Neuromuscular junctions of the posterior cricoarytenoid muscle in multiple system atrophy: a case study.

Conclusion: The present study showed a variety of stages of neurogenic degeneration of the muscle fibers and the neuromuscular junctions (NMJs) of the posterior cricoarytenoid (PCA) muscle in multiple system atrophy (MSA). These findings coincide with abductor paralysis of vocal cords. Ultrastructural features of the NMJs of the PCA muscle in MSA were different from those of previous studies on experimental resection of recurrent nerve and amyotrophic lateral sclerosis (ALS).

Objectives: MSA may influence various respiratory functions. Upper airway tracts including larynx are affected without exception during its clinical course. Morphological changes of NMJs of the intrinsic laryngeal muscle in MSA were examined ultrastructurally.

Patient and methods: The patient was a 68-year-old male complaining of recurrent aspiration pneumonia, dysphagia, respiratory disturbance, and abductor paralysis of vocal cords. The motor nerve terminals of the PCA muscle in a patient with MSA were investigated electron microscopically.

Results: The NMJs showed varying degrees of ultrastructural changes by motor nerve degeneration. They were seen in the pre- and post-synaptic regions. Muscle fibers losing nerve terminals showed severe damage in their cytoplasm.