Chronic hereditary ataxic polyneuropathy.

Sensory ataxic polyneuropathies are characterised by the presence of sensor y ataxia due to damage to large myelinated sensory fibres, with total or re lative preservation of muscle strength, pain and temperature sensation. Her editary ataxic polyneuropathies are exceptional and very few families with this disorder have been reported so far. We here describe the neurologial, electrophysiological and sural nerve biopsy data of four siblings with an a taxic chronic polyneuropathy, starting after age 50. They had an ataxic gai t which worsened in darkness, horizontal nystagmus, hypo or arreflexia, and severe impairment of limbs' proprioception. Nerve conduction studies showe d absent sensory nerve action potentials in all nerves tested. Somatosensor y evoked potentials showed reduced amplitude and prolonged latencies. Sural nerve biopsy showed a severe loss of myelinated and unmyelinated fibres. S ymptoms slowly progressed over the years. The recognition of this syndrome is important in the search for the etiology of chronic ataxic neuropathies.