Paradoxical clinical consequences of peripheral nerve injury: A review of anatomical, neurophysiological and psychological mechanisms

This paper reviews some of the possible explanations and mechanisms that may be responsible for variation from expected clinical findings soon after nerve injury in certain patients, and for subjective sensations and objective sensibility which can appear to arise from within the autonomous zone of the cutaneous distribution of a divided nerve. A number of features of peripheral innervation, central nervous system physiology and sensory psychology are discussed. These include: (1) the normal extent of overlap- or cross-innervation between the territories of adjacent peripheral nerves; (2) anomalous innervation due to normal anatomical variation; (3) ectopic impulse generation and cross-excitation between neurons in the peripheral nervous system after nerve injury; (4) neurophysiological responses and mechanisms of re-innervation other than axon regeneration across the site of nerve repair; (5) cortical somatotopic reorganisation in response to nerve injury; and (6) phantom sensory phenomena including the psychology of sensory perception.