circuit) may prevent current from leaking into amplifier inputs associated with electrodes configured to receive current. This blocking or isolation feature may result in more current available for electrodes intended to receive current and less amplifier recovery time. 
         [0045]    The isolation circuit  426  may include a RS485 transceiver  428  connected to the SSU interface  248  and the Opto isolation  430 . The Opto isolation  430  recieves an input from a serial port in the uP  304 . An Opto isolation  432  may receive uP control signals and an Auxiliary +3.3V input. An Opto isolation  434  may receive CPLD control signals and an Auxiliary +3.3V input and may be connected to switches, a current limit  438  and 24V or 100V clamps  440 , and a channel marking  438  as shown. An isolated 5V supply  436  may also be part of the isolation circuit  426  While example voltages have be described herein, it should be understood that these are examples only and other voltages may be used in accordance with the invention. 
         [0046]    The microprocessor  304  used inside the SCU  110  may perform several tasks. For example, the microprocessor  304  may: enable a ±24V DC at output, set a Stim level, request positive stim pulses, request negative stim pulses, enable output relays to export the stimulating current, and monitor the stimulating current via in-built 16-bit ADC. The microprocessor may also monitor the state of the front panel switches  202 - 230 , monitor the position of a rotary encoder and associated switch and the present information on the LCD  244 . The microprocessor  304  may interact with a remote computer via the RS232 link. The microprocessor  304  may interact with a remote computer to validate parameter settings and return status information. The microprocessor  304  may interact with the SSU  130  to set the SSU  130  configuration and monitor the SSU  130  status. The microprocessor  304  may also monitor the stim level and the +12 V and −15V voltage rails. 
         [0047]    The microprocessor will access the LCD  249  and CPLD (complex programmable logic device  303 ) components via its external memory interface. 
         [0048]    Assuming that the microprocessor  304  is functional, it will be able to check the operational status. 
         [0049]    Before stimulation is activated, the microprocessor  304  will check that the stim intensity level, set by the 16-bit DAC, is at the expected level. 
         [0050]    The microprocessor  304  may monitor the stimulator output current, even if it is not meant to be stimulating. If the output current is not within a set percentage of the expected output current, then the microprocessor  304  will switch off the stimulator circuit and de-energize the photo-mos relay. 
         [0051]    The microprocessor  304  may have a supply voltage monitor that may be used to halt the processor in the event that the 3.3V voltage rail goes outside of the expected range. 
         [0052]    The microprocessor  304  is interrupted by a timer on a regular basis (every 10 uS). Towards the start and end of the interrupt service routine, the microprocessor  304  refreshes registers within the CPLD  303 . If this process does not take place, then the CPLD  303  will be able to interrupt any current flow by switching off some of the photo-mos relays in the stimulator output stage. The two stim enable outputs from the CPLD  303  may also be switched off and this, in turn, will guard against any stimulator pulses that are generated by the microprocessor  304  from having any further effect. 
         [0053]    Complex programmable logic device (CPLD)  303  also inside the Stimulus Control Unit  110  is used to interface several signals to be microprocessor  304  and to monitor its operation. 
         [0054]    The CPLD  303  will disable stimulation by inhibiting the stimulator pulses generated by the microprocessor  304  and by de-energizing one of the stimulator output relays. 
         [0055]    The CPLD  303  is provided with its own reference oscillator for timing purposes, making it independent of the microprocessor system clock. 
         [0056]    The CPLD  303  also monitors the frequency and duration of any stimulation. The stimulator configuration is written to registers within the CPLD  303  and it is the contents of these registers that are used to present data on the LCD  244 . This latter process ensures that any defects within the memory inside the microprocessor  304  will not be propagated through to the CPLD  303  without being noticed either by a user operating the unit in the Local mode or by a system that interrogates the Stimulus Control Unit  110  remotely. 
         [0057]    When stimulation is in progress, the CPLD  303  will check that the microprocessor  304  is generating the expected pulse train. If the microprocessor  304  deviates from what is expected, then the CPLD  303  will switch off its two stim enable outputs and this in turn will guard against any stimulator pulses that are generated by the microprocessor  304  from having any further effect. The CPLD  303  will also switch off some of the photo-mos relays in the output stage. 
