Various types of sleep disruption or even disorganization are often caused by brain dysfunction secondary to traumatic brain injury, encephalitis, cerebral stroke, etc., depending on the brain regions mainly affected. Thus, lesions of the pontine tegmentum result in reduction of REM sleep, whereas lesions of the lower brainstem cause elimination of slow-wave sleep. Moreover, clinical observation shows that some neurological patients present with somnolence whereas others exhibit sleeplessness and some others a disruption of the normal circadian alternation of sleep and wakefulness. On the other hand, primary sleep disorders such as fatal familial insomnia, narcolepsy, and REM sleep behavior disorder are often associated with neuropathological or neurophysiological alterations and are accompanied by neuropsychological manifestations. Also, organicity, mainly in the form of neurodevelopmental aberrations, is strongly suggested in many cases of sleepwalking and night terrors. Finally, serious cognitive and psychosocial consequences of curtailed or otherwise disturbed sleep are often observed in sleep deprivation, chronic insomnia, obstructive sleep apnea syndromes, and narcolepsy. Therefore, to optimize the management of patients with sleep disorders, it is important to specify the exact nature and the degree of any coexisting neuropsychiatric manifestations.
