Patent Publication Number: US-2023149068-A1

Title: Method and apparatus for treating peripheral olfactory dysfunction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Prov. App. 63/264,074 filed Nov. 15, 2021, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The olfactory system is generally comprised of olfactory neurons embedded within an epithelium layer that covers part of the nasal cavity including over the cribriform plate. The location of the olfactory epithelium exposes it to environmental odors that trigger the primary olfactory neurons to send signals to the central nervous system via the olfactory bulb. While the location of the olfactory epithelium provides for easy access to airflow and odors it also exposes it to environmental toxins, infectious diseases or trauma that could results in its dysfunction. To solve for this vulnerability, the olfactory system has developed a unique ability for regeneration. Experimental studies have shown the extraordinary capacity of the olfactory epithelium to regenerate following injury (Schwob, 2002). 
     Olfaction dysfunction can present in different ways: such as decreased sensitivity, distorted quality of an odorant stimulation, and perceived order when no odor is present (phantosmia). Olfactory dysfunction can be a result of either dysfunction of the olfactory neurons (peripheral dysfunction) or can be triggered through the central nervous system without the involvement of the primary neurons (central dysfunction). 
     No definitive treatment for olfactory dysfunction exists today. Strategies such as scent therapy, saline irrigation, local cocaine administration, antidepressant and anti-inflammatory medication are commonly used with limited benefits. New strategies to accelerate olfactory neural regeneration are currently the subject of research in treating peripheral olfactory dysfunction. In the only surgical treatment for olfactory dysfunction Leopold et al. performed excision of the olfactory epithelium through an intra nasal procedure (Leopold et al., 1991). 
     The results of the work performed by (Leopold et al., 1991) has shown that after removing the olfactory epithelium in patients with peripheral olfactory dysfunction, such as phantosmia, a new functional epithelium regenerates, resolving the dysfunction. However, the surgical procedure to remove the olfactory mucosa is technically difficult to perform and carries the risk of cerebrospinal fluid (CSF) leak due to potential damage to cribriform plate, compromised efficacy due to incomplete removal of the epithelium and general surgical complications (Morrissey et al., 2016). 
     Nerve ablation (destruction) is a minimally invasive procedure commonly used to treat pain (Filippiadis et al., 2019). In this procedure, all or part of a nerve is ablated to interrupt the pain signal resulting in pain relief (Gage et al., 2009). Different methods of nerve ablation exist, for example it can be done by heat, such as radiofrequency or microwave ablation, cold such as cryoablation, chemicals (such as ethanol, phenol, and zinc sulfate), and electromagnetic field such as pulsed radiofrequency. Cryo nerve ablation is reversible, meaning the ablated nerves regenerate over time and regain their original function (Whittaker, 1974). 
     More specifically, John Hunter in 1777 observed that upon exposing tissue to freezing temperature, tissue necrosis occurs followed by healing and regeneration. Local tissue freezing, or cryosurgery has been commercially available since the 1960s and the advances of the technology has resulted in its widespread use especially in causing reversible destruction of nerves or cryoneurolysis in treatment of pain. Cryoneurolysis has been used to treat head and neck disorders such as vasomotor rhinitis (Hwang et al., 2017), nasal polyposis (Rezaeian, 2018) and mucosal healing post functional endoscopic sinus surgery (Albu et al., 2016), demonstrating its safety and efficacy. 
     The present invention intends to teach methods and minimally invasive apparatus to treat peripheral olfactory dysfunction by intentionally creating localized neurolysis of the olfactory neurons, prompting neuroepithelium regeneration and therefore treating the dysfunction. At first glance, this method might be considered counter intuitive as recent efforts in treating olfactory dysfunction have focused on assisting regenerative processes, making destruction and ablation of olfactory neurons counter to such effort. However, the methods and apparatus disclosed intends to cause regeneration of neurons by first reversibly destroying malfunctioning neurons without causing injury to anatomic structures therefore setting the stage for regeneration of functional neurons. Methods and apparatus disclosed are minimally invasive procedures therefore the risk of intensive surgery under general anesthesia is eliminated making this treatment modality safer than the alternative surgical procedure. 
