Faculty Bibliography

Subglottic stenosis remains a difficult clinical problem with varied management approaches. An accepted procedure has been anterior and posterior cricoid incisions through an external approach for treatment of severe stenoses without a tracheotomy. The holmium:yttrium-aluminum-garnet laser, 2.1 microns wavelength with a pulsed output, is transmissible through standard fibers and ablates soft tissue and cartilage with minimal surrounding damage. This study in in vitro and in vivo animal models shows that this new laser can be used to incise the anterior and posterior cricoid and tracheal cartilages with precise control and may be suitable for endoscopic laryngotracheoplasty

Three postlingually deafened adults who received cochlear implants read passages before and after their prostheses were activated while their lung volumes were measured with an inductive plethysmograph that transduced the cross-sectional areas of the speaker's chest and abdomen. Lung volumes at the initiation and termination of the speakers' expiratory limbs, their average air flow, and the volume of air they expended per syllable were derived from tracings of calibrated lung volume displayed by computer. The activation of the speakers' cochlear prostheses was followed in every case by a significant change in average airflow, which rose for two subjects with initially low flow rates and fell for one subject who had a much higher average preimplant flow rate. These changes in average flow rate were accompanied by corresponding changes in volume of air expended per syllable, statistically reliable in two of the three cases. There were no significant changes in the levels at which speakers initiated their expiratory limbs, but one speaker, after his prosthesis was activated, reliably increased the level of air in his lungs at the end of expiratory limbs to an average value that no longer required him to draw on expiratory reserve volume

We have previously described a model for in utero cleft lip repair in rabbits. Cleft lip and alveolus (CL) were created in fetal rabbits at 24 days gestation (term, 31 days). In this study, postnatal maxillary growth was evaluated in three groups of animals: 1) unoperated controls, 2) unrepaired CL, and 2) repaired CL. The animals were killed at 4, 12, and 26 weeks after birth. Direct cephalometry was performed on dry skulls to evaluate premaxillary width, anterior maxillary length and width, and posterior maxillary width. The results of this study indicate that rabbits that undergo an in utero CL procedure, with or without repair, exhibit no significant decrease in maxillary length and width when compared with controls.

Two experiments investigating the effects of auditory stimulation delivered via a Nucleus multichannel cochlear implant upon vowel production in adventitiously deafened adult speakers are reported. The first experiment contrasts vowel formant frequencies produced without auditory stimulation (implant processor OFF) to those produced with auditory stimulation (processor ON). Significant shifts in second formant frequencies were observed for intermediate vowels produced without auditory stimulation; however, no significant shifts were observed for the point vowels. Higher first formant frequencies occurred in five of eight vowels when the processor was turned ON versus OFF. A second experiment contrasted productions of the word 'head' produced with a FULL map, OFF condition, and a SINGLE channel condition that restricted the amount of auditory information received by the subjects. This experiment revealed significant shifts in second formant frequencies between FULL map utterances and the other conditions. No significant differences in second formant frequencies were observed between SINGLE channel and OFF conditions. These data suggest auditory feedback information may be used to adjust the articulation of some speech sounds

The course of the facial nerve may place it within the current field generated by an activated cochlear implant to produce incidental facial movement. We investigated the presence of facial nerve stimulation associated with cochlear implants in the VA Cooperative Study of Advanced Cochlear implants. Twelve of 82 patients enrolled in this study demonstrated facial nerve stimulation within 2 years of implant activation. Facial nerve stimulation in six patients with multiple channel implants (Nucleus or ineraid devices) either resolved spontaneously (n = 2), or was eliminated by deactivating basal (n = 2) or apical (n = 2) electrodes. Two of six patients with single-channel electrodes (3-M/Vienna devices) demonstrated facial nerve stimulation that resolved spontaneously (n = 2), resolved with lowering current output (n = 2), or was refractory to processor adjustment (n = 2). Intraoperative assessment in one of the refractory cases indicated that facial nerve stimulation resulted from current spread through the modiolus to activate the facial nerve. A variety of factors, including implant design, stimulus parameters, and local tissue impedances, may interact to produce incidental facial stimulation. Low-impedance pathways between the scala tympani and the modiolus may deserve increased recognition as an interactive factor in cochlear implant performance

It is a clinical challenge to distinguish patients with parotid abscesses from those with acute sialadenitis. A case of parotid abscess is presented in which a CT scan with intravenous contrast enhancement localized the abscess cavity and guided its aspiration and drainage with an indwelling catheter. By using this percutaneous technique, the need for early surgical intervention by incision and drainage was eliminated. The dense overlying parotid fascia and position of the deep parotid lobe make differentiating between these two clinical entities difficult. Parotid abscesses are readily apparent on computerized tomographic (CT) scanning evaluation with intravenous contrast enhancement, presenting as discrete fluid-filled areas unlike the amorphous appearance of acute sialadenitis. CT scanning with intravenous contrast enhancement has been the preferred radiographic study of choice for evaluating parotid masses or parapharyngeal masses. The treatment of a patient with acute sialadenitis differs from that of a patient with a parotid abscess. Patients with acute sialadenitis will usually respond to vigorous intravenous (IV) hydration, use of sialagogues and appropriate antibiotic coverage. Following a period of conservative treatment with antibiotics and warm soaks, patients with parotid abscesses will usually undergo an incision and drainage procedure, and later, parotidectomy. A case of parotid abscess is presented in which a CT scan with intravenous contrast enhancement localized the abscess cavity and guided its aspiration and drainage with an indwelling catheter. Percutaneous drainage of parapharyngeal abscesses guided by CT has been previously described by Cole. By using this percutaneous technique, the need for early surgical intervention by incision and drainage was eliminated

Tumor invasion of the carotid artery is a potential indication for brachytherapy, which delivers a high dose of irradiation to residual tumor while limiting the dose to adjacent healthy tissues. The tolerance of carotid-sheath contents to varying doses of brachytherapy, however, has not been clearly established. In order to evaluate brachytherapy effects on carotid-sheath contents, after-loading catheters were implanted bilaterally in 3 groups of 6 rabbits each (18 rabbits). Iridium 192 brachytherapy doses of either 5000 cGy (rad), 9000 cGy, or 13,000 cGy were delivered unilaterally, with the contralateral neck serving as a nonirradiated control in each animal. There were no carotid ruptures and wound healing was normal. Two animals from each group were killed at 6, 20, and 48 weeks. Even at the highest dose (13,000 cGy), nerve conduction studies performed on the vagus nerve prior to sacrifice revealed no increased latency, histologic changes were minimal, and carotid arteries were patent. These observations suggest that the carotid-sheath contents in healthy rabbits could tolerate high doses (up to 13,000 cGy) of low-dose-rate interstitial brachytherapy without complications

A two-microphone dereverberation technique was evaluated by obtaining speech recognition measures and preference judgments from normal-hearing and hearing-impaired listeners. Monaural speech recognition performance was measured for two reverberation conditions (0.4 second and 1.2 seconds) with and without processing. Binaural speech recognition performance was also measured for the unprocessed conditions. In addition, paired-comparison judgments of preference were obtained for all combinations of the processed and unprocessed monaural stimuli. For both groups of subjects, scores at the shorter reverberation time were significantly higher than scores for the longer reverberation time. For the normal-hearing subjects, processing to dereverberate had no significant effect on speech recognition performance. Binaural presentation of the unprocessed signal yielded significantly higher scores. For the hearing-impaired subjects, performance was significantly better in the unprocessed condition than the processed condition, but was not significantly different from the binaural condition. Paired-comparison judgments revealed differences in patterns of preference between normal-hearing and hearing-impaired listeners