MRI exploration of pineal volume in bipolar disorder.

BACKGROUND: Circadian rhythm instability and abnormalities of melatonin secretion are considered as trait markers of bipolar disorder. Melatonin is secreted by the pineal gland. We investigated pineal volume in patients with bipolar disorder, and expected to observe smaller than normal pineal glands in cases of bipolar disorder.

METHODS: The primary outcome was the total pineal volume measured for each pineal gland with T1 MRI sequence. Twenty patients with bipolar I and II disorder and twenty controls were recruited. Pineal glands with large cysts (type 3) were excluded.

RESULTS: After exclusion of individuals with type 3 cysts, 32 subjects were analyzed for total pineal volume (16 patients with bipolar disorder and 16 controls). Total pineal volume did not differ significantly between patients (total pineal volume=115+/-54.3mm(3)) and controls (total pineal volume=110+/-40.5mm(3)).

CONCLUSIONS: Contrary to our hypothesis, no difference in total pineal volume between patients with bipolar disorder and healthy subjects was observed. These results indicate that the putative dysfunction of the pineal gland in bipolar disorder could be not directly related to an abnormal volume of the pineal gland.