Near-infrared stimulation of the auditory nerve: A decade of progress toward an optical cochlear implant.

OBJECTIVES: We provide an appraisal of recent research on stimulation of the auditory system with light. In particular, we discuss direct infrared stimulation and ongoing controversies regarding the feasibility of this modality. We also discuss advancements and barriers to the development of an optical cochlear implant. METHODS: This is a review article that covers relevant animal studies. RESULTS: The auditory system has been stimulated with infrared light, and in a much more spatially selective manner than with electrical stimulation. However, there are experiments from other labs that have not been able to reproduce these results. This has resulted in an ongoing controversy regarding the feasibility of infrared stimulation, and the reasons for these experimental differences still require explanation. The neural response characteristics also appear to be much different than with electrical stimulation. The electrical stimulation paradigms used for modern cochlear implants do not apply well to optical stimulation and new coding strategies are under development. Stimulation with infrared light brings the risk of heat accumulation in the tissue at high pulse repetition rates, so optimal pulse shapes and combined optical/electrical stimulation are being investigated to mitigate this. Optogenetics is another promising technique, which makes neurons more sensitive to light stimulation by inserting light sensitive ion channels via viral vectors. Challenges of optogenetics include the expression of light sensitive channels in sufficient density in the target neurons, and the risk of damaging neurons by the expression of a foreign protein. CONCLUSION: Optical stimulation of the nervous system is a promising new field, and there has been progress toward the development of a cochlear implant that takes advantage of the benefits of optical stimulation. There are barriers, and controversies, but so far none that seem intractable. LEVEL OF EVIDENCE: NA (animal studies and basic research).

Review of Audiovestibular Symptoms Following Exposure to Acoustic and Electromagnetic Energy Outside Conventional Human Hearing.

Objective: We aim to examine the existing literature on, and identify knowledge gaps in, the study of adverse animal and human audiovestibular effects from exposure to acoustic or electromagnetic waves that are outside of conventional human hearing. Design/Setting/Participants: A review was performed, which included searches of relevant MeSH terms using PubMed, Embase, and Scopus. Primary outcomes included documented auditory and/or vestibular signs or symptoms in animals or humans exposed to infrasound, ultrasound, radiofrequency, and magnetic resonance imaging. The references of these articles were then reviewed in order to identify primary sources and literature not captured by electronic search databases. Results: Infrasound and ultrasound acoustic waves have been described in the literature to result in audiovestibular symptomology following exposure. Technology emitting infrasound such as wind turbines and rocket engines have produced isolated reports of vestibular symptoms, including dizziness and nausea and auditory complaints, such as tinnitus following exposure. Occupational exposure to both low frequency and high frequency ultrasound has resulted in reports of wide-ranging audiovestibular symptoms, with less robust evidence of symptomology following modern-day exposure via new technology such as remote controls, automated door openers, and wireless phone chargers. Radiofrequency exposure has been linked to both auditory and vestibular dysfunction in animal models, with additional historical evidence of human audiovestibular disturbance following unquantifiable exposure. While several theories, such as the cavitation theory, have been postulated as a cause for symptomology, there is extremely limited knowledge of the pathophysiology behind the adverse effects that particular exposure frequencies, intensities, and durations have on animals and humans. This has created a knowledge gap in which much of our understanding is derived from retrospective examination of patients who develop symptoms after postulated exposures. Conclusion and Relevance: Evidence for adverse human audiovestibular symptomology following exposure to acoustic waves and electromagnetic energy outside the spectrum of human hearing is largely rooted in case series or small cohort studies. Further research on the pathogenesis of audiovestibular dysfunction following acoustic exposure to these frequencies is critical to understand reported symptoms.

A time-sensitive rubric for assessing mastoidectomy proficiency.

