Faculty Bibliography

A cochlear lubricant may facilitate the surgeon's ability to place the electrode array deep within the cochlea. Patient performance with the multichannel cochlear implant may be enhanced with a deeper electrode insertion. Theoretically, deeper insertion and stimulation will recruit and activate more surviving spiral ganglion neurons. Several studies have shown that neuron survival is a factor for cochlear implant success, especially in the postmeningitis patient. We studied the histologic and electrophysiologic effects of the intracochlear injection of three potential lubricants in the guinea pig: glycerin, hyaluronic acid, and hydroxypropyl methylcellulose. All three have approved medical uses, reduce friction, and are readily available. Results show that when compared to surgical controls (cochleostomy without injection), there is no significant reduction in the spiral ganglion neuronal count at 2 and 8 weeks postinjection, and the dendrite and axon histology is well preserved. Injection of any of the substances within the cochlea causes severe hearing loss (detected by direct round window electrocochleographic responses to auditory stimuli) that only partially recovers with time. These findings suggest that any of the three tested substances could be considered as lubricants for intracochlear electrode insertion

Congenital saccular cysts of the larynx are unusual lesions that commonly present with respiratory obstruction in infants and children. The saccular cyst may result from an atresia of the laryngeal saccule orifice or may represent the retention of mucus in the collecting ducts of submucosal glands located around the ventricle. Traditionally, the treatment of the lesions has been endoscopic unroofing or marsupialization. Frequently, this modality requires multiple procedures as well as concomitant tracheotomy. There also have been reports of acquired subglottic stenosis. We have found that removal of the recurrent saccular cyst can be achieved relatively safely and effectively via a lateral cervical approach to the thyrohyoid membrane. We review our experience with four patients with congenital saccular cysts and detail the evaluation and surgical management of these lesions

Respiratory distress in premature newborns is associated with deficiency of surfactant in the bronchoalveolar lining fluid; this may be influenced by a local deficiency of antioxidants. Severe L-buthionine-S,R-sulfoximine-induced depletion of glutathione (GSH, a major antioxidant) in rodents is associated with lung type 2 cell lamellar body damage and decreased concentrations in lung and bronchoalveolar lavage fluid (BALF) of phosphatidyl choline (a major component of surfactant). At birth, prematurely born newborns (30-34 weeks) had lower peripheral venous plasma GSH concentrations than term (> 36 weeks) babies; these levels decreased further with increasing prematurity (< 27 weeks, with respiratory distress). On day 2, the peripheral venous plasma GSH concentrations reached a nadir, and the lowest levels were found in the most premature newborns. Lymphocyte GSH concentrations were lowest on day 2 and day 7, and in prematures (< 27 weeks, with respiratory distress) remained below adult lymphocyte GSH levels for at least 4 weeks. At birth, prematures (< 27 weeks, with respiratory distress) had a central plasma arterio-venous (A-V) GSH gradient across the lung (an estimate of lung uptake of GSH) of 0.72 +/- 0.15 (mean +/- SD) mumol/L; on day 2, the A-V gradient did not change significantly (0.49 +/- 0.09 mumol/L). At birth, these prematures had markedly decreased BALF GSH concentrations (compared with adult levels), and they were not significantly changed during the first 4 weeks of life. These results suggest that GSH deficiency is present in prematures and that it increases with the degree of prematurity. At birth, GSH deficiency will compromise the lungs' defense against oxidative stress injury. Oxidative stress is likely to increase if hyperoxic treatment is given for respiratory distress in these infants

The ostiomeatal complex has been identified as an important anatomic region in the pathogenesis of sinusitis. Functional endoscopic techniques rely on removal of mucosal disease from this site to improve drainage and aeration. Structural variations and the use of a sharp blade to create the infundibulotomy can result in inadvertent injury to the orbit. To avoid orbital penetration we perform the infundibulotomy with a curved, blunt dental elevator and displace the uncinate with its medial and lateral mucosa toward the middle turbinate. This stretches the infundibulum to reveal the maxillary ostium at its depth. The remaining mucosal attachments of the uncinate process are then incised under direct vision, and the complex is resected, creating an initial wide antrostomy. This technique has avoided orbital penetration in 700 cases in patients with early or late stages of mucosal disease

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

Metastases are occasionally associated with cutaneous squamous cell carcinoma but only rarely with basal cell carcinoma. There are approximately 200 cases of metastases from basal cell carcinoma reported in the world literature. We describe 6 additional cases. All of our patients demonstrated recurrence at the primary site before they developed their metastases. Metastases presented in subcutaneous tissue, cervical lymph nodes, bone, and lung between 1.5 and 14 years after initial treatment of the primary lesion. The long interval seen in these patients between the initial treatment of the primary and the development of metastases underscores the need for long-term follow-up in what is often thought to be a nonaggressive, nonmetastasizing malignancy

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.