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.