Biomedical subjects
Publications and source records attributed to S H Selesnick.
Hearing impairment is among the most common medical condition presenting to health care professionals. Ear anatomy, physiology, and pathology resulting in hearing loss are discussed. A systematic approach to evaluation, diagnosis, and treatment is presented.
OBJECTIVE: To define the clinical presentation, treatment options, and outcomes for a subset of meningiomas of the posterior fossa skull base that arise from the posterior petrous face between the region of the porus acousticus and the sigmoid sinus. STUDY DESIGN AND SETTING: A retrospective chart review from a large skull base surgery practice at a tertiary care institution. RESULTS: This cohort of patients presented with minimal symptoms, yet large tumors, averaging 3.8 cms and causing significant cerebellar compression. Retrosigmoid craniotomies afforded excellent exposure. CONCLUSION AND SIGNIFICANCE: Patients with large tumors emanating from the posterior fossa aspect of the temporal bone should be evaluated on the basis of their site of origin. Patients with tumors emanating from the anterior or ventral portion of the temporal bone have greater symptoms and greater operative complications than those emanating from the posterior petrous face, between the porus acousticus and sigmoid sinus.
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OBJECTIVE: Facial paralysis can occur after surgery for cholesteatoma. The risk of facial nerve injury is great when the nerve is not covered by its normal bony Fallopian canal. The objective of this study was to identify the incidence of facial nerve dehiscence in patients undergoing surgery for cholesteatoma. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral hospital. PATIENT POPULATION: An assessment of all cases performed by the senior author from 1991 to 1999 revealed 59 patients with adequate data available for analysis. These patients ranged in age from 3 to 92 years. In all, 67 surgical procedures. INTERVENTION: Surgery for cholesteatoma, including tympanoplasty and mastoidectomy. MAIN OUTCOME MEASURE: The presence of facial nerve bony dehiscence after exenteration of disease, and postoperative facial nerve function. RESULTS: In 33% of the total procedures analyzed, 30% of the initial procedures, and 35% of the revision procedures, the patients were found to have facial nerve bony dehiscence. The dehiscence was present in the tympanic portion of the facial nerve in the vast majority of patients. Of the 97% of patients with normal preoperative facial nerve function, all retained normal function postoperatively. CONCLUSIONS: Facial nerve dehiscence in our series was far greater than that reported in the literature, underscoring the fact that this is an under-appreciated condition. These findings suggest that surgeons should be highly vigilant when dissecting near the facial nerve. Intraoperative facial nerve monitoring has been shown to be of value in facial nerve preservation during acoustic neuroma resections, and may have a role during surgery for cholesteatoma.
OBJECTIVE: Factors that play a role in the selection of surgical approach for acoustic neuromas include patient health and age, size of tumor, hearing status, and location of tumor in the internal auditory canal (IAC) and the cerebellopontine angle. Deep extension into the IAC makes hearing preservation extremely difficult when a retrosigmoid craniotomy is used, and the best approach is a middle fossa subtemporal route. Modern gadolinium-enhanced magnetic resonance imaging (MRI) can be inaccurate in identifying the presence of tumor laterally in the IAC. This may affect the selection of a surgical approach. STUDY DESIGN: This study was a retrospective case review. SETTING: Patients were accrued from a tertiary referral otologic practice. PATIENTS: From 1997 through 2000, the authors identified six patients who had undergone acoustic neuroma surgery, had adequate imaging and intraoperative data, and demonstrated a lack of correlation between MRI and intraoperative findings of the lateral IAC. INTERVENTION: The interventions were preoperative MRI of the IAC and surgical resection of an acoustic neuroma. MAIN OUTCOME MEASURE: Comparison of MRI and intraoperative findings of the lateral IAC were the main outcome measures. RESULTS: Six patients demonstrated a lack of correlation between MRI and intraoperative findings of the lateral IAC. CONCLUSIONS: Gadolinium-enhanced T1-weighted MRI findings of the depth of penetration into the lateral aspect of the IAC do not always correlate with intraoperative findings and thus may have implications in the selection of surgical approaches to acoustic neuromas.
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Our objective is to report 4 cases of incidentally discovered acoustic neuromas (ANs) and to determine the incidence of asymptomatic ANs. A prospective study of 161 consecutive patients undergoing gadolinium-enhanced MRI (Gd-MRI) at a tertiary-care university-affiliated medical center was carried out from September 1994 to April 1995. The Gd-MRI scans were performed for tentative diagnoses other than AN or sensorineural hearing loss. In 161 consecutive patients examined, no ANs were found incidentally on Gd-MRI scans. Previous studies have suggested that the incidence of occult ANs is as high as 1%. On the basis of our results, we suggest that the actual incidence may be lower. However, our study is limited by its small size and the low incidence of ANs in the general population. Also reported are the clinical and MRI characteristics of 4 patients with incidentally diagnosed ANs.
