CEREBRAL STRUCTURAL ABNORMALITIES IN OBSESSIVE-COMPULSIVE DISORDER - A QUANTITATIVE MORPHOMETRIC MAGNETIC-RESONANCE-IMAGING STUDY

Background: A previous pilot study of only posterior brain regions fou nd lower white-matter volume in pao tients with obsessive-compulsive d isorder than in normal control subjects. We used new cohorts of patien ts and matched normal control subjects to study whole-brain volume dif ferences between these groups with magnetic resonance imaging-based mo rphometry. Methods: Ten female patients with obsessive-compulsive diso rder and 10 female control subjects, matched for handedness, age, weig ht, education, and verbal IQ, underwent magnetic resonance imaging wit h a 3-dimensional volumetric protocol. Scans were blindly normalized a nd segmented by means of well-characterized semiautomated intensity co ntour mapping and differential intensity contour algorithms. Brain str uctures investigated included the cerebral hemispheres, cerebral corte x, diencephalon, caudate, putamen, globus pallidus, hippocampus, amygd ala, third and fourth ventricles, corpus callosum, operculum, cerebell um, and brain stem. Anterior to posterior neocortical regions, includi ng precallosum, anterior pericallosum, posterior pericallosum, and ret rocallosum, with adjacent white matter were also measured. Volumes fou nd different between groups were correlated with Yale-Brown Obsessive Compulsive Scale score and Rey-Osterieth Complex Figure Test measures. Results: Confirming results of our earlier pilot study and expanding the findings to the whole brain, patients with obsessive-compulsive di sorder had significantly less total white matter but, in addition, sig nificantly greater total cortex and opercular volumes. Severity of obs essive-compulsive disorder and nonverbal immediate memory correlated w ith opercular volume. Conclusions: Replication of volumetric white-mat ter differences suggests a widely distributed structural brain abnorma lity in obsessive-compulsive disorder. Whereas determining the etiogen esis may require research at a microscopic level, understanding its fu nctional significance can be further explored via functional neuroimag ing and neuropsychological studies.