     SUMMARY OF THE INVENTION 
     The olfactory mucosa (OM) includes a specialized olfactory epithelium and the lamina propria, in which Bowman glands, bundles of olfactory neurons and ensheathing glia are present. Peripheral olfactory dysfunction such as phantosmia is thought to be due to the dysfunction of the olfactory neurons, leading to an inability to form a complete picture of the odor and hence the erroneous interpretation of the odor centrally. 
     The devices and methods are disclosed for treating peripheral olfactory dysfunction by ablating the olfactory neurons to cause reversible destruction prompting regeneration of the olfactory neurons and olfactory epithelium, “resetting” the olfactory function. 
     The size of the olfactory mucosa can vary among individuals, however all primary olfactory neurons leaving the epithelium go through the cribriform plate, a sieve-like bony structure, to reach the olfactory bulb, making it a specifically suitable target for ablation. In one embodiment of the present invention the OM over the cribriform plate is the ablation target in order to ablate all primary neurons. 
     The devices disclosed used to ablate olfactory neurons may be comprised of an elongated shaft having a proximal end and a distal end, where the distal end of the device can navigate through the nasal cavity under endoscopic visualization. The proximal end of the device is used to control the navigation and the ablation procedure. In one embodiment of the above configuration the distal and proximal end of the device are in fluid communication (e.g., liquid and/or gas). 
     In another embodiment of the device, the distal end of the device is designed to be atraumatic to the nasal mucosa as it navigates through the nasal cavity or when it reaches its target tissue. 
     In one embodiment, the distal end can have a collapsed and an expanded configuration so that during navigation to the target site the distal end is in the collapsed state and is expanded once it reaches the target tissue to cover the surface area of the OM or conform to its form without compromising its ability to navigate through tight spaces. Upon completion of the ablation procedure the distal end is collapsed before the device is removed from the nasal cavity. 
     In another embodiment, the ablation device is a cryogenic device. In this configuration the distal end is placed directly adjacent to the OM. The temperature of the distal end is then reduced to temperatures in the range of, e.g., −20° C. to −100° C., freezing the adjacent tissue causing neurolysis. The tissue may be kept frozen for a period of time before the temperature of the distal end is returned to environmental temperature, thawing the tissue at the same time. The freeze and thaw cycle can be carried out multiple times to produce the desired effect. The preferred period of time for keeping tissue frozen is from about 10 seconds to about 120 seconds or more preferably between 10 seconds to about 60 seconds. 
     In another embodiment, the device is a cryogenic device that uses the Joules-Thomson (JT) effect to produce the ultra-low temperature. In such a configuration the high-pressure refrigerant gas, liquid, or a mixture thereof is injected through an internal lumen to the distal end of the device such that when the gas leaves the internal lumen at the proximity of the distal end, it expands into an outer lumen causing a drop in temperature. The exhaust gas is then released back to the environment. In another embodiment, the refrigerant gas used to produce the JT effect can also be used to expand the distal end of the device when the distal end is designed to be expandable. 
     In another embodiment, the refrigerant gas or liquid is directly sprayed on the target tissue. In this embodiment the proximal end of the device, the shaft and the distal end are in fluid communication (e.g., liquid and/or gas). The proximal end of the device is connected to a source of pressurized refrigerant gas, liquid, or a mixture thereof. The device shaft and distal end are designed so that they can navigate through the nasal cavity to reach the target tissue. Once in place, the refrigerant gas or liquid is sprayed on the tissue through the distal end. The distal end is designed to optimize spray pattern and size. 
     In another embodiment another principle other than the JT system is used to cool the distal end of the device in order to freeze tissue. 
