CMT/HMSN Type L

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J. Neurol. Neurosurg. Psychiatry, June 1, 2005; 76(6)

The electrophysiological profile of hereditary motor and sensory

neuropathy-Lom.

BA Ishpekova, LG Christova, AS androv, and PK

Department of Medical Neurology, Medical University, Sofia, Bulgaria.

OBJECTIVE: To make electrophysiological observations on a large

kindred with hereditary motor and sensory neuropathy-Lom (HMSN-L)

containing 27 affected individuals.

CLINICAL FINDINGS: Onset was in early childhood with gait difficulty

related to progressive lower limb weakness. Upper limb weakness

developed later. Bulbar involvement was present in one third of the

patients, and deafness appeared during the second or third decades.

ELECTROPHYSIOLOGICAL FINDINGS: Electromyographic evidence of

denervation was progressive, more severe distally, and greater in the

legs, being total in distal lower limb muscles in most patients.

Sensory action potentials were absent and motor nerve conduction was

severely slowed. This included proximal upper limb (musculocutaneous

and axillary), hypoglossal, and facial nerves. The severity of

slowing increased during childhood. M waves, often multiple, were

recorded in all affected individuals. The blink reflex showed an

unusual three component response. The latencies of all three

components were prolonged.

CONCLUSIONS: HMSN-L is shown to be a demyelinating neuropathy

involving severe and early axonal loss. The progressive slowing of

nerve conduction during childhood differs from the static reduction

seen in type I HMSN.