Marc D. Eisen

Preoperative imaging to predict orbital invasion by tumor.

Our purpose was to examine the accuracy of preoperative imaging in assessing tumor invasion of the orbit and nasolacrimal system.

Lipomas of the internal auditory canal and cerebellopontine angle

Objective: To evaluate lipomas of the internal auditory canal (IAC) and cerebellopontine angle (CPA). Study Design: Retrospective review. Methods: Review of a multi‐institutional series of 17 lipomas of the IAC/CPA, combined with a Medline review of the 67 cases reported in the world literature. Results: This series of 17 IAC/CPA lipomas is the largest reported series to date, bringing the total number of documented cases to 84. There appears to be a nearly 2:1 male to female predominance. Sixty percent were leftsided lesions, and three were bilateral. Hearing loss, dizziness, and tinnitus were the most common presenting symptoms. Surgical resection was performed in 52 (62%) of these lesions; however, total tumor removal was accomplished in only 17 (33%), which is most likely because of the fact that these tumors tend to have a poorly defined matrix and a dense adherence to neurovascular structures. Sixty‐eight percent of patients experienced a new deficit postoperatively, 11% were unchanged, and only 19% improved with no new deficit. Only one documented case of tumor growth was identified; however, the reported follow‐up was short (average, less than 3 years). Conclusion: With the magnetic resonance imaging techniques now available, lipomas can be reliably differentiated from other masses within the CPA and IAC, so histopathologic diagnosis is rarely necessary. Because of the potential for significant morbidity with resection of these lesions, we believe that conservative follow‐up is the best treatment option for patients with these rare lesions. Surgery is indicated only when significant progressive or disabling symptoms are present. Laryngoscope, 108:1459–1469, 1998

Electrically evoked compound action potential amplitude growth functions and HiResolution programming levels in pediatric CII implant subjects.

Objective: To characterize the amplitude growth functions of the electrically evoked compound action potential (ECAP) in pediatric subjects implanted with the Clarion HiFocus electrode array with respect to electrode position and the presence or absence of a Silastic positioner. Electrophysiologic growth function data are compared with HiResolution (HiRes) psychophysical programming levels. Design: ECAP growth functions were measured for all electrodes along the implant’s array in 16 pediatric subjects. Nine of the patients were implanted with a Silastic positioner, whereas seven had no positioner. ECAP thresholds and growth function slopes were calculated. Fifteen of the 16 patients had psychophysical threshold and maximum comfort levels available. Programming levels and ECAP thresholds were compared within and among the subjects. Results: ECAP thresholds showed variability among patients, ranging from 178 to 920 nA at 32 μsec pulse width. ECAP thresholds did not depend on electrode position along the cochlea but were lower in the presence of the Silastic positioner (p < 0.001). Thresholds determined with the masker-probe versus the alternating polarity paradigms revealed moderate (r = 0.76) correlation. Growth function slopes also showed considerable variation among patients. Unlike thresholds, slopes decreased from apical to basal cochlear locations (p < 0.001) but showed no difference between the absence and presence of the positioner. Programming levels in HiRes were correlated with ECAP threshold levels. When ECAP thresholds were adjusted for each patient by the difference between M level and ECAP threshold at electrode 9, however, overall correlation between the two measurements was excellent (r = 0.98, N = 224). Conclusions: In pediatric subjects with the Clarion HiFocus electrode, ECAP growth function thresholds appear to decrease with the presence of the Silastic positioner but are unaffected by electrode position along the array. Growth function slope, however, depends on electrode position along the array but not on the presence of the positioner. ECAP programming levels can reliably predict stimulus intensities within the patients’ dynamic ranges, but considerable variability is seen between ECAP thresholds and HiRes programming levels.

