Enlargement of the Third Ventricle in affective disorders

There have been inconsistent reports of dilation of the third ventricle (lll-V) in bipolar disorder. Within the lateral walls of lll-V are hypothalamic nuclei which mediate the neuroendocrine, sleep, appetite and autonomic disturbances which characterise a depressive episode.

The lll-V width, immediately anterior to the mamillary bodies, was measured in 74 bipolar I or II subjects (m=25, f=49, mean age 36.1(1 l.3yr) and 33 healthy controls (m= 17, f= 16, mean age 35.6( 12.6yr) from MRI coronal inversion recovery scans.

Bipolar subjects had significantly (t=2.l6,p=0.03) wider lll-V (0.45(0.15cm) than controls (0.40(0.12cm). Examining data with a General Linear Model with gender and diagnoses as categoric variables and age as a continuous variable, lll-V width depended significantly on gender (p=O.OI6), age (p< 0.00l) and differed significantly (p=0.03) between bipolar subjects and controls. The rate of lll-V dilation was estimated to be 0.0048cm/yr in male bipolar subjects and 0.0040cm/yr in females.

Bipolar disorder is associated with increased lll-V width and progressive dilation. It is proposed that dilation may be associated with dysfunction of hypothalamic nuclei in the lll-V lateral walls.