Results of radiosurgery for brain stem arteriovenous malformations
- Hiroki Kuritaa,
- Shunsuke Kawamotoa,
- Tomio Sasakia,
- Masahiro Shina,
- Masao Tagob,
- Atsuro Teraharab,
- Keisuke Uekia,
- Takaaki Kirinoa
- aDepartment of Neurosurgery, Graduate School of Medicine, University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–8655, Japan, bDepartment of Radiology
- Dr Hiroki Kurita, Department of Neurosurgery, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka-City, Tokyo 181-8611, Japan
- Received 6 April 1999
- Revised 8 September 1999
- Accepted 23 September 1999
Abstract
OBJECTIVE To assess the treatment results of radiosurgery for brain stem arteriovenous malformations (AVMs) and to seek optimal dose and treatment volume prescription for these lesions.
METHODS The clinical and radiological data of 30 consecutive patients with brain stem AVM treated with gamma knife radiosurgery were retrospectively reviewed with a mean follow up period of 52.2 months. There were 26 patients with previous haemorrhages and 21 with neurological deficit. Seventeen AVMs were located in the midbrain, 11 in the pons, and two in the medulla oblongata. All of the lesions were small with the intra-axial component occupying less than one third of the area of brain stem parenchyma on axial section of multiplaner MRI or CT. The mean diameter of the nidus was 1.26 cm, and the nidus volume within the brain stem parenchyma ranged from 0.1 to 2.0 cm3. The mean radiation dose to the AVM margin was 18.4 Gy.
RESULTS The actuarial 3 year obliteration rate was 52.2%; 69.4% in cases treated with standard doses (minimum target dose, 18–20Gy), and 14.3% in cases treated with low doses (<18 Gy) (p<0.05). Two patients sustained symptomatic radiation injury, but there was no permanent neurological deficit caused by radiosurgery. Five patients had haemorrhage from the AVM after irradiation, including four fatal cases, resulting in a 4.0% annual rate of post-treatment bleeding.
CONCLUSIONS Radiosurgery is a viable treatment modality for patients with small deep parenchymal brain stem AVMs. A standard radiosurgical dose is safe and effective when directed to a small treatment volume. However, latent interval haemorrhage remains a significant problem until the nidus is obliterated completely.