OBJECTIVE: To develop a time-sensitive, standardized rubric for cadaveric temporal bone dissection for otolaryngology resident education. METHODS: This is a five-year prospective cohort study that evaluated otolaryngology resident performance during sequential cadaveric temporal bone dissection courses at a single otolaryngology residency training program. A canal-wall-up mastoidectomy with a facial recess approach was performed adhering to a 30-minute time limit and graded according to a standardized rubric. Main outcome measures included: (1) correct structure identification and (2) injuries sustained to structures as compared by resident post-graduate year (PGY) level. RESULTS: Thirteen residents were evaluated from October 2012 to March 2017. This included 57 individual graded exercises performed over ten dissection courses. The average score for PGY-2 residents was lowest (68.9), and PGY-5 residents achieved the highest average score (87.7). Junior residents correctly identified fewer structures (77.5%) when compared to senior residents (91.3%), p < 0.0001. Correct performance of a facial recess approach was achieved by 100% of senior residents, but only 59.3% of junior residents (p = 0.0003). The percentage of major injuries, which included the facial nerve, tegmen, labyrinth, and ossicular chain, decreased each PGY-level from a maximum of 17% by PGY-2 residents to a minimum of 5% by PGY-5 residents. CONCLUSION: Senior residents correctly identify more structures and are able to complete a facial recess approach with higher fidelity when subjected to a time-sensitive graded mastoidectomy rubric.

Bone Pate Obliteration in Canal Wall Down Mastoidectomy: Modifications of an Established Technique.

OBJECTIVE: To describe outcomes with obliteration of the mastoid and medial attic following canal wall down mastoidectomy for cholesteatoma. Our technique uses bone pate in the mastoid and cartilage in the epitympanum and supratubal recess. STUDY DESIGN: Retrospective observational study. SETTING: Tertiary medical center. PATIENTS: Ten years of sequential canal wall down mastoidectomies with obliteration from one neurotologist were reviewed. This included primary and revision cases in adults and children. MAIN OUTCOME MEASURES: Complications, location and extent of cholesteatoma, the presence of a dry ear after surgery, cholesteatoma recidivism, revision procedures, and postoperative hearing. RESULTS: Seventy-eight patients (79 ears) met inclusion criteria. There were few major complications. There was active follow-up of a year or more in 61. For these, the mean follow-up was 3.1 years, and approximately 90% had a dry cavity for the remainder of their follow-up. About half required minimal (if any) maintenance. There were five cases with residual disease, and no cases with recurrent disease. There were five cases that were considered failures, with three taking several years to manifest. There were no cases where cholesteatoma was buried in bone pate. A sizeable minority continued to have active tubotympanic disease despite successful treatment of the attic and mastoid. CONCLUSIONS: This seems to be a safe and reliable means to eradicate cholesteatoma and create a dry, low-maintenance cavity. It is not a cure for tubotympanic disease, and a small minority of initially stable cavities may fail several years following surgery. LEVEL OF EVIDENCE: 4.

Long-Term Sensorineural Hearing Loss in Patients With Blast-Induced Tympanic Membrane Perforations.

OBJECTIVE: To describe characteristics of sensorineural hearing loss (SNHL) in patients with blast-induced tympanic membrane (TM) perforations that required surgery. DESIGN: A retrospective review of hearing outcomes in those who had tympanoplasty for combat blast-induced TM perforations. These were sequential cases from one military otolaryngologist from 2007 to 2012. A total of 87 patients were reviewed, and of those, 49 who had appropriate preinjury, preoperative, and long-term audiograms were included. Those with pre-existing hearing loss were excluded. Preinjury audiograms were used to assess how sensorineural thresholds changed in the ruptured ears, and in the contralateral ear in those with unilateral perforations. RESULTS: The mean time from injury to the final postoperative audiogram was 522 days. In the ears with TM perforations, 70% had SNHLs of 10 dB or less (by bone conduction pure tone averages). Meanwhile, approximately 8% had threshold shifts >30 dB, averaging 50 dB. The strongest predictor of severe or profound hearing loss was ossicular discontinuity. Thresholds also correlated with bilateral injury and perforation size. In those with unilateral perforations, the SNHL was almost always larger on the side with the perforation. Those with SNHL often had a low-to-mid frequency threshold shift and, in general, audiograms that were flatter across frequencies than those of a typical population of military personnel with similar levels of overall hearing loss. CONCLUSIONS: There is a bimodal distribution of hearing loss in those who experience a blast exposure severe enough to perforate at least one TM. Most ears recover close to their preinjury thresholds, but a minority experience much larger sensorineural threshold shifts. Blast exposed ears also tend to have a flatter audiogram than most service members with similar levels of hearing loss.

