John T. Roland

An evidence-based algorithm for intraoperative monitoring during cochlear implantation.

Objective To generate an evidence-based algorithm for the use of intraoperative testing during cochlear implantation (CI). Study Design Retrospective review. Setting Tertiary referral center. Patients A total of 277 children (aged 6 mo to 17 yr) and adults 18 years and older with normal cochlear anatomy who underwent primary and revision cochlear implantation at a single center between 2005 and 2010 were included. Intervention Intraoperative electrophysiologic monitoring and intraoperative Stenver’s view plain film radiography. Main Outcome Measure Intraoperative testing included the following: 1) individual electrode impedance measurements; 2) neural response telemetry (tNRT) levels for electrodes E20, E15, E10, and E5; and 3) plain film radiograph assessment of electrode position. Results No patient demonstrated abnormalities on all 3 modalities. Open or short electrodes on impedance testing were found in 6% of patients; half of these normalized when remeasured. Absent tNRT responses on 1 or more electrodes occurred in 14% of patients, although complete lack of response was rare (1.4%) and did not correlate with a dysfunctional device. Spread of excitation was performed in 1 patient and was consistent with a tip rollover. Intraoperative radiography identified tip-rollover and extracochlear electrode placement in all cases (n = 5, 1.8%) and prompted the use of the backup device. Conclusion Immediate intraoperative determination of device functionality and optimal electrode placement is advantageous. Of the modalities tested, including electrode impedance, tNRT, and plain radiograph, only the radiographic results impacted intraoperative surgical decision making and led to the use of the backup device.

The effects of residual hearing in traditional cochlear implant candidates after implantation with a conventional electrode.

Objective To analyze the effects of residual hearing on postoperative speech performance in traditional cochlear implant (CI) patients implanted with a conventional electrode. Study Design Retrospective review. Setting Academic tertiary referral center. Patients A total of 129 adults implanted by a single surgeon at a tertiary care facility between June 2005 and November 2010 with measurable preoperative pure tone thresholds at any frequency were included. Intervention Cochlear implantation with a conventional electrode via an anterior inferior cochleostomy. Main Outcome Measure Speech perception using monosyllabic word scores in quiet and sentences in quiet and noise in the electric (CI-only) condition of the implanted ear. Preservation of hearing was defined as complete for postoperative thresholds within 10 dB of preimplant values and partial if greater than 11 dB. Pure tone audiometry and speech perception testing were performed preoperatively and at regular intervals postoperatively, with the 1-year evaluation being the final outcome period. Results Preservation at any frequency or level was not a factor in speech perception outcome, although preservation was more common in low frequencies. Hearing preservation was correlated with younger age at implantation, but was not related to length of hearing loss, cause of deafness, device type, sex, preoperative speech performance, or low-frequency pure-tone average. Conclusion Hearing can be preserved in traditional CI patients implanted with a conventional electrode. Although preservation of hearing may have implications for future technology, it is not currently correlated with speech performance in the CI-only condition.

Intraoperative neural response telemetry as a predictor of performance.

Objective: To determine whether intraoperative neural response telemetry (tNRT) is predictive of postoperative speech perception. Study Design: Retrospective review. Setting: Tertiary referral center. Patients: Children (n = 24) aged between 5 and 17 years and adults 18 years and older (n = 73) with severe-to-profound hearing loss and implanted with the Nucleus Freedom device between 2005 and 2008 and observed at least 1 year were included. Intervention: Intraoperative neural response telemetry after insertion of the electrode array. Main Outcome Measure: Measures included 1) intraoperative tNRT measurements and 2) preoperative and 1-year postoperative open-set word recognition scores using age-appropriate open-set tests for children and adults. Intraoperative neural response telemetry levels for electrodes E20, E15, E10, and E5 in each patient were correlated to performance at the 1-year evaluation interval. Results: No correlation existed between tNRT responses and open-set speech performance at the 1-year evaluation. Several patients had absent tNRT in the OR but developed speech recognition abilities, whereas the remaining patients had intraoperative responses with levels of postoperative performance ranging from 0% to 100%. Conclusion: This study suggests that there is no significant correlation between intraoperative tNRT and speech perception performance at 1 year. At the time of surgery, tNRT provides valuable information regarding the electrical output of the implant and the response of the auditory system to electrical stimulation and preliminary device programming data; however, it is not a valuable predictor of postoperative performance. Furthermore, the absence of tNRT does not necessarily indicate a lack of stimulation.

Diplopia due to skew deviation following neurotologic procedures.

Objective To describe and characterize diplopia resulting from skew deviation after cerebellopontine angle (CPA) surgery and labyrinthectomy. Patients and Interventions Retrospective case series of 4 patients who developed vertical diplopia from skew deviation after resection of tumors in the CPA or labyrinthectomy Main Outcome Measure Complete neuro-opthalmologic examination including opticokinetic testing, confrontational visual field assessment, color plate, pupillary reflex, slit lamp examination, and head tilt test. Results Four patients with residual hearing preoperatively developed skew deviation immediately after surgical intervention, including translabyrinthine (n = 1) and retrosigmoid (n = 2) approaches to the CPA and labyrinthectomy (n = 1). Neuro-ophthalmologic examination demonstrated intact extraocular movements, and 2- to 14-mm prism diopter hypertropia on both primary gaze and head tilt testing. In all cases, skew deviation resolved spontaneously with normalization of the neuro-ophthalmologic examination within 10 weeks. Conclusion Patients undergoing CPA surgery or labyrinthectomy can develop postoperative diplopia due to skew deviation as a consequence of acute vestibular deafferentation. Patients with significant hearing preoperatively, a probable marker for residual vestibular function, may be especially at risk for developing skew deviation postoperatively.

