Brachial plexus involvement in familial pressure-sensitive neuropathy: electrophysiological and morphological findings.

Two family members with hereditary pressure-sensitive neuropathy are reported. One patient presented atypically with acute brachial plexus neuropathy following transaxillary removal of the first rib. Electrophysiological studies showed slowing of motor nerve conduction in clinically affected and unaffected nerves. In vitro recording of the compound action potential of the subclinically involved sural nerve showed pronounced slowing in conduction of large and small myelinated fiber groups. These alterations correlated with morphological studies of the sural nerve that showed tomacula with acute and healed segmental demyelination. An inherited, generalized neuropathy manifested by a morphological abnormality of myelination may render peripheral nerves unduly susceptible to mechanical trauma, including positional pressure or traction effects during general anesthesia.