Idiopathic intracranial hypertension is a syndrome in which increased intracranial pressure (ICP) occurs in patients who have no history of an acute insult to the nervous system such as hypoxic-ischemic disease or trauma, no acute encephalopathy such as Reye syndrome, no focal or lateralizing neurologic signs, no evidence of intracranial tumor or obstruction to cerebrospinal fluid (CSF) flow, and normal results of CSF analyses except for increased pressure. This syndrome occurs in children of all ages. No gender predilection exists as it does in adults, in whom a significant preponderance is noted in women. The syndrome has been recognized for more than 80 years. Most of the earlier reported cases were associated with otitis media, mastoiditis, and lateral sinus thrombosis. The condition then was described as otitic hydrocephalus. Complications of otitis media have become less frequent precipitating factors, presumably related to the more aggressive use of antibiotics in the treatment of middle-ear infections. Various conditions have been associated with this syndrome (Box 399.1). A common cause now is catch-up growth, which occurs in pediatric patients after the successful treatment of an underlying illness. It may be associated with numerous conditions such as cystic fibrosis and nutritional deprivation syndromes, correction of chronic conditions such as patent ductus arteriosus, and complications of prematurity. Rarely, a familial form of the syndrome has been reported.

Recently, diagnostic criteria for idiopathic intracranial hypertension have been proposed, as reported by Friedman and Jacobson. These criteria include the following: (a) if symptoms
are present, they may reflect only those of generalized intracranial hypertension or papilledema; (b) if signs are present, they may reflect only those of generalized intracranial hypertension or papilledema; (c) elevated ICP measured in the lateral decubitus position is documented; (d) CSF composition is normal; (e) no evidence of hydrocephalus, mass, structural or vascular lesion is seen on magnetic resonance imaging (MRI) and magnetic resonance (MR) venography; and (f) no other cause of intracranial hypertension is identified. Thus, increased ICP associated with many of the conditions listed in Box 399.1 would be excluded from the idiopathic intracranial hypertension syndrome using this definition.