Hemisomatic central sensitivity Pain DisorDer (“Hemi-fibromyalgia synDrome”)

Background: We describe a poorly recognized central sensitivity pain disorder (CSPD) presenting with moderate to severe chronic hemisomatic pain (limited to half of the body). In 7 patients, the syndrome developed spontaneously and masqueraded as common spinal or arthritic disorders, but none of these patients responded to standard therapies for the disorders they resembled. A key feature in the patients was the presence of hemisomatic myofascial tenderness reminiscent of fibromyalgia syndrome (FMS), but it was only present on half of the body. However, most patients did not meet current diagnostic criteria for FMS. Objective: To describe a new (or poorly recognized) clinical entity characterized by chronic hemisomatic pain. Study Design: An observational study and case series. Observations: Seven patients exhibiting unilateral hemisomatic pain affecting the trunk and upper and lower extremities were identified at a subspecialty pain medicine clinic from 2013 to 2016. The pain was moderate to severe in 6 patients and mild to moderate in one patient. In contrast to FMS, the patients had minimal psychological comorbidities and low indexes for somatic complaints. Conclusions: Despite its relatively high frequency, neurologists and pain specialists are unfamiliar with this syndrome of chronic hemisomatic pain. This entity appears to represent a CSPD of cryptic etiology rather than a somatoform or psychiatric condition. Although most of these patients had previously been evaluated at academic centers by different specialists, they frequently underwent invasive interventions which were not efficacious. Diagnostic criteria for its identification are proposed in this paper.