Insomnia after bilateral stereotactic thalamotomy in man.

We think it interesting to report a case of insomnia, occurring in a Parkinsonian patient after bilateral stereotactic thalamotomy, as a clinical contribution to the physiopathology of variations of consciousness and regulation of the sleep-wakefulness rhythm. Neurophysiological experimental findings in animals suggest that in addition to the activating or arousing mechanisms of the reticular formation, deactivating or hypnogenic mechanisms, also localized in the brain-stem,' play a prominent part in the regulation of sleep-wakefulness alternation (Hess, 1944; Moruzzi, 1963; Rossi, 1964 and 1965). This hypothesis rests on the observation that an enduring sleep-like state, as well as a long-lasting insomnia, may be produced by brain-stem lesions, the sign of the effect being dependent exclusively on the site of the brain-stem damage (Batini, Magni, Palestini, Rossi, and Zanchetti, 1959a; Batini, Moruzzi, Palestini, Rossi, and Zanchetti, 1959b; Cordeau and Mancia, 1959, Candia, Favale, Giussani, and Rossi, 1962a; Candia, Minobe, and Rossi, 1962b; Jouvet, 1962, 1965a, b and c; Minobe, Candia, and Rossi, 1962). In man there is much clinical, E.E.G., and anatomical evidence pointing to the existence of a passive mechanism for the reduction of consciousness; conversely, evidence supporting the theory of an active mechanism is scanty and not nearly so convincing. In fact, in neurosurgical and neurological experience, reduction of consciousness and vigilance levels (drowsiness, obnubilation, hypersomnia, coma, and prolonged coma) as a consequence of more or less localized brain lesions, is frequently observed, while it is rare to find the opposite condition of insomnia. The latter or, more often, inversion of sleep rhythm, has been reported to follow diffuse rather than focal lesions (see the classical works of Von Economo, 1929 and 1930); these cases are of little interest to those who wish to determine a structural site for the neurophysiological mechanisms responsible for changes in the vigilance level. CASE REPORT