Faculty Bibliography

Paralysis of the tongue due to isolated bilateral hypoglossal nerve palsy is a rare occurrence. Due to a trauma the cause in our case may have been a traction injury to both hypoglossal nerves at the base of skull. In some cases a contributing factor may be malformation of the skull base. Most cases have a good prognosis for recovery

Robust determination of the concentration-time profile of anti-infective agents in certain specialized compartments is often limited by the inability to obtain more than a single sample from such a site in any one subject. Vitreous humor and cerebrospinal fluid are obvious examples for which the determination of concentrations of anti-infective agents is limited. Advances in pharmacodynamics have pointed out the importance of understanding the profiles of drugs in the plasma and in specialized compartments in order to dose the drugs to obtain the best patient outcomes. Advances in population pharmacokinetic modeling hold the promise of allowing proper estimation of drug penetration into the vitreous (or other specialized compartment) with only a single vitreous sample, in conjunction with plasma sampling. We have developed a rabbit model which allows multiple samples of vitreous to be obtained without breaking down the blood-vitreous barrier. We have employed this model to test the hypothesis that robust estimates of vitreous penetration by the fluoroquinolone ciprofloxacin can be obtained from a traditional intensive plasma sampling set plus a single vitreous sample. We studied 33 rabbits which were receiving 40 mg of ciprofloxacin per kg of body weight intravenously as short infusions and from which multiple plasma and vitreous samples were obtained and assayed for ciprofloxacin content by high-performance liquid chromatography. Data were analyzed by the iterative two-stage population modeling technique (IT2S), employing the iterative two-stage program of Forrest et al. (Antimicrob. Agents Chemother. 37:1065-1072, 1993). Two data sets were analyzed: all plasma and vitreous samples versus all plasma samples and the initially obtained single vitreous sample. The pharmacokinetic parameter values identified were used to calculate the percent vitreous penetration as the ratio of the area under the concentration-time curve for the vitreous to that for the plasma. The values identified, 4% penetration for the full data set versus 3% penetration for the single vitreous sample data set, and their corresponding estimates were not statistically significantly different. We conclude that population modeling holds promise for the analysis of penetration of antimicrobiol agents into specialized spaces from which only single samples can be obtained, particularly for patients with whom robust plasma sampling can be performed.

OBJECTIVE: The purpose of the present experiment was to determine the relationship between most comfortable listening level and preferred listening levels for linear and slow-acting compression hearing aids as a function of variations in speech and noise level. DESIGN: A digital hearing aid test system was used to simulate six hearing aids having compression ratios of 1, 1.5, 2, 3, 5, and 10:1. Speech was presented in three different noises (vent, apartment, and cafeteria), with speech input level being varied (55, 70, 85 dB SPL). Subjects were 20 listeners with sensorineural hearing loss (half with a dynamic range < or = 30 dB and half with a dynamic range >30 dB). The boundaries of the most comfortable listening range were measured to estimate most comfortable listening level. Preferred listening level was measured by having subjects adjust the output of the hearing aid for satisfactory listening. RESULTS: On average, the deviation of preferred listening level from most comfortable loudness (MCL) was less than 5 dB. Dynamic range, noise type, and input level were all found to have small, but significant, effects on the deviation of preferred listening level from MCL. On average, subjects with a small dynamic range listened slightly below MCL, and subjects with a larger dynamic range listened slightly above MCL. For favorable signal-to-noise ratios, preferred listening levels were highest for high input levels and for conditions that resulted in high output levels before level adjustment. Although the pattern of average performance differed slightly at poorer signal-to-noise ratios, all preferred listening levels were close to MCL. CONCLUSIONS: The gain of a slow-acting compression hearing aid should place the output within 5 dB of MCL. The output for low and medium inputs should approximate MCL and the output for high input levels should be slightly above MCL. This pattern of gain may be obtained with mild compression ratios and a gain rule that places a speech input of 70 dB at MCL

20 cadaver mandibles were studied for the presence of an antilingula and its relationship to the true lingula and mandibular foramen. Three independent observers evaluated the mandibles for the presence of an antilingula. It could be identified on all 40 sides. On 9 of the sides, there was complete concordance on the position of the antilingula between the three observers. On the other 31 sides, however, there was a variation between observers of up to 11 mm. In only 43% of the cases was the antilingula within 5 mm of the true lingula. In most cases, the true lingula was postero-inferior to the antilingula. There was a negative horizontal and positive vertical correlation between the position of the antilingula on one side and its position on the contralateral side

PURPOSE: To present the postoperative radiographic appearance of the multichannel cochlear implant and to suggest criteria for the radiographic evaluation of postimplant patients. METHODS: One hundred forty-one patients, 73 female and 68 male, had multichannel cochlear implants inserted. One hundred thirty-five intraoperative radiographs, 31 postoperative radiographic examinations, and 10 postoperative CT examinations were retrospectively reviewed. RESULTS: In 135 patients, a Stenver's or anteroposterior projection confirmed the normal placement of the implant by demonstrating the electrodes to be regularly spaced and gently curved within the first turn of the cochlea. The insertion depth was determined by counting the number of electrodes that projected medial to the cochlear promontory. In 5 patients in whom intracochlear placement of the electrode array could not be confirmed on plain radiographs, CT demonstrated the location of the electrode array. In 3 patients with postoperative infections, CT either correctly identified or excluded the presence of a collection beneath the implant. CONCLUSION: Plain radiographs of the temporal bone are sufficient for the postoperative treatment of the majority of postimplant patients. CT should be performed when plain radiographs cannot adequately show the location of the electrode array or if postoperative infection is suspected

This is a case report of non-Hodgkin's lymphoma of the external auditory canal, and infratemporal fossa, which presented with multiple cranial nerve palsies. The diagnosis was achieved via biopsy of tissue from the external auditory canal, and treatment with radiation therapy led to improvement of the symptoms. The management of AIDS-related lymphoma of the skull base with cranial neuropathies is reviewed.

The viewing wand is a frameless stereotactic arm that can be used in conjunction with computerized tomography (CT) or magnetic resonance (MR) imaging to provide image-based intraoperative navigation. The authors report a series of 325 cases in which the viewing wand was used and evaluated for its utility, ease of integration into the standard surgical setup, reliability, and real-world accuracy. The use of the system was associated with minimal additional effort or time spent in setting up the procedure as long as a trained technician performed the data transfer and reconstruction. The viewing wand was used in 165 cases in conjunction with CT and 145 cases with MR imaging. The system was reliable, achieving a useful registration in 310 of 325 cases (95.4%). Fiducial-based registration was more accurate than an anatomical landmark-surface fit algorithm method of registration (mean 2.8 vs. 5.6 mm error, respectively, for CT; and mean 3.0 vs. 6.2 mm for MR imaging). The actual error of the system in estimating the position of the probe tip just after registration was judged by the operating surgeon to be less than 2 mm in 92% of MR imaging cases and in 82% of CT cases, between 2 and 5 mm in 7% of MR imaging and 17% of CT cases, and greater than 5 mm in less than 1% of MR imaging and 1.2% of CT cases. The accuracy of the system degraded during the operation, so that by the third evaluation the error was estimated to be less than 2 mm in 77% of MR imaging and 62% of CT cases. Overall, the viewing wand was found to be reliable and accurate. This real-world accuracy was sufficient for a broad range of applications including glioma resection, cerebrospinal fluid shunting procedures, resection of small subcortical masses, and temporal lobe resection. The system is a useful navigational aid that allows a direct approach to intracranial pathology without the drawbacks of application and the limitations of a stereotactic frame