Midline Cavum Variants and Adhesio Interthalamica in Psychiatric Disorders: Prevalence and MRI Morphometry

Cavum septum pellucidum (CSP), cavum vergae (CV), cavum veli interpositi (CVI), and interthalamic adhesion (IA) are midline developmental variants and their associations with psychiatric disorders are unclear. Our study aimed to compare the prevalence of these four structures and the dimensional features of CSP in bipolar disorder (BD), major depression (MD), and obsessive-compulsive disorder (OCD) with healthy controls (HC) under a single MRI protocol. A total of 454 adults with 1.5T brain MRI were examined retrospectively. CSP length ≤6 mm was classified as “small,” >6 mm as “large”; the presence of CV, CVI, and IA was evaluated by two blinded radiologists. When all participants (patients and healthy controls) were considered together, CSP prevalence was 61.5%. “Large” CSP was observed only in clinical groups (BD 23.8%; MD 38.1%; OCD 38.1%). CVI was found in 37.4% of OCD and 29.9% of MD patients, showing a significant increase compared to 10.5% in HC (p