THE PATHOPHYSIOLOGY OF FATAL FAMILIAL INSOMNIA

The key clinical aspects of FFI, i,e, hypovigilance and attention defi cit, inability to generate EEG sleep patterns, sympathetic hyperactivi ty and attenuation of vegetative and hormonal circadian oscillations, are related to selective atrophy of the anteroventral and mediodorsal thalamic nuclei, These nuclei constitute the limbic part of the thalam us interconnecting limbic and paralimbic regions of the cortex and oth er subcortical structures in the limbic system including the hypothala mus, The hypothalamus released from cortico-limbic control is shifted to a prevalence of activating, as opposed to deactivating, functions i ncluding loss of sleep, sympathetic hyperactivity and the attendant at tenuation of autonomic circadian and endocrine oscillations. These fin dings document that the limbic thalamus has a strategic position in th e central autonomic network running from the limbic cortical regions t o the lower brain stem which regulates the body's homeostasis in an in tegrated fashion.