Background: The neuropathogenesis of bipolar disorder remains poorly descri
bed. Previous work suggests that patients with bipolar disorder may have ab
normalities in neural pathways that are hypothesized to modulate human mood
states. We examined differences in brain structural volumes associated wit
h these pathways between patients with bipolar disorder hospitalized with m
ania and healthy community volunteers.
Methods: Twenty-four patients with bipolar disorder and mania were recruite
d from hospital admission records. Twenty-two healthy volunteers were recru
ited from the community who were similar to the patients in age, sex, race,
height, handedness, and education. All subjects were scanned using a 3-dim
ensional radiofrequency-spoiled Fourier acquired steady state acquisition s
equence on a 1.5-T magnetic resonance imaging scanner. Scans were analyzed
using commercial software. Prefrontal, thalamic, hippocampal, amygdala, pal
lidal, and striatal volumetric measurements were compared between the 2 gro
ups.
Results: Patients with bipolar disorder demonstrated a significant (Lambda
= 0.64; F-6,F-37 = 3.4; P = .009) overall difference in structural volumes
in these regions compared with controls. In particular, the amygdala was en
larged in the patients. Brain structural volumes were not significantly ass
ociated with duration of illness, prior medication exposure, number of prev
ious hospital admissions, or duration of substance abuse. Separating patien
ts into first-episode (n = 12) and multiple-episode (n = 12) subgroups reve
aled no significant differences in any structure (P>.10).
Conclusion: Patients with bipolar disorder exhibit structural abnormalities
in neural pathways thought to modulate human mood.