In the clinic at the University of Helsinki, 17 patients were examined who presented widespread chronic pain with no visible lesions in brain magnetic imaging. Because the majority had herpes simplex virus (HSV) infections, the researchers studied a possible association between herpes and neuropathic pain. They hypothesized that in HSV-positive patients, the active virus may alter pain processing at different levels of the central nervous system (CNS).
Results of the study showed 80 percent of the patients reported at least moderate pain relief with anti-herpetic medication, and in more than half there was positive correlation between the activity of the HSV infection and pain.
The authors concluded that a CNS dysfunction is the most likely explanation for the widespread pain. Latency and possible activations of the herpes virus in brain areas involved in pain processing might cause functional changes in the pain matrix, even if there are no detectable lesions in anatomical MRI. Further, the strong inflammatory reactions in the CNS caused by activation of the virus may sensitize nerves at different levels.