Nondermatomal somatosensory deficits: overview of unexplainable negative sensory phenomena in chronic pain patients

Purpose of review To review the literature and our current understanding of nondermatomal somatosensory deficits (NDSDs) associated with chronic pain in regards to their prevalence, assessment and clinical presentation, cause and pathophysiology, relationship with conversion disorder and psychological factors, as well as their treatment and prognosis. Recent findings NDSDs are negative sensory deficits consisting of partial or total loss of sensation to pinprick, light touch or other cutaneous modalities. Although they had been noted more than a century ago and appear prevalent in chronic pain populations, they are poorly studied. They may be very mild or very dense, may occupy large body areas, are often highly dynamic and changeable or, to the contrary, very stable and long lasting. NDSDs may occur in the absence of biomedical pathology or coexist with structural musculoskeletal or nervous system abnormalities. They appear to be associated with psychological factors and a poor prognosis for response to treatment and return to work. Recent brain imaging studies provide a basis for understanding NDSD pathophysiology. Summary NDSDs represent prevalent phenomena associated with chronic pain. Further, research is needed to elucidate their origin, response to treatment, and prevalence in the general population, primary care settings, and nonpain patients.