The occurrence of cavum septi pellucidi enlargement is increased in bipolar disorder patients.

OBJECTIVES This study was conducted to evaluate the prevalence of cavum septi pellucidi (CSP) enlargement in patients with bipolar disorder (BD) and healthy comparison subjects. METHODS The occurrence of enlarged CSP in patients with BD (n = 41, age 35.4 +/- 10.8 years) and healthy volunteers (n = 41, age 35.3 +/- 10.0 years) was studied using magnetic resonance imaging. The length of the CSP was measured by counting the number of consecutive resliced coronal 0.5-mm images in which the CSP was present. A CSP length > or = 6 mm was a priori defined as abnormal enlargement of the CSP. RESULTS Bipolar subjects exhibited a significantly higher prevalence of abnormal CSP enlargement (8 of 41 subjects, 19.5%) than healthy comparison subjects (1 of 41 subjects, 2.4%) (logistic regression analysis: Wald statistic = 5.07, df = 1, p = 0.024). The prevalence of abnormally enlarged CSP was not significantly different between drug-naïve and drug-exposed bipolar subjects or when comparing bipolar I and II sub-diagnoses. Bipolar subjects with abnormal CSP enlargement had a significantly earlier onset of BD than those without (14.3 +/- 3.6 versus 20.1 +/- 7.4 years, respectively). CONCLUSIONS The current study is the first to report an increased prevalence of abnormally enlarged CSP in a well-characterized bipolar population. Our finding that an abnormal enlargement of CSP, a neurodevelopmental abnormality, is associated with early onset of illness implicates early maturational processes as contributing to BD.