Yuji Kawamura

Motor Innervation of the Guinea Pig Interarytenoid Muscle: Reinnervation Process Following Unilateral Denervation

The authors investigated the process of denervation and reinnervation of the interarytenoid (IA) muscle in the guinea pig using transmission electron microscopy and glycogen depletion technique after unilateral transection of the recurrent laryngeal nerve (RLN) and superior laryngeal nerve to clarify the innervation pattern of the unpaired IA muscle. Anastomosis between the bilateral arytenoid branches was confirmed in the belly of the IA muscle. Five weeks after transection, all of the IA muscle fibers appeared to have been reinnervated by the contralateral RLN. As the arytenoid branch of the RLN runs together with that of the contralateral RLN in a single intramuscular nerve funiculus, it is possible that collateral sprouting branches grow and extend into the adjacent denervated Schwanns sheaths. The authors conclude that the unpaired IA muscle, as a whole, receives specific motor nerve supply from the bilateral RLNs, although each muscle fiber is innervated unilaterally.

Motor Innervation of the Arytenoid Muscle Viewed from

Seij i Kawakita ), Ryuichi Aibara 2 ), Masamitsu Hyodo ), Yuji Kawamura 3) and Eiji Yumoto 1) Using 38 guinea pigs with unpaired arytenoid muscle (AR) , the innervation pattern of the AR was studied viewed from reinnervation process following unilateral (left) recurrent laryngeal nerve (RLN) transection. Light and electron microscopic observation, glycogen depletion experiment, and histochemical study using the adenosine triphosphatase (ATPase) stain were carried out. Seven days after transection, both myelinated and unmyelinated fibers were noted in the intramuscular nerve funiculus. Thus, the anastomosis of the arytenoid branches between both RLNs was found in the belly of AR. Three types of the neuromuscular junctions (NMJs) were observed; normal, degenerated, and regenerated NMJs. Five weeks after transection, however, neither degeneration nor regeneration of the NMJ were seen. Until three weeks after transection, half of the AR fibers were stained with PAS staining following electrical stimulation of the contra lateral (right) RLN. Five weeks after transection, all the AR fibers were unstained. Therefore, all the AR fibers were considered to have been reinnervated by the contra lateral RLN. ATP stain of the AR showed that type 2 fibers were predominant regardless of the period following unilateral denervation. The present study indicates that transection of the unilateral RLN facilitates collateral sprouting from the contra lateral RLN, and that these collateral sprouting reinnervated the denervated muscle fibers before degeneration occurs. Therefore the AR, as a whole, receives a specific motor innervation from the bilateral RLNs, although each muscle fiber is innervated by the unilateral RLN.

Gadolinium-enhanced MR imaging in Bell's palsy. A preliminary report.

We carried out magnetic resonance imaging (MRJ) in 3 cases of Bells palsy. Case 1 was a 43 y. o. male, case 2 was a 21 y. o. female and case 3 was a 64 y. o. male. The diagnosis was in complete: Bells palsy. Tl-weighted images (TR500/TE25-33) were taken before and after the intravenous administration of Gd-DTPA (0.1mmol/kg) using 0.5 Tesla superconductive type MRI 3, 8, and 11 days respectively after the onset. In the ipsilateral intratemporal facial nerve, enhancement of signalintensity was seen in the geniculate ganglion in casel, in the mastoid portion in case 2, and in the labyrinthine portion and geniculate ganglion in case 3. The possibility of imaging the facial nerve in Bells palsy was demonstrated, and the diagnostic significance of Gd-enhanced MRI was discussed in this preliminary investigation.