Regional xenon 133 cerebral blood flow and cerebral technetium 99m HMPAO uptake in unmedicated patients with obsessive-compulsive disorder and matched normal control subjects. Determination by high-resolution single-photon emission computed tomography
R. T. Rubin, J. Villanueva-Meyer, J. Ananth, P. G. Trajmar and I. Mena
Department of Psychiatry, Harbor-UCLA Medical Center, Torrance.
We measured regional cerebral blood flow (rCBF) with the xenon 133 (133Xe)
inhalation method and with regional cerebral uptake of technetium 99m
d,l-hexamethyl propyleneamine oxime (99mTc-HMPAO) by single-photon emission
computed tomography in 10 adult male patients with obsessive-compulsive
disorder (OCD) and in 10 age-matched adult male normal controls. With the
133Xe method, there were no significant differences in cortical or basal
ganglia blood flow between the patients with OCD and their matched
controls. In the patients, there was a positive relationship between rCBF
and the severity of both obsessive and compulsive symptoms (average r =
.48). These rCBF findings were consistent with those of earlier reports of
increased rCBF in patients with OCD who were undergoing imaginal flooding
and who had exacerbation of symptoms following m-CPP administration.
99mTc-HMPAO is a lipophilic molecule that crosses the blood-brain barrier
and is converted to a hydrophilic form that is trapped in the brain. The
amount that is trapped is determined primarily by blood flow, but also by
membrane permeability and kinetics of conversion of the 99mTc-HMPAO to the
hydrophilic form. Compared with their matched controls, the patients with
OCD had significantly increased 99mTc-HMPAO uptake in the high dorsal
parietal cortex bilaterally, in the left posterofrontal cortex, and in the
orbital frontal cortex bilaterally. Possible explanations include (1)
increased rCBF that was not detected with 133Xe, (2) increased permeability
of the blood-brain barrier and/or cell membranes, and (3) increased
conversion and trapping of the lipophilic, injected form of 99mTc-HMPAO in
these regions.(ABSTRACT TRUNCATED AT 250 WORDS)
