Object. The authors analyzed of the long-term complications that occur 2 or more years after gamma knife surgery (GKS) for intracranial arteriovenous malformations (AVMs). Methods. Patients with previously untreated intracranial AVMs that were managed by GKS and followed for at least 2 years after treatment were selected for analysis (237 cases). Complete AVM obliteration was attained in 130 cases (54.9%), and incomplete obliteration in 107 cases (45.1%). Long-term complications were observed in 22 patients (9.3%). These complications included hemorrhage (eight cases), delayed cyst formation (eight cases), increase of seizure frequency (four cases), and middle cerebral artery stenosis and increased white matter signal intensity on T2-weighted magnetic resonance imaging (one case of each). The long-term complications were associated with larger nidus volume (p < 0.001) and a lobar location of the AVM (p < 0.01). Delayed hemorrhage was associated only with incomplete obliteration of the nidus (p < 0.05). Partial obliteration conveyed no benefit. Delayed cyst formation was associated with a higher maximal GKS dose (p < 0.001), larger nidus volume (p < 0.001), complete nidus obliteration (p < 0.01), and a lobar location of the AVM (p < 0.05). Conclusions. Incomplete obliteration of the nidus is the most important factor associated with delayed hemorrhagic complications. Partial obliteration does not seem to reduce the risk of hemorrhage. Complete obliteration can be complicated by delayed cyst formation, especially if high maximal treatment doses have been administered.

Using a similar target, the incidence of trigeminal dysfunction and the pain relief rate can vary according to the radiation energy received by the retrogasserian part of the trigeminal nerve root. The prescription dose and the use of beam channel blocking modify the integrated dose delivered to the nerve and may contribute to the different rates of trigeminal numbness and pain outcome. The radiobiological effect of gamma knife radiosurgery may be related to the energy delivered to nerve root volume, rather than to the maximal dose delivered.

Optimal management of cavernous sinus hemangiomas remains unclear. Total microsurgical removal of these neoplasms may be extremely difficult due to their rich vascularization. Three cases of cavernous sinus hemangioma treated with low-dose Gamma Knife radiosurgery are presented. Marginal dose varied from 10 to 13 Gy. Treatment planning and radiation dosimetry were done with a goal of conformal and selective coverage of the lesion with 50% prescription isodose line using multiisocenter technique. In all cases significant shrinkage of the neoplasm was marked at 3 months after treatment. Mean volume reduction at 12 months after radiosurgery was 60% (range: 45-75%). In all patients the shrinkage of the neoplasm was accompanied by notable improvement of the preexistent oculomotor nerve palsy. No radiosurgery-related complications were met during follow-up. In conclusion, low-dose Gamma Knife radiosurgery seems to be very effective for management of cavernous sinus hemangiomas, and can be considered as a treatment modality of choice for these lesions.