"Pseudo-conduction block" in a patient with vasculitic neuropathy.

A 63-year-old man presented with progressive asymmetric weakness and numbness in his hands of 2 weeks duration. Nerve conduction studies showed low amplitude motor evoked potentials of both median nerves. The right ulnar, left tibial and peroneal nerves had normal potentials on distal stimulation with markedly decreased amplitudes proximally, suggestive of "conduction block". Three weeks later, amplitudes were decreased throughout. The patient was diagnosed with vasculitis. The acute ischemic injury presumably resulted in axonal damage between the distal and proximal stimulation sites, with subsequent Wallerian degeneration.