Paralimbic hypoperfusion in unipolar depression.

METHODS: Relative regional cerebral blood flow was measured with SPECT using 99mTc-hexamethylpropyleneamine oxime in 13 patients with severe unipolar depression that was nonresponsive to drug therapy and 11 age-matched nondepressed controls.
RESULTS: All patients were clinically depressed and taking antidepressant drugs at the time of the study. The relative blood flow was significantly decreased bilaterally in the frontal cortex, anterior temporal cortex, anterior cingulate gyrus and caudate in the depressed patients compared with the nondepressed healthy controls. The greatest decreases were seen in the paralimbic regions, specifically, the inferior frontal and cingulate cortex. No significant changes were seen in the parietal cortex, occipital cortex or thalami. Psychiatric rating scales correlated poorly with regional blood flow, except for the degree of psychomotor slowing, which was negatively correlated with frontal and cingulate perfusion.
CONCLUSION: These findings implicate selective dysfunction of paralimbic brain regions in clinically depressed patients, independent of their medication use, and support the concept of specific neural systems that regulate mood. Recognition of these regional abnormalities may have clinical utility in both the diagnosis and treatment of depression.