Asymmetric Hearing Loss Prompting MRI Referral in a Military Population: Redefining Audiometric Criteria.

Objective To reevaluate asymmetric sensorineural hearing loss (ASNHL) criteria used to justify magnetic resonance imaging (MRI) in the evaluation of retrocochlear tumors in a military population. Study Design Retrospective case-control study. Setting Tertiary care military medical center. Subjects and Methods Patients with military service and a history of ASNHL prompting referral for MRI, with or without retrocochlear tumors, were compared between 2005 and 2016. Predictor variables included pure tone ASNHL, speech audiometry, and a history of noise exposure. Logistic regression models for hearing asymmetries were performed, and receiver operator curves were used to calculate sensitivity and specificity. Results Thirty-eight retrocochlear tumors were identified. The MRI diagnosis rate for patients with ASHNL was 0.85%. Patients with tumors were slightly older (42 vs 37 years, P = .021) and had less noise exposure (47% vs 85%, P < .001). A sensitivity of 0.83 and a specificity of 0.58 were calculated for asymmetries ≥10 dB at 2000 Hz without adjusting for noise exposure. Instituting this imaging threshold would have reduced the number of MRI scans by half while missing 16% of tumors. Conclusion The tumor diagnosis rate among those undergoing MRI for ASNHL is low in the military population, likely because service-related noise exposure commonly causes ASNHL. Optimal MRI referral criteria should conserve resources while balancing the risks of over- and underdiagnosis. For those with a history of military service, an asymmetry ≥10 dB at 2000 Hz among patients meeting current ANSHL referral criteria is most predictive of a retrocochlear tumor.

The effects of repeated low-level blast exposure on hearing in marines.

BACKGROUND: The study evaluates a group of Military Service Members specialized in blast explosive training called "Breachers" who are routinely exposed to multiple low-level blasts while teaching breaching at the U.S. Marine Corps in Quantico Virginia. The objective of this study was to determine if there are any acute or long-term auditory changes due to repeated low-level blast exposures used in training. The performance of the instructor group "Breachers" was compared to a control group, "Engineers". METHODS: A total of 11 Breachers and four engineers were evaluated in the study. The participants received comprehensive auditory tests, including pure-tone testing, speech-in-noise (SIN) measures, and central auditory behavioral and objective tests using early and late (P300) auditory evoked potentials over a period of 17 months. They also received shorter assessments immediately following the blast-exposure onsite at Quantico. RESULTS: No acute or longitudinal effects were identified. However, there were some interesting baseline effects found in both groups. Contrary to the expected, the onsite hearing thresholds and distortion product otoacoustic emissions were slightly better at a few frequencies immediately after blast-exposure than measurements obtained with the same equipment weeks to months after each blast-exposure. CONCLUSIONS: To date, the current study is the most comprehensive study that evaluates the long-term effects of blast-exposure on hearing. Despite extensive testing to assess changes, the findings of this study suggest that the levels of current exposures used in this military training environment do not seem to have an obvious deleterious effect on hearing.

Dizziness, malpractice, and the otolaryngologist.

PURPOSE: To assess malpractice claims related to the management of dizziness in otolaryngology in order to improve care and minimize the risk of litigation. MATERIALS AND METHODS: This is a retrospective review of the LexisNexis "Jury Verdicts and Settlements" database. All lawsuits and out of court adjudications related to the management of dizziness by otolaryngologists were collected. Data including patient demographics, plaintiff allegation, procedure performed, and indemnities were analyzed. RESULTS: Of 21 cases meeting inclusion criteria, 17 were decided by a trial jury and four were resolved out of court. Jury verdicts favored the plaintiff 53% of the time and a payout was made in 57% of cases overall. Average payments were higher for jury verdicts in favor of the plaintiff ($1.8 million) as compared to out of court settlements ($545,000). Two-thirds of cases involved surgery, most commonly stapes surgery. Legal allegations, including physical injury, negligence, and lack of informed consent failed to predict the legal outcome. CONCLUSIONS: Appropriate examination, testing, and referrals within a timely manner are crucial in the management of dizzy patients to avoid misdiagnoses. It is imperative that patients undergoing ear surgery are appropriately counseled that dizziness is a potential complication. The analysis of malpractice literature is complementary to clinical studies, with the potential to educate practitioners, improve patient care, and mitigate risk.

