Radiation-induced arteritis: thickened wall with prominent enhancement on cranial MR images report of five cases and comparison with 18 cases of Moyamoya disease

PURPOSE: To evaluate magnetic resonance (MR) imaging findings of radiation-induced cranial arteritis regarding arterial wall thickening and degree of enhancement, as well as to compare the findings with those of idiopathic moyamoya disease. MATERIALS AND METHODS: We reviewed cerebral MR images in five patients with radiation-induced large cerebral arteritis. All patients had undergone irradiation 2-25 years prior to this study. Conventional nonenhanced MR, MR angiographic, and contrast material-enhanced MR images were evaluated. Special attention was paid to wall enhancement of the affected arteries (distal internal carotid artery). Wall enhancement was staged in three levels by two neuroradiologists. We also reviewed MR images in 18 patients with primary moyamoya disease for comparison and analyzed them statistically (Fisher exact test). RESULTS: Wall thickening and prominent ring enhancement of the wall of the affected large cerebral arteries were observed in all (five of five) patients with radiation-induced arteritis. In contrast, wall thickening and prominent ring enhancement of the wall of the occluded arteries either were not seen (13 of 18 patients) or were faint (five of 18 patients) in patients with moyamoya disease. Contrast enhancement of the arterial walls in patients with radiation-induced arteritis was significantly more prominent than in patients with moyamoya disease (P =.003). CONCLUSION: MR images of wall thickening and prominent ring enhancement of the wall of affected large cerebral arteries may be a diagnostic clue in differentiating radiation-induced arteritis from moyamoya disease.