Abstract Body: Introduction
Fibromuscular dysplasia (FMD) is a rare, nonatherosclerotic, non-inflammatory vasculopathy for which only limited population-level data are available. We aimed to evaluate the prevalence and characteristics of cerebrovascular fibromuscular dysplasia (cFMD) in a population-level cohort of patients with ischemic stroke(IS) and transient ischemic attack (TIA).
Methods
We studied a population-level cohort of all patients diagnosed with IS/TIA in an entire Canadian province (Alberta) from April 1, 2016, to March 31, 2017, followed for at least 5 years until March 31,2022 for recurrent IS/TIA using administrative health data. We used overlapping approaches of direct neuroimaging review as well as keyword searches (FMD, tortuosity, string of beads, and medial fibroplasia) of radiologist reports to identify cases of suspected cFMD. Following confirmatory review of neurovascular imaging by at least two readers, relevant data on clinical characteristics, risk factor profile, tortuosity index, and anatomical extent of the vascular disease were ascertained from imaging review and clinical records. The 5-year risk of recurrent events was estimated using logistic regression adjusted for age, sex and vascular risk factors.
Results
Among 7,745 patients with IS/TIA found 34 cases of cFMD in the cohort, accounting for a population prevalence of 0.44% or 439/100,000 cases of IS/TIA. Patients with cFMD were similar in age to those without (median age: 74 years, IQR:60-84 vs 71, IQR:60-82, p=0.52) and had similar vascular risk factors (Table 1) but were significantly more likely to