SENSORY NERVE PATHOLOGY IN MULTIFOCAL MOTOR NEUROPATHY

The nosological status of multifocal motor neuropathy remains controve rsial. The clinical and electrodiagnostic hallmarks suggest selective motor fiber involvement. In this study, we asked to what extent sensor y nerves might be involved pathologically in multifocal motor neuropat hy. Examination of sensory nerve biopsy specimens from 11 patients did reveal pathological findings in all, but they were very mild. An incr eased number of thinly myelinated, large-caliber fibers was the unifyi ng feature common to each specimen. By electron microscopy, each biops y specimen had thinly myelinated fibers surrounded by minor onion bulb s. Active demyelination, though scant, was seen in 3 nerves. Myelinate d fiber density was normal. Subperineurial edema and inflammation were not present We conclude that multifocal motor neuropathy is not an ex clusively motor abnormality, although it appears to be so clinically a nd electrophysiologically. The frequent, albeit mild, pathological abn ormalities in sensory fibers suggest that the demyelinating pathophysi ology also affects sensory fibers, but to a lesser degree than motor f ibers. Some investigators maintain that multifocal motor neuropathy is within the spectrum of chronic inflammatory demyelinating polyneuropa thy. The very mild degree of sensory fiber involvement, the absence of inflammation or edema, and the distinctive clinical features support the concept of multifocal motor neuropathy as distinct from chronic in flammatory demyelinating polyneuropathy.