Painful diabetic neuropathy.

PDN is commonly caused by involvement of either the C fibres or the Aδ fibres. PDN caused by the involvement of small nerve fibers (C fibres), may present without objective clinical findings, such as decreased peripheral reflexes or abnormalities, on routine electrophysiological studies. Small fiber neuropathies may manifest as a number of different clinical symptoms, including allodynia, burning pain, defective warm thermal sensation, and defective autonomic function, e.g. decreased sweating, dry skin, and impaired vasomotor control. Large fibre (Aδ) pain is deepseated gnawing, dull or cramping with impaired vibration perception and position sense, depressed tendon reflexes, and sensory ataxia with marked electrophysiological abnormalities.