Conduction block in hereditary neuropathy with susceptibility to pressure palsies.

Slow nerve conduction velocities, temporal dispersion of action potentials and conduction block occur in polyneuropathies with segmental demyelination. Conduction block has been reported in focal compressive neuropathies and in acute and chronic autoimmune polyneuropathy but not in hereditary motor and sensory demyelinating neuropathy. We report conduction block in five nerves of four patients from two families with a hereditary neuropathy with susceptibility to pressure palsies and pathologic changes of segmental demyelination and tomaculous swellings. Conduction block that may be long lasting is a feature of this type of hereditary neuropathy, which should be considered in the differential diagnosis of this electrophysiologic finding.