Monitoring Cochlear Health With Intracochlear Electrocochleography During Cochlear Implantation: Findings From an International Clinical Investigation.

OBJECTIVES: Electrocochleography (ECochG) is emerging as a tool for monitoring cochlear function during cochlear implant (CI) surgery. ECochG may be recorded directly from electrodes on the implant array intraoperatively. For low-frequency stimulation, its amplitude tends to rise or may plateau as the electrode is inserted. The aim of this study was to explore whether compromise of the ECochG signal, defined as a fall in its amplitude of 30% or more during insertion, whether transient or permanent, is associated with poorer postoperative acoustic hearing, and to examine how preoperative hearing levels may influence the ability to record ECochG. The specific hypotheses tested were threefold: (a) deterioration in the pure-tone average of low-frequency hearing at the first postoperative follow-up interval (follow-up visit 1 [FUV1], 4 to 6 weeks) will be associated with compromise of the cochlear microphonic (CM) amplitude during electrode insertion (primary hypothesis); (b) an association is observed at the second postoperative follow-up interval (FUV2, 3 months) (secondary hypothesis 1); and (c) the CM response will be recorded earlier during electrode array insertion when the preoperative high-frequency hearing is better (secondary hypothesis 2). DESIGN: International, multi-site prospective, observational, between groups design, targeting 41 adult participants in each of two groups, (compromised CM versus preserved CM). Adult CI candidates who were scheduled to receive a Cochlear Nucleus CI with a Slim Straight or a Slim Modiolar electrode array and had a preoperative audiometric low-frequency average thresholds of ≤80 dB HL at 500, 750, and 1000 Hz in the ear to be implanted, were recruited from eight international implant sites. Pure tone audiometry was measured preoperatively and at postoperative visits (FUV1 and follow-up visit 2 [FUV2]). ECochG was measured during and immediately after the implantation of the array. RESULTS: From a total of 78 enrolled individuals (80 ears), 77 participants (79 ears) underwent surgery. Due to protocol deviations, 18 ears (23%) were excluded. Of the 61 ears with ECochG responses, amplitudes were < 1 µV throughout implantation for 18 ears (23%) and deemed "unclear" for classification. EcochG responses >1 µV in 43 ears (55%) were stable throughout implantation for 8 ears and compromised in 35 ears. For the primary endpoint at FUV1, 7/41 ears (17%) with preserved CM had a median hearing loss of 12.6 dB versus 34/41 ears (83%) with compromised CM and a median hearing loss of 26.9 dB ( p < 0.014). In assessing the practicalities of measuring intraoperative ECochG, the presence of a measurable CM (>1 µV) during implantation was dependent on preoperative, low-frequency thresholds, particularly at the stimulus frequency (0.5 kHz). High-frequency, preoperative thresholds were also associated with a measurable CM > 1 µV during surgery. CONCLUSIONS: Our data shows that CM drops occurring during electrode insertion were correlated with significantly poorer hearing preservation postoperatively compared to CMs that remained stable throughout the electrode insertion. The practicality of measuring ECochG in a large cohort is discussed, regarding the suggested optimal preoperative low-frequency hearing levels ( < 80 dB HL) considered necessary to obtain a CM signal >1 µV.

Histopathology of the Clarion cochlear implant electrode positioner in a human subject.

A Silastic electrode positioner was introduced by the Advanced Bionics Corporation in 1999 and it was designed to achieve a perimodiolar position of the stimulating electrode. The positioner was voluntarily recalled in the United States in July 2002 due to an apparent higher risk of bacterial meningitis in patients in whom the electrode positioner had been placed. A detailed histopathologic study of the positioner in the human has not previously been published. The histopathologic findings in a 74-year-old woman who underwent bilateral cochlear implantation using the positioner are presented. Findings include a large track caused by the combined electrode and its positioner with considerable disruption of the basilar membrane and osseous spiral lamina. Although there was a fibrous sheath around the electrode and positioner at the cochleostomy in both ears, this fibrous sheath did not extend deeply into the cochlea except at the apical end of the electrode beyond the positioner. This resulted in a large fluid space around and between the positioner and electrode within the cochlea and presumably in fluid continuity with the cerebrospinal fluid space. Possible clinical implications are discussed.

TNRT profiles with the nucleus research platform 8 system.

