Subdural haematoma in an adult after air encephalography.

Air encephalography in the absence of a spaceoccupying lesion of the brain is usually a harmless but unpleasant investigation that is necessary in the differential diagnosis of organic dementias and neurological syndromes of uncertain origin. It is known that subdural effusions may follow encephalography in children (Smith and Crothers, 1950). The development of a subdural haematoma in an adult after air studies has been rarely recorded. Such a complication has an important bearing on the management of the patient who occasionally deteriorates and may die after what has been considered to be a normal investigation.