         [0058]      FIG. 5  is a perspective schematic view of a portion of a cortical stimulator in accordance with an embodiment of the present invention. A stimulus switching device  400  may include a first amplifier  120 , a stimulus switching unit (SSU)  130 , and a headbox  140 . First and second cable connectors  410 ,  420  provide inputs to the stimulus switching device  400  via the stimulus switching unit  130 . 
         [0059]    As shown in  FIG. 6 , at bottom  442  of the stimulus switching device  400  are multiple terminals  444 . The multiple terminals  444  are configured to provide a place of various electrodes (not shown in  FIG. 6 ) to plug in to. The electrodes may be part of a grid, matrix, or strips of electrodes. The electrodes may be inserted onto the brain of a subject undergoing a stimulation procedure. 
         [0060]      FIG. 7  is a block diagram of a stimulus switching unit  130  in accordance with an embodiment of the present invention. The stimulus switching unit  130  may include head inputs  501  from a head box  140 . The output  502  of the stimulus switching unit  130  may be provided to an amplifier, e.g., the first amplifier  120 , at a fourth output  464 . In the illustrated example, there are between one (1) and sixty-four (64) input/output sets, i.e., channels. 
         [0061]    A low-dropout (LDO) regulator  504  may receive an input from the stimulation input  503 . The stimulation input  503  may communicate via a communications channel  505 , e.g., an RS-485 communications channel, with a processor  506 . The processor  506  can communicate with a first photoMOS array  507 , i.e., an optical isolator that uses a short optical transmission path to transfer a signal between elements of a circuit, while keeping them electrically isolated. A transistor or other switching array may also be used. A BCD SEl. Switch and LEDs  519  are also operatively connected to the controller  506 . A first input/output (I/O) expander  508  may be communicatively connected to the processor  506  for providing signals to the first photoMOS array  507 . A reference voltage REF (for example 5V) may also be provided by the stimulation input  503  to the first photoMOS array  507 . The above-described elements  503 - 508  may be provided on a first circuit board  446 . Although some of the elements  503 - 508  may optionally be contained on second circuit board  448 . An output from the photoMOS array  507  may be combined with the output from the head inputs  501  in a second output  450 , which may be, for example, on a 100 pin board-to-board connector. 
         [0062]    The second output  450  may be provided to a first male/female interface  510 . The second photoMOS array  512  may also receive an outlet  452  from the processor  506 . The second photoMOS array  512  may provide an output  454 , which may be combined with the output  456  from the male/female interface  510  to the male/female interface  520 . 
         [0063]    The second male/female interface  520  may provide an output  458  to a third I/O expander  521 , which may provide an output  460  to a third photoMOS array  522 . The output  462  from the male/female interface  520  may be provided as a second input to the third photoMOS array  522 , which may include a load  523 , e.g., a resistor having a value of 80 kΩ. The third photoMOS array  522  may provide the fourth output  464 , which may be, for example, on a 100 pin board-to-board connector. The third I/O expander  521  and the third photoMOS array  522  may be provided on a third circuit board  466 . 
         [0064]      FIG. 8  depicts a graph showing a biphasic waveform  468  in accordance with an embodiment of the present invention. The biphasic waveform  468  is a pulse having positive and negative voltage for stimulating a patient over a period of a few milliseconds. It should be appreciated that the voltage levels, pulse time, and initial direction, i.e., positive or negative voltage, may be adjusted as required for the particular application within the scope of embodiments of the invention. 
         [0065]    The cortical stimulator system describe herein may be used in at least two basic modes. A first mode may be referred to a an OR probe Biphasic mode and a second mode may be referred to as an Electrode Mode. As used herein, the terms “probe” and “electrode” are used interchangeably are not meant to be mutually exclusive. The OR probe Biphasic mode may be used when a set of probes (a cathode and an anode such as those  470  shown in  FIG. 14 ) are moved from place to place on the brain of a subject during a procedure. 
         [0066]    In the electrode mode, a series of probes (or electrodes) have been attached to the brain of a subject. The series of electrodes may be configured as pairs (an cathode and an anode) and arranged in a grid, matrix or in strips. The series of electrodes maybe be secured to the subject&#39;s brain so that they will remain in place as the subject moves about. In some instances the series of electrodes may have been placed earlier and may have been used in a procedure prior to the cortical stimulation procedure. 
