We report a young stroke patient with history of radiotherapy. We considered right posterior cerebral artery as the responsible vessel. HR-MRI showed vascular inflammatory changes in vessel wall, without dissection and premature atherosclerosis. As there was no history of infectious, auto-immune and inherited disease in our patient, we believed that intracranial artery stenosis was caused by radiation-induced arteriopathy.
Multiple CMBs were detected in our patient. CMB is a common type of radiation-induced vascular complication, indicating microvascular injury. Previous study showed that CMB could progress with each year from time of radiotherapy, which predominately located in bilateral occipital lobes. In our patient, we believed that CMB is related with radiotherapy but not cerebral amyloid angiopathy (CAA) because of patient’s young age and absence of cerebral hemorrhage and cognitive impairment.
Radioactive damage to brain tissues is a long-term process. However, vascular changes after radiotherapy over 15 years were rarely reported. In our patient, vascular inflammatory changes were still detected by HR-MRI after his first radiotherapy 19 years ago. The exact mechanisms were not fully understood. An autoimmune inflammatory changes induced by radiation has been proposed [7]. Vascular changes has been considered as key feature of delayed radiation injury, which includes marked atypia or loss of endothelial cells, vascular fibrosis leading to luminal occlusion, and fibrinoid vascular necrosis. Vascular changes after radiotherapy may be a dynamic process involving increased expression of vascular endothelial growth factor (VEGF), blood brain barrier damage, oxidative stress and inflammation. Therefore, radiation-induced arteriopathy may be an important cause of stroke in patients with radiotherapy and more attention should be paid to it.
HR-MRI has been considered as a useful tool for distinguishing intracranial vascular lesions by displaying both lumen and vessel wall [8]. Many etiologies can lead to similar lumen stenosis, including intracranial atherosclerosis, vasculitis, intracranial arterial dissection and moyamoya disease. On HR-MRI, eccentric and irregular plaques are the characteristic finding of atherosclerosis, whereas patterns of concentric arterial wall thickening and homogeneous enhancement of the vessel wall indicate vasculitis. The decreasing vessel wall enhancement after anti-inflammatory treatment also supports the diagnosis of vasculitis [9, 10]. With HR-MRI, intimal flap and double lumen are typical imaging findings in patients with intracranial artery dissections, and intramural hematoma and aneurysmal dilatation can also be detected [11, 12]. A decrease in the outer diameter and concentric and weaker enhancement in the bilateral terminus of the internal cerebral artery, proximal anterior cerebral artery, or middle cerebral artery are characteristics of moyamoya disease [13]. The right middle cerebral artery and posterior communicating artery of our patient, concentric thickening of vascular wall in HR-MRI T1 sequence, strong and concentric wall enhancement in T1 post-contrast HR-MRI, the whole features of multiple cerebral arteries support the diagnosis of central nervous system vasculitis (CNSV). And secondary CNSV was considered in our case because of negative blood tests and history of radiotherapy.
Effective treatments of radiation-induced brain injury are limited. In our case, the patient received low-dose hormone therapy for 3 months in order to regulate autoimmune inflammation. The clinical symptoms disappeared after 3 months. In the latest report, addition of an anti-angiogenic agent enzastaurin decelerated appearance of CMBs, showing radioprotective effect on microvasculature [14]. However, the exact mechanism is still largely unknown and more studies are needed.
In conclusion, radiation-induced cerebrovascular damage is a long-lasting progress. HR-MRI can provide sensitive and accurate diagnostic assessment of radiation-induced arteritis and can be used as a useful tool for the screening of causes of cryptogenic stroke.
