Fixation of the electrode cable during cochlear implantation: the split bridge technique.
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Cochlear Implants↗
Biomedical subjects
F F Telischi
Publications and source records attributed to F F Telischi.
Reducing temporal lobe retraction with the middle fossa approach using a lumbar drain.
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Brain Edema↗
Patterns of evoked otoacoustic emissions associated with acoustic neuromas.
Evoked otoacoustic emissions (OAEs) are assumed to reflect healthy outer hair cell function. Over the past few years, evoked OAEs have been shown to be useful as indicators of cochlear hearing loss. Because basic studies have shown that OAEs are extremely sensitive to cochlear anoxia and hypoxia, as well as to the adverse effects of many inner ear diseases, it is possible that these objective tests can provide some insight into the fundamental basis of the hearing loss exhibited by patients with acoustic neuromas. The primary aim of the present study was to examine the effects of acoustic neuromas on the amplitudes of evoked OAEs and to compare these findings with tumor-induced hearing levels. To this end, tests of behavioral audiometry, distortion-product otoacoustic emissions and transiently evoked otoacoustic emissions were performed on 44 patients with verified acoustic neuromas. The results demonstrated that the majority of ears with acoustic neuromas displayed one of two distinct patterns of evoked OAEs: a cochlear pattern or a noncochlear pattern. Although behavioral hearing thresholds were higher with larger tumors, OAE levels exhibited no clear relationship to tumor size. The present findings support the notion that acoustic neuromas may cause hearing impairment according to two types of influence that act at different levels of the peripheral auditory system. The tumor's cochlear effect on evoked OAE activity is most likely caused by an indirectly mediated compromise of the organ of Corti's vascular supply. It is probable that the direct pressure of the tumor on the eighth cranial nerve is responsible for the observed noncochlear effects.
Audiometry↗
Traumatic facial nerve injuries: review of diagnosis and treatment.
Both blunt and penetrating craniofacial trauma may lead to severe facial nerve injury and sequelae of facial paralysis. Initial evaluation involves quantitation of motor deficits using a clinical grading system, such as the House-Brackmann scale. High resolution computed tomography is used for localization of nerve injury in suspected cases of temporal bone trauma. In the absence of gross radiographic abnormalities, electrophysiologic testing helps predict the likelihood of spontaneous recovery. In patients with deteriorating facial nerve injuries by electroneuronography, surgical exploration is the preferred management. Primary end-to-end neurorrhaphy is the preferred management for transection injuries, while facial nerve decompression may benefit other forms of high-grade nerve trauma. Secondary facial reanimation procedures, such as cranial nerve crossovers, dynamic muscle slings or various static procedures, are useful adjuncts when initial facial nerve repair is unsuccessful or impossible. A review of facial nerve trauma management and case illustrations are presented.
Adult↗
Monitoring cochlear function intraoperatively using distortion product otoacoustic emissions.
Distortion product otoacoustic emissions (DPOAEs) elicited by a bitonal stimulus complex are low-level sounds that are generated within the cochlea, and are easily measured by a miniature microphone system placed in the external auditory canal. Under conditions of rapid measurement, DPOAEs have been shown in an animal model to be exquisitely sensitive to interruption of the blood supply to the inner ear. Currently, there is no real-time procedure available for monitoring hearing function intraoperatively during neurotologic surgery. The goal of the present study was to determine the utility of DPOAEs in monitoring cochlear status intraoperatively, particularly during procedures commonly used to remove acoustic neuromas. Distortion product otoacoustic emissions were measured pre- and intraoperatively in 11 patients, who were under general anesthesia for a variety of otolaryngologic procedures, including acoustic neuroma resection. High frequency emissions (i.e., > or = 4 kHz) were less affected by the elevated levels of acoustic noise present in the operating-room environment, thus permitting emitted responses to be updated as quickly as every 2 seconds. However, a number of technical problems were encountered and addressed during development of the emission monitoring technique. Despite these difficulties, overall, DPOAEs appear to be a promising adjunct to the intraoperative monitoring of auditory function.
Acoustic Impedance Tests↗
High-resolution computed tomography in evaluation of cochlear patency in implant candidates: a comparison with surgical findings.
High-resolution computed tomography (HRCT) is important in the evaluation of cochlear implant candidates. This study examines the accuracy of radiological assessment of cochlear patency in relation to findings at the time of surgery. Older and newer HRCT methods and attending and senior radiologist interpretations are compared in a large series of cochlear implant patients. Subjects were 50 adults (22 to 74 years) and 31 children (2.4 to 11.7 years) who received either a 3M/House or a Nucleus 22-channel cochlear implant. Attending radiologist reports were obtained by chart review and the scans were re-reviewed for this study by a senior radiologist. Accuracy in detecting cochlear ossification ranged from 86.4 per cent for attending radiologists, with all HRCT scans, to 94.7 per cent for the senior radiologist with newer HRCT scans. False positives were rare, but false negatives did occur. Overall, best results were obtained with newer HRCT scans and a senior radiologist. Knowledge of the presence and extent of cochlear ossification is important to the implant surgeon and for patient counselling. Technical guidelines and a check list for interpretation of results are presented.
