The Perception of a Tactile Illusion in Central and Peripheral Nervous System Injury

Neuropathic pain patients often have lemniscal-mediated symptoms such as tactile allodynia. A novel method and device for testing lemniscal pathway integrity is described using a tactile illusion (TI) in patients with neuropathic pain resulting from peripheral nervous system (PNS) or central nervous system (CNS) injury. An unexpected enhanced perception of the TI was found in some PNS injured pain patients with mononeuropathies, in the majority of cervical spinal cord injured and in nearly half of brainstem injured central pain patients. A disinhibition of lemniscal pathway mediated TI was found in these patients. A subset of thalamic pain patients have a unique TI perseveration or persistent after-sensation despite reduced TI perception on their affected side compared to their normal side. The results of these studies indicate a unique form of sensory disinhibition not previously described.