Phillip Ashley Wackym

Objective: Preliminary studies show that bilateral cochlear implantation improves speech-recognition ability in many subjects; however, the magnitude of this improvement has been variable. The objective of our research was to explore means to better differentiate the binaural benefit that many patients who receive bilateral cochlear implants (CIs) describe. Hypothesis: Binaural improvements in speech-perception performance will be consistently evident across patients when they are tested in more challenging listening situations. Design: This was a prospective clinical study. Speech-perception performance was compared between the unilateral and bilateral cochlear implant conditions. Because the purpose was to investigate testing parameters that would demonstrate binaural benefit, word- and sentence-recognition tests were administered under several stimulation conditions: with and without noise and at three presentation levels. In addition, all subjects completed the Abbreviated Profile of Hearing Aid Benefit as a measure of subjective benefit. Subjects were adult cochlear implant recipients. Three device manufacturers were represented (Advanced Bionics Corporation, Cochlear Americas, and the Med-El Corporation); three patients received simultaneous implantation, and the other four patients received sequential CIs. The setting was a comprehensive cochlear implant program/tertiary referral center. The main outcomes measures were speech-recognition scores in percent correct, mean score difference for unilateral versus bilateral conditions, and subjective benefit scores. Results: The most significant improvements in binaural cochlear implant use were found when subjects were tested with sentence material presented at 60 dB SPL with a +8 dB signal-to-noise ratio. Six of seven subjects showed significant binaural improvement, with a mean improvement score of 12.43% (SD = 5.32). All subjects preferred the binaural listening condition. Measured improvements in quality of life were seen. Conclusions: Preliminary study findings suggest that significant cochlear implant binaural benefit in speech perception may be observed when testing in more difficult listening situations (i.e., lower presentation levels and in noise). According to the outcome of our study, testing the binaural benefit of CIs requires consideration of suitable test materials and stimulation parameters.

The inserts from 2400 cDNA clones isolated from a normalized Rattus norvegicus vestibular periphery cDNA library were sequenced and characterized. The Wackym-Soares vestibular 3′ cDNA library was constructed from the saccular and utricular maculae, the ampullae of all three semicircular canals and Scarpa’s ganglia containing the somata of the primary afferent neurons, microdissected from 104 male and female rats. The inserts from 2400 randomly selected clones were sequenced from the 5′ end. Each sequence was analyzed using the BLAST algorithm compared to the Genbank nonredundant, rat genome, mouse genome and human genome databases to search for high homology alignments. Of the initial 2400 clones, 315 (13%) were found to be of poor quality and did not yield useful information, and therefore were eliminated from the analysis. Of the remaining 2085 sequences, 918 (44%) were found to represent 758 unique genes having useful annotations that were identified in databases within the public domain or in the published literature; these sequences were designated as known characterized sequences. 1141 sequences (55%) aligned with 1011 unique sequences had no useful annotations and were designated as known but uncharacterized sequences. Of the remaining 26 sequences (1%), 24 aligned with rat genomic sequences, but none matched previously described rat expressed sequence tags or mRNAs. No significant alignment to the rat or human genomic sequences could be found for the remaining 2 sequences. Of the 2085 sequences analyzed, 86% were singletons. The known, characterized sequences were analyzed with the FatiGO online data-mining tool (http://fatigo.bioinfo.cnio.es/) to identify level 5 biological process gene ontology (GO) terms for each alignment and to group alignments with similar or identical GO terms. Numerous genes were identified that have not been previously shown to be expressed in the vestibular system. Further characterization of the novel cDNA sequences may lead to the identification of genes with vestibular-specific functions. Continued analysis of the rat vestibular periphery transcriptome should provide new insights into vestibular function and generate new hypotheses. Physiological studies are necessary to further elucidate the roles of the identified genes and novel sequences in vestibular function.

Guanine nucleotide binding proteins (G-proteins) play an important role in mediating signals transduced across the cell membrane by membrane-bound receptors. The precise role of these proteins and their coupled receptors in the physiology of the vestibular neuroepithelium is poorly understood. Although Golfalpha was originally discovered in the olfactory neuroepithelium and striatum, we recently identified this G-protein alpha subunit in a normalized cDNA library constructed from rat vestibular end organs and vestibular nerves including Scarpa's ganglia. In order to further characterize Golfalpha in the rat vestibular periphery, we used in situ hybridization and reverse transcription polymerase chain reaction to determine the anatomic context of this gene expression. Golfalpha was found in both the end organs and the ganglia and could serve unique roles in the physiology of the vestibular neuroepithelium.

