Recurrent laryngeal nerve alterations in developing spontaneously hypertensive rats.

OBJECTIVES/HYPOTHESIS: It is well known that the recurrent laryngeal nerve not only innervates the larynx but also contains baroreceptor fibers, as demonstrated by physiological studies. Because hypertension has a negative impact on both peripheral nerve morphology and the baroreflex, we investigated the recurrent laryngeal nerve morphological alterations related to the development of hypertension. METHODS: We compared morphological and morphometric aspects of different segments of the recurrent laryngeal nerve in male and female spontaneously hypertensive rats in different ages: 5, 8, and 20 weeks (n = 6 per group). Blood pressure and heart rate were recorded in anesthetized animals, followed by removal of the right and left recurrent laryngeal nerves for epoxy resin embedding and light microscopy analysis. Computer software was used for morphometric analysis. RESULTS: The blood pressure was significantly higher in 20-week-old animals compared to those at 5 weeks. Body weight increased significantly with age, as did the nerve fascicles. For the myelinated fibers and respective axons, there was a reduction of fiber size, more evident on the axon, associated with a reduction of the small myelinated fibers percentage in animals with high blood pressure. Also, 20-week-old animals showed a significant reduction of the blood vessel percentage of occupancy compared to younger ages. No differences were observed between genders. CONCLUSION: Hypertension development impaired axon growth, affecting mainly the small myelinated fibers. Males and females were affected equally. The alterations of the endoneural blood vessels probably played an important role on the small fibers alterations.

Synchronous electrical stimulation of laryngeal muscles: an alternative for enhancing recovery of unilateral recurrent laryngeal nerve paralysis.

BACKGROUND: Although electrical stimulation of the larynx has been widely studied for treating voice disorders, its effectiveness has not been assessed under safety and comfortable conditions. This article describes design, theoretical issues, and preliminary evaluation of an innovative system for transdermal electrical stimulation of the larynx. The proposed design includes synchronization of electrical stimuli with laryngeal neuromuscular activity. OBJECTIVE: To study whether synchronous electrical stimulation of the larynx could be helpful for improving voice quality in patients with dysphonia due to unilateral recurrent laryngeal nerve paralysis (URLNP). MATERIALS AND METHODS: A 3-year prospective study was carried out at the Instituto Nacional de Rehabilitacion in the Mexico City. Ten patients were subjected to transdermal current electrical stimulation synchronized with the fundamental frequency of the vibration of the vocal folds during phonation. The stimulation was triggered during the phase of maximum glottal occlusion. A complete acoustic voice analysis was performed before and after the period of electrical stimulation. RESULTS: Acoustic analysis revealed significant improvements in all parameters after the stimulation period. CONCLUSION: Transdermal synchronous electrical stimulation of vocal folds seems to be a safe and reliable procedure for enhancing voice quality in patients with (URLNP).

Endoscopic laser thyroarytenoid myoneurectomy in patients with adductor spasmodic dysphonia: a pilot study on long-term outcome on voice quality.

OBJECTIVES: Adductor spasmodic dysphonia (ADSD) is a focal laryngeal dystonia, which compromises greatly the quality of life of the patients involved. It is a severe vocal disorder characterized by spasms of laryngeal muscles during speech, producing phonatory breaks, forced, strained and strangled voice. Its symptoms result from involuntary and intermittent contractions of thyroarytenoid muscle during speech, which causes vocal fold to strain, pressing each vocal fold against the other and increasing glottic resistance. Botulinum toxin injection remains the gold-standard treatment. However, as injections should be repeated periodically leading to voice quality instability, a more definitive procedure would be desirable. In this pilot study we report the long-term vocal quality results of endoscopic laser thyroarytenoid myoneurectomy. STUDY DESIGN: Prospective study. METHODS: Surgery was performed in 15 patients (11 females and four males), aged between 29 and 73 years, diagnosed with ADSD. Voice Handicap Index (VHI) was obtained before and after surgery (median 31 months postoperatively). RESULTS: A significant improvement in VHI was observed after surgery, as compared with baseline values (P=0.001). The median and interquartile range for preoperative VHI was 99 and 13, respectively and 24 and 42, for postoperative VHI. Subjective improvement of voice as assessed by the patients showed median improvement of 80%. CONCLUSIONS: Because long-term follow-up showed significant improvement of voice quality, this innovative surgical technique seems a satisfactory alternative treatment of ADSD patients who seek a definite improvement of their condition.

Age-related changes in human laryngeal nerves.

OBJECTIVES: We sought to perform a morphometric analysis of myelinated fibers from laryngeal nerves with the aim of verifying quantitative changes due to the aging process. METHODS: A 1-cm fragment was collected from the superior laryngeal nerves and recurrent laryngeal nerves from 12 cadavers during autopsy. The sample was divided in two groups: an adult group (aged <60 years) and an elderly group (aged > or =60 years). RESULTS: The total number of myelinated fibers from the superior laryngeal nerves was similar in both groups (adult group = 9017 +/- 1692, elderly group = 7918 +/- 1624; P = 0.79). The adult group had a higher total number of myelinated fibers in the recurrent laryngeal nerves than that of the elderly group (adult group = 3276 +/- 383, elderly group = 2381 +/- 669; P = 0.005), as well as a higher total number of fibers in the laryngeal nerves (both superior and recurrent) than the elderly group (P = 0.02). CONCLUSIONS: The adult group has a higher total number of myelinated fibers in the laryngeal nerves than the elderly group.

Laryngeal electromyography: contribution to vocal fold immobility diagnosis.

Laryngeal Electromyography (LEMG) is a diagnostic test commonly used in patients with vocal fold movement disorder. The aim of this study is to describe LEMG in patients with vocal fold immobility. A total of 55 dysphonic patients with vocal fold immobility diagnosed by laryngeal endoscopy were grouped according to probable clinical cause: 1) unknown; 2) traumatic; or 3) tumoral compression. They were submitted to LEMG by percutaneous insertion of concentric needle electrode. LEMG was conclusive in all patients and showed a majority with peripheral nerve injury. LEMG diagnosed peripheral nerve damage in 25 group 1, 12 group 2, and 11 group 3 patients. LEMG was normal in 4 patients, suggesting cricoarytenoid joint fixation. Central nervous system disorders was suggested in 2 and myopathic pattern in 1. As the major cause of vocal fold immobility is peripheral nerve damage, LEMG is an important test to confirm diagnosis.