Age-related changes in rat intrinsic laryngeal muscles: analysis of muscle fibers, muscle fiber proteins, and subneural apparatuses.

We compared age-related changes in the intrinsic laryngeal muscles of aged and young adult rats by determining the number and diameter of muscle fibers, contractile muscle protein (myosin heavy chain isoforms, MHC) composition, and the morphology of the subneural apparatuses. In aged rats, both the numbers and the diameters of muscle fibers decreased in the cricothyroid (CT) muscle. The number of fibers, but not diameter, decreased in the thyroarytenoid (TA) muscle. In the posterior cricoarytenoid (PCA) muscle, neither the number nor the diameter of fibers changed significantly. Aging was associated with a decrease in type IIB and an increase in type IIA MHC isoform levels in CT muscle, but no such changes were observed in the TA or PCA muscles. Morphological examination of primary synaptic clefts of the subneural apparatus revealed that aging resulted in decreased labyrinthine and increased depression types in only the CT muscle. In the aged group, morphologically immature subneural apparatuses were found infrequently in the CT muscle, indicating continued tissue remodeling. We suggest, therefore, that age-related changes in the intrinsic laryngeal muscles primarily involve the CT muscle, whereas the structures of the TA and PCA muscles may better resist aging processes and therefore are less vulnerable to functional impairment. This may reflect differences in their roles; the CT muscle controls the tone of the vocal folds, while the TA and PCA muscles play an essential role in vital activities such as respiration and swallowing.

Restoring vocal fold movement after transection and immediate suturing of the recurrent laryngeal nerve with local application of basic fibroblast growth factor: an experimental study in the rat.

OBJECTIVE: To evaluate the effects of basic fibro-blast growth factor (bFGF) on the recovery of vocal fold movement and the attenuation of laryngeal muscle atrophy after transection of the recurrent laryngeal nerve (RLN). STUDY DESIGN: Quantitative assessment of vocal fold movement using the video cassette recorder (VCR) image-analysis method and histologic examination of the laryngeal muscle. METHODS: Fifty-eight Wistar rats underwent RLN transection and one of the following three procedures: 1) transection of the RLN alone (transection group, n = 18), 2) suture of the nerve stumps followed by local administration of phosphate-buffered saline (PBS) solution using an osmotic pump (PBS group, n =20), or 3) suture of the nerve stumps followed by local administration of bFGF (FGF group, n = 20). Vocal fold movements were recorded with VCR by way of a rigid endoscope, and the VCR images were analyzed on a computer. Histologic changes in the thyroarytenoid (TA) muscle were evaluated by measuring the cross-sectional area of the muscle and average size of muscle fibers. RESULTS: In the transection group, vocal fold movement did not recover, and atrophy of the TA muscle gradually progressed after sectioning the nerve. In contrast, vocal fold movement as assessed by VCR image-analysis recovered in some cases in the immediate suturing groups, more markedly in the FGF group (34.1 +/- 29.1%) than in the PBS group (5.5 +/- 7.9%) (P <.05). Histologically, atrophy of the laryngeal muscle was significantly attenuated by the local administration of bFGF. CONCLUSION: bFGF facilitates regeneration of the transected RLN and attenuation of intrinsic laryngeal muscle atrophy, thereby restoring laryngeal function.

Incidence of long-term ipsilateral and contralateral ototoxicity following radiotherapy for nasopharyngeal carcinoma.

OBJECTIVE: To characterize the long-term adverse effects of radiotherapy on the ears in patients with nasopharyngeal carcinoma (NPC), we investigated ipsilateral and contralateral ototoxicities in the external, middle, and inner ear. METHODS: The records of 48 ears in 24 radiotherapy-treated NPC patients were retrospectively analyzed. Radiotherapy doses varied between 60 and 70 Gy in 2-Gy fractions at 5 fractions/week. Ototoxicities were identified by otoscope and pure-tone audiograms conducted at 2-3 month intervals for ≥12 months. The relationship between radiation dosage and sensorineural threshold deterioration was statistically compared using the Mann-Whitney U-test. RESULTS: Post-radiotherapy, 50% of all ears (3 of 6) that developed severe otitis externa were on the contralateral side. There was a post-radiotherapy increase in contralateral otitis media with effusion (OME) (1-7 ears), but a decrease in ipsilateral cases (16-12 ears), with 2 ears on either side subsequently developing chronic otitis media (COM). All ears that showed sensorineural hearing loss (SNHL) before radiotherapy exhibited a further threshold deterioration of more than 15 dB. No statistically significant difference (p=0.086) in average radiation dose was seen between ears with sensorineural threshold deterioration (50.0 Gy) and those without (48.2 Gy). CONCLUSION: Long-term ototoxicity following radiotherapy for NPC can occur in either the ipsilateral or contralateral ears. Pathophysiology varies between and within each side. The post-therapy increase in OME on the contralateral side was thought to be due to radiotherapy-induced Eustachian tube damage, and the sensorineural threshold deterioration in at least 4 ears was thought to be due to chronic cochlea damage secondary to COM.

Laterofixation of the vocal fold using an endo-extralaryngeal needle carrier for bilateral vocal fold paralysis.

OBJECTIVES: Laterofixation of the vocal fold is a simple and reliable surgical intervention for laryngeal obstruction due to bilateral vocal fold fixation to obtain sufficient glottal space. Nevertheless, it has some technical disadvantages. This report summarizes the surgical outcomes in patients who underwent laterofixation of the vocal fold with or without the use of an endo-extralaryngeal needle carrier (EENC). METHODS: A prospective study of 11 consecutive patients with bilateral vocal fold paralysis. All of the patients underwent unilateral vocal fold laterofixation. Six patients were assigned to the non-EENC group and five to the EENC group. The surgical outcomes were evaluated, including the operating time and respiratory and phonatory functions. RESULTS: The operating time was 44% shorter in the EENC group and less skin incisions were required. Postoperatively, the dyspnea was eliminated in all of the patients in both groups, and the six patients who required a tracheotomy were successfully decannulated. Spirometry confirmed the improvements in %FEV(1) and %PEF in the two groups. Postoperative voice function was socially acceptable in all patients, and it tended to be better in the non-EENC group. In the EENC group, one patient developed a minor submucosal hematoma and another patient had a recurrence of dyspnea 2 months postoperatively, probably due to thread disruption. CONCLUSION: The present study confirms that laterofixation of the vocal fold with or without EENC relieves laryngeal obstruction. Surgery with the EENC is simpler and quicker than the conventional procedure. However, the surgery with the EENC has some disadvantages, including likely problems with the thread and downward traction on the vocal fold. Surgeons should be aware of these possible shortcomings.