Biomedical subjects

Steven Y Ho

Publications and source records attributed to Steven Y Ho.

6 recordsLinked to original sources

PubMed2004

Modifying cochlear implant design: advantages of placing a return electrode in the modiolus.

HYPOTHESIS: A modiolar return electrode significantly increases the current flow across spiral ganglion cells into the modiolus, and may decrease the cochlear implant's power requirements. BACKGROUND: Ideal cochlear implants should maximize current flow into the modiolus to stimulate auditory neurons. Previous efforts to facilitate current flow through the modiolus included the fabrication and use of precurved electrodes designed to "hug" the modiolus and silastic positioners designed to place the electrodes closer to the modiolus. In contrast to earlier efforts, this study explores the effects of return electrode placement on current distributions in the modiolus. METHODS: The effects of return electrode positioning on current flow in the modiolus were studied in a Plexiglas model of the cochlea. Results of model measurements were confirmed by measurements in the modiolus of human temporal bones. The return electrode was placed either within the modiolus, or remotely, outside the temporal bone, simulating contemporary cochlear implant configurations using monopolar stimulation. RESULTS: Cochlear model results clearly show that modiolar current amplitudes can be influenced significantly by the location of the return electrode, being larger when placed into the modiolus. Temporal bone data show similar findings. Voltages recorded in the modiolus are, on average, 2.8 times higher with the return electrode in the modiolus compared with return electrode locations outside the temporal bone. CONCLUSION: Placing a cochlear implant's return electrode in the modiolus should significantly reduce its power consumption. Reducing power requirements should lead to improved efficiency, safer long-term use, and longer device life.

Cochlea↗

PubMed2003

Efficacy of the 2-staged procedure in the management of cholesteatoma.

OBJECTIVE: To demonstrate the efficacy of intact canal wall procedure coupled with a second-stage exploration for the treatment of cholesteatoma. DESIGN: Retrospective case study of patients with cholesteatomas treated with staged surgical extirpation. A minimum of 6 months' postoperative follow-up time was required for inclusion into the study. SETTING: Tertiary academic referral center. Patients A total of 35 adult and pediatric patients, ranging from 9 to 65 years of age, who underwent 2-stage procedures for removal of cholesteatomas. INTERVENTIONS: Two-stage procedures, separated by 6 months, performed with posterior tympanotomy approaches. MAIN OUTCOME MEASURES: The presence or absence of cholesteatoma on second-stage look and the subsequent surgical treatment for recurrent cholesteatoma. The overall hearing results after the completion of the 2-staged procedure were calculated. RESULTS: Disease was controlled in 26 (74%) of the patients. Residual and/or recurrent cholesteatomas were found in 9 (26%) of the patients during the second-stage operation. Of these patients, 5 (14% of the total group) ultimately required conversion to canal-wall-down procedure. Average hearing gain at the completion of the second-stage procedure was 9 dB. CONCLUSIONS: A planned 2-stage procedure that uses the posterior tympanotomy approach for the control of cholesteatoma is an effective technique. This approach offers significant potential for hearing preservation and restoration.

Adolescent↗

PubMed2003

Comparison of postoperative facial nerve outcomes between translabyrinthine and retrosigmoid approaches in matched-pair patients.

OBJECTIVES/HYPOTHESIS: The objective was to assess whether the translabyrinthine approach for acoustic tumor removal offers better postoperative facial nerve function compared with the retrosigmoid approach. STUDY DESIGN: Retrospective case review from a tertiary otology referral center. METHODS: Patients who had undergone either retrosigmoid or translabyrinthine approach for removal of acoustic neuroma from January 1, 1980, to December 31, 1999, were included in the study. Two groups of patients were created, one containing retrosigmoid cases and the other, translabyrinthine. Attempts were made to match each retrosigmoid case to a translabyrinthine case with regard to tumor size, patient age, and date of operation. This matching served to eliminate these variables from influencing postoperative facial nerve outcomes. From an initial pool of 450 patients, 35 pairs of patients were matched for the study. Facial nerve functions were reported at immediate, 3-month, and 1-year postoperative periods. RESULTS: Patient demographics demonstrated that matched patients had almost identical tumor size, patient age, and date of operation. Comparisons of postoperative facial nerve functions between the matched groups revealed that retrosigmoid approach carried 2.86 times higher risk of facial nerve dysfunction during the immediate postoperative period. However, by 1 year, the facial nerve outcomes were similar between the two groups. CONCLUSION: Compared with the translabyrinthine approach, retrosigmoid approach carries a higher risk of postoperative facial nerve dysfunction during the immediate postoperative period. However, long-term facial nerve outcomes are identical between the two approaches.

