Idiopathic distal small fiber neuropathy.

We describe the clinical details of 20 elderly patients with idiopathic small fiber neuropathy. This neuropathy is ubiquitous in practice but has not been well characterized. The clinical syndrome is relatively stereotyped and appears to be a frequent cause of burning feet in the elderly. The main features were burning, painful paresthesias and dysesthesias in the feet, lancinating pains, moderate to severe distal small fiber sensory loss, absent ankle reflexes, and minimal or no distal foot weakness. All but 2 had mild loss of vibration sense but none had significant proprioceptive loss or sensory ataxia. EMG was normal in 9 while the others had a mild sensorimotor axonal neuropathy. Sural nerve biopsy was normal in 3 and showed axonal loss in 6. Progression was slow, and although pain was a troublesome symptom, no patient became disabled. Symptoms were refractory to most symptomatic therapies but several patients improved with gammaglobulin infusions.