         [0067]    A software graphical user interface (GUI) may present the grid/strip electrode arrays shown on the brain view. The GUI facilitates ease of use. Pairs of electrodes can be selected for stimulation by pointing and clicking on the specific electrodes illustrated in the GUI. At the beginning of stimulation, the EEG acquisition window may open immediately, permitting the attending physicians an instant view of any seizure related, ictal and interictal activity (like “after discharges”, auras, and seizures) on all the electrodes including the pair being stimulated. Ictal/Interictal annotations can be made directly on the relevant electrodes as indicated by the observed EEG activity. In addition, a Functional Annotation field may be available to document any motor, sensory, speech and visual responses elicited by the stimulated pair of electrodes. The responses may be recorded as various colored bars linking the stimulated electrode pair combined with a legend that correlates to the specific function. 
         [0068]    Electrodes stimulated and “cleared” may be marked with a gray border to avoid unintentional repetition of stimulation. Ictal and interictal responses may be indicated by filling in the corresponding electrode symbol with a specific color indicating the exact nature of the physiological response. 
         [0069]    In addition to the features described above, other features may be included. Circuitry may be designed to block stimulation current from escaping into the amplifier, which assures that all of the current flows through the selected electrode pair and decreases amplifier recovery time post stimulation, which may be less than 1 second. A convenient small size may enable use as a hand held stand alone unit. The device may be used with a bipolar probe for manual brain mapping during surgery or with intracranial electrodes for bedside procedures. Two or more stimulus switching units may be coupled to electronically select additional electrodes and electrode pairs. In one embodiment of the present invention, two stimulus switching units are coupled to allow selection of up to 128 electrodes (i.e., 64 electrode pairs). It should be appreciated that additional or fewer units and electrodes may be used, as desired. 
         [0070]    The device may also have a user-configurable pulse frequency, pulse duration, train duration, and current level, for example, respectively set by the pulse frequency selector  206 , pulse duration selector  208 , train duration selector  210 , and set stimulus selector  216 . Moreover, the stimulator may also include a “single stimulus pulse” mode allowing a single pulse to be generated, rather than a pulse train, e.g., selectable by the ictal disrupt selector  226 . A “continuous stimulus pulse” mode may also be available for use, for example, with the bipolar probe. An actual reading of the current delivered may also be displayed, e.g., selectable by the stimulus check selector  220 . A stimulus time remaining may count down to zero, or may count up, as appropriate, for example, to a preset time or without bound, which may be displayed, e.g., on the display  244 . Continuous error detection may provide a high level of patient safety. There may also be an “active stimulation” indicator to indicate that stimulation is in progress, e.g., the status indicator  202 . A “trigger out” may permit synchronization of additional equipment, e.g., the trigger out connector input  234 . 
         [0071]    The EEG acquisition amplifier and stimulus switching unit may be mechanically connected to form a single robust unit. When not needed for cortical stimulation, the unit can be used for routine long-term monitoring with no degradation of signal quality. 
         [0072]    An ictal disrupt feature may stop after discharges before they can propagate into seizures which may result in premature termination of the session, which may be selectable by the ictal disrupt selector  226 . Stimulus trains can be aborted prematurely with a “stop” button, e.g., the stop selector  230 . A “check stim” feature may measure and verify accurate stimulator operation, e.g., selectable by the stimulus check selector  220 . A “channel mark” feature may confirm that a correct electrode pair has been selected and stimulated, e.g., selectable by the mark channel selector  222 . An annotation log may be automatically updated with stimulus settings. Multiple color coded functional and ictal event brain mapping with description legend. 
         [0073]    A grid/strip editor may provide a complete list of available grid, strip, and depth electrodes to select from. Brain map size can be scaled to cover the range from infants to adults. Report results may be displayed by response category in a tabular format. An automatic report may provide visual documentation and an audit trail of stimulations and responses. Control of stimulus parameters may be available in multiple languages. 
         [0074]      FIGS. 9-15  show various systems in accordance with different embodiments of the invention.  FIGS. 9-12  and block diagrams and  FIGS. 13-15  show the various componets in the system.  FIG. 9  shows a hospital power supply  472  supplying power to the SCU  110 . The SCU  110  is operatively connected to a computer  474  having an USB interface board  476  which permits the computer to communicate with a headbox  484  and the amplifier  120 . The computer  474  has a digital video capability  478  that is operatively connected to a camera  480 . The camera  480  may be used to record the procedure. Pictures from the camera  480  may by used in making a map of the brain to the subject. 