Adverse Events Following Vestibular Schwannoma Surgery: A Comparison of Surgical Approach.

OBJECTIVE: Compare complications of vestibular schwannoma (VS) resection by surgical approach. STUDY DESIGN: Retrospective cohort. SETTING: The 2008 to 2013 American College of Surgeons-National Surgical Quality Improvement Program. PATIENTS: Adult patients with VS resection by an otolaryngologist. INTERVENTIONS: VS resection via transtemporal (TT), retrosigmoid (RS), or middle cranial fossa (MCF) approaches. MAIN OUTCOME MEASURES: Hearing preservation approaches were compared with hearing sacrificing approaches. Demographics and intraoperative factors were analyzed to identify predictors of medical and surgical complications, return to the operating room, and death. The effect of trainee presence was evaluated with respect to complications, operative length, and hospital length of stay. RESULTS: One hundred eleven VS resections were identified. Patients were predominantly women (57%) and older than 50 years (69%). The TT approach accounted for 50% of the cases, while RS (36%) and MCF (14%) were less common. The risk of any postoperative complication was 17%. There were no patient deaths. There was no difference in the overall complication rate among surgical approaches, nor in the overall, surgical, or medical complication rates between hearing preservation and hearing sacrificing approaches. Trainee presence did not change operation length, hospital length of stay, or complication rates. CONCLUSIONS: Complication rates of VS resection are no different when comparing TT, RS, or MCF approaches. Trainee involvement did not significantly affect complications. This study is limited by the inability to evaluate procedure-specific variables (e.g., facial nerve weakness and hearing preservation rates), but offers a unique survey of global 30-day complication rates reported to a large, multi-institutional, publically available database.

Tympanoplasty Outcomes for Blast-Induced Perforations from Iraq and Afghanistan.

Objective To describe characteristics of blast-induced tympanic membrane perforations that do not spontaneously heal, evaluate the outcomes of tympanoplasty techniques, and understand the factors associated with surgical success. Setting Two tertiary military health care institutions. Study Design Case series with chart review. Subjects and Methods This study reviewed the practice of 1 military neurotologist and included all tympanoplasties for combat blast-induced perforations from 2007 to 2012, which comprised a total of 55 patients. Surgical outcomes and associated perioperative factors were examined to include size, location, bilateral involvement, timing of surgery, and surgical technique. Results Fifty-five patients (68 ears) met inclusion criteria. Thirty-six (53%) were total or near-total perforations, and 51% of patients had bilateral perforations. The overall success rate was 77%. It was 82% for lateral grafts and 70% for medial grafts, but the difference between these was not statistically significant. Age was a significant factor, with a success rate of 56% for ages 25 to 34 years, compared with 90% for 20 to 24 and >34 years. Patients who had bilateral sequential tympanoplasties also had lower success rates than those who had only unilateral surgery (62% vs 87%, P = .002). Ossicular disruptions were found in 5 ears, and cholesteatoma was discovered in 8. Surgical timing did not predict success, as the average time until repair was 153 days in successful cases and 151 days in failures. The mean conductive hearing improvement was 13.6 dB, and there were no major complications. Conclusion Tympanoplasty can be challenging in this population. Age and bilateral surgery were the only independent variables that showed significance.

Ceruminous adenocarcinoma: An analysis of the Surveillance Epidemiology and End Results (SEER) database.

OBJECTIVES: Ceruminous adenocarcinoma is a rare malignancy. However, due to the paucity of cases, this has been difficult to study. Using a population-based national database, patient demographics and survival trends were analyzed to further elucidate the management of this malignancy. METHODS: The SEER database was queried for patients diagnosed with ceruminous adenocarcinoma between 1973 and 2010. RESULTS: Twenty-two patients were identified in the database. The average age of diagnosis was between 60 and 64 years. All of the patients underwent surgical resection of the primary malignancy. Eight patients (36%) also had postoperative radiation. CONCLUSIONS: Ceruminous adenocarcinoma is uncommon but may not have as poor a prognosis as previously thought. Surgical resection alone appears to be a reasonable treatment option. Larger prospective studies are needed, but database analysis like this may provide clarity on the management of uncommon diseases.