Adult↗
Early effects of cerebellopontine angle compression on rabbit distortion-product otoacoustic emissions: a model for monitoring cochlear function during acoustic neuroma surgery.
A rabbit model was developed to simulate the effects of ischemia that may occur during surgical removal of tumors involving the cerebellopontine angle or internal auditory canal. Specifically, the internal auditory artery was visualized through a posterior craniotomy and mechanically compressed for repetitive 1-minute intervals with a micromanipulator-controlled glass pipet terminating in a smooth bead. The 2f1-f2 distortion-product otoacoustic emissions were used to monitor the susceptibility of cochlear function to compressive effects. Distortion-product otoacoustic emissions were measured during discrete preblock, block, and postblock periods to determine the time course of distortion-product otoacoustic emission reduction and its return to baseline levels after rapid obstruction and resumption, respectively, of the cochlear vascular supply. Comparisons during these times indicated that preblock distortion-product otoacoustic emission levels were very stable, often varying by less than 1 dB. Additionally, distortion-product otoacoustic emissions were very sensitive to brief vascular occlusions in that, within approximately 25 seconds of blockage onset, emission levels at all frequencies decreased at rates of about -1.5 dB/second. On alleviation of the occlusion, distortion-product otoacoustic emissions rapidly and completely returned to preblock levels with a delay of about 4 seconds and recovery slopes of about 10.5 dB/second. A notable finding in some animals was that early and reproducible variations in distortion-product otoacoustic emission levels occurred within 5 to 8 seconds of internal auditory artery compression. When present, these transitory changes in distortion-product otoacoustic emission levels acted as early warning signs for vascular compromise of cochlear function.
Animals↗
Blast injuries to the facial nerve.
The recommended treatment of penetrating traumatic facial nerve injuries associated with immediate, total paralysis of the ipsilateral facial muscles generally includes facial nerve exploration and repair. We reviewed our experience with bullet injuries to the extratemporal facial nerve to determine the efficacy of this approach. Five patients with immediate, total facial nerve paralysis caused by bullet wounds near the extratemporal facial nerve were seen between July 1990 and December 1992. Of four patients who underwent surgical exploration, only one demonstrated complete transection of the facial nerve. Two of these four were followed up with serial electroneuronography, which demonstrated complete degeneration within the first week after injury. The fifth patient was followed up with serial electroneuronography without complete degeneration, and partial recovery was observed. We conclude that penetrating bullet injuries with immediate, total facial paralysis may not necessarily be associated with transection of the facial nerve. We propose a method of treating patients with these injuries using electroneuronography.
Adult↗
Surgical management of previously untreated glomus jugulare tumors.
The treatment of glomus jugulare tumors is controversial. Changes in the surgical treatment of glomus jugulare tumors at The House Ear Clinic have allowed complete resection in 85% of patients with minimal morbidity and no surgical mortalities. Our experience with 52 previously untreated patients with glomus jugulare tumors is reviewed. Two primary surgical techniques were used. The mastoid/neck approach was used in 9 patients with small tumors limited to the jugular bulb. The infratemporal fossa approach was used in the remaining 43 tumors. Lower cranial nerve preservation was possible in the majority of patients with normal preoperative function. Modifications in the management of the facial nerve during the infratemporal fossa approach have resulted in good recovery of facial function (House grade I/VI or II/VI) in 95% of patients. Most patients (85%) were able to fully resume all preoperative activities. Our results suggest that surgical management is the treatment of choice in younger patients with glomus jugulare tumors.
Adult↗
Lateral extent of internal auditory canal involvement by acoustic neuromas: a surgical-radiologic correlation.
The sensitivity of gadolinium-enhanced magnetic resonance imaging (MRI) is such that inflamed areas of individual nerves can be visualized. Given this, might the lateral extent of an acoustic neuroma in the internal auditory canal be inaccurately depicted by MRI with gadolinium contrast due to variable enhancement in inflamed neural tissues? The authors studied the correlation between preoperative MRI and intraoperative observation of the lateral extent of tumor in the internal auditory canal (IAC) of 82 patients with acoustic neuromas. The surgeon made a visual determination of tumor extent when the lateral-most aspect of the tumor was exposed. The radiologist, blind to surgical findings, noted the degree of extension into the IAC based on the MRI. The majority (83%) of the tumors involved the lateral third and fundus of the IAC. Agreement between scans and surgical findings was excellent for tumors extending into the lateral third of the IAC, with a test sensitivity of 94 percent and a positive predictive value of 98.5 percent. Knowledge of the accuracy of MRI in demonstrating extent of tumor in the IAC is important in making decisions regarding surgical approach.
