Authors: Jannis Constantinidis¹; Arasch Akbarian²; Helmut Steinhart¹; Heinrich Iro¹; Angelika Mautes²

Source: Acta Oto-Laryngologica, Volume 123, Number 8, October 2003 , pp. 998-1003(6)

Publisher: Informa Healthcare

Abstract:

Objective--To investigate regeneration of the mimic musculature after delayed facial nerve repair. Materials and Method--In 30 rats the facial nerve on the right side was resected and immediately repaired with an end-to-end anastomosis. The entire levator labii muscle was removed on the right side and histochemically and morphometrically analyzed at 7, 14, 21, 28, 90 and 180 days after immediate nerve repair. In a further 20 rats, reinnervation was performed after 4 weeks in a further operation and the muscle was assessed at 14, 28, 90 and 180 days. Seven muscles of four normal rats were used as controls. Results--Three muscle fiber types could be identified by comparative histochemical analysis of two enzymes of succinate dehydrogenase (SDH) and m-ATPase: oxidative glycolytic (FOG) fibers, fast glycolytic (FG) fibers and intermediate muscle fibers that were designated SDH-INT. The number of fibers and the frequency distribution of single-fiber cross-sectional areas were determined for each type of fiber. No significant difference in the cross-sectional area of all fiber types was noted after 180 days when comparing immediate and delayed end-to-end sutures. In contrast, comparison of the fiber-type composition showed a significant increase in the number of FG fibers in the delayed suture, at the expense of FOG fibers. After immediate reinnervation the muscle approximately attained its natural fiber-type composition, whereas after delayed reinnervation the muscle showed an overall loss of oxidative capacity and differentiation towards phasic activity. Conclusion--Changes in fiber-type composition following delayed nerve suture are irreversible and have specific effects on the precise function of the muscle. Immediate nerve repair improves axonal reinnervation.

Keywords: enzyme histochemistry; experimental reinnervation; fiber typing; mimic muscle

Document Type: Research article

DOI: http://dx.doi.org/10.1080/00016480310001853

Affiliations: 1: Department of Otorhinolaryngology University of Erlangen--Nuremberg Erlangen 2: Department of Neurosurgery University of Saarland Homburg

Publication date: 2003-10-01

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