Katrina R. Stidham

Cochleostomy site: Implications for electrode placement and hearing preservation

Conclusions. With recent increased interest in minimizing intracochlear trauma and preserving residual hearing during cochlear implantation, increased attention must be paid to the cochleostomy site. The results of this paper demonstrate that the cochleostomy must be made inferior, rather than anterior, to the round window to ensure scala tympani insertion and to decrease the likelihood of insertion-induced intracochlear damage during electrode insertion. Objective. To describe the complex anatomy of the hook region of the cochlea, specifically in relation to the optimal placement of the cochleostomy for cochlear implant electrode insertion to potentially achieve hearing preservation. The authors believe that previous industry recommendations and described surgical techniques have resulted in cochleostomies being placed in anatomical positions that possibly result in electrode insertions that damage the basilar membrane and/or other cochlear structures. Material and methods. The results of a number of temporal bone studies were reviewed with attention being paid to the anatomical relationship of the basilar membrane and spiral ligament to the round window membrane. For different cochleostomy sites the potential for damage to intracochlear structures, particularly the basilar membrane and organ of Corti, was assessed. Results. The review of electrode insertion studies into human temporal bones, as well as a post-mortem anatomical study of implanted temporal bones, showed an increased risk of scala vestibuli insertions and insertion-induced damage to intracochlear structures when the cochleostomy was performed more anterior to the round window. These results were endorsed by studies detailing the anatomy of the hook region of the cochlea.

Mastoid obliteration: autogenous cranial bone pAte reconstruction.

Objective To review the outcome in consecutive patients who have undergone complete epitympanic and mastoid obliteration and concurrent tympanic membrane reconstruction over a 53-month period. Study Design Retrospective review. Setting Tertiary referral center. Patients Sixty-two ears in 56 sequential patients undergoing mastoid obliteration with major indications including recurrent infection, debris trapping in the canal wall-down cavity, intolerance of water exposure, calorically induced vertigo in an existing cavity, a semicircular canal fistula, and inability to wear a hearing device. Thirty-six ears in 33 patients who underwent second-stage surgery for ossicular reconstruction during the same time period are also reviewed. Intervention Transplanted autogenous cranial bone is used to induce osteoneogenesis resulting in complete obliteration of the epitympanic and mastoid spaces while maintaining a mesotympanic space. Main Outcome Measures Success of obliteration, incidence of symptoms prompting intervention, hearing outcome, incidence of recurrent cholesteatoma, and incidence of eustachian tube dysfunction necessitating treatment and need for revision surgical procedures. Results Complete take of the bony obliteration occurs in over 95% of cases; 90% of treated patients enjoy complete absence of original symptoms, whereas symptoms improved in the remainder. For over 95% of patients, existing eustachian tube function has been adequate after obliteration. To date, no patient has required revision surgical intervention. Conclusion Mastoid obliteration with autogenous cranial bone is a safe and extremely effective option for treatment of problematic canal wall-down mastoid cavities. Surgical techniques that include sterile harvest of the cranial bone graft mixed with antibiotic, revision of the cavity to expose viable native bone, inclusion of the epitympanic spaces in the obliteration, and complete coverage of the pÂte with autogenous fascia have proven critical to successful outcome.

Silicone allergy: A new cause for cochlear implant extrusion and its management.

Objective: We introduce silicone allergy as a rare cause for cochlear implant extrusion and discuss its management. Study Design: Retrospective case series and literature review. Setting: Tertiary referral centers. Patients: Primary eligibility criteria included patients who experienced a delayed extrusion of their cochlear implants with negative wound cultures and had a suspected or a test-proven allergy to silicone components of an implant. Interventions: Silicone allergy testing, explantation of a cochlear implant containing allergenic silicone materials, reimplantation with a custom-made cochlear implant excluding an allergenic silicone component. Outcome Measures: Uneventful wound healing and extrusion-free long-term follow-up after the reimplantation with a custom-made cochlear implant excluding an allergenic silicone component. Results: Three known cases of cochlear implant extrusion as a result of silicone allergy have been noted from 1991 through 2004 in three cochlear implant programs in the United States. All three devices extruded, resulting in explantation of the old device and reimplantation with a new custom-made device eliminating the allergenic silicone component. Wound cultures were negative in all cases. All three patients experienced a delayed extrusion of their devices. Two of these patients had a test-proven allergy to the implants silicone components, whereas the third patient was presumed to have a hypersensitivity solely on the basis of a clinical presentation. Conclusion: We propose that silicone allergy is a rare cause of cochlear implant extrusion. Patients experiencing cochlear implant extrusion, particularly with a delayed onset and negative wound culture results, should be tested for silicone allergy.