This study investigates the effect of the Nucleus CI24RE implant's neural response telemetry (NRT) system, which has less internal noise compared to its predecessor, the CI24M/R implant, on the NRT threshold (TNRT) profile across the array. CI24M/R measurements were simulated by ignoring CI24RE measurements with response amplitudes below 50 uV. Comparisons of the estimated TNRTs from the CI24RE measurements and the CI24M/R simulations suggest that, apart from a constant level difference, the TNRT profiles from the newer implant generally would not have differed very much from those of its predecessor. This view was also reflected by principal component analysis (PCA) results which revealed a 'shift' component similar to that reported by Smoorenburg et al (2002). On the whole, there is no indication that current practices of using the TNRT profiles for assisting with speech processor programming need to be revised for the CI24RE implant.

Cementoma Gigantiforme Mandibular en Paciente Pediátrico: Reporte de Caso y Revisión de la Literatura

RESUMEN: El cementoma gigantiforme (CG) es una lesión fibrocemento-ósea benigna de muy baja prevalencia y de etiología desconocida que se presenta con mayor frecuencia en pacientes jóvenes y que se caracteriza por generar movilidad de dientes y asimetrías faciales importantes. Radiográficamente se expresa como una lesión mixta, con presencia de áreas radiopacas y algunas radiolúcidas, bien circunscrita, que se observa principalmente en la mandíbula. El CG se comporta de manera similar a otras lesiones de los maxilares, tanto en su clínica como en la histopatología, lo que podría dificultar y confundir su diagnóstico. Debido a su comportamiento localmente agresivo y deformante, el tratamiento sugerido es la resección de la lesión con márgenes de seguridad.

ABSTRACT: The gigantiform cementoma (GC) is a benign bone-fibrocement lesion of very low prevalence and of unknown etiology that occurs more frequently in young patients and is characterized by generating mobility of teeth and significant facial asymmetries. Radiographically it is expressed as a mixed lesion, with the presence of radiopaque and some radiolucent areas, well circumscribed, which is observed mainly in the mandible. GC behaves in a similar way to other maxillary lesions, both clinically and in histopathology, which could make its diagnosis difficult and confusing. Due to its locally aggressive and deforming behavior, the suggested treatment is resection of the lesion with safety margins.

Phenotypic variability in monozygotic twins with neurofibromatosis 2.

Mutations in the neurofibromatosis 2 (NF2) tumor suppressor gene on chromosome 22q12 cause a clinically variable autosomal dominant syndrome characterized by bilateral vestibular schwannomas (VSs), other nervous system tumors, and early onset lenticular cataracts. We studied three pairs of monozygotic (MZ) twins with NF2, all with bilateral VSs, to separate genetic from nongenetic causes of clinical variability. The evaluation included gadolinium-enhanced high-resolution magnetic resonance imaging of the head and spine, neuro-ophthalmic examination with slit lamp, physical examination, and zygosity testing with microsatellite markers. Each MZ pair was concordant for general phenotypic subtype (mild or severe) and often for the affected organ systems. However, the MZ pairs were discordant for some features of disease presentation or progression. For example, all three pairs were discordant for presence or type of associated cranial tumors. We hypothesize that phenotypic differences between NF2 MZ twins are at least partly due to stochastic processes, such as the loss of the second NF2 allele or alleles of other genes.

Gadolinium-enhanced MR of the postoperative internal auditory canal following acoustic neuroma resection via the middle fossa approach.

PURPOSE: To evaluate the ability of gadolinium-enhanced MR in detecting recurrent tumor in patients whose acoustic neuromas were surgically removed via the middle cranial fossa approach. PATIENTS AND METHODS: Postoperative gadolinium-enhanced exams of 13 of 44 patients who underwent excision of acoustic neuromas via the middle cranial fossa approach were reviewed. RESULTS: Postoperative enhancement was seen in 12 of the 13 patients; two patients underwent serial exams without significant change. On the basis of a single exam, we were unable to conclusively differentiate postoperative enhancement from residual or recurrent tumor. CONCLUSIONS: A single exam is of limited value. Serial studies are recommended to identify changes that would indicate tumor growth. A proposed MR follow-up schedule is an initial baseline exam within 2 months of surgery and a repeat exam during the second postoperative year.

Anatomical and physiological measures of auditory system in mice with peripheral myelin deficiency.

