Regional ¹³³Xenon cerebral blood flow and cerebral ^99mTc-HMPAO uptake in patients with obsessive-compulsive disorder before and during treatment

We previously reported increased regional cerebral cortical uptake and decreased caudate nucleus uptake of ^99mTc-HMPAO in patients with obsessive-compulsive disorder (OCD) before treatment compared to matched normal controls. In the present study, we determined whether or not these changes persisted during treatment. Single-photon emission computed tomography was used to measure regional cerebral blood flow (rCBF) by ¹³³Xe inhalation and regional cerebral uptake of ^99mTc-HMPAO in eight adult male OCD patients before and during treatment with clomipramine, and in eight age-matched normal male controls. With ¹³³Xe, there were no significant differences in rCBF between the patients with OCD and their matched controls, and no significant differences in rCBF in the patients before and during treatment. Significantly increased HMPAO uptake in the orbital frontal cortex, posterofrontal cortex, and high dorsal parietal cortex bilaterally occurred in the OCD patients before treatment compared to their matched controls, and there were significant reductions of HMPAO uptake, into the normal range, in all these areas in the patients during treatment. Significantly reduced HMPAO uptake in the caudate nucleus bilaterally occurred in the patients before treatment compared to their matched controls, and these reductions persisted during treatment. This study provides additional support for the involvement of both the orbital frontal cortex and the caudate nuclei in the pathophysiology of OCD.