OBJECTIVES/HYPOTHESIS: The charge delivered to the facial nerve during intraoperative facial nerve monitoring (IOFNM) is the product of the stimulation amplitude and the duration for which the pulse of charge is applied. In the literature, no standard for pulse duration exists, precluding meaningful comparison of IOFNM between studies. The optimal stimulus pulse duration can be derived from facial nerve strength duration curve analysis and calculation of chronaxy. Chronaxy is directly related to the time constant, tau, of the neuronal membrane, and is a function of neuronal membrane resistance and capacitance. STUDY DESIGN: A prospective trial of facial nerve stimulation in both an animal and a human model. METHODS: Five rabbits and 17 humans underwent intraoperative stimulation of healthy facial nerves. Pulse durations using pulses of 10, 20, 50, and 100 microseconds were employed, and the corresponding threshold stimulation amplitudes were recorded. From these data sets, strength duration curves were plotted and chronaxy values calculated. RESULTS: Average chronaxy values of 18 microseconds in the rabbit and 32 microseconds in the human were found. Given IOFNM system accuracy limitations, the optimal pulse duration for facial nerve stimulation is 50 microseconds. CONCLUSION: Most commercially available intraoperative monitoring systems employ a pulse duration default setting of 100 microseconds. Doubling of the 50-microsecond optimal pulse duration may result in a loss of sensitivity of predictive facial nerve data. Both the stimulation amplitude and the selected pulse duration should be reported by investigators so that meaningful comparison of the IOFNM data in the literature can be made.
OBJECTIVE: The objective of the study was to describe the clinical presentation and treatment of exophytic fibro-osseous temporal bone lesions, a clinical entity never previously reported, and to consider the differential diagnosis. STUDY DESIGN: The design of the study was a retrospective case review. SETTING: The setting was a tertiary referral center. PATIENTS: Two patients diagnosed with exophytic fibro-osseous temporal bone lesions were included in the study. INTERVENTION: The intervention used was surgical excision. MAIN OUTCOME MEASURE: The main outcome measures were clinical, radiographic, and histopathologic examination. RESULTS: There was no evidence of recurrence at 15 and 17 months after surgery. CONCLUSION: Although fibro-osseous lesions of the temporal bone have been previously reported, there have been no reported cases of an exophytic variant.
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OBJECTIVE: To review the impetus for the development of image-guided surgical navigation, its technologies, and the few prior outcome studies, and to make recommendations for its role in otologic and neurotologic surgery. DATA SOURCES: A literature search of English language publications by Medline from 1966 to 1998, using the key words: stereotactic, stereotaxy, navigation, intraoperative, and surgery. DATA EXTRACTION: Attempted review of the literature on image-guided surgical navigation in otology and neurotology revealed little relevant data. CONCLUSION: There are many possible applications for image-guided surgical navigation in otology and neurotology, but technologic limitations preclude its extensive application. There are no data available that assesses whether image-guided surgical navigation can reduce operative time, hospital stay, or cost. Clinical outcomes have not been studied in patients with otologic and neurotologic disease. In this scenario, image-guided surgical navigation is an adjuvant tool that aids in navigation of the skull base but is not a substitute for sound surgical principles and knowledge of microsurgical anatomy.
HYPOTHESIS: Topical application of 3% papaverine hydrochloride in the cerebellopontine angle (CPA) produces reversible conduction block of the facial nerve. BACKGROUND: A case of loss of spontaneous and evoked facial muscle activity, and transient postoperative facial paralysis, after topical application of papaverine in the CPA during surgery for an acoustic neuroma using intraoperative cranial nerve monitoring is reported. Other cases of transient neurologic dysfunction after use of this drug have been reported. METHODS: A rabbit model of CPA surgery via suboccipital craniectomy, with intraoperative monitoring of the facial nerve, was used in this experiment. RESULTS: No significant difference in facial muscle stimulation thresholds was identified after application of varying concentrations of papaverine to the facial nerve in the CPA. CONCLUSION: Although the intraoperative event described in the report is suggestive of an effect of papaverine on facial nerve function, this effect could not be reproduced in an established animal model of CPA surgery.