Evaluation of botulinum toxin A in treatment of tinnitus

OBJECTIVES: The purpose of this study was to evaluate the potential benefit of botulinum toxin A in treatment of tinnitus with a prospective, double-blinded study design. STUDY DESIGN : Double-blinded, prospective clinical study. METHODS : Thirty patients with tinnitus were randomly placed into 1 of 2 treatment arms. Patients either received botulinum toxin A (20 to 50 units) or saline injection at the first treatment, and the opposite treatment 4 months later. Prospective data including tinnitus matching test, tinnitus handicap inventory (THI), tinnitus rating scale (TRS), and patient questionnaires were obtained over a 4-month period after each injection. RESULTS : Twenty-six patients completed both injections and follow-up and were included in data analysis. After botulinum toxin A, subjective tinnitus changes included 7 patients improved, 3 worsened, and 16 unchanged. Following placebo, 2 patients were improved, 7 worsened, and 17 unchanged. Comparison of the treatment and placebo groups was statistically significant (P >0.005) when including better, worse, and same effects. A significant decrease in THI scores between pretreatment and 4 month postbotulinum toxin A injection (P = 0.0422) was recorded. None of the other comparisons of pretreatment to 1 month, or pretreatment to 4 months were significantly different. CONCLUSIONS : This small study found improvement in THI scores and patient subjective results after botulinum toxin A injection compared with placebo, suggesting a possible benefit of botulinum toxin A in tinnitus management. Larger studies need to be completed to further evaluate potential benefits of botulinum toxin A in treatment of this difficult problem.

Auditory steady-state response testing in children: Evaluation of a new technology

OBJECTIVE The purpose of this study was to evaluate auditory steady-state responses (ASSR) for determining frequency-specific hearing impairment and to compare this technology with conventional auditory brainstem responses (ABR). Study design The study was a prospective clinical trial. Twenty-eight pediatric patients ranging in age from 7 to 61 months who were undergoing sedated ABR testing for evaluation of hearing impairment were also evaluated using ASSR. Estimated audiograms of the ASSR are compared with the ABR results. RESULTS ASSR estimated audiograms with frequency-specific information were produced for all patients in whom an ABR recording was obtained. In 20 ears in which an ABR tracing was absent at the maximum level of 90 dB, 13 ears had measurable ASSR thresholds with an average threshold of 98.9 dB at 250 to 8000 Hz. CONCLUSION ASSR showed sensitivity equal to that of ABR for individuals with hearing levels (HL) from 0 to 90 dB HL. In patients with hearing impairment greater than 90 dB normal HL (nHL), ASSR showed distinct advantage over ABR testing in that recordings were reliably produced up to 127 dB nHL.

Hearing improvement after middle fossa resection of vestibular schwannoma.

Objective The preoperative, intraoperative, and postoperative variables of patients experiencing hearing improvement after middle fossa resection of vestibular schwannomas were evaluated as potential prognostic indicators. Study Design Retrospective case review with new objective postoperative data collected on patients with documented hearing improvement. Setting California Ear Institute at Stanford and Stanford University Hospital, a tertiary referral center. Patients The patient group consisted of 30 consecutive patients undergoing middle fossa approach to vestibular schwannoma between October 24, 1994, and November 11, 1998. Intervention Hearing preservation surgery via the middle cranial fossa approach was performed on all patients. Main Outcome Measures Pure-tone averages (PTAs) and speech discrimination scores (SDS) were used to document hearing preoperatively and postoperatively. Preoperative electrophysiologic studies of auditory brainstem response, electronystagmography, electrical neuronography, transient evoked otoacoustic emissions, and distortion product otoacoustic emissions were evaluated. Intraoperative continuous nerve action potential and auditory brainstem response tracings were reviewed. Postoperative auditory brainstem response and transient evoked otoacoustic emissions were obtained when possible on patients whose hearing improved. Statistical analysis was completed using Students t test and chi-square test. Results Seventeen (57%) of 30 patients with tumors ranging from 2 to 31 mm maintained hearing postoperatively. Among patients with hearing preservation, 7 (41% or 23% of the overall group) exhibited hearing improvement (PTA 2 improved by ≥5 dB and/or SDS improved by ≥12%). Three of these 7 patients moved from nonfunctional (AAOHNS class C/D) to functional (AAOHNS class A/B) categories. All patients who enjoyed postoperative hearing improvement had preoperative absence or abnormality of ABRs. No patient with normal preoperative ABR experienced hearing improvement. Hearing improvement patients also had lower preoperative caloric function on electronystagmography compared with the entire group (p < 0.02) and were more likely to have superior vestibular nerve tumors. No differences were noted for electrical neurography and otoacoustic emissions. Conclusions Middle fossa resection of vestibular schwannoma offers patients the possibility of hearing improvement after treatment. The chance of hearing improvement is significantly higher than with other forms of treatment such as radiation therapy or translabyrinthine surgery. Although preoperative ABR abnormality may be an indicator of poor prognosis for hearing preservation, those patients who enjoy hearing improvement come from the group of patients with abnormal preoperative ABRs. Other factors identified as associated with hearing improvement include poor SDS with more normal PTA 2 , and significantly decreased electronystagmographic caloric function (as an indicator of superior vestibular nerve tumors). Hearing improvement to the functional range after surgical resection is possible in some patients previously thought to be poor candidates for hearing preservation attempts. Hearing improvement may continue for many months after surgery.

