Age-dependent development of chronic neuropathic pain, allodynia and sensory recovery after upper limb nerve injury in children.

Forty-nine children with distal upper limb nerve injury were studied at a mean follow-up of 2 years 3 months. Patients who were aged 5 years or younger at the time of nerve injury (15/49) had no chronic neuropathic pain symptoms or allodynia. Patients with allodynia on quantitative sensory testing but no spontaneous pain (8/49) were all older than 5 years and those reporting spontaneous chronic neuropathic pain (5/49) were all older than 12 years at the time of injury. Previous studies of adults with similar nerve injuries report chronic hyperaesthesia in up to 40% of cases. Semmes-Weinstein monofilament testing showed a positive correlation between age at injury and abnormal sensory threshold (r = 0.60, P<0.0001). These findings indicate that young children show better sensory recovery and are less likely to develop long-term chronic neuropathic pain syndromes than adults following nerve injury.