Djourno, Eyries, and the first implanted electrical neural stimulator to restore hearing

The cochlear implant has created a revolution in the treatment of deafness. There are approximately 25,000 individuals with implants worldwide, and the demand for cochlear implants increases nearly 20% each year (1). Although numerous attempts to treat deafness with electricity have been reported over the last several centuries (2), the first reported direct stimulation of the cochlear nerve aimed at generating hearing appeared as recently as 1957 with the work of André Djourno and Charles Eyriès. Despite the revolutionary impact that the cochlear implant has had on otology, these beginnings in Paris with Djourno and Eyriès received little attention. Although they are credited with the first cochlear implant, the details of the work and the subsequent events that led to the hostile parting of the two men have not been reported in the English literature. The purpose of this study is first to present biographical information of these two pioneers and describe the details of the events associated with their efforts. The source of most of this information comes from personal interviews with both men by historian Phillip Seitz. The work will then be revisited, addressing the possibility that Djourno and Eyriès did not perform the first direct cochlear nerve stimulation at all but rather the first cochlear nucleus prosthesis.

Electrode interaction in pediatric cochlear implant subjects.

Multielectrode cochlear implants rely on differential stimulation of the cochlear nerve for presenting the brain with the spectral and timing information required to understand speech. In implant patients, the degree of overlap among cochlear nerve fibers stimulated by the different electrodes constitutes the electrode interaction. Electrode interaction degrades the spectral resolution of the implant’s stimulus. We sought to define electrode interaction in a cohort of pediatric cochlear implant subjects as a function of both stimulus intensity and electrode location along the array. The 27 pediatric subjects that completed the study were implanted with either the Clarion Hi-Focus array with or without positioner, the Nucleus 24 Contour array, or the Nucleus 24 Straight array. All but two of the patients had congenital hearing loss, and none of the patients had meningitis prior to the onset of deafness. The cochlear nerve response was measured with the electrically evoked compound action potential (ECAP). A forward masking protocol was used such that a probe stimulus electrode remained fixed while a preceding masker was moved across the array. Electrode interaction was estimated by measuring the unmasked probe response minus the masked probe response. Three probe locations and three probe intensities were examined for each subject. At all probe locations, electrode interaction increased as probe intensity increased (p < 0.05). Interaction at the basal probe was less than that at either the middle or apical probe locations (p < 0.05), and significant correlation found between probe distance from the basal end of the array and electrode interaction (p < 0.001). These results demonstrate that in this cohort of pediatric subjects, electrode interaction depended on both stimulus intensity and probe location. Implications of these findings on future implant array design and current implant fitting strategies are discussed. The impact of electrode interaction on implant performance is yet to be elucidated.

Inverted papilloma of the sphenoid sinus presenting with auditory symptoms: a report of two cases.

Objectives The report aims to inform the reader of cases of inverted papilloma involving the sphenoid sinus presenting with auditory symptoms.

Distal separation of chick cochlear hair cell stereocilia: Analysis of contact-constraint models

One model often used in the study of hair bundle micromechanics assumes simple geometric relationships between hair displacements, constrained by contact between neighboring hairs at their distal tips. Recent observations of hair bundle motion provided the opportunity to evaluate the contact-constraint model against measured displacements for the tallest and shortest sensory hairs. A contact-constraint model was developed based on the geometry of a single column of stereocilia. The model used morphological data from chick hair bundles for which displacement data in the excitatory and inhibitory directions were also available. For each hair bundle, a unique sensory hair radius was determined so that the calculated resting bundle morphology matched the measured values. The model was then evaluated against the displacement data for each hair bundle. In each case, the model underestimated the excitatory displacement of the shortest hairs. Failure of the model to accurately predict bundle motion raises the possibility of a distal separation between the hairs at rest. It is suggested that tip links pull the hairs through this separation during excitatory deflections. Perhaps at damaging levels of displacement, the hairs suddenly come into contact, tip-link tension dramatically increases, and the tip-links are fractured.

Frequency and electrode discrimination in children with cochlear implants.

