[Chronic hereditary ataxic polyneuropathy].

Sensory ataxic polyneuropathies are characterised by the presence of sensory ataxia due to damage to large myelinated sensory fibres, with total or relative preservation of muscle strength, pain and temperature sensation. Hereditary ataxic polyneuropathies are exceptional and very few families with this disorder have been reported so far. We here describe the neurological, electrophysiological and sural nerve biopsy data of four siblings with an ataxic chronic polyneuropathy, starting after age 50. They had an ataxic gait which worsened in darkness, horizontal nystagmus, hypo or areflexia, and severe impairment of limbs' propriocaption. Nerve conduction studies showed absent sensory nerve action potentials in all nerves tested. Somatosensory evoked potentials showed reduced amplitude and prolonged latencies. Sural nerve biopsy showed a severe loss of myelinated and unmyelinated fibres. Symptoms slowly progressed over the years. The recognition of this syndrome is important in the search for the etiology of chronic ataxic neuropathies.