Faculty Bibliography

OBJECTIVES: To date, numerous studies have compared functional outcomes between stereotactic radiosurgery (SRS) and microsurgery (MS) in the treatment of vestibular schwannomas (VS). However, most of them involve tumors of difference sizes, radiation dosages, and surgical approaches. Few have systematically compared issues of dysequilibrium. By studying only patients with small tumors and no hearing, we sought to minimize confounding variables. STUDY DESIGN: A retrospective chart review and telephone questionnaire. METHODS: From 1998-2006, 31 patients with small (<1.5 cm) VS and nonserviceable hearing (American Academy of Otolaryngology-Head and Neck Surgery [AAO-HNS] Class C or D) were treated at our institution. Twenty-two were available for follow-up and telephone questionnaire, including the University of California Los Angeles Dizziness Questionnaire (UCLA-DQ). Twelve underwent SRS and 10 underwent MS. All MS patients underwent the translabyrinthine approach to their tumors. Outcomes measurements included tumor control, facial nerve function, tinnitus, trigeminal function, and imbalance. RESULTS: Patients undergoing SRS had comparable rates of tumor control, facial nerve function, tinnitus, and trigeminal function to MS patients. However, SRS did result in statistically significantly worse long-term imbalance when compared with MS patients. Detailed comparisons of the two modalities are made. CONCLUSIONS: In our study population, patients with small tumors and no serviceable hearing, these data suggest that MS results in comparable minimal morbidity with SRS, though posttreatment dysequilibrium is significantly decreased. While the authors recommend translabyrinthine resection of small VS with no hearing in patients able to tolerate surgery, the need for further prospective investigation is clear

OBJECTIVE AND IMPORTANCE: In rare cases, posterior fossa meningiomas can involve the endolymphatic sac. Such involvement can result in endolymphatic hydrops and a constellation of symptoms suggestive of Meniere's disease. The diagnosis and management of patients with these tumors is discussed. CLINICAL PRESENTATION: Three patients, each of whom presented with symptoms consistent with Meniere's disease, were found to have posterior fossa meningiomas limited to the dura overlying the endolymphatic sac. INTERVENTION: All 3 patients were diagnosed by magnetic resonance imaging and underwent complete surgical resection. In all cases, the symptoms resolved after tumor removal. CONCLUSION: Clinicians should have a degree of suspicion of posterior fossa meningioma when patients present with symptoms suggestive of Meniere's disease. Failure to do so may result in delayed diagnosis or worse outcomes for an otherwise treatable tumor

OBJECTIVE: To review our experience with partial standard and double-array cochlear implantation in the ossified cochlea. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Twenty cochleae in 19 adult and pediatric patients with ossified cochleae. INTERVENTION(S): Patients underwent either partial insertion of a standard electrode array or double-array electrode insertion for their cochlear implantation. MAIN OUTCOME MEASURE(S): Number of electrodes inserted, number of active electrodes at follow-up, and open-set speech performance. RESULTS: Twelve patients (four children and eight adults) had partial insertion of standard array electrode. The mean number of electrodes inserted and active at follow-up was 14.8 and 11.3, respectively. Eight patients (four children and four adults) had a double-array electrode implanted. The mean number of electrodes inserted and active at follow-up was 18.1 and 16.3, respectively. Open-set speech recognition was better in children regardless of duration of deafness. There were no complications. CONCLUSION: These findings suggest that the double array allows for more usable electrodes than in partially inserted cochlear implant. Compared with adults, children with ossified cochlea do well both in partial standard and double-array insertion. Both insertion techniques are safe, with no complications occurring in our patients. Straight and double arrays should be available in the operating suite for any patient in whom suspected cochlear ossification is confronted

OBJECTIVE: To describe a safe and effective technique for the implantation of common cavity cochleae. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Fifteen cochleae in 9 adults and children with common cavity deformities implanted with and without the use of intraoperative fluoroscopy. INTERVENTION(S):: Fluoroscopically assisted cochlear implantation. MAIN OUTCOME MEASURE(S): Rates of extracochlear placement, bending, kinking, intrameatal placement, and complications were analyzed. Numbers of electrodes inserted, number of active electrodes, and speech performance were compared between the 2 groups. RESULTS: Half of the nonfluoroscopy group had suboptimal placement of their electrode arrays. This group also had a higher rate of complications, lower numbers of electrodes implanted, and lower number of active electrodes at follow-up. Results of speech perception testing suggest that fluoroscopically assisted implantation of the common cavity results in improved performance. CONCLUSION: Intraoperative fluoroscopy is an easy, safe, and effective technique that results in improved outcomes for cochlear implant patients with common cavity deformities

OBJECTIVES: Intraoperative testing of cochlear implant devices, establishment of electrical threshold for acoustic reflex, and recording neural responses to electrical stimulation have traditionally required the presence of a cochlear implant audiologist in the operating room. The goal of this study was to determine the feasibility of remote testing to improve time efficiency and reduce cost. STUDY DESIGN: Prospective. METHODS: A standard PC with Tridia VNC software and either Cochlear Corporation or Advanced Bionics Corporation mapping software was configured to perform remote testing. The time required to perform on-site or remote testing was measured. RESULTS: With the availability of the laptop and internet access, there were no geographic restrictions regarding the site of remote testing. Remote testing was time efficient, requiring 9 minutes of audiologist's time compared with 93 minutes when the audiologist had to travel to the operating room. CONCLUSION: Remote testing of the cochlear implant device and patient's response to electrical stimulation is technically feasible. It is timesaving, practical, and cost efficient

This article describes results on using steered molecular dynamics (SMD) simulations and experimental single molecule force spectroscopy (SMFS) to investigate the relationship between hydrogen bonding and mechanical stability of a series of homodimeric beta-sheet mimics. The dimers consisting of 4, 6, and 8 H-bonding sites were modeled in explicit chloroform solvent and the rupture force was studied using constant velocity SMD. The role of solvent structuring on the conformation of the dimers was analyzed and showed no significant contribution of chloroform molecules in the rupture event. The simulated stability of the dimers was validated by force data obtained with atomic force microscopy (AFM)-based SMFS in toluene. The computational model for the 8H dimer also offered insight into a possible mismatched dimer intermediate that may contribute to the lower than expected mechanical stability observed by single molecule AFM force studies. In addition, atomic level analysis of the rupture mechanism verified the dependence of mechanical strength on pulling trajectory due to the directional nature of chemical bonding under an applied force. The knowledge gained from this basic study will be used to guide further design of modular polymers having folded nanostructures through strategic programming of weak, non-covalent interactions into polymer backbones

In previous works, the authors showed that using robot-assisted steerable electrode array insertions can significantly reduce the insertion forces compared to non-steerable electrode arrays. In addition to steering the electrode array, it is possible to change its angle of approach with respect to the scala tympani. This paper focuses on determining the relevance of changing the angle of approach of the electrode array by comparing steerable electrode array insertions using a two Degrees-of-Freedom (DoF) robot versus a four DoF robot. Optimal insertion path planning strategies are presented for both two and four DoF insertions. Simulation results and experiments show that the four DoF insertions can improve over two DoF insertions. Moreover, changing the angle of approach can further reduce the insertion forces. The simulation results also provide the workspace requirements for designing a custom parallel robot for robot-assisted cochlear implant surgery