The objective of this study was to develop reliable pediatric psychophysical methodologies in order to address the limits of frequency and electrode discrimination in children with cochlear implants. Discrimination was measured with a two-alternative, adaptive, forced choice design using a video game graphical user interface. Implanted children were compared to normal-hearing children in the same age ranges. Twenty-nine implanted children and 68 children with normal-hearing performed frequency discrimination studies at varying frequencies. Electrode discrimination was assessed in thirty-four implanted children at varying electrode locations and stimulation intensities. Older children had better frequency discrimination than younger children, both for implanted and hearing subjects. Implanted children had worse frequency discrimination overall and exhibited learning effects at older ages than hearing children. Frequency discrimination Weber fractions were smallest in low frequencies. Electrode discrimination improved with stimulus intensity level for older but not younger children at all electrode locations. These results support the premise that developmental changes in signal processing contribute to discrimination of simple acoustic stimuli. For implanted children, auditory discrimination improved at lower frequencies and with electrodes at higher intensity. These findings imply that spatial separation may not be the key determinant in creating discriminable electrical stimuli for this population.

The tip link's role in asymmetric stereocilia motion of chick cochlear hair cells

The symmetry of chick cochlear hair bundle motion was examined in this study. Isolated segments from the basilar papilla were incubated in vitro in either normal or low calcium medium, which is known to disrupt tip links. Stereociliary bundles, stimulated with an oscillating water microjet, were oriented in profile and viewed in slow motion at high magnification with stroboscopic illumination. The displacement of the tallest hair in the bundle was fixed to 20 degrees peak-to-peak (P-P) motion. The angular deflections of the shortest and tallest hairs were then measured in both the positive (towards the tallest hair) and negative (towards the shortest) directions with respect to the non-stimulated position of the hair. The tallest hairs exhibited nearly symmetric motion in medium containing normal and low calcium. The shortest hairs, in normal calcium, displayed considerable asymmetry with angular deflections in the positive direction significantly larger than in the negative direction. This asymmetric motion disappeared after incubation in low calcium. The shortest hair angular displacement in the negative direction, however, was the same in both normal and low calcium conditions. These results indicated that the tallest and shortest hairs moved with equal angular deflection in the negative direction, while in the positive direction the shortest hair moved through a significantly greater angular deflection than the tallest hair. The implication of this finding is that the tip links contributed significantly to hair bundle motion in the positive direction only.

Cerebrospinal fluid cytology to aid the diagnosis of cerebellopontine angle tumors.

Objective: To determine if cerebrospinal fluid (CSF) cytology can be useful in the workup of patients with internal auditory canal/cerebellopontine angle (IAC/CPA) tumors and facial paralysis to diagnose metastatic disease before surgical intervention. Study Design: Retrospective case series. Setting: Tertiary referral center. Patients: Patients who presented with or developed facial paralysis and IAC/CPA tumors. Outcome Measure: Lumbar puncture and CSF cytological analysis. Results: Seven patients presented with or developed high-grade facial paralysis (greater than House-Brackmann Grade II). In the first patient, excision of the tumor revealed adenocarcinoma. All subsequent patients were evaluated with CSF cytological analysis. In five of these patients, cytological CSF analysis revealed malignant cells, suggesting a diagnosis of a metastatic lesion rather than acoustic neuroma. Primary neoplasms were identified in all but one of these patients. A sixth patient had metastatic breast cancer, but negative CSF cytology and a stable CPA tumor after radiation treatment. Two patients who were being conservatively followed up for their IAC/CPA tumor developed a nonprogressive but persistent mild Grade II facial weakness and underwent CSF analysis which tested negative. One patient had surgical resection with pathologic findings consistent with a typical acoustic schwannoma, and the other patient has been conservatively followed up without change. Conclusion: Our experience suggests that patients presenting with IAC/CPA tumors and progressive facial paralysis of House-Brackmann Grade III or greater should have a CSF cytological examination before surgical intervention to evaluate for a malignant process.