Stereotactic radiosurgical treatment of cerebral arteriovenous malformations. Gamma Unit Radiosurgery Study Group

To assess the role of clinical factors, size of lesion, site of involvement, and radiation dose in patients with cerebral arteriovenous malformations (AVMs) who underwent stereotactic radiosurgical treatment.

We reviewed the results in 121 patients with cerebral AVMs treated with the Leksell "Gamma Knife" between January 1990 and December 1993 at the Mayo Clinic in Rochester, Minnesota.

The following strict dose-volume protocol was used: AVMs 2.0 cm or smaller in diameter (volume, 4.2 cm3 or less) received 20 Gy to the margin of the nidus, those between 2.1 and 3.0 cm in diameter (4.3 to 14.1 cm3) received 18 Gy to the margin, and those that exceeded 3.0 cm in diameter (more than 14.1 cm3) received 16 Gy to the margin. Lesions that involved the brain stem received a radiosurgical dose of 18 Gy or less to the margin. Patients participated in regular follow-up clinical and imaging studies for up to 55 months.

Follow-up cerebral angiography in 43 patients demonstrated total obliteration of the AVM nidus in 31 (72.1%), including 5 of 7 (71.4%) who had AVMs with a volume larger than 10 cm3. Clinical follow-up revealed that 111 patients (91.7%) had a stable or improved outcome, 3 had a nonfatal AVM hemorrhage, 2 suffered a fatal hemorrhage, and 2 died of causes not directly attributed to the AVM or radiosurgical treatment. Two patients had new or increased, nondisabling neurologic deficits as a result of treatment, and one patient had a temporary partial eyelid ptosis.

Our findings suggest that previous theories about the relationship between AVM size and rate of obliteration after radiosurgical treatment may need revision. Our experience confirms that radiosurgical treatment for cerebral AVMs is safe and effective, even in cases for which the latency period before obliteration is longer than 2 years.