     In another embodiment the cryogenic device uses nitrous oxide as the refrigerant gas. In another embodiment the cryogenic device uses carbon dioxide as the refrigerant gas. In another embodiment the cryogenic device uses any chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon or any mixtures thereof as refrigerant. In yet another embodiment the cryogenic device uses liquid nitrogen as refrigerant. 
     In one embodiment, the cryogenic device is designed so that the freezing depth of the device matches the thickness of the OM to prevent damage to the underlying bone. The preferred freezing depth is between 100 μm to 5 mm or more preferably between 100 μm to 3 mm. 
     In another embodiment the device used to ablate olfactory neurons uses radiofrequency energy for ablation. In yet another embodiment the device used to ablate olfactory neurons uses pulsed radiofrequency energy for ablation. In yet another embodiment the device used to ablate olfactory neurons uses microwave energy for ablation. In yet another embodiment the device used to ablate olfactory neurons uses laser for ablation. 
     In another embodiment one point or multiple points of the shaft is malleable so that the angle between the distal end and the shaft can be controlled to allow for the exact positioning of the distal end or to place the distal end in parallel to the target tissue. Such an angle can be controlled in-situ during operation, or the angle can be adjusted according to the patient&#39;s anatomy prior to the start of the operation. In another embodiment, the distal end of the device is malleable. 
     In another embodiment the ablation device operates under endoscopic visualization. In another embodiment the device comprises a visualization component eliminating the need for using another visualization device such as endoscope. 
     In one method of use, a patient may be selected for the operation to be treated for peripheral olfactory dysfunction upon consultation with physician. The device is then navigated through the nasal cavity of the patient under endoscopic visualization. Once the distal end of the device is placed in proximity of the OM, especially OM over the cribriform plate, an ablation mechanism is triggered resulting in ablation of tissue and substantially all olfactory neurons. Once the ablation procedure is completed the device is navigated out of the nasal cavity. The patient will lose sense of smell for a period of time. Once the ablated neurons regenerate sense of smell may return without the dysfunction. 
     One variation of a method for treating peripheral olfactory dysfunction in a patient may generally comprise introducing a treatment device into a nasal cavity of the patient, the treatment device having a proximal end, a distal end, an elongated shaft therebetween, and a treatment end effector disposed on or near the distal end. The distal end of the treatment device may be advanced into proximity of a cribriform plate within the nasal cavity and at least one olfactory neuron may be ablated through the cribriform plate via the treatment end effector to reduce at least one symptom of olfactory dysfunction. 
     Another variation of a method for treating peripheral olfactory dysfunction in patient may generally comprise introducing a treatment device into a nasal cavity of the patient, the treatment device having a proximal end, a distal end, an elongated shaft therebetween, and a spray component disposed on or near the distal end. The distal end of the treatment device may be advanced into proximity of at least one olfactory neuron associated with olfactory mucosa and at least one chemical may be sprayed to ablate the at least one olfactory neuron to reduce at least one symptom of olfactory dysfunction. 
     Another variation of a method for treating peripheral olfactory dysfunction in patient may generally comprise introducing a treatment device into a nasal cavity of the patient, the treatment device having a proximal end, a distal end, an elongated shaft therebetween, and an injection instrument disposed on or near the distal end. The distal end of the treatment device may be advanced into proximity of at least one olfactory neuron associated with olfactory mucosa and at least one chemical may be injected to ablate the at least one olfactory neuron to reduce at least one symptom of olfactory dysfunction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  illustrates the position of the olfactory apparatus within nasal cavity and a schematic of an example of the device. 
         FIG.  1 B  illustrates the position of the olfactory apparatus within nasal cavity and a schematic of the device where the distal end is positioned at an angle in relation to the device shaft. 
         FIG.  1 C  is a schematic of cross section view of the distal end of an example of the device. 
         FIG.  1 D  illustrates an example of a navigation system being used to accurately guide the distal end of the device within the nasal cavity. 
         FIG.  2    illustrates the position of the olfactory apparatus within a nasal cavity and a schematic of an example of the device, where  FIG.  2 A  shows a configuration of the device where the distal end is in collapsed state and  FIG.  2 B  shows the distal end of the device expanded. 
