Jose N. Fayad

Multichannel Cochlear Implants: Relation of Histopathology to Performance

Objectives: To determine the relationship of surviving neural elements to auditory function in multichannel cochlear implant temporal bones.

Transcranial Contralateral Cochlear Stimulation in Unilateral Deafness

OBJECTIVES: The purpose of this study is to evaluate the effectiveness of Bone Anchored Cochlear Stimulator (BAHA) in transcranial routing of signal by implanting the deaf ear. STUDY DESIGN AND SETTINGS: Eighteen patients with unilateral deafness were included in a multisite study. They had a 1-month pre-implantation trial with a contralateral routing of signal (CROS) hearing aid. Their performance with BAHA was compared with the CROS device using speech reception thresholds, speech recognition performance in noise, and the Abbreviated Profile Hearing Benefit and Single Sided Deafness questionnaires. RESULTS: Patients reported a significant improvement in speech intelligibility in noise and greater benefit from BAHA compared with CROS hearing aids. Patients were satisfied with the device and its impact on their quality of life. No major complications were reported. CONCLUSION AND SIGNIFICANCE: BAHA is effective in unilateral deafness. Auditory stimuli from the deaf side can be transmitted to the good ear, avoiding the limitations inherent in CROS amplification.

Cochlear implants : histopathologic findings related to performance in 16 human temporal bones

This paper presents results of a histologic study of 16 temporal bones with cochlear implants from 13 subjects. Damage caused by electrode insertion in the basal turn of the cochlea was evaluated. Dendrite and spiral ganglion cell populations were compared to clinical performance scores to determine structures necessary for stimulation and the minimum number needed for electrical stimulation. Results show that damage from insertion of long electrodes was located mainly at the most anterior part of the basal turn; that despite total degeneration of dendrites in the area near the electrode, some spiral ganglion cells remained; and that spiral ganglion cells or possibly axons are the stimulated structures and that fewer of them than previously thought are necessary to achieve a hearing sensation from electrical stimulation.

Auditory Brainstem Implant: II. Postsurgical Issues and Performance

The auditory brainstem Implant (ABI) restores some hearing sensations to patients deafened by bilateral acoustic tumors. Electrodes are stable for more than 10 years. In most cases nonaudltory side effects can be avoided by judicious selection of the stimulating waveform and electrode configuration. Most perceptual measurements demonstrate that the ABI produces psychophysical and speech performance similar to that of single-channel cochlear implants. ABI patients receive suprasegmental Information in speech and significant enhancement of speech understanding when the sound from the ABI is combined with Ilpreading.

GRM7 variants confer susceptibility to age-related hearing impairment

Age-related hearing impairment (ARHI), or presbycusis, is the most prevalent sensory impairment in the elderly. ARHI is a complex disease caused by an interaction between environmental and genetic factors. Here we describe the results of the first whole genome association study for ARHI. The study was performed using 846 cases and 846 controls selected from 3434 individuals collected by eight centers in six European countries. DNA pools for cases and controls were allelotyped on the Affymetrix 500K GeneChip for each center separately. The 252 top-ranked single nucleotide polymorphisms (SNPs) identified in a non-Finnish European sample group (1332 samples) and the 177 top-ranked SNPs from a Finnish sample group (360 samples) were confirmed using individual genotyping. Subsequently, the 23 most interesting SNPs were individually genotyped in an independent European replication group (138 samples). This resulted in the identification of a highly significant and replicated SNP located in GRM7, the gene encoding metabotropic glutamate receptor type 7. Also in the Finnish sample group, two GRM7 SNPs were significant, albeit in a different region of the gene. As the Finnish are genetically distinct from the rest of the European population, this may be due to allelic heterogeneity. We performed histochemical studies in human and mouse and showed that mGluR7 is expressed in hair cells and in spiral ganglion cells of the inner ear. Together these data indicate that common alleles of GRM7 contribute to an individuals risk of developing ARHI, possibly through a mechanism of altered susceptibility to glutamate excitotoxicity.

Clinical practice guideline: Cerumen impaction

Objective This guideline provides evidence-based recommendations on managing cerumen impaction, defined as an accumulation of cerumen that causes symptoms, prevents assessment of the ear, or both. We recognize that the term “impaction” suggests that the ear canal is completely obstructed with cerumen and that our definition of cerumen impaction does not require a complete obstruction. However, cerumen impaction is the preferred term since it is consistently used in clinical practice and in the published literature to describe symptomatic cerumen or cerumen that prevents assessment of the ear. This guideline is intended for all clinicians who are likely to diagnose and manage patients with cerumen impaction. Purpose The primary purpose of this guideline is to improve diagnostic accuracy for cerumen impaction, promote appropriate intervention in patients with cerumen impaction, highlight the need for evaluation and intervention in special populations, promote appropriate therapeutic options with outcomes assessment, and improve counseling and education for prevention of cerumen impaction. In creating this guideline the American Academy of Otolaryngology-Head and Neck Surgery Foundation selected a panel representing the fields of audiology, family medicine, geriatrics, internal medicine, nursing, otolaryngology-head and neck surgery, and pediatrics. Results The panel made a strong recommendation that 1) clinicians should treat cerumen impaction that causes symptoms expressed by the patient or prevents clinical examination when warranted. The panel made recommendations that 1) clinicians should diagnose cerumen impaction when an accumulation of cerumen is associated with symptoms, or prevents needed assessment of the ear (the external auditory canal or tympanic membrane), or both; 2) clinicians should assess the patient with cerumen impaction by history and/or physical examination for factors that modify management, such as one or more of the following: nonintact tympanic membrane, ear canal stenosis, exostoses, diabetes mellitus, immunocompromised state, or anticoagulant therapy; 3) the clinician should examine patients with hearing aids for the presence of cerumen impaction during a healthcare encounter (examination more frequently than every three months, however, is not deemed necessary); 4) clinicians should treat the patient with cerumen impaction with an appropriate intervention, which may include one or more of the following: cerumenolytic agents, irrigation, or manual removal other than irrigation; and 5) clinicians should assess patients at the conclusion of in-office treatment of cerumen impaction and document the resolution of impaction. If the impaction is not resolved, the clinician should prescribe additional treatment. If full or partial symptoms persist despite resolution of impaction, alternative diagnoses should be considered. The panel offered as an option that 1) clinicians may observe patients with nonimpacted cerumen that is asymptomatic and does not prevent the clinician from adequately assessing the patient when an evaluation is needed; 2) clinicians may distinguish and promptly evaluate the need for intervention in the patient who may not be able to express symptoms but presents with cerumen obstructing the ear canal; 3) the clinician may treat the patient with cerumen impaction with cerumenolytic agents, irrigation, or manual removal other than irrigation; and 4) clinicians may educate/counsel patients with cerumen impaction/excessive cerumen regarding control measures. Disclaimer This clinical practice guideline is not intended as a sole source of guidance in managing cerumen impaction. Rather, it is designed to assist clinicians by providing an evidence-based framework for decision-making strategies. It is not intended to replace clinical judgment or establish a protocol for all individuals with this condition, and may not provide the only appropriate approach to diagnosing and managing this problem.