Intraoperative Transcranial Motor-Evoked Potential Monitoring of the Facial Nerve during Cerebellopontine Angle Tumor Resection.

Objective To determine whether transcranial motor-evoked potential (TCMEP) monitoring of the facial nerve (FN) during cerebellopontine angle (CPA) tumor resection can predict both immediate and long-term postoperative FN function. Design Retrospective review. Setting Tertiary referral center. Main Outcome Measures DeltaTCMEP (final-initial) and immediate and long-term facial nerve function using House Brackmann (HB) rating scale. Results Intraoperative TCMEP data and immediate and follow-up FN outcome are reported for 52 patients undergoing CPA tumor resection. Patients with unsatisfactory facial outcome (HB >2) at follow-up had an average deltaTCMEP of 57 V, whereas those with HB I or II had a mean deltaTCMEP of 0.04 V (t = -2.6, p < 0.05.) Intraoperative deltaTCMEP did not differ significantly between groups with satisfactory (HB I, II) and unsatisfactory (HB > 2) facial function in the immediate postoperative period. Conclusion Intraoperative TCMEP of the facial nerve can be a valuable adjunct to conventional facial nerve electromyography during resection of tumors at the CPA. Intraoperative deltaTCMEP >57 V may be worrisome for long-term recovery of satisfactory facial nerve function.

Temporal bone histopathology case of the month: Malignant peripheral nerve sheath tumor arising within vestibular schwannoma.

A 41-year-old woman with no significant past medical history presented with hypesthesia of the left upper extremity and the lower 2 divisions of the trigeminal nerve. Magnetic resonance imaging of the brain revealed a 2.6 2.2 2.7Ycm mass in the right cerebellopontine angle exerting mass effect on the right pons and middle cerebellar peduncle as well as secondary distortion of the fourth ventricle. Within days, the patient developed sudden sensorineural hearing loss and sudden onset rightsided facial paresis (House-Brackmann grade III). Given the rapid progression of symptoms, the patient underwent urgent translabyrinthine approach resection of the tumor. During the dissection, the outer circumference of the tumor possessed normal gross features of vestibular schwannoma, whereas the central tumor was softer and more friable than typical of vestibular schwannoma. The procedure and postoperative course were otherwise unremarkable. The permanent sections histopathology revealed a neoplasm with 2 well-demarcated components (Fig. 1). The first component exhibited histologic features consistent with a schwannoma including S-100 positive, spindleshaped cells forming intersecting fascicles, variably pleomorphic nuclei, abundant eosinophilic cytoplasm, and at least 1 Verocay body (Fig. 2). The MIB-1 immunostain, which recognizes the ki-67 nuclear proliferation antigens, showed a variable labeled index up to 12%. The second component exhibited malignant features including higher cellularity, hyperchromatic nuclei, scant cytoplasm, and many mitotic figures (Fig. 3). The MIB-1 immunostain revealed a high labeling index up to 90%. In both components, there was abundant immunoreactivity for vimentin. Ultrastructural analysis revealed lipid droplets, glycogen, sparse floccular basal lamina-like matrix, pinocytotic vesicles andperi-plasmalemmal actin filaments.

Reduced Cochlear Implant Performance After the Use of Growth Hormone With Regain of Function After Cessation of Growth Hormone Therapy.

Objective To assess whether recombinant growth factor (hGH) therapy has an effect on cochlear implant (CI) performance. Patients Two pediatric CI recipients (S1, S2) who underwent treatment with hGH for short stature were identified for review. S1 has bilateral labyrinthine dysplasia and received implants at ages 10 months (right) and 4 years 3 months (left). S2 was diagnosed with severe to progressive sensorineural hearing loss bilaterally and received a CI at age 9 years 10 months (left). Intervention(s) Case series. Main Outcome Measure(s) Cochlear implant, hGH, and speech perception data were collected. Phonetically Balanced Kindergarten (PBK) and Consonant Nucleus Consonant (CNC) word recognition scores were reviewed to assess auditory perception. Electrode impedances, threshold levels, and comfort levels were also reviewed. Results After 4 months of hGH, word recognition scores for S1 were observed to decrease from 90 to 72% (right) and were stable at 40% (left). Despite troubleshooting, performance continued to decline bilaterally to 52% (right) and 28% (left), and the decision was made to discontinue hGH. One month after cessation of hGH, word recognition scores began improving to 74% (right) and 68% (left). Word recognition scores for S2 were observed to have decreased from 92% the previous year to 82% after taking hGH for 2 months. Given both our previous experience with S1 and discussions with S2’s parents, hGH was discontinued after 10 months of therapy. Two months after cessation of hGH, S2’s word recognition had improved to 86% (left). Conclusions Our case studies illustrate that implanted children undergoing treatment with hGH may experience a decrease in speech perception, which recovers after the cessation of treatment. Since hGH use has become more prevalent in recent years, it is important to inquire whether children undergoing, or who have undergone, implantation are receiving hGH so that they may be appropriately monitored.