An MRI scan of the brain of a 69-year-old woman, carried out in July 2001, showed an incidental right parietal meningioma (fig 1) that was initially managed conservatively. Two years later, the patient developed episodes of left-sided partial seizures, and a CT scan of the brain showed the central mass to be unchanged, but the surrounding oedema was more extensive, and hence an elective right frontoparietal craniotomy and resection was carried out in May 2003. The dural defect was repaired with a pericranial graft. A histological examination confirmed the diagnosis of a meningioma. She was subsequently discharged and given carbamazepine and tapering doses of dexamethasone.

One week later, she developed an expressive dysphasia and weakness in the left arm, with the CT scan of the cranium showing a large area of oedema in the excision bed. Some hypodense collection was also evident beneath the bone flap (fig 2A,B). After being started on an increased dose of dexamethasone (16 mg/day) in the local hospital, her symptoms resolved, but had a tendency to recur on attempted weaning down of the steroid dose. This happened on three occasions, so she was kept on a maintenance dose of …