         FIG.  3    is a schematic of the device from front and side views where only a portion of the distal end is an ablation effector. 
         FIG.  4    illustrates the position of the olfactory apparatus within the nasal cavity and a schematic of an example of the device, where the distal end includes a spraying instrument. 
         FIG.  5    illustrates the method of treating an olfactory dysfunction in a patient by ablating olfactory nerves using the devices disclosed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1 A  shows patient anatomy, including nasal cavity  100 , olfactory bulb  101 , cribriform plate  102 , primary olfactory neurons  103 , and olfactory mucous membrane  104 . Device  105  may be comprised of proximal end  105 A connected to the distal end  105 B by elongated shaft  105 C. The distal end  105 B is maneuvered through the nasal cavity  100  to reach the proximity of olfactory mucosa  104  covering the cribriform plate  102 . The distal end  105 B includes a treatment end effector which is used to treat the olfactory dysfunction, for example by ablating substantially all primary olfactory neurons of the olfactory mucosa  104 . 
     In one embodiment the distal end  105 B is designed to be atraumatic to the structures it encounters. 
     In another embodiment the device  105  has a cryogenic component. In other embodiments the treatment end effector of device  105  uses radiofrequency, pulsed radiofrequency, laser, microwave, or other methods to ablate olfactory neurons  103 . 
     In another embodiment the device  105  has a cryogenic component that uses compressed gas, liquid, or a mixture thereof as refrigerant. In this embodiment the expansion of the refrigerant gas inside device  105  causes the cooling of the distal end  105 B. 
     In another embodiment the dimensions of device  105  are such that it can operate within the confines of nasal cavity  100  in conjunction with a visualization device such as nasal endoscope. For example, the device  105  may have a shaft with a length ranging from, e.g., 4 cm to 12 cm. The diameter of the distal end of the device is such to provide easy navigation to OM and can range in diameter from, e.g., 0.5 mm to 5 mm, and from 2 mm to 30 mm in length. 
       FIG.  1 B  shows patient anatomy, including nasal cavity  100 , olfactory bulb  101 , cribriform plate  102 , primary olfactory neurons  103 , and olfactory mucous membrane  104 . Device  105  may be comprising proximal end  105 A connected to the distal end  105 B′ by elongated shaft  105 C. The distal end  105 B′ sits at an angle relative to shaft  105 C making it easier for the device to contact the target tissue. The shaft  105 C may accordingly include a proximal portion extending longitudinally and a distal portion which is angled relative to the proximal portion about an inflection point such as a curved or bent portion or pivoted portion where the angle may range from, e.g., 5 to 30 degrees. 
     In another embodiment, all or part of shaft  105 C is malleable allowing for adjusting the angle between distal end  105 B and shaft  105 C. In another embodiment, distal end  105 B′ is malleable. 
       FIG.  1 C  shows the cross section of distal end  105 B of another embodiment where distal end  105 B comprises ablation effector  105 B 1 , illumination component  105 B 2  (e.g., optical fibers coupled to a light source or conductive wires coupling a light emitter such as an LED located in the distal end  105 B to a power supply) and imaging component  105 B 3  (e.g., optical fibers for transmitting images or conductive wires coupled to an imager such as a CCD or CMOS imager, etc. located in the distal end  105 B). This embodiment of device  105  makes it possible for device  105  to complete the ablation procedure without the need of an additional visualization instrument. In yet another embodiment device  105  includes a component to facilitate its navigation using various visualization modalities for example facilitating its use with commercially available navigation systems such as the StealthStation™ ENT (Medtronic, Inc.). 