The Vestibular Effects of Repeated Low-Level Blasts.

The objective of this study was to use a prospective cohort of United States Marine Corps (USMC) instructors to identify any acute or long-term vestibular dysfunction following repeated blast exposures during explosive breaching training. They were assessed in clinic and on location during training at the USMC Methods of Entry School, Quantico, VA. Subjects received comprehensive baseline vestibular assessments and these were repeated in order to identify longitudinal changes. They also received shorter assessments immediately following blast exposure in order to identify acute findings. The main outcome measures were the Neurobehavioral Symptom Inventory, vestibular Visual Analog Scale (VAS) of subjective vestibular function, videonystagmography (VNG), vestibular evoked myogenic potentials (VEMP), rotary chair (including the unilateral centrifugation test), computerized dynamic posturography, and computerized dynamic visual acuity. A total of 11 breachers and 4 engineers were followed for up to 17 months. No acute effects or longitudinal deteriorations were identified, but there were some interesting baseline group differences. Upbeat positional nystagmus was common, and correlated (p<0.005) with a history of mild traumatic brain injury (mTBI). Several instructors had abnormally short low-frequency phase leads on rotary chair testing. This study evaluated breaching instructors over a longer test period than any other study, and the results suggest that this population appears to be safe from a vestibular standpoint at the current exposure levels. Upbeat positional nystagmus correlated with a history of mTBI in this population, and this has not been described elsewhere. The data trends also suggest that this nystagmus could be an acute blast effect. However, the reasons for the abnormally short phase leads seen in rotary chair testing are unclear at this time. Further investigation seems warranted.

Updates in medical malpractice: an otology perspective.

PURPOSE OF REVIEW: Most surgeons at some point are involved in a medical malpractice case. There has been an increase in the number of manuscripts that analyse malpractice databases and insurance claims, as well as commentaries on the current medicolegal climate recently. This manuscript broadly reviews articles of interest to all providers and then focuses on malpractice in otology. RECENT FINDINGS: Medical malpractice articles (particularly topics related to otologic surgery published within the last 1-2 years) were searched. The growing body of literature can be divided into the themes of general negligence, mitigating injuries and the use of clinical practice guidelines in the courtroom as guidance for expert witnesses. SUMMARY: Recent findings suggest that the frequency of malpractice claims may be decreasing. Hearing loss and facial nerve injury are the most common injuries associated with otologic surgery. These injuries can be costly when negligence is found. Clinic practice guidelines are slowly being used as evidence in the courtroom and there are established guidelines that an expert witness must follow should a surgeon be called to give testimony.

Total Auricular Rehabilitation: Combined Cosmetic and Functional Lateral Temporal Bone Reconstruction.

OBJECTIVE: The aim of the study was to describe 3 cases of total auricular rehabilitation, including the novel use of iliac crest bone grafts to support bone-anchored auricular prostheses. STUDY DESIGN: This study is a retrospective case series from a single institution. RESULTS: Three cases with large lateral temporal bone and soft tissue defects were successfully treated with total auricular rehabilitation. Rehabilitation included the following: soft tissue coverage with an anterolateral thigh microvascular free flap, iliac crest-free bone graft with staged placement of a bone-anchored auricular prosthesis into the bone graft, and audiologic rehabilitation with a bone-anchored hearing aid (BAHA). All of the cases with grafts and flaps survived and were without significant donor site morbidity. Bone-anchored hearing aid abutment skin overgrowth was seen in 2 cases and was revised under local anesthesia. All of the patients had expected functional recovery on postoperative audiologic testing. Each patient continues to consistently wear his/her auricular prosthesis and BAHA during 3 years of follow-up. CONCLUSIONS: Total auricular rehabilitation is a complex task involving reconstruction of extensive soft tissue defects, bony defects, and the hearing apparatus. Acceptable cosmetic and functional outcomes and high patient satisfaction is possible in committed patients.

