Ectopic mechanosensitivity in injured sensory axons arises from the site of spontaneous electrogenesis

Injured sensory axons trapped in a neuroma or freely regenerating in the distal nerve stump, frequently display ectopic mechanosensitivity, spontaneous impulse discharge or both. This abnormal neural activity is thought to contribute to spontaneous and movement-evoked neuropathic paraesthesias, dysaesthesias and pain, as well as to allodynia and hyperalgesia. The present paper examines the relationship between mechanosensitivity and spontaneous discharge in three distinct sciatic nerve injury models in the rat: nerve transection (neuroma), nerve crush and chronic nerve constriction injury (CCI). Impulse pattern analysis was used to determine that the sites of mechanosensitivity and of spontaneous electrogenesis are either identical or very close to one another. This suggests that mechanosensitivity and spontaneous firing are aspects of a single underlying pathophysiological process.