Unexplainable nondermatomal somatosensory deficits in patients with chronic nonmalignant pain in the context of litigation/compensation: a role for involvement of central factors?

Objective. To address the prevalence and characteristics of nondermatomal s omatosensory deficits (NDSD) in subjects with chronic pain in the context o f compensation/litigation. Methods. Data were collected via standardized history, examination, and pat ient- as well as physician-drawn body maps in a consecutive series of 194 s ubjects seen for the purpose of an independent medical examination. Results. Forty-nine subjects (25.3%) with primarily widespread pain (often diagnosed as fibromyalgia) presented with hemisensory or quadrotomal defici ts to pinprick and other cutaneous stimuli on the side of lateralized pain or worse pain. The NDSD limbs often had impairment of vibration sense (not infrequently associated with "forehead vibration split"), reduced strength, dexterity or movement, and extreme sensitivity to superficial skin palpati on or profound insensitivity to deep pain. Spatial, temporal, qualitative, and evolutionary patterns of NDSD emerged associated with cognitive/affecti ve symptoms. NDSD subjects were more often born outside Canada, more likely to be injured at work, present with abnormal pain behavior, and have negat ive investigations. Conclusion. NDSD are a prevalent problem associated with chronic pain. Futu re research should explore the prevalence of NDSD in other pain populations , the role of personality and related factors, and the underlying biologica l substrate of these deficits.