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Unilateral decrease in thalamic activity observed with positron emission tomography in patients with chronic neuropathic pain

Iadarola, Michael J.*,a; Max, Mitchell B.a; Berman, Karen Faithb; Byas-Smith, Michael G.a; Coghill, Robert C.a; Gracely, Richard H.a; Bennett, Gary J.a

a Neurobiology and Anesthesiology Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892 USA

b Clinical Brain Disorders Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892 USA

*Corresponding author: Dr. M. J. Iadarola, Bldg. 49/Room 1A08, 49 Convent Drive, MSC-4410, National Institutes of Health, Bethesda, MD 20892-4410, USA. FAX: (301) 402-0667.

(Received 10 January 1995; accepted 20 January 1995.)

Abstract

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