Middle cerebral artery stenosis caused by relatively low-dose irradiation with stereotactic radiosurgery for cerebral arteriovenous malformations: case report.

OBJECTIVE AND IMPORTANCE: There have been occasional reports of stenosis or occlusion of major cerebral arteries occurring several years after stereotactic radiosurgery for cerebral arteriovenous malformations. Nevertheless, little information is available regarding the actual irradiation dose to which the affected artery had been exposed.

CLINICAL PRESENTATION: We present a patient with arteriovenous malformations who, although asymptomatic, developed remarkable stenosis of the middle cerebral artery trunk (M1) 3 years after gamma knife radiosurgery. The nidus was covered with a 50% isodose volume. A central dose of 36 Gy was used. A gradual decrease in nidus volume had been suggested by 1- and 2-year postradiosurgical neuroimaging examinations. Three-year postradiosurgical angiography revealed severe segmental stenosis of the M1, as well as remarkable nidus shrinkage.

INTERVENTION: The actual irradiation dose delivered to the affected portion of the artery, as retrospectively determined using a highly accurate three-dimensional analysis technique, was estimated to be 5.1 to 9.8 Gy.

CONCLUSION: This case suggests that a normal major artery, if located close to the target volume, may be affected by low-dose irradiation (10 Gy or even slightly less) delivered with radiosurgery, although a decrease in blood flow through the M1 because of nidus shrinkage or associated stenosis of the distal middle cerebral artery, as well as other unknown factors, may also contribute to proximal M1 stenosis.