Animal models with genetic abnormalities have been increasingly used in auditory research. Both TrJ mice and Po-DT-A mice are animals with peripheral myelin deficiency. In TrJ mice, the defect is due to a mutated PMP-22 gene. In Po-DT-A mice, the defect is produced by a transgene using the rat Po promotor to direct the expression of gene encoding for the bacterial diphtherial toxin A chain (DT-A). This study evaluates the auditory system both physiologically and histologically in these two strains of mice. Histological examination revealed that there was myelin deficiency of the auditory nerve fibers, accompanied by a loss of dendrites and a loss of spiral ganglion cell bodies in both strains of mice. In general, histological deficits in TrJ mice were greater than those in Po-DT-A mice. There was a strong correlation between the degree of myelin deficiency and the survival of spiral ganglion neurons. ABR measurements exhibited differences in threshold, latency and slope of the ABR growth function between myelin-deficient mice and their respective controls. These results suggest that the integrity of the myelin in the auditory nerve is important both for neural survival and for normal electrophysiological function of spiral ganglion neurons.

Insertional trauma of multichannel cochlear implants.

Insertional trauma to the cochlea from three different multichannel cochlear implant electrodes was evaluated in a single-blind controlled study in fresh human temporal bones. Sixteen fresh human temporal bones were implanted with one of three types of multichannel electrodes (Symbion/InnerAid, Cochlear/Nucleus, or Storz/UCSF). Seven temporal bones were used as controls where a cochleostomy only was created. The temporal bones were evaluated histologically and cochlear histograms of the trauma were created. Although the three electrode designs caused damage which was unlikely to hinder implant performance, a distinct pattern of trauma was seen with each of the three electrode types. The least traumatic of the three electrode designs in this study was the Nucleus type. The degree of insertional trauma may be relevant to changing indications for insertion of cochlear implants as well as for patients with device failure who require reimplantation.

Surgical management of Bell's palsy.

OBJECTIVES: Incomplete return of facial motor function and synkinesis continue to be long-term sequelae in some patients with Bell's palsy. The aim of this report is to describe a prospective study in which a well-defined surgical decompression of the facial nerve was performed in a population of patients with Bell's palsy who exhibit the electrophysiologic features associated with poor outcomes. In addition, management issues related to Bell's palsy including herpes simplex virus typel etiology, the natural history, electrodiagnostic testing, and efficacy of surgical strategies are reviewed. STUDY DESIGN AND METHODS: A multicenter prospective clinical trial was designed utilizing electroneurography (ENOG) and voluntary electromyography (EMG) to identify patients with Bell's palsy who would most likely develop poor return of facial function, as suggested by Fisch and Esslen. Patients who displayed electrodiagnostic features of poor outcome, >90% degeneration on ENOG testing and no voluntary motor unit EMG potentials within 14 days of onset of total paralysis, were offered a surgical decompression of the facial nerve through a middle cranial fossa surgical exposure, including the tympanic segment, geniculate ganglion, labyrinthine segment, and meatal foramen. Control subjects were those who displayed similar electrodiagnostic features and time course. RESULTS: Subjects who did not reach 90% degeneration on ENOG within 14 days of paralysis all returned to House-Brackmann grade I (n = 48) or II (n = 6) at 7 months after onset of the paralysis. Control subjects self-selecting not to undergo surgical decompression when >90% degeneration on ENOG and no motor unit potentials on EMG were identified had a 58% chance of developing a poor outcome at 7 months after onset of paralysis (House-Brackmann grade III or IV [n = 19]). A group with similar ENOG and EMG findings undergoing middle fossa facial nerve decompression exhibited House-Brackmann grade I (n = 14) or II (n = 17) in 91% of the cases. An exact permutation test confirmed that the surgical group had a significantly higher proportion of patients with a good outcome (House-Brackmann grade I or II) (P = .0002). CONCLUSION: Electroneurography in combination with voluntary EMG successfully identified patients who will most likely return to normal from those who had a greater chance of long-term sequelae from Bell's palsy. Surgical decompression medial to the geniculate ganglion significantly improves the chances of normal or near-normal return of facial function in the group that has a high probability of a poor result. Surgical decompression must be performed within 2 weeks of onset of total paralysis for it to be effective.

Hearing results after cholesteatoma surgery: the Iowa experience.

