MR imaging of diseases of the limbic system.

The limbic system refers to the part of the brain that is involved in emotional expression and in cognitive and somatomotor control systems; it most likely also has a significant role in the pathogenesis of certain dementias, neuropsychiatric disturbances, and seizure disorders. This system, as originally defined, has no clear anatomic boundaries. Limbic regions of the telencephalon include a continuous medial zone of cortical regions, including the hippocampal formation; a perihippocampal zone, including the cingulate gyrus, prefrontal region, and perirhinal region; along with subcortical areas, including the septum pellucidum and the amygdala. A distinguishing characteristic of the limbic region is that it is highly interconnected and appears to form the only major route for information transfer between the neocortex and the hypothalamus. With the multiplanar capability and resolution of MR imaging, the individual parts of the limbic system and the diseases that affect them can be studied. In this review, we discuss MR imaging of the diseases that affect this system.