     An example is illustrated in  FIG.  1 D  showing how a commercially available navigation system may be used to provide guidance in accurately positioning the distal end  105 B of the device against a preselected tissue region or nerve fiber for treatment. The example shown illustrates how a camera or imaging system  110  may be positioned into proximity of the patient&#39;s head and nasal cavity  100 . The imaging system  110  may be in communication with a controller  111  which may be under the control of the practitioner. A display and/or user interface  112  may also be available for displaying the images of the nasal cavity  110  and its anatomical features obtained by the imaging system  110 . The images may be displayed  112  as the device and distal end  105 B are navigated within the nasal cavity  100  allowing for the practitioner to guide the distal end  105 B into proximity and/or against the preselected tissue region or nerve fiber for treatment. 
       FIG.  2 A  depicts patient anatomy, including the nasal cavity  200 , olfactory bulb  201 , cribriform plate  202 , primary olfactory neurons  203 , and olfactory mucous membrane  204 . Device  205  may be comprised of proximal end  205 A connected to the distal end  205 B by elongated shaft  205 C. In this embodiment the distal end  205 B is in a collapsed format while navigating though the nasal cavity  200 .  FIG.  2 B  depicts nasal cavity  200 , olfactory bulb  201 , cribriform plate  202 , primary olfactory neurons  203 , and olfactory mucous membrane  204 . Once device  205  reaches the proximity of the mucous membrane  204  covering the cribriform plate  202 , collapsed distal end  205 B is expanded to distal end  205 B′. Expanded distal end  205 B′ meets the mucosal membrane  204  and ablates the target tissue. The expanded format of distal end  205 B′ allows it to cover and conform to the shape of the tissue to be ablated. Once the ablation procedure completes expanded distal end  205 B′ is collapsed to distal end  205 B to facilitate navigation of device  205  out of nasal cavity  200 . 
     In another embodiment the device  205  has cryogenic component that uses compressed gas or liquid as a refrigerant. In this embodiment the expansion of the refrigerant gas or liquid inside device  205  causes the cooling of the distal end  205 B. In this embodiment the refrigerant gas used to cool cryogenic device  205  may be used to expand the distal end from configuration  205 B to configuration  205 B′. Once the flow of the refrigerant gas or liquid into device  205  is stopped, device  205  warms to environmental temperatures and distal end  205 B′ deflates to distal end  205 B and device  205  is navigated out of nasal cavity  200 . 
     In another embodiment device  205  may use two or more different mechanisms to expand distal end  205 B and to ablate olfactory neurons  203 . As an example embodiment, device  205  may use saline injection to expand distal end  205 B to distal end  205 B′ and radiofrequency energy to ablate olfactory neurons  203 . 
     In another embodiment the expandable component of distal end  205 B is a balloon. In yet another embodiment the expandable component of distal end  205 B is an expandable structure made of thermally conductive materials such as metals or shape memory alloys. 
       FIG.  3    depicts device  300  comprising proximal end  301 , distal end  302  and elongated shaft  304 . In this embodiment only a portion of distal end  302 , section  302 A, is capable of effecting tissue ablation. As olfactory mucosa is located in tight areas of nasal cavity, having only section  302 A to effect ablation ensures other nearby structures are not affected by the procedure. The section  302 A is illustrated in the embodiment shown as being located along a single side of the shaft  304  near or at the distal end  302 . The section  302 A may alternatively be formed along a section of the circumference or entirely around the circumference of the shaft  304 . In another alternative, the section  302 A may instead be formed as multiple sections separated from one another rather than a single continuous portion. Other configurations which may provide partial ablation along selected tissue regions are also contemplated. 
     In an example of the embodiment above, device  300  is a cryogenic device and section  302 A is made of expandable material capable of expanding using the cryogenic refrigerant gas or liquid, in this example section  302 A comes in contact with target tissue causing localized ablation. 
       FIG.  4    depicts patient anatomy, including nasal cavity  400 , olfactory bulb  401 , cribriform plate  402 , primary olfactory neurons  403 , and olfactory mucous membrane  404 . Device  405  is comprised of proximal end  405 A connected to the distal end  405 B by elongated shaft  405 C. In this embodiment distal end  405 B has a spray component capable of spraying liquid or gas ablation material directly on the target tissue. In another configuration of this embodiment device  400  is a cryogenic device and distal end  405 B sprays cryogenic material directly on target tissue to effect ablation. In another example the device  400  sprays chemicals capable of inducing tissue ablation directly on the target tissue. Examples of such chemicals include ethanol, phenol, and zinc sulphate, etc. 