Late presentation of subcutaneous emphysema and pneumomediastinum following elective tonsillectomy.

Subcutaneous emphysema and pneumomediastinum are rare complications following elective tonsillectomy. Although the mechanism of injury is unclear, air is thought to enter through either the buccopharyngeal mucosa during surgery or via alveolar rupture during positive pressure ventilation. Patients typically present immediately after surgery or upon anesthesia emergence. We describe a case of delayed pneumomediastinum in a 30year-old female who presented 4days after surgery. With only one other case described, we review the literature and remind the reader to be cognizant of this late complication.

Lessons learned in otologic surgery: 30 years of malpractice cases in the United States.

OBJECTIVE: To analyze malpractice litigation trends to better understand the causes and outcomes of suits involving otologic surgeries to prevent future litigation and improve physician awareness. METHODS: Court records of legal trials from 1983 to 2012 were obtained from 2 major computerized databases-WESTLAW and LexisNexis. Data were compiled on the demographics of the defendant, plaintiff, use of otolaryngologists/otologists as expert witnesses, nature of injury, type of surgery, legal allegations, verdicts, and judgments. RESULTS: Fifty-eight unique cases met inclusion criteria and were selected for review. The most common surgeries that went to trial were mastoidectomy (48%), ossiculoplasty (21%), and tympanoplasty (16%). Eleven (19%) of the cases were resolved through a settlement before a verdict was reached. Verdicts in favor of the plaintiffs (31%) were awarded an average of $1,131,189. The most common alleged injuries were hearing loss (45%) and facial nerve injury (38%). Of the cases found in favor of the plaintiff, the most common reasons cited were improper performance of the surgery (50%), failure to properly diagnose and treat (33%), and inadequate informed consent and delay in diagnosis (22% each). Case outcomes involving pediatric patients were not significantly different than those of adults (p = 0.34); however, adults received higher financial awards on average ($1 million versus $232,000; p < 0.0003). CONCLUSION: Obtaining an appropriate diagnosis, thoroughly discussing all options and potential risks, presenting realistic expectations, and executing the surgery correctly are crucial to patient care. Understanding the reasons surgeons go to trial may assist in mitigating risk for potential lawsuits.

Tympanoplasty for blast-induced perforations: the Walter Reed experience.

OBJECTIVE: To review our tympanoplasty results for blast-induced tympanic membrane perforations and evaluate the association of various clinical factors with surgical success. STUDY DESIGN: Case series with chart review. SETTING: Two tertiary military healthcare institutions. METHODS: This is a retrospective review of all patients who had nonrevision tympanoplasty during a 1-year period for blast-induced perforations by the 2 neurotologists at Walter Reed Army Medical Center and National Naval Medical Center. Various perioperative clinical factors were analyzed for relations to successful perforation closure, the need for a second operation, and postoperative hearing. RESULTS: Thirty-four patients met inclusion criteria. All were male, and the average age was 24.0 years. Twenty-two (65%) were total or near-total perforations, of which 12 (35%) were repaired using lateral graft technique. The remainder had various medial graft procedures. Ossicular abnormalities were found in 6 (18%) patients. Cholesteatoma was discovered in 3 (9%) patients. Closure was complete in 82% of patients. The incomplete closures were with large perforations, those with foreign bodies (shrapnel), and in 1 with postoperative water exposure. There were no major complications, and the mean conductive hearing improvement was 11.3 dB. CONCLUSION: Blast-induced tympanic membrane perforations are common in our population of wounded warriors. These cases are challenging because most have total or near-total perforations, the ossicles can be out of place, the blast itself can implant epithelium in the middle ear, and foreign bodies can create a hostile middle ear environment. However, given attention to detail, we found that standard tympanoplasty techniques work well.

Evidence of central and peripheral vestibular pathology in blast-related traumatic brain injury.