Animals↗
Auditory brainstem implant: I. Issues in surgical implantation.
Most patients with neurofibromatosis type 2 (NF2) are totally deaf after removal of their bilateral acoustic neuromas. Twenty-five patients with neurofibromatosis type 2 have been implanted with a brainstem electrode during surgery to remove an acoustic neuroma. The electrode is positioned in the lateral recess of the fourth ventricle, adjacent to the cochlear nuclei. The present electrode consists of three platinum plates mounted on a Dacron mesh backing, a design that has been demonstrated to be biocompatible and positionally stable in an animal model. Correct electrode placement depends on accurate identification of anatomic landmarks from the translabyrinthine surgical approach and also on intrasurgical electrophysiologic monitoring. Some tumors and their removal can result in significant distortion of the brainstem and surrounding structures. Even in the absence of identifiable anatomic landmarks, electrode location can be adjusted during surgical placement to find the location that maximizes the auditory evoked response and minimizes activation of other monitored cranial nerves. Stimulation of the electrodes produces auditory sensations in most patients, with results similar to those of single-channel cochlear implants. A coordinated multidisciplinary team is essential for successful application of an auditory brainstem implant.
Brain Stem↗
Long-term efficacy of endolymphatic sac surgery for vertigo in Menière's disease.
The long-term efficacy of endolymphatic sac procedures for control of vertigo in Menière's disease has been controversial. We evaluated results of sac shunt surgery for 234 patients having at least 10 years followup (mean, 13.5 years). All patients had persistent vestibular symptoms despite medical therapy. All underwent endolymphatic subarachnoid shunt as their original operation. Data were collected by chart review and questionnaire regarding: (1) the number of additional surgical procedures to control vertigo, (2) remaining dizziness, and (3) level of disability. One hundred forty-seven of the patients (63%) did not undergo any further surgery to control vertigo, and an additional 17% had only revisions of the endolymphatic sac shunt. Thus, 80% never required a destructive procedure. Long-term effectiveness of surgery in regard to dizziness and disability was determined from the questionnaire. Of the 147 patients with only the original sac shunt surgery, 93% reported no dizziness or mild to no disability. Of the group who underwent only revisions of the original shunt, 96% stated they had no more dizziness or mild to no disability. We conclude that endolymphatic sac shunt operations are effective as initial surgical procedures for long-term control of disabling vertigo of Menière's disease.
Adolescent↗
Facial paralysis of pregnancy attributable to an arteriovenous steal syndrome.
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Adult↗
Hemifacial spasm. Occurrence in multiple sclerosis.
We present six patients with hemifacial spasm and multiple sclerosis. To our knowledge, this association has not been described previously in the North American literature. Magnetic resonance imaging was obtained in all the patients and plaques consistent with multiple sclerosis were identified. In two patients the plaques were seen in the area of the facial nucleus on the involved side. We suggest that hemifacial spasm can be a manifestation of multiple sclerosis. These cases illustrate the utility of magnetic resonance imaging in the investigation of hemifacial spasm. Our findings also support a central (nuclear) origin in multiple sclerosis associated with hemifacial spasm.
Adrenocorticotropic Hormone↗
111In octreotide scintigraphy in the evaluation of head and neck lesions.
PURPOSE: To evaluate indium 111 octreotide scintigraphy for the detection of suspected neuroendocrine lesions of the head and neck. METHODS: After receiving 6 mCi of 111In octreotide, 22 patients with suspected lesions of the head and neck were examined with both planar and single-photon emission CT (SPECT). Static images, obtained at 4 hours, included the head/neck, chest, abdomen, and pelvis. Additional SPECT images were obtained at 4 or 24 hours. Studies were compared with available conventional radiologic examinations (12 CT, 11 MR, and three angiographic studies) as well as with clinical and pathologic findings. RESULTS: Eighteen of the 22 patients had abnormal findings at scintigraphy. Eleven paragangliomas were seen in 10 patients, metastatic medullary thyroid carcinoma in three patients, thyroid adenoma in two patients, and Merkel cell tumor, carcinoid, and plasmacytoma in one patient each. Surgical confirmation was available in 13 patients. The smallest lesion detected was 1.5 cm. There was one false-positive and one false-negative examination. CONCLUSION: 111In octreotide scintigraphy is a useful imaging tool for the detection of primary and metastatic neuroendocrine tumors of the head and neck that are larger than 1.5 cm. This technique enables distinction of glomus tumors from other masses (such as neuromas) and can be used in the postoperative setting to distinguish scar from recurrent paraganglioma. Since it is an examination of the entire body, it has great utility for detecting multicentric paraganglioma and for screening patients with familial paraganglioma.
Adult↗