Adult↗

PubMed2003

Early results with titanium ossicular implants.

OBJECTIVE: To report the efficacy of titanium middle ear prosthesis for ossicular reconstruction. STUDY DESIGN: Retrospective chart reviews were performed for 25 patients who had undergone titanium ossicular implants between January 1, 1999, and June 1, 20001. SETTING: Tertiary otology referral center. PATIENTS: All patients had a minimum of 6 months of postoperative follow-up and no evidence of recurrent otologic disease. INTERVENTION: All patients had undergone ossiculoplasty using titanium middle ear implants. MAIN OUTCOME MEASURES: Comparisons of preoperative and postoperative pure tone averages were performed. Air-bone gap closures and implant extrusion rates were measured. RESULTS Overall mean pure tone averages improved 22.2 dB with air-bone gap improvement at 20.9 dB. Fifty-six percent of patients achieved air-bone gap less than 20 dB postoperatively. The overall extrusion rate was 4%. However, with the placement of cartilage graft interposed between the prosthesis and the tympanic membrane, no extrusion was observed. CONCLUSION: Titanium implants provide comparable hearing improvement compared with other materials. The extrusion rate seems quite low if cartilage interposition graft is inserted. Its ease of handling, biocompatible properties, and sound conducting properties improve its efficacy as an ossicular implant.

Adolescent↗

PubMed2002

Acoustic neuroma. Assessment and management.

Acoustic neuroma results from abnormal proliferation of Schwann cells. These tumors originate in the region of Scarpa's ganglion at the junction of peripheral and central myelin of the vestibular nerve located in the internal auditory canal (IAC). The bony confine of the IAC houses the VII and the VIII cranial nerves. The presence of tumor mass compresses these structures. The growing tumor mass may also prolapses into the cerebellopontine angle (CPA). With continued growth, the tumor eventually compresses on the brain stem and cerebellum. Despite the benign nature of these tumors, the clinical course of this disease may be fraught with complications.

Facial Nerve↗

PubMed2002

Rapid growth of acoustic neuromas after stereotactic radiotherapy in type 2 neurofibromatosis.

We describe a rare complication of stereotactic radiotherapy for large acoustic neuromas in a patient with type 2 neurofibromatosis. We retrospectively reviewed the case of a 14-year-old girl who had been referred to our tertiary care center. Prior to referral, the patient had been evaluated for hoarseness. During the work-up, magnetic resonance imaging (MRI) detected two large bilateral acoustic neuromas and two bilateral jugular foramen tumors. The patient was diagnosed with type 2 neurofibromatosis, and she underwent stereotactic radiotherapy for treatment of the two acoustic neuromas; the jugular foramen tumors were not irradiated. The patient's post-treatment course was complicated by hydrocephalus and symptoms of brainstem compression, which required urgent surgical intervention. Follow-up MRI 7 months following radiotherapy demonstrated a rapid growth of the acoustic neuromas, but no appreciable change in the size of the jugular foramen neuromas. These findings suggest that the radiotherapy might have been the cause of the rapid growth of the acoustic neuromas. To our knowledge, no such report has been published in the literature, and this phenomenon might be unique. Our findings suggest that radiotherapy might not be the optimal first-line treatment for acoustic neuromas in patients with type 2 neurofibromatosis.

Adolescent↗