Unilateral thalamodiencephalic syndrome presenting with severe hypersomnia

Abstract

Thalamic and brainstem strokes can cause organic hypersomnia. Paramedian thalamus is believed to play an important role in the regulation of sleep, and disturbances of sleep regulation are known to occur in paramedian thalamic stroke (PTS). In patients with PTS, slight sleepiness is reported with unilateral and limited lesions. In this paper we report on a patient presenting with severe hypersomnia who has a limited, unilateral thalamodiencephalic ischemic lesion on magnetic resonance imaging (MRI). A 54 year-old man referred to our hospital with the complaint of excessive day time sleepiness. His cranial MRI revealed a unilateral ischaemic lesion beginning at the level of left thalamus and extending to nucleus Ruber and Edinger Westpall. His total day time sleep was about 23-24 hours in the first week. He had been put on dopamine agonist therapy (bromocriptine 2.5mg/day up to dose 7.5mg/day). During this medication his total day time sleep decreased gradually and after two months he returned to his normal vigilance. Lesions affecting thalamus and mesencephalic or pontine tegmental reticular formation are a cause of hypersomnia but clinical presentation and degree of hypersomnia can be various due to the affected region of the brain. We think that regulation of sleep and wakefulness by different brain structures are still elusive and new case reports and clinical trials would be helpful about clarification of this condition.