The functional organization of the nucleus ambiguus

OtolaryngologyHead and Neck Surgery Scientific Sessions--Tuesday

Volume 121 Number 2

symptoms were measured using an independent rating scale without knowledge of subject identity. The numbers of speech breaks were counted before and after treatment. Results: In contrast to normal research volunteers, some patients had reduced adductor muscle activation in one or both thyroarytenoid muscles during speech breaks. These patients were more severely affected on initial evaluation. Other abnormalities observed were increased activity in the cricothyroid and posterior cricoarytenoid muscles. Less than half the patients had a significant speech benefit following bilateral injections of the posterior cricoarytenoid muscle. Conclusions: Our results suggest that the pathophysiology of abductor spasmodic dysphonia can involve reduced activation of the thyroarytenoid muscles during vocal fold adduction for speech tasks rather than only being due to hyperactivity of the laryngeal abductor muscles. This was further supported by the limited improvement of symptoms observed in some patients receiving botulinum injections in the posterior cricoarytenoid muscle. Clinical Significance of Study: These results may provide an improved understanding of the pathophysiology of abductor spasmodic dysphonia. Ultimately, we hope this knowledge will contribute to developing more effective treatments for this poorly understood disorder. 8:50 AM

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(100%, injections _<5.0 p.L), CT (100%, excluding those that arise from the retrofacial nucleus), CN (100%), and horizontal compartment of the PCA (>75%). Motoneurons supplying the vertical compartment of the PCA (inspiratory) were located medially, and those from the muscularis (lateral part of TA) were located laterally. Conclusion: The NA of the dog appears to be organized into 3 distinct cell columns with each being primarily concerned with different functions of the vocal folds. The largest column is the dorsal, and it appears to be related to phonation. The smallest column is the medial and is believed to be respiration related. The motoneurons of the medial column were quite distinct, being smaller and having a different size and shape than other NA motoneurons. Finally, the lateral column, which appears to innervate the muscularis, may primarily be concerned with reflex glottic closure. Clinical Significance: The apparent functional organization of the NA seems to remove some of its ambiguity. The ability to localize function to different parts of the NA will allow further research to be done into the organization of brain stem systems controlling phonation, respiration, and glottic protection, both in animal models and human pathologic material. Dysfunction in these systems is a common manifestation of neurologic disease and is often life-threatening. (Supported by grant DC 01764 from the NIDCD.)

The Functional Organization of the Nucleus Ambiguus IRA SANDERS MD

(presenter); BEI-LIAN WU MD; New York NY

Problem: It is hypothesized that the laryngeal muscles are composed of functionally distinct compartments that are specialized for phonation, respiration, or reflex glottic closure. Numerous studies show that the laryngeal muscles of both the dog and the human have distinctive anatomical specializations within these hypothesized muscle compartments. In this study, the location of motoneurons within the NA that innervate different compartments was studied to determine whether they are grouped according to function. Methods: Twenty separate neural tract tracing experiments using horseradish peroxidase or cholera toxin were performed in dogs. Injections of tracer were made into the vocalis (the medial compartment of the thyroarytenoid muscle) (TA, n = 6), the cricothyroid muscle (CT, n = 1), or the compartments of the posterior cricoarytenoid muscle (PCA, n = 10). In addition, the communicating nerve (CN), a newly described source of motor innervationto the vocalis, was also traced (n = 3). Brain stem sections from each experiment were examined, and the location of labeled motoneurons was recorded. Results: It was found that the NA of the dog is separable into 3 longitudinal columns: dorsal, medial, and lateral. The dorsal column appeared to contain motoneurons innervating putative phonatory-related muscle compartments: vocalis

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Objective Measures of Improved Voice Following Medialization Laryngoplasty CHERYL R BILLANTE PHD (presenter); JANYE R MOORE MS; JAMES L NEI-rERVILLEMD; Nashville TN

Problem: Medialization laryngoplasty for unilateral vocal fold paralysis restores normal or near-normal voice. Preoperative voice data confirm instability in the acoustic signal with elevated measures of perturbation. Frequency and intensity ranges are typically narrowed. Glottal flow rates are abnormally high, indicative of a laryngeal valve inefficient in the modulation of airflow during vocal fold vibration. Perceptual analysis confirms loss of vocal volume, breathy voice quality, and in some patients, elevated pitch. The purpose of this investigation was to evaluate and compare perceptual, acoustic, and aerodynamic measures of voice in patients with unilateral vocal fold paralysis prior to medialization laryngoplasty, and at 3 months and 1 year after surgery. Methods: Forty patients with unilateral vocal fold paralysis underwent type I thyroptasty with or without arytenoid adduction. Preoperative and postoperative perceptual judgments of pitch, loudness, and quality were made by 2 speechlanguage pathologists. A digital audiotape recorder (Sony) and microphone (AKG) with a fixed mouth-to-microphone