Brandon Isaacson

Cochlear implant electrode insertion: the round window revisited.

Objective: To examine aspects of round window (RW) anatomy that are relevant to its use as a portal for atraumatic insertion of cochlear implant electrodes.

A Dominantly Inherited Progressive Deafness Affecting Distal Auditory Nerve and Hair Cells

We have studied 72 members belonging to a large kindred with a hearing disorder inherited in an autosomal dominant pattern. We used audiological, physiological, and psychoacoustic measures to characterize the hearing disorders. The initial phenotypic features of the hearing loss are of an auditory neuropathy (AN) with abnormal auditory nerve and brainstem responses (ABRs) and normal outer hair cell functions [otoacoustic emissions (OAEs) and cochlear microphonics (CMs)]. Psychoacoustic studies revealed profound abnormalities of auditory temporal processes (gap detection, amplitude modulation detection, speech discrimination) and frequency processes (difference limens) beyond that seen in hearing impairment accompanying cochlear sensory disorders. The hearing loss progresses over 10–20 years to also involve outer hair cells, producing a profound sensorineural hearing loss with absent ABRs and OAEs. Affected family members do not have evidence of other cranial or peripheral neuropathies. There was a marked improvement of auditory functions in three affected family members studied after cochlear implantation with return of electrically evoked auditory brainstem responses (EABRs), auditory temporal processes, and speech recognition. These findings are compatible with a distal auditory nerve disorder affecting one or all of the components in the auditory periphery including terminal auditory nerve dendrites, inner hair cells, and the synapses between inner hair cells and auditory nerve. There is relative sparing of auditory ganglion cells and their axons.

Management of spontaneous cerebrospinal fluid otorrhea.

Objectives/Hypothesis: To describe the surgical approaches and materials used to repair spontaneous cerebrospinal fluid (CSF) otorrhea of temporal bone origin.

A gene responsible for autosomal dominant auditory neuropathy (AUNA1) maps to 13q14–21

Hearing loss is most commonly defined as either conductive, affecting the sound conduction mechanism comprised of the external auditory canal, tympanic membrane, and middle ear ossicles, or sensorineural (SNHL), affecting the cochlea, the auditory nerve, or the central auditory pathway. However, the recent discovery that outer hair cells (OHC) generate otoacoustic emissions (OAEs) has allowed differentiation of sensory hearing loss (in which OAEs are absent) from neural hearing loss, which is caused by a lesion of inner hair cells and/or the auditory nerve. The hallmark of auditory neuropathy (AN), a neural type of hearing loss, is preservation of OAEs and abnormal or absent auditory brainstem responses.1 Most patients with SNHL are found to have a sensory type of hearing loss, and numerous genes for both syndromic and non-syndromic forms have been identified (Hereditary Hearing Loss Homepage, http://www.uia.ac.be/dnalab/hhh/). However, none of the approximately 50 dominant (DFNA) loci are known to represent an auditory neuropathy phenotype. AN may accompany peripheral neuropathy in a variety of dominant syndromes such as Charcot-Marie-Tooth disease2 and Freidreich’s ataxia.3 AN unassociated with peripheral neuropathy most commonly occurs as a sporadic or recessive trait,4–6 but X linked recessive6 and autosomal dominant7 forms have also been described. We have mapped a gene responsible for autosomal dominant auditory neuropathy in a multigenerational family from the United States to a novel locus, AUNA1 (auditory neuropathy, dominant, 1) on 13q14–21. The family is of European descent and was ascertained through two different probands by both the University of Michigan and the University of California at Irvine. The Institutional Review Boards of the University of Michigan Medical School, Louisiana State University Health Sciences Center, and the University of California at Irvine approved the study, and informed consent was obtained from all subjects. Four generations were available …

Cochlear implantation in children with enlarged vestibular aqueduct

To determine audiometric outcomes and complications of cochlear implantation in patients with enlarged vestibular aqueduct (EVA).

Cochlear Implantation in Children With Cochlear Nerve Absence or Deficiency

Objective: To evaluate speech perception after cochlear implantation in children with cochlear nerve absence or deficiency. Methods: A retrospective case review was performed to identify children who underwent cochlear implantation with cochlear nerve absence or deficiency. The cochlear nerve was evaluated by high-resolution three-dimensional T2-weighted fast spin echo MR in the oblique sagittal and axial planes. A deficient cochlear nerve was defined as a cochlear nerve that is smaller in diameter when compared with the adjacent facial nerve in the midportion of the internal auditory canal. The cochlear nerve was considered absent if there was no imaging evidence of a cochlear nerve. Speech awareness threshold and the speech perception category score were used to measure speech perception after cochlear implantation. Results: Seven children who underwent cochlear implantation in an ear without imaging evidence of a cochlear nerve were identified. One child developed early closed-set speech recognition. The other 6 children developed only speech detection or pattern perception. Two children underwent cochlear implantation with a deficient cochlear nerve. One developed consistent closed-set word recognition and the other developed early closed-set word recognition. The mean follow-up time for all patients was 3.8 years (range, 1.1-7.1 yr). Conclusion: Cochlear nerve deficiency is not an uncommon cause for profound sensorineural hearing loss and presents a challenge in the decision-making process regarding whether to proceed with a cochlear implant. Children with a deficient but visible cochlear nerve on magnetic resonance image can expect to show some speech understanding after cochlear implantation; however, these children do not develop speech understanding to the level of implanted children with normal cochlear nerves. Children with an absent cochlear nerve determined by magnetic resonance imaging can be expected to have limited postimplantation sound and speech awareness.