OBJECTIVE: To prospectively assay the vestibular and oculomotor systems of blast-exposed service members with traumatic brain injury (TBI). STUDY DESIGN: Prospective, nonblinded, nonrandomized descriptive study. SETTING: Tertiary care facility (Department of Defense Medical Center). PATIENTS: Twenty-four service members recovering from blast-related TBI sustained in Iraq or Afghanistan. INTERVENTIONS: Focused history and physical, videonystagmography (VNG), rotational chair, cervical vestibular-evoked myogenic potentials, computerized dynamic posturography, and self-report measures. RESULTS: Vestibular testing confirms a greater incidence of vestibular and oculomotor dysfunction in symptomatic (vestibular-like dizziness) personnel with blast-related TBI relative to asymptomatic group members. VNG in the symptomatic group revealed abnormal nystagmus or oculomotor findings in 6 of 12 subjects tested. Similarly, rotational chair testing in this group revealed evidence of both peripheral (4/12) and central (2/12) vestibular pathology. By contrast, the asymptomatic group revealed less vestibular impairment with 1 of 10 rotational chair abnormalities. The asymptomatic group was further characterized by fewer aberrant nystagmus findings (4/12 abnormal VNGs). Computerized dynamic posturography testing revealed no significant differences between groups. Self-report measures demonstrated differences between groups. CONCLUSION: Vestibular function testing confirms a greater incidence of peripheral vestibular hypofunction in dizzy service members with blast-related TBI relative to those who are asymptomatic. Additionally, oculomotor abnormalities and/or nystagmus consistent with central involvement were present in 10 of the 24 study participants tested. The precise cause of these findings remains unknown.

Laser stimulation of single auditory nerve fibers.

OBJECTIVES/HYPOTHESIS: One limitation with cochlear implants is the difficulty stimulating spatially discrete spiral ganglion cell groups because of electrode interactions. Multipolar electrodes have improved on this some, but also at the cost of much higher device power consumption. Recently, it has been shown that spatially selective stimulation of the auditory nerve is possible with a mid-infrared laser aimed at the spiral ganglion via the round window. However, these neurons must be driven at adequate rates for optical radiation to be useful in cochlear implants. We herein use single-fiber recordings to characterize the responses of auditory neurons to optical radiation. STUDY DESIGN: In vivo study using normal-hearing adult gerbils. METHODS: Two diode lasers were used for stimulation of the auditory nerve. They operated between 1.844 µm and 1.873 µm, with pulse durations of 35 µs to 1,000 µs, and at repetition rates up to 1,000 pulses per second (pps). The laser outputs were coupled to a 200-µm-diameter optical fiber placed against the round window membrane and oriented toward the spiral ganglion. The auditory nerve was exposed through a craniotomy, and recordings were taken from single fibers during acoustic and laser stimulation. RESULTS: Action potentials occurred 2.5 ms to 4.0 ms after the laser pulse. The latency jitter was up to 3 ms. Maximum rates of discharge averaged 97 ± 52.5 action potentials per second. The neurons did not strictly respond to the laser at stimulation rates over 100 pps. CONCLUSIONS: Auditory neurons can be stimulated by a laser beam passing through the round window membrane and driven at rates sufficient for useful auditory information. Optical stimulation and electrical stimulation have different characteristics; which could be selectively exploited in future cochlear implants.

Transforming superior canal dehiscence to chronic subjective dizziness: from SCD to CSD.

Patients presenting with chronic dizziness and no identifiable vestibular impairments have been described as having "extravestibular" symptoms, or "psychogenic dizziness." In 2005, Staab and Ruckenstein described a syndrome they referred to as "chronic subjective dizziness" (CSD), which characterized this concept more clearly. According to Staab and Ruckenstein (2003), the primary physical symptoms of CSD are continual nonvertiginous dizziness or subjective imbalance that persists for 3 mo or longer. Patients suffering from CSD often describe their dizziness as a rocking or swaying when sitting or standing. This case study describes a 41-yr-old female who originally presented with complaints of noise-induced vertigo. The patient's history, imaging studies, and balance function examinations led to the diagnosis of a right-sided superior canal dehiscence (SCD). After surgical repair of the dehiscence, the quantitative electrophysiological tests returned to normal. However, the patient's scores on measures of anxiety, depression, and self-perceived dizziness handicap increased significantly postoperatively. This case illustrates the transformation of a peripheral end-organ impairment (i.e., SCD) into a psychiatric condition (i.e., CSD).