A 43 year old man suffered several episodes of dyspnoea occurring during sleep and while awake in the supine position; no respiratory disturbances were reported when standing or sitting. Two weeks later, headache and vomiting also occurred. At observation, 1 month after the clinical onset, the neurological examination revealed bilateral papillo-oedema. There were no abnormalities of the heart, upper respiratory pathways, or lungs. Spirometric and blood gas studies were normal. Brain magnetic resonance imaging (MRI) showed tetraventricular hydrocephalus and a posterior fossa tumour arising from the posterior aspect of the …