Background: The phenomenon of flow diversion in high grade internal carotid artery (ICA) stenosis and secondary head and facial pain from increased regional flow in the external carotid artery (ECA) system remains under-recognized and unreported. We examine this phenomenon in a large study population of Asymptomatic Carotid Atherosclerosis Study
Methods: We utilized the Asymptomatic Carotid Atherosclerosis Study (ACAS) data to explore the relationship between ICA stenosis and headache. In ACAS, eligible patients with carotid stenosis ≥ 60 % were randomized to endarterectomy or medical management and risk of stroke or stroke & death over 5 years was observed. Information on headache and its characteristics was collected at the baseline visit and comprised questions inquiring self-reported history of headache, including characteristics of migraine, and physician diagnosis of headache. Carotid stenosis was evaluated by doppler ultrasound (as <60%, 60-80%, 81-99%, and 100%) and catheter angiography (as percent stenosis). All analyses were performed using IBM SPSS (version 20) software.
Results: In this study (n= 1662), patients with stenosis (measured by Doppler) of 60% or higher in the right ICA or left ICA, self-reported headache within the past year was reported in 424, and physician diagnosed headache in only 68 patients. Significant relationship was noted between physician diagnosis of headache and right ICA (χ2=10.3, df=4, p 0.036), and left ICA (χ2=15.6, df=4, p=0.004) stenosis categories. Self-reported history was associated with left ICA stenosis (χ2=26.6, df=4, p<0.001). Average stenosis measured by angiogram was 57% in the right ICA and 56% in the left ICA in this study population. No relationship with self-reported or physician diagnosed headache was noted with percent stenosis measured by catheter angiogram.
Conclusion: Recognition of flow-diversion into the ECA as a possible mechanism for headaches may help in further understanding of ICA disease, its progression, and the effects of carotid revascularization on quality of life. Headache as a likely surrogate marker of carotid stenosis with flow-diversion warrants more research, and may be critical in the early identification of significant ICA stenosis and prevention of TIA or stroke.