[A case of narcolepsy with increased cataplectic attacks after suffering from cerebrovascular disease].

It is well known that narcoleptic patients have DR2 and DQw-1 on HLA typing. The development of narcolepsy is considered to depend on the two factors; genetic predispositions and exogenous factors such as head trauma, encephalitis, etc., mainly affecting the brainstem or diencephalon. We reported a 46-year-old man who had occasional sleep attacks after suffering from left thalamic hemorrhage and pontine vascular disorders. Rehabilitation was markedly disturbed due to frequent episodes of cataplectic attacks which was triggered by emotional lability such as laughing, anxiety, and excitement. HLA type examination showed both DR-2 and DQw-1 loci in the proband and his four other siblings. His elder brother also suffered from mild excessive daytime sleepiness during his younger age, but it subsided gradually. Analysis of overnight polysomnography in the patient revealed remarkable paradoxical alpha-blocking and frequent sleep onset REM stages as typically observed in narcoleptic patients. MRI examination showed multiple small hemorrhages and infarctions in the pontine tegmentum, in addition to the left thalamic hemorrhage and multiple subcortical ischemic lesions. Concerning the mechanism of frequent cataplexy in this patient, it is postulated that increased emotional incontinence might have stimulated the descending reticular system in the brainstem which in turn may inhibit anterior horn motor cell activities. Methylphenidate was initially given to the patient, resulting in some relief of attacks, and addition of imipramine dramatically suppressed cataplectic attacks. Imipramine is considered to inhibit the excitatory afferent pathway to the brainstem suppressing the hyperactivity of descending motor inhibitory system due to its anti-muscarinergic action.