This study compared the hearing outcome of canal-up and canal-down mastoidectomies for removal of cholesteatoma in 455 ears. An intact canal wall procedure was performed in 92 patients while the remainder (N = 363) underwent a canal-down operation. The hearing results for both procedures are dependent on the presence of the stapes superstructure. When the stapes superstructure was intact, 52% of the patients with canal-up operations had an air-bone gap of less than 20 dB. The corresponding figure for canal-down cases was 37%. When there was no stapes superstructure, 54% of the canal-up cases and 19% of the canal-down cases obtained a similar ABG closure. Preserving the posterior external auditory canal wall results in slightly better hearing function. However, when the stapes superstructure is intact, the difference in hearing function is not remarkable, and must be weighed against the potential for residual disease or recurrence associated with canal-up procedures.

Avulsion of the anomalous facial nerve at stapedectomy.

Injury to the facial nerve in an anomalous location overlying the oval window at the time of stapedectomy has rarely been reported. The authors recently have encountered three patients with such injuries. The facial nerve was found at the time of reexploration to run directly over the oval window. A fourth patient was explored primarily for a conductive hearing loss and the same anomalous course was discovered. The purpose of this report is to alert the otologic surgeon to this rare but potentially catastrophic anomaly and to review the pertinent embryology and management of these malformations.

Polymerase chain reaction amplification of DNA from archival celloidin-embedded human temporal bone sections.

A method was developed for fast and efficient isolation of DNA from formalin-fixed, decalcified, celloidin-embedded human temporal bone sections for subsequent use in polymerase chain reaction (PCR) DNA amplification. The method relies on the use of an enzymatic digestion with proteinase K to release and solubilize the patient's DNA from an individual 20- to 25-microns temporal bone section. The method described should be of great value to those investigators extracting DNA from archival individual human temporal bone sections for polymerase chain reaction assays of specific genetic alterations associated with temporal bone pathologies. The molecular characterization of viral infections, oncogenes, or other etiological agents of disease using PCR could provide important information regarding the etiopathogenesis of many auditory, vestibular, and facial nerve disorders, such as autoimmune hearing loss, congenital hearing losses, Meniere's disease, otosclerosis, or Bell's palsy.

Pseudoepitheliomatous hyperplasia versus squamous cell carcinoma of the external auditory canal.

Four case reports are presented to demonstrate the clinical and histopathologic similarity of pseudoepitheliomatous hyperplasia (PH) to squamous cell carcinoma (SCC) in the external auditory canal (EAC). In all four cases the original report of SCC on a biopsy specimen of an EAC lesion was corrected on review to PH. In one patient conservative management resulted in resolution of the EAC lesion. A second patient underwent radiation therapy and partial temporal bone resection with no SCC found in the surgical specimen. A third patient's ear canal had healed with conservative treatment and repeated biopsy revealed no malignancy. After a 6-year symptom-free interval, she developed invasive SCC with bone involvement that required surgery and radiation treatment. A fourth patient underwent a sleeve resection of the skin of the EAC that proved to be PH, and no evidence of SCC was found. A thoughtful clinical history, careful physical examination, response to conservative treatment, and close communication with the pathologist should be exercised in the evaluation of EAC lesions.

Evaluation of five different cochlear implant designs: audiologic assessment and predictors of performance.

The audiologic performance of 54 postlingually deafened adults wearing cochlear implants was uniformly evaluated. The participants had 9 months' or more experience with one of five different cochlear prostheses (Los Angeles Single Channel (N = 11), Vienna Single Channel (N = 4), Melbourne Multichannel (N = 18), Utah Multichannel (N = 19), San Francisco Multichannel (N = 2). The multichannel designs enabled participants to recognize more environmental sounds, provided more speech reading enhancement, and enabled most users to understand limited speech in the sound-only condition, compared to the single-channel implant group.

Iowa cochlear implant clinical project: results with two single-channel cochlear implants and one multi-channel cochlear implant.

