Radiotherapy is an important treatment modality for patients with head and neck cancer. With improved patient survival, attention has focused on radiation-induced deficits (6). One such complication is carotid artery stenosis following radiation for NPC (3, 4, 7-18) (Table 1). Cheng et al (10) studied 96 patients who had undergone cervical radiotherapy for NPC at least 12 months previously (mean 79.9 months) and 96 healthy individuals as controls. Using color-flow duplex ultrasonography, these investigators found 18 patients (16%) had marked stenosis (70%-99%) and 35 (37%) had moderate stenosis (30%-69%) of either the common carotid or internal carotid artery. Four of the former vessels and 6 of the latter were totally occluded at the time of examination. In the control group 8 patients (8%) were found to have moderate stenosis (30%-69%) and none had marked stenosis or total occlusion. Multivariate logistic regression analysis found that smoking, post-radiotherapy interval, cerebrovascular symptoms, and absence of head and neck surgery were independent predictive factors of severe common carotid artery/internal carotid artery stenosis following radiation therapy. The development of carotid stenosis as well as vertebral artery stenosis following radiotherapy for NPC was confirmed by Lam and co-workers (12), although hypercholesterolemia, hyperglycemia and smoking were not found to be independent risk factors. In a follow-up study, Cheng et al (16) reported an annualized progression rate from less than 50% stenosis to 50% or greater stenosis in 15.4% of irradiated arteries compared to 4.8% in non-irradiated arteries.
Our patient developed OIS due to impaired flow of multiple vessels of the cerebrovascular system. It appears advisable that regular diagnostic follow-up studies of the carotid and vertebral systems be undertaken in patients following radiotherapy for NPC until treatment guidelines are developed based on longterm observational studies. As in our patient, stenting of the vertebral and carotid systems may offer a successful form of therapy in selected cases.
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