OBJECTIVE: This study aimed to define the incidence and rate of tumor growth of acoustic neuromas (ANs) in patients who have undergone radiologic surveillance. DATA SOURCES: MEDLINE literature searches covering the period of January 1966-June 1997 were performed as well as a review of the bibliographies of the studies that were found. STUDY SELECTION: Criteria for inclusion of a study in this metaanalysis were: a defined group of patients diagnosed with an AN for whom radiologic surveillance was the selected strategy of management, limited inclusion of patients with neurofibromatosis type II (NF II) ANs, no recurrent ANs, data that could be extracted and pooled with other studies, and no duplication of patient populations between studies. Thirteen studies were selected. DATA EXTRACTION: Quality of the studies was determined by the design of each study and the ability to combine the data with the results of other studies. All of the studies were biased by their retrospective, nonrandomized nature. DATA SYNTHESIS: Paired t-tests (p < 0.05) and correlation coefficients were used to assess pooled data. CONCLUSIONS: A total of 571 ANs were studied, with an average patient age of 64 years. Given an average follow-up period of 3 years, 54% of patients showed evidence of radiologic growth. No reliable predictors of tumor growth have been identified. The authors suggest that radiologic surveillance may best be applied to those patients who refuse treatment, who have a tumor in the only-hearing ear, or who are medically unable to undergo treatment. Small tumor size and advanced age should not be viewed as absolute contraindications for treatment.
OBJECTIVE: To assess the efficacy of intraoperative brainstem auditory evoked responses (BAER) in predicting postoperative hearing improvement in surgery for conductive hearing loss. STUDY DESIGN: A prospective study of consecutive patients undergoing surgery for conductive hearing loss under general anesthesia by a single surgeon. SETTING: A tertiary care university affiliated medical center. PATIENTS: All patients undergoing surgery for conductive hearing loss by the senior author between June 25, 1993 and March 20, 1995. INTERVENTIONS: Pre- and postreconstruction intraoperative BAERs; pre- and postoperative pure tone and speech audiometry. MAIN OUTCOME MEASURES: Changes in audiometric pure tone air-conduction thresholds, bone-air gaps (BAG), and speech reception thresholds (SRT), compared with changes in BAER wave five (V) latencies. RESULTS: A decrease in the wave V latency on the intraoperative BAER correlates significantly with improvement in postoperative pure-tone air-conduction, BAG, and SRT using chi 2 and linear regression analyses. CONCLUSIONS: Improvement in intraoperative BAER correlates with postoperative hearing improvement in surgery for conductive hearing loss done under general anesthesia in our population.
The predictive value of intraoperative stimulation thresholds for facial nerve function, using a constant-current system, was examined in 49 patients undergoing resection of cerebellopontine-angle tumors. Immediately after surgery, 75% of the 0.1-mA threshold group, 42% of the 0.2-mA group, and 18% of the 0.3-mA or greater group had good (grade I or II) facial nerve function. One year after surgery, 90% of the 0.1-mA group, 58% of the 0.2-mA group, and 41% of the 0.3-mA or greater group had grade I or II function. A statistically significant breakpoint of 0.2 mA was found to predict good postoperative facial function. Delayed facial paralysis occurred in 22% of patients, but the prognosis for these patients was favorable. Both current stimulation threshold and duration are necessary for a meaningful comparison of data between investigators.
Anterior rerouting of the intratemporal facial nerve in the infratemporal fossa approach is employed to access to the jugular bulb, hypotympanum, and lateral skull base, whereas posterior rerouting of the facial nerve, as employed in the transcochlear craniotomy, is most frequently used for surgery of the posterior fossa, cerebellopontine angle, prepontine region, and petrous apex. Facial nerve rerouting may lead to facial paresis or paralysis. This review of the literature is intended to define the physiologic "cost" of these procedures, so that the neurotologic surgeon can determine if the morbidity incurred in these techniques is worth the resultant exposure. Inconsistencies in reporting facial function places into question the validity of some of the cumulative data reported. Postoperatively, grades I-II facial nerve function was seen in 91% of patients undergoing short anterior rerouting, 74% of patients undergoing long anterior rerouting, and 26% of patients undergoing posterior complete rerouting. Although facial nerve rerouting allows unhindered exposure to previously inaccessible regions, it is achieved at the cost of facial nerve function. Facial nerve dysfunction increases with the length of facial nerve rerouted.
Benign mass lesions of the external auditory canal, such as exostoses and osteomas, are common findings on physical examination but most often do not require treatment. The differential diagnosis of lesions in the external auditory canal, however, should not be limited to those benign processes discussed here, but should also include infectious, dermatologic, congenital, and malignant processes.