Hypothesis: Monopolar electrosurgery below the neck in cochlear implant recipients can be performed without damage to the internal cochlear stimulator, electrode array, and the cochlear nerve.Study Design: Prospective pre‐ and postintervention electrically evoked compound action potential (ECAP) study of cochlear nerve function and behavioral sound perception assessment.Methods: Neural response telemetry (NRT) was used to measure ECAPs before and after the use of monopolar electrosurgery during coronary artery bypass surgery to assess prosthetic device function and electrophysiologic function of the cochlear nerve. In addition, electrode voltage impedances and behavioral sound perception was measured at the same time intervals.Results: ECAPs, behavioral sound perception, and electrode voltage impedances were within the normal range, within compliance, and similar preoperatively and on postoperative day 6.Conclusion: The studies reported herein were a series of measurements designed to test neural integrity and prosthetic device function before and after the use of monopolar electrosurgery. With appropriate precautions, use of monopolar electrosurgery below the neck in cochlear implant recipients can be performed safely.

To assess early outcomes after Gamma knife radiosurgery of acoustic neuromas and other skull base tumors. Gamma knife radiosurgery is one of the available methods to treat acoustic neuromas, in addition to micro-surgical resection. Neurootologists have long been associated with microsurgical resection of these tumors; however, the application of Gamma knife radiosurgery to the treatment of these tumors by neurootologists has not been previously described. Acoustic Neuroma and Skull Base Surgery Program / Tertiary Referral Center. Prospective clinical study of all patients treated by the senior author and our gamma knife team beginning in June 2000. Preoperative MRI, audiometry, vestibular testing and facial nerve electromyography were completed. At six-month intervals postoperatively, audiometry, caloric testing and MRI were performed to determine thresholds and speech discrimination ability, vestibular function, and the size of the tumor. From June 2000 until March 2004, 38 patients were treated, and these included 33 acoustic neuromas, two meningiomas, one glomus jugulare tumor, and two facial neuromas. Greater than 36 month follow-up was available in 7 patients, > 24 months in 24, > 12 months in 31, and > 6 months in 34 patients. Statistically significant reduction in tumor size was seen over time, and tumor control was achieved in all but two patients. Various patterns of changes in auditory function, both in threshold and speech discrimination were observed in either positive or negative directions. Preliminary experience with Gamma knife radiosurgery indicates that this treatment method represents another option for neurootologists to use in managing patients with skull base tumors.

Objectives/Hypothesis Mutations in the connexin 26 (Cx26) or gap junction beta 2 gene are the leading cause of hereditary nonsyndromic sensorineural hearing loss in Caucasians. The Cx26 coding region of 68 children with nonsyndromic sensorineural hearing loss was sequenced to determine the frequency and type of Cx26 mutations in this population. Screening was also performed for a common connexin 30 (Cx30) or gap junction beta 6 mutation (del [GJB6‐D13S1830]). Children also underwent audiological testing to determine whether any correlation exists between Cx26 mutations and severity of hearing loss.Study Design In all, 68 children with nonsyndromic sensorineural hearing loss were screened for Cx26 and Cx30 mutations by polymerase chain reaction and direct sequencing.Methods Genomic DNA was amplified by polymerase chain reaction using primers that flank the entire Cx26 coding region. Screening for the 342‐kb Cx30 deletion was performed using primers that amplified the breakpoint junction of the deletion. The amplicons were then sequenced in both directions and analyzed for mutations. Audiometric testing, including pure‐tone audiometry and auditory evoked brainstem response, was also performed to determine the degree of hearing loss.Results Twenty‐seven of 68 children tested had mutations in Cx26 with 35delG being the most prevalent. Ten additional Cx26 mutations were detected including a novel compound heterozygote. Two children were heterozygous for the Cx30 del (GJB6‐D13S1830) mutation.Conclusion Cx26 and Cx30 mutations were present in 41.2% of children tested in the study population. Audiometric data supported previous studies demonstrating a greater degree of hearing loss in subjects who are homozygous for the 35delG mutation.