We describe a 24-year-old man with episodes of intense desire to sleep for periods ranging from 2min to 3h, episodes of generalized weakness and inability to speak without alteration of consciousness, frequent hypnagogic hallucinations during sleep and occasionally transient paralysis of limbs upon awakening. Brain MRI demonstrated elevation of the third ventricle, a characteristic lack of depiction of the corpus callosum and extension of the bihemispheric fissure to the third ventricle. We assume that structural changes of the base of frontal lobes, diencephalon and brainstem, can be accountable for symptomatic narcolepsy and cataplexy.