Do cerebral arteriovenous malformations increase in size?

Six patients are reported with cerebral arteriovenous malformations which have enlarged over follow up periods of from 4 to 20 years. The frequency of spontaneous enlargement is estimated to range from 0.2% to 2.8% per annum. This rate of enlargement should be considered when treatment options are reviewed in individual patients, and should be added to the risk of haemorrhage.