Peripheral neuropathy in hereditary spastic paraplegia due to spastin (SPG4) mutation--a neurophysiological study using excitability techniques.

OBJECTIVE

To identify peripheral nerve abnormalities in hereditary spastic paraplegia (HSP) due to mutations in the spastin gene (spastic paraplegia 4, SPG4) using standard nerve conduction (NCS) and novel tests of axonal excitability.

METHODS

Eleven patients with known mutations in spastin were assessed with NCS for the upper and lower limbs, and axonal excitability testing on the median nerve.

RESULTS

Standard nerve conduction studies revealed a sensorimotor neuropathy in two patients. Excitability studies on median motor axons showed an isolated abnormality (increased strength-duration time constant), but those on sensory axons were normal in nine patients with normal routine nerve conduction studies.

CONCLUSIONS

Peripheral neuropathy occurs in HSP patients with SPG4 mutations, but axonal excitability studies provide limited additional evidence for subclinical peripheral nerve dysfunction, and add little further to standard nerve conduction studies.

SIGNIFICANCE: The features of HSP due to SPG4 mutations include sensorimotor polyneuropathy. The value of excitability studies is limited in individual patients.