Electrode Insertion Trauma in Cochlear Implantation

Residual hearing conservation may be important in cochlear implantation of children and of adults with disabling tinnitus responsive to extracochlear stimulation. Damage to the neural elements of the cochlea during electrode insertion may have a negative impact on residual hearing conservation. Histologic analysis of eight temporal bones with cochlear implants reveals trauma at essentially two locations: The round window insertion site and along the basal turn of the cochlea. In four of the bones, insertion at the round window resulted in damage to the osseous spiral lamina and the electrode was inserted through the scala media into the scala vestibuli. Evidence of secondary reactive osseous formation was also noted in these bones. This paper relates the surgical anatomy of the round window to histologic findings and microanatomical dissections. Recommendations for implantation surgery include creation of a cochleostomy by removal of the floor of the round window niche and a superior-to-inferior angle of electrode insertion.

Revision cochlear implant surgery in children.

Objective: To determine the incidence of revision cochlear implant (CI) surgery in children and the indications for revision surgery and to examine the pattern of events that lead to revision CI surgery. Study Design: Retrospective case review. Setting: Two tertiary pediatric CI centers. Patients: Pediatric CI patients who underwent revision surgery related to their CI. Main Outcome Measures: Reasons for revision, surgical outcomes, complications, performance, and device analyses were sought. Results: Nine hundred fifty-two pediatric CI operations were performed between 1991 and 2005. Ninety-three patients underwent 107 (11.2%) revision operations. Hard device failure occurred in 46% (n = 49); soft failure occurred in 15% (n = 16); medical/surgical causes were responsible for 37% (n = 40); and magnet dislodgement requiring revision surgery occurred in 2% (n = 2). Head trauma was associated with 41% of the hard failure cases (n = 20). Device analyses revealed identifiable abnormalities in most of both hard and soft failure cases. In most patients, auditory performance equaled or surpassed the best preoperative performance by 6 to 12 months after revision. Conclusion: Revision CI surgery is common among pediatric CI recipients. Hard failure is the most common reason for undertaking revision surgery, and this mode of failure is frequently associated with preceding head trauma. Patients and parents should be counseled that performance is expected to equal or surpass the childs best level of performance before revision surgery, although this may take some time, and exceptions do exist.

Spiral Ganglion Cell Loss is Unrelated to Segmental Cochlear Sensory System Degeneration in Humans

Objective: To demonstrate that contrary to what occurs in animals, neuron loss in the human spiral ganglion is not in proportion to organ of Corti hair or supporting cell loss. Study Design: Histopathological review of archival temporal bone histological sections. Setting: Nonprofit research facility. Methods: Four temporal bones, from an archival collection of 1,448 temporal bones, were found that had a total loss of hair and supporting cells limited to the basal segment of the cochlea and a hearing loss of 3 or more years (range, 3-28 yr). Cochlear reconstructions were conducted to demonstrate the populations of hair and supporting cells, peripheral processes (dendrites), spiral ganglion cells, and the amount of surviving stria vascularis in different cochlear segments. Results: The total loss of hair and supporting cells of the organ of Corti in the base of the cochlea is not accompanied by a proportional loss of spiral ganglion cells in the modiolar base. Conclusion: A long-term loss of hearing in frequencies greater than 2 kHz, and corresponding hair cell loss, does not result in a subsequent loss of spiral ganglion cells in humans, in contrast to what has been reported in association with animals. These findings suggest that the poor performance of cochlear implant in patients after prolonged deafness is not caused by ongoing degeneration of ganglion cells.

Understanding drug ototoxicity: molecular insights for prevention and clinical management

Ototoxicity is a trait shared by aminoglycoside and macrolide antibiotics, loop diuretics, platinum-based chemotherapeutic agents, some NSAIDs and antimalarial medications. Because their benefits in combating certain life-threatening diseases often outweigh the risks, the use of these ototoxic drugs cannot simply be avoided. In this review, the authors discuss some of the most frequently used ototoxic drugs and what is currently known about the cell and molecular mechanisms underlying their noxious effects. The authors also provide suggestions for the clinical management of ototoxic medications, including ototoxic detection and drug monitoring. Understanding the mechanisms of drug ototoxicity may lead to new strategies for preventing and curing drug-induced hearing loss, as well as developing new pharmacological drugs with less toxic side effects.