UNILATERAL DECREASE IN THALAMIC ACTIVITY OBSERVED WITH POSITRON EMISSION TOMOGRAPHY IN PATIENTS WITH CHRONIC NEUROPATHIC PAIN

The oxygen-15 water bolus positron emission tomography (PET) method wa s used to image regional brain activity in 4 patients with chronic pos t-traumatic neuropathic pain confined to one lower limb and in 1 patie nt with post-herpetic neuralgia. In comparison to 13 normal subjects, scans of the patients disclosed a statistically significant decrease i n thalamic activity contralateral to the symptomatic side. Examination of the right/left ratio for all the subjects showed that the values f or the patients fell at the extremes of the normal range, according to the side of the affected body part. These initial observations sugges t that functional alterations in thalamic pain processing circuits may be an important component of chronic neuropathic pain.