An MRI study of temporal lobe structures in men with bipolar disorder or schizophrenia

Hippocampal atrophy has been described in postmortem and magnetic resonance imaging studies of schizophrenia. The specificity of this finding to schizophrenia remains to be determined. The neuropathology of bipolar disorder is understudied, and temporal lobe structures have only recently been evaluated.

Twenty-four bipolar, 20 schizophrenic, and 18 normal comparison subjects were evaluated using magnetic resonance brain imaging. Image data were acquired using a three-dimensional spoiled GRASS sequence, and brain images were reformatted in three planes. Temporal lobe structures including the amygdala, hippocampus, parahippocampus, and total temporal lobe were measured to obtain volumes for each structure in the three subject groups. Severity of symptoms in both patient groups was assessed at the time the magnetic resonance images were obtained.

Hippocampal volumes were significantly smaller in the schizophrenic group than in both bipolar and normal comparison subjects. Further, amygdala volumes were significantly larger in the bipolar group than in both schizophrenic and normal comparison subjects.

The results suggest differences in affected limbic structures in patients with schizophrenia and bipolar disorder. These specific neuroanatomic abnormalities may shed light on the underlying pathophysiology and presentation of the two disorders.