gms | German Medical Science

Objective: Large arteriovenous malformations (AVMs) are considered unfavorable for Gamma Knife radiosurgery (GKRS) because of possible adverse effects. Some AVMs still pose a challenge to the neurosurgeon. Since AVMs often grow very slowly or remain stable in size, partial radiosurgical treatment is an alternative in cases with a high risk for unacceptable surgical morbidity. The obliteration response to radiosurgery is strongly dependent on dose and volume. For larger volumes the applied dose must be reduced for safety reasons, which may compromise obliteration.

Methods: Since April 1992 290 patients with cerebral AVMs underwent GKRS at our department. 20 patients (considered to be unsuitable for surgery) treated by staged procedures had a follow-up of more than 36 months. 13 female and 7 male patients (age ranging from 10–48 years) had undergone previous embolization at least once, 11 patients suffered previous hemorrhages. Marginal doses of 15–22 Gy at 40–50% isodose lines were applied to volumes ranging from 11 to 27 cm³. The time interval between the radiosurgical treatments varied between 4 and 28 months. 14 patients had two-staged, 5 patients three-staged radiosurgery, and one patient underwent GKRS 4 times. Median follow-up after the last staged radiosurgery was 72 months (range, 38–169 months).

Results: Neurological follow-up examinations showed a clinical improvement in 10 patients (50%). Seizures improved in 4 patients and remained unchanged in 5 patients. 2 patients developed epileptic seizures and suffered from hemiparesis following hemorrhage. Follow-up MRI, MRA and cerebral angiographies of the residual nidus disclosed no rebleeding but total, partial or moderate nidus obliteration in 10 (50%), 8 (40%) and 2 patients (10%), respectively.

Conclusions: For selected patients with large, otherwise unmanageable AVMs, staged GKRS can be recommended due to a low risk of both mortality and morbidity.