         [0075]      FIG. 10  is similar to  FIG. 9  but adds the SSU  130  to provide the switching capability to the system.  FIG. 11  is similar to  FIG. 10  but uses a lap top computer  490  rather than a desktop type computer  474 . To aid in communicating with the computer  490 , an I box  494  with a power supply  492  are used. While the camera  480  is not shown it could be added to the components shown in  FIG. 11 .  FIG. 12 . is similar to that shown in  FIG. 10  but does not show the digital video capability  478  and camera  480 . 
         [0076]      FIG. 13  shows a cortical stimulator system  496  used in a hand held manor. This system includes probes  470  connected to the SCU  110  which is connected to a power supply  472 . The probes  470  may be 2.3 mm electrodes or equivalent.  FIG. 14  shows a system  496  benefiting from the added capabilities of a computer  474 . The probes  470  are connected to the SCU  110  which in turn is connected to a power supply  472  and a computer  474 . The computer  474  and the SCU  110  are both operatively connected to the amplifiers  120  and SSUs  130 .  FIG. 15  is similar to  FIG. 14  but uses a laptop type computer  490 . The laptop computer  490  is connected to the stimulus switching device  400  via an I box  494 . The I box  494  is connected to a power supply  492 . 
         [0077]    While  FIGS. 14 and 15  show probes  470 , it should be understood that a grid, matrix, or strips of electrodes  482  may be connected to the SSU  130  and used rather than probes  470 . 
         [0078]      FIG. 16  shows a table of error codes and the corresponding meaning of the error codes. In the event that the SCU  110  or the system  496  detects an error or fault, the error code will be displayed to assist a user in troubleshooting. 
         [0079]      FIG. 17  shows stimulus switching device  400  having terminals  444  located at the bottom portion  442 . A switch user interface  600  permits a user to switch which channels will be active. The channels may correspond to specific terminals  444 . By manually setting the channel selector  602  a group of channels will be activated and may electronically be controlled by the SSU  130 . LED lights  604  will illuminate and comparing the illuminated lights  604  with the indicators  606  a user will be able to tell which channels are active. 
         [0080]      FIG. 18  show attitudes a channel indicator  602  may take. The rotator switch  610  will align with various indicator lines  608  to indicate what channels are selected.  FIG. 19  is a table showing what LED lights  604  will be illuminated when specific channels are activated. 
         [0081]      FIG. 20  shows a flow chart  700  showing various steps that may be accomplished while using the system  496 . The steps shown in the flow chart  700  presuppose that the system  496  has been set up and the various parameters have been already set. The steps listed are not limited to the order they are shown and scribed. In step S50 the probes  470  (or a matrix/strip of electrodes  482  are inserted into the brain of a subject. In S52 the probes/electrodes  470 / 482  are connected to the stimulation device (optionally via a SSU). In S54 a selected pair of probes/electrodes  470 / 482  are stimulated by being sent a signal of current. In S56 the subject is observed. The subject may be asked to do a simple task and the subject&#39;s response will be observed. In S58 it is determined whether the subject is showing signs of an ictal response. If yes, the stimulation is stopped as shown in step S59. To prevent/abort or remediate the ictal response a portion of the previously applied current train may be applied to the probes/electrodes that precipitated the ictal response as shown in step S60. 
         [0082]    If the ictal response has been aborted or none was observed, a user may enter the observations of the subject into the system as indicated in step S62. The user may associate a color with the observation. The system will associate the color and/or observation with the set of probes/electrodes and a portion of the brain that the probes/electrodes have been inserted. This information will be saved as shown in step S66. If additional probes/electrodes are to be stimulated, the method may then revert to S54 as shown. The information with be used to generate a map of the subject&#39;s brain as shown in step S68. As shown in step S70 the map may be printed or displayed. The map may be useful in assisting determining what parts of a subject&#39;s brain perform specific and or significant functions. 
         [0083]    The processes and devices in the above description and drawings illustrate examples of some methods and devices of many that could be used and produced to achieve the objects, features, and advantages of embodiments described herein. Thus, they are not to be seen as limited by the foregoing description of the embodiments, but only limited by the appended claims. Any claim or feature may be combined with any other claim or feature within the scope of the invention. The many features and advantages of the invention are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention.