Takumi Miura

Functional roles of the superior laryngeal nerve afferents in electrically induced vocalization in anesthetized cats

Our purpose was to elucidate the functional roles of the laryngeal afferents in controlling vocalization. We investigated the effects of laryngeal deafferentation (sectioning the internal branch of the superior laryngeal nerve (ISLN)) on respiration and voice quality during electrically-induced vocalization in twelve ketamine anesthetized cats. Co-ordinated vocal activity was obtained by electrical stimulation to the pontine call site. After the bilateral ISLN section, the respiratory, expiratory and inspiratory durations during induced vocalization became 0.56 +/- 0.15, 0.44 +/- 0.12 and 0.67 +/- 0.19 (mean +/- S.D., n = 9) times, respectively, compared with those before the ISLN section. A decrease in respiratory duration was also observed when local anesthetics were applied to the laryngeal mucosa. The laryngeal deafferentation increased the degree of hoarseness with a decrease in the fundamental frequency. Since the laryngeal deafferentation caused a decrease in the intralaryngeal adductor activities, it was suspected that the voice quality change was partly caused by the reduction in adductor activities. It was thus concluded that feedback via laryngeal afferents plays an important role in controlling vocalization.

Laryngeal afferent inputs during vocalization in the cat.

To reveal the kind of information about the larynx which is transmitted to the central nervous system during vocalization, we studied discharge patterns of single fibers of the laryngeal afferent nerve during electrically induced vocalization in ketamine-anesthetized cats. Recorded fibers were classified into four types based on their discharge patterns. Type A fibers responded to vocal fold vibration during vocalization. Type B fibers increased their activity during vocalization without synchronization with vocal fold vibration. Type C fibers decreased their activity during vocalization. Type D fibers discharged only at the onset of vocal fold adduction and abduction. We discuss the functional properties of these afferents and the possibility that these afferent inputs participate in the feedback control of vocalization.

Recent Experiences with Four Patients with Rhinogenic Intracranial Complications.

Case 1: A 21-year-old male had abscess of the brain and interhemispheric subdural area secondary to acute frontal sinusitis. Case 2: A 55-yera-old female had two brain abscesses. Case 3: A 15-year-old female had an epidural abscess secondary to acute frontal sinusitis. Case 4: A 15-year-old male had a subdural abscess. All 4 patients were treated successfully. The developpment of antibiotic therapy has reduced the incidence of rhinogenic intracranial complications, but 38 cases were reported in the past 10 years. Careful observation, prompt diagnosis and early treatment are very important.