Bell's palsy and pregnancy

Objective To describe the epidemiology, pathophysiology, presentation, treatment, and prognosis of Bells palsy (BP) in pregnancy. RESULTS The incidence of BP in pregnant women is not significantly greater than expected compared to all women of childbearing age. There is a high incidence of cases in the third trimester and corresponding low incidence during early pregnancy. CONCLUSION There is no conclusive evidence that the etiology of BP in pregnancy is different than in nonpregnant patients. Altered susceptibility to herpes simplex viral reactivation during pregnancy is the most likely explanation for concentration of cases in the third trimester. Outcome may be poorer in pregnant patients, though historically, treatment is often withheld from these patients. SIGNIFICANCE Management of BP in pregnancy can mirror that of nonpregnant individuals with the exception of first-trimester cases.

Labyrinthitis ossificans: How accurate is MRI in predicting cochlear obstruction?

Objective: To determine the accuracy of preoperative MRI in predicting cochlear obstruction in pediatric patients with a history of bacterial meningitis. Methods: A case series with chart review was performed at a tertiary care multidisciplinary cochlear implant program. Forty-five children with hearing loss that resulted from bacterial meningitis were implanted from 1991 to 2006. Twenty-five children had preoperative MRI with high-resolution axial T2-weighted images to assess for cochlear patency. Results: Seventeen of 25 patients (68%) had surgical evidence of cochlear obstruction. Six patients (37.5%) required circummodiolar drill-outs, and one patient (6.25%) underwent placement of a double array cochlear implant. The nine remaining patients (56%) with cochlear obstruction required removal of fibrous tissue or drilling of the inferior basal turn, but did not require manipulation of the ascending basal turn to achieve full electrode insertion. The sensitivity, specificity, and positive and negative predictive value of MRI predicting intraoperative cochlear obstruction with 95 percent confidence intervals was 94.1 percent (71–99), 87.5 percent (47–99), 94.1 percent (71–99) and 87.5 percent (47–99), respectively. Conclusion: Preoperative high-resolution T2 MRI may be useful in predicting cochlear obstruction in patients with a prior history of bacterial meningitis.

Intraoperative monitoring and facial nerve outcomes after vestibular schwannoma resection.

Objective To determine the predictive value of proximal facial nerve electrical threshold and proximal-to-distal facial muscle compound action potential amplitude ratio on facial nerve outcomes after resection of vestibular schwannomas. Study Design Retrospective case review. Setting Tertiary care hospital. Patients Two hundred twenty-nine patients undergoing resection of vestibular schwannomas with intraoperative facial nerve monitoring at a single institution. Intervention All patients underwent resection of vestibular schwannomas with the use of intraoperative monitoring. Main Outcome Measure Facial nerve function was classified according to the House-Brackmann scale at the patients last office follow-up. Last follow-up was at least 6 months after surgery. Results Good facial nerve function (House-Brackmann Grade I or II) was observed in 87% of the patients at their last office follow-up. Proximal-to-distal amplitude ratio and proximal electric threshold were statistically significant in predicting facial nerve outcome. A mathematical model predicting the probability of good outcome on the basis of the intraoperative parameters is presented. Conclusion Intraoperative monitoring has significantly decreased facial nerve morbidity in vestibular schwannoma surgery. Despite the advances in surgery and monitoring, a group of patients still have poor facial nerve outcomes. The use of intraoperative nerve monitoring may be able to predict poor long-term facial nerve outcomes and thus modify the timing of rehabilitation.

Prediction of long-term facial nerve outcomes with intraoperative nerve monitoring.

Objective: Evaluate the utility of a statistical equation using two independent intraoperative monitoring parameters in predicting long-term facial nerve function. Study Design: Retrospective case review. Setting: Tertiary care hospital. Patients: Sixty patients undergoing resection of vestibular schwannomas with intraoperative facial nerve monitoring at a single institution. Intervention: All patients underwent microsurgical resection of vestibular schwannomas with the use of intraoperative cranial nerve monitoring. Main Outcome Measure: Final facial nerve outcome measured using the House-Brackmann scale at least 6 months after microsurgical resection. Results: Five out of 60 (8.3%) patients demonstrated significant long-term weakness (i.e., House-Brackmann grade III or worse). Intraoperative monitoring parameters (proximal stimulation threshold, proximal-to-distal response amplitude ratio) were accurate in predicting increased risk of long-term facial nerve dysfunction when used in a logistic regression model. A Students t test confirmed the equation result was statistically significant in differentiating long-term facial nerve outcomes. Conclusion: Patients with immediate weakness are at higher risk of having long-term poor facial nerve function. The use of intraoperative monitoring parameters was reliable in predicting facial nerve outcomes. Patients with permanent facial nerve dysfunction often require rehabilitative procedures. The ability to predict facial nerve outcomes with intraoperative monitoring may allow early rehabilitative procedures to improve quality of life and prevent ocular complications.