Pseudotumour cerebri occurring in association with the Chiari malformation

The case is described of a 12-year-old girl presenting with raised intracranial pressure without ventricular dilatation and a type 1 Chiari malformation. This was taken to be a coincidental association of pseudotumour cerebri and the Chiari malformation. Treatment of the pseudotumour with Diamox gave rapid and sustained relief of the intracranial hypertension without change in the Chiari malformation. In addition, a series of 156 cases of pseudotumour cerebri was reviewed for evidence of the Chiari malformation. An overall incidence of 1.3%, rising to 2.7% in patients with MR scanning [excluding the case described] was found.