Motor root conduction in neuralgic amyotrophy: evidence of proximal conduction block
- Clinical Neurophysiology Unit, University Department of Clinical Neurology, The Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK
- Professor K R Mills, Clinical Neurophysiology Unit, University Department of Clinical Neurology, The Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK. Telephone 0044 1865 224709; fax 0044 1865 790493.
- Received 6 August 1998
- Revised 12 November 1998
- Accepted 20 November 1998
Abstract
OBJECTIVE To determine the presence and role of proximal conduction block in neuralgic amyotrophy.
METHODS Percutaneous electrical stimulation of cervical roots and brachial plexus was employed in eight patients with neuralgic amyotrophy. Root to Erb’s point compound muscle action potential amplitude ratios for abductor digiti minimi, extensor digitorum communis, biceps, and deltoid muscles were compared with results obtained from 10 healthy controls.
RESULTS Conduction block in the nerve to one muscle was found in three of eight patients (38%) suggesting focal proximal demyelination. Repeat studies showed axonal degeneration, resolution, and persistence of conduction block in these three patients respectively.
CONCLUSION Focal conduction block plays a significant part in the pathogenesis of neuralgic amyotrophy, which is generally regarded as an axon loss process. Therapeutic intervention should be directed to patients with persistent conduction block, with the aim of eradicating the block and possibly minimising subsequent axon loss.