     In yet another example device  400  is used to spray therapeutic agents directly unto the target tissue. In one example the therapeutic agent is capable of selectively ablating primary olfactory neurons  405 , sparing other components of the olfactory mucosa  404 . Example of such therapeutic agents include capsaicin and its analogues, including but not limited to Zucapsaicin, ALGRX-4975, Nonivamide, Resiniferatoxin, or combinations thereof, or sympatholytic agents such as alpha- and beta-adrenergic receptor antagonists (alpha blockers and beta blockers) as well as centrally acting agents such as clonidine, guanabenz, methyldopa, minoxidil, and reserpine. 
     In another embodiment distal end  405 B is an injection needle capable of injecting liquid chemicals or therapeutic agents directly into olfactory mucous membrane  404 . Such liquid chemicals or therapeutic agents are capable of effecting ablation once injected. Examples of chemicals used for ablation include ethanol, phenol, zinc sulphate and examples of therapeutic agents include capsaicin and its analogues. 
       FIG.  5    shows a flowchart that incorporates olfactory ablation in the management of a patient with peripheral olfactory dysfunction. Initially treating physician consults with the patient to ensure the dysfunction is of peripheral origin  500 . This can be done for example by temporary blocking of the primary olfactory neurons with numbing medication such as lidocaine or cocaine. If the numbing completely resolves the dysfunction, for example in case of parosmia and phantosmia, resolve the presence of the phantom smell, it is determined that the dysfunction is of peripheral origin. Other techniques or procedures can be used for different dysfunctions to ascertain the peripheral nature of the issue. 
     After the patient is deemed a candidate for the procedure  500 , olfactory ablation may be performed by first inserting an endoscope into the nasal cavity  501 . The endoscope contains an optical or visual system that allows the physician to see into the nasal cavity. With this optical or visual system, the physician identifies the cribriform plate  502 . Alternatively, if the device includes a visualization component, the device itself may be introduced into the nasal cavity directly without a separate endoscope. In yet another alternative, the device may be introduced simultaneously with a separate endoscope or in yet another alternative, the device may be introduced without an endoscope or with an external imaging device. 
     The device of the current invention is then inserted through the nasal cavity and navigated to the proximity of the cribriform plate and the olfactory mucous membrane  503 . The device may include an endoscope for visualization and navigation eliminating the need for the use of an additional endoscope. In one embodiment, the device is navigated to the target with assistance from navigation systems. 
     The device is then used to ablate the primary olfactory neurons using various ablative technologies examples of which include cryogenic ablation, radiofrequency ablation, laser ablation, chemical ablation, etc.  504 . The ablation procedure will cause olfactory neurolysis and effectively destroy some or substantially all of the targeted neurons. Multiple ablations can be optionally performed to increase the efficacy of the procedure. Once the ablation procedure is complete, the device is navigated proximally out of the patient&#39;s nasal cavity followed by removing the endoscope if one is used  505 . 
     With olfactory ablation, the patient may experience a cessation in his or her existing sense of smell including the olfactory dysfunction such as phantosmia. New olfactory neurons regenerate over the course of several months, and with that regeneration may come a return of the patient&#39;s sense of smell Additional ablation procedures might be necessary to completely resolve the issue. 
     The ablation procedure described in the present invention can be followed by additional treatment modalities, for example local administration of stem cells, growth factors, or anti-inflammatory agents to accelerate or modulate the regeneration of neurons. 
     The applications of the devices and methods discussed above are not limited to the treatments described but may include any number of further treatment applications. Moreover, such devices and methods may be applied to other treatment sites within the body. Modification of the above-described assemblies and methods for carrying out the invention, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.