Cochlear Promontory Stimulation for Treatment of Tinnitus

Tinnitus is the perception of sound when no external noise is present. The Center for Disease Control (CDC) estimates over 50 million - nearly 15% of the general public -experience some form of tinnitus. Roughly 20 million people struggle with burdensome chronic tinnitus, with 2 million experiencing extreme and debilitating symptoms. The 2014 Clinical Practice Guideline on tinnitus from the American Academy of Otolaryngology - Head and Neck Surgery summarized the existing state of tinnitus management by stating "A cure for primary tinnitus does not yet exist, and despite claims to the contrary, no method has been proven to provide long-term suppression of tinnitus." The purpose of this study is to look at the safety and efficacy of cochlear promontory stimulation in the short term relief of tinnitus. The secondary goal of the study is to determine the optimum region(s) of the cochlear promontory in planning for an implantable electrical device for long term tinnitus suppression.

Candidate subjects will undergo a temporal bone Computed Tomography (CT) scan, contrast enhanced head Magnetic Resonance Imaging (MRI), audiogram with immittance testing, pitch and level matching of tinnitus, Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem Response (ABR) testing prior to promontory stimulation. Head MRI, DPOAE, audiogram and immittance testing are considered clinically routine for assessment of asymmetric tinnitus. Temporal bone CT, ABR, tinnitus pitch, level matching, masking levels and residual inhibition testing are not standard clinical assessments for asymmetric tinnitus. In addition, subjects will complete the Tinnitus Handicap Inventory (THI), Tinnitus Functional Index (TFI) and Visual Analog Scale (VAS) questionnaires three separate times within the week prior to promontory stimulation testing. Additional testing for comorbid anxiety and depressive conditions will be a screening Generalized Anxiety Disorder (GAD7), Patient Health Questionnaire (PHQ8), and short Health Anxiety Inventory (HAI-S). The NEO Personality Inventory (NEO PI) will be administered to provide baseline information. The initial session of promontory stimulation will define optimal stimulation parameters (i.e., location, current level, pulse-width, phase polarity), where maximal tinnitus suppression occurs with minimal or no auditory percept. After these parameters are established, the patient will complete the THI, TFI, and VAS immediately prior to stimulation, during stimulation, and following completion of stimulation at 10-minutes, 1-hour, 24-hours, 48-hours, and 1-week following completion of stimulation. In addition, pitch and level matching of tinnitus will be completed immediately upon completion of each promontory stimulation session. Each patient will undergo three successive treatments separated by 1-week. Prior to each treatment, the patient will receive an audiogram and DPOAE testing to document interval safety. At the conclusion of the study, subjects will be asked about their willingness to undergo surgical implantation of a device capable of long-term scheduled or on-demand electrical stimulation for tinnitus suppression

The electrode will be placed in the middle ear. The patient and investigator will be blinded to the "on-off" status of the device. The patient will report if they have improvement of their tinnitus while both the patient and investigator are blinded to the "on-off" status.

There will only be one arm. The patient and investigator will initially be blinded to the "on-off" status of the electrode. The patient will thus serve as an internal control for testing. Once device integrity and possible benefit is confirmed, the patients will undergo non-tactile electrical stimulation to the bone of the inner ear (cochlear promontory) for short term relief of tinnitus via Cochlear promontory stimulation.

Promontory stimulation is an established otologic procedure that was initially developed as a diagnostic tool to assess patient candidacy for cochlear implantation. Promontory stimulation is most commonly performed in the outpatient setting on an awake patient by placing a single insulated probe through a topically anesthetized tympanic membrane and applying monopolar current for several seconds to minutes. The initial session of promontory stimulation will define optimal stimulation parameters (i.e., location, current level, pulse-width, phase polarity), where maximal tinnitus suppression occurs with minimal or no auditory percept. Additional stimulation testing visits will confirm these findings.

The Tinnitus Handicap Inventory (THI) has 25 questions with possible answers of Yes (4 points), Sometimes (2 points), and No (0 points). Scores categories are (1-16: Slight or no handicap - Grade 1), (18-36: Mild handicap - Grade 2), (38-56: Moderate handicap - Grade 3), (58-76: Severe handicap - Grade 4), (78-100: Catastrophic handicap - Grade 5).

The Tinnitus Functional Index (TFI) contains eight subscales (domains), of which seven contain 3 items and one contains 4. The possible responses for each item range from 0 (did not interfere) to 10 (completely interfered). The total score is transformed to a scale ranging from 0 (no interference) to 100 (completely interfered with activities).

The Visual Analog Scale (VAS) for Numeric Pain Distress was used for this outcome. The VAS has pre-set marks between the extremes of 0 (no pain) and 10 (unbearable pain).

Inclusion Criteria: Normal to moderate sensorineural hearing loss (based on pure tone audiometry (PTA) of 500, 1000 and 2000 Hz) and a word recognition score greater than 75% Asymmetric subjective tonal tinnitus Tinnitus that is disruptive Determined by THI score (in the severe range i.e. >56/100) TFI (in the severe range i.e. >52/100) VAS (> 5/10 ) Tinnitus that is intractable, and has not been ameliorated by conventional measures such as a hearing aid or masking Normal contrast-enhanced MRI of the head Exclusion Criteria: Tinnitus present less than 6 months or longer than 3 years History of brain or major ear surgery Prior major head trauma History of depression or anxiety Determined by screening using the GAD 7, PHQ8, and HAI-S GAD7 > 9 (indicates clinically significant anxiety) PHQ > 9 (indicates clinically significant depression) HAI-S > 25 (hypochondriacal level illness anxiety) Inability to assess, continue or complete trial Currently on antidepressants, anxiolytics or antipsychotics Active use of other tinnitus treatments MRI Incompatible Devices Known pregnancy

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