We present a case of a man with headache and progressive behavioural disturbance. His cognitive decline progressed over a few months such that he was unable to hold a conversation or carry out any daily tasks such as washing and dressing. He had some upper motor neurone signs in his limbs and features of brainstem dysfunction including dysarthria and ocular abnormalities. His brain magnetic resonance imaging showed signs of brain 'sagging'. He was thought to have frontotemporal brain sagging syndrome. Prior to any treatment, he began to improve. Over the course of a week he became markedly better, was back to normal within 3 months and remains so 7 months later. We propose that resolution of spontaneous intracranial hypotension led to resolution of frontotemporal brain sagging syndrome. We believe this is the first case described where this has occurred without any intervention. It is important to recognise this condition as a potentially reversible cause of dementia.