Massive nerve root enlargement in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE To report three patients with chronic inflammatory demyelinating polyneuropathy (CIDP) presenting with symptoms suggestive of cervical (one patient) and lumbar root disease. METHODS Nerve conduction studies, EMG, and nerve biopsy were carried out, having found the nerve roots to be very enlarged on MRI, CT myelography, and at surgery. RESULTS Clinically, peripheral nerve thickening was slight or absent. Subsequently one patient developed facial nerve hypertrophy. This was mistaken for an inner ear tumour and biopsied, with consequent facial palsy. Neurophysiological tests suggested a demyelinating polyneuropathy. Sural nerve biopsy showed in all cases some loss of myelinated fibres, inflammatory cell infiltration, and a few onion bulbs. Hypertrophic changes were much more prominent on posterior nerve root biopsy in one patient: many fibres were surrounded by several layers of Schwann cell cytoplasm. There was an excellent response to steroids in two patients but not in the third (most advanced) patient, who has benefited only marginally from intravenous immunoglobulin therapy. CONCLUSIONS MRI of the cauda equina may be a useful adjunct in the diagnosis of CIDP.