Teaching NeuroImages: awakening ptosis (unilateral hypnopompic eyelid palsy).

A healthy 68 year old woman presented with two years of recurrent episodes of right ptosis, constantly present after waking from sleep. Clinical examination, brain MRI, EMG, and polysomnography were unremarkable. In particular there was no cranial nerve impairment. Few cases of idiopathic ptosis on awakening have been described, and attributed to eyelid opening apraxia. This disorder needs to be differentiated from Myasthenia Gravis and other neuromuscular disorders. We propose that the term “apraxia” is not suitable to describe this clinical phenomenon, which could result from an abnormal, transient persistence of focal, sleep-related muscular atonia.