Cochlear hook anatomy: Evaluation of the spatial relationship of the basal cochlear duct to middle ear landmarks

The cochlear hook is an important anatomical area for the otologist performing cochlear implants and other otological procedures, who requires knowledge of the basal cochlea. A total of 15 human temporal bones were dissected and the spatial relationship of the hook segment of the cochlear duct to the stapes, round window, cochleariform process and ductus reuniens were evaluated. Inter-individual variability was noted for widths of scala tympani (average width 1.36 +/- 0.25 mm) and scala vestibuli (average width 1.18 +/- 0.18 mm) in the region of typical cochlear implant placement, with the scala vestibuli occasionally being wider than the scala tympani. The cochlear duct was in closest proximity to the stapes at the midportion of the footplate, with an average distance of 1.23 mm at this narrowest width. A fibrous anchor, not previously described in otology literature, was identified securing the most basal end of the cochlear duct. Knowing the spatial relationship of the cochlear duct to the middle and inner ear structures could prevent damage to the basilar membrane in procedures around or involving the basal cochlear, such as cochlear implantation, stapedotomy, or implantable hearing devices.

Cochlear implantation: Minimal hair removal technique ☆

This prospective study was undertaken to evaluate the safety and patient acceptance of minimal hair removal during cochlear implantation. Forty-six consecutive patients (17 adults, 29 children; age range 13 months to 84 years) received cochlear implantation with a minimal hair removal technique. A questionnaire was used to evaluate acceptance and value of this technique among the first 15 patients and parents. Postoperative examinations were completed 1 and 4 weeks after implantation. Patients were monitored for complications, which included 3 cases of transient seroma, 2 cases of transient dysequilibrium, 2 individual electrode failures, and 1 facial nerve stimulation. Importantly, no wound infections were documented. Use of a small shave technique did not increase surgical risk. This technique has proved to be cosmetically and psychologically more desirable for the patients and their families than complete hair removal in the operative field.

Modifications of standard cochlear implantation techniques for children under 18 months of age

Abstract Cochlear implantation is being performed in increasingly younger children. We present a retrospective cohort of 19 patients with 23 ears implanted under 18 months of age. The mean age at implantation was 11.9 months, with the youngest being 6.8 months. The facial recess was narrow in nine ears (39%), including all premature infants. An inferiorly located stapedius tendon was sectioned in seven ears (30%) to facilitate round window access. Countersinking of the receiver-stimulator required dural exposure in 22 ears (96%). The receiver-stimulator was secured with sutures in 15 ears (65%) and within a tight pocket in eight ears (35%). Tympanostomy tubes were placed in 10 ears (43%). Cochlear implantation in very young children frequently necessitates modified surgical techniques. Copyright

Effects of Estrogen and Tamoxifen on Growth of Human Vestibular Schwannomas in the Nude Mouse

Vestibular schwannomas have been noted to have increased frequency and aggressivity in female patients, suggesting a possible role of estrogen. This study evaluated the effects of estrogen and tamoxifen on the growth of human vestibular schwannoma tissue implanted in subcutaneous pockets of nude mice. Animals were implanted with 1 of 3 human vestibular schwannomas and observed for 28 days. Mice were then separated into 3 treatment groups: controls, estrogen (receiving 1.7 mg of 17B-estradiol), and estrogen + tamoxifen (receiving 1.7 mg of 17B-estradiol + 10 mg of tamoxifen), and treated for 28 days. Mice treated with estrogen showed increased growth that was statistically significant (P < 0.05) when compared with that of both the controls and the animals treated with estrogen + tamoxifen. Controls and animals treated with estrogen + tamoxifen showed a general trend of decreased volume during the treatment period. These early results support the hypothesis that estrogen modulates the growth of vestibular schwannomas in the nude mouse model and that these effects can be blocked by tamoxifen administration.