Cochlear implants have become a realistic alternative for the management of profoundly deaf patients. A variety of implants with differing electrode designs and coding strategies have been developed by nine major implant centers around the world. Each center has their "star" patient, but objective comparisons between these different implant designs are unavailable. In order to determine the performance characteristics of the present generation of cochlear implants, comparison data are vital. We have developed an independent center where uniform objective comparisons of different cochlear implants can be performed longitudinally. This report will present results of nine patients implanted with three different cochlear implant prostheses. Four patients have been implanted with the Los Angeles (House) single-channel implant, three patients have received the Vienna (Hochmair) single-channel intracochlear device, and two patients have been implanted with the Melbourne (Clark) 21-channel unit. All patients have had 11 months or more of experience with their cochlear prostheses. The results of a comprehensive audiologic battery which includes audiovisual and environmental tasks are presented. All implants provide significant improvement in speechreading and sound awareness. The findings to date suggest that there is strong correlation between top-down cognitive processing (as reflected by lip reading skills) and performance with cochlear implants.

Glomus jugulare tumors masquerading as benign intracranial hypertension.

Intracranial hypertension has been reported as a complication of massive glomus jugulare tumors with intracranial extension. We describe a patient with papilledema, failing vision, and a diagnosis of benign intracranial hypertension with bilateral glomus jugulare tumors that went undetected for 2 years. There was no evidence of intracranial invasion by the tumors to explain the elevation of intracranial pressure. Embolization followed by surgical removal of the left tumor resulted in stabilization of the neurologic condition and preservation of the lower cranial nerves, including intact hearing. The likely mechanism of intracranial hypertension in this case is an impairment of cerebrospinal fluid absorption. This unusual presentation should be recognized to avoid delayed diagnosis and treatment. Furthermore, intracranial hypertension is not always associated with massive intracranial tumor involvement, as had been previously proposed.

Cerebellopontine angle tumor composed of Schwann and meningeal proliferations.

Tumors found in the cerebellopontine angle are predominantly vestibular schwannomas. Mixed tumors found within the cerebellopontine angle are thought to be exceedingly rare and exclusively associated with neurofibromatosis 2. We report a case of a mixed tumor composed of Schwann and meningeal cell proliferations in a patient who was not diagnosed as having neurofibromatosis 2. Mixed tumors composed of neoplastic Schwann and meningeal cells have rarely been reported. However, new evidence indicates that these mixed tumors may be more common than was previously thought and may have an interrelated mechanism of pathogenesis. Although the case we describe does not fulfill the current diagnostic criteria for neurofibromatosis 2, a presumptive diagnosis was given, suggesting that the current diagnostic criteria for neurofibromatosis 2 may be too narrow.

Vestibular schwannoma presenting with sudden facial paralysis.

Facial paralysis is an unusual manifestation of vestibular schwannoma, and generally signifies an advanced stage of tumor growth. We describe a case of eighth-nerve schwannoma that presented initially with rapid-onset complete unilateral facial paralysis. At the time of operation the nerve was found to be electrically intact despite marked compression by tumor. The facial nerve was preserved and facial motion has partially recovered postoperatively. All unexplained persistent facial paralysis should be evaluated by magnetic resonance imaging with paramagnetic contrast enhancement.

Relationships among loudness indexes in cochlear-implant patients.

The purpose of the experiment was to determine if the most-confortable-listening (MCL) levels and loudness-discomfort levels (LDLs) can be predicted from threshold measurements obtained from patients with cochlear implants using direct electrical stimulation. Psychophysical measurements of thresholds, MCLs, and LDLs with 125-Hz and 2000-Hz sinusoids were obtained from 16 patients with cochlear-implants 1 month after the connection of their ineraid processor (an auditory prosthesis). In general, the correlation coefficients among the loudness indexes obtained with a 125-Hz stimulus were similar to those for a 2000-Hz stimulus. Correlations between thresholds and MCLs were moderate, whereas correlations for thresholds and LDLs were fair. Correlations between MCLs and LDLs were high. This suggests that LDLs cannot be predicted from thresholds. On the other hand, these preliminary data suggest that MCLs may be reliably predicted from thresholds or LDLs to set the gain on a cochlear-implant processor.

Undifferentiated small-cell neoplasm of the petrous apex. A case report.

We present a rare case of undifferentiated small-cell neoplasm involving the temporal bone petrous apex. The symptoms, physical examination, importance of roentgenographic findings, and pathologic findings are reviewed. While not absolutely conclusive, the collective evidence in this case supports a diagnosis of small-cell carcinoma of the lung with metastasis to the petrous apex. A discussion of temporal bone malignancies, their frequencies, and characteristics is included. To our knowledge, a review of the literature over the past 25 years reveals no other published cases of an undifferentiated small-cell carcinoma in the temporal bone.