Neurohemodynamic Correlates of Washing Symptoms in Obsessive-compulsive Disorder: A Pilot fMRI Study Using Symptom Provocation Paradigm

BACKGROUND: Obsessive-compulsive disorder (OCD) is increasingly being viewed as a multidimensional heterogeneous disorder caused due to the dysfunction of several closely related, overlapping frontostriatal circuits. A study investigating the dimensional construct in treatment naïve, co-morbidity free patients with identical handedness is likely to provide the necessary homogeneity and power to elicit neural correlates of the various symptom dimensions, and overcome the limitations of previous studies. MATERIALS AND METHODS: Nine DSM-IV OCD patients with predominant contamination-related obsessive-compulsive symptoms (age=29.8±7.1 years; five males: four females; years-of-education=13.9±1.6, YBOCS total score=28.8±4.7, DYBOCS Contamination dimension score=10.7±1.8) and nine healthy controls matched one to one with the patients for age, sex, and years of education (age=27.8±5.4, five males: four females; years-of-education=14.9±3.0), were examined during symptom provocation task performance in 3TMRI. Paired samples t test of brain activation differences (contamination relevant pictures – neutral pictures), limited to apriori regions of interest was done using SPM8 (uncorrected P<0.005). RESULTS: Patients found significantly more pictures to be anxiety provoking in comparison to healthy controls. Patients were found to have deficient activation in the following areas in comparison with healthy controls: bilateral anterior prefrontal, dorsolateral prefrontal, orbitofrontal, anterior cingulate, insular and parietal cortices, precuneus, and caudate. CONCLUSIONS: Results underscore the importance of frontal, striatal, parietal, and occipital areas in the pathophysiology of OCD. Divergence of findings from previous studies might be attributed to the absence of confounding factors in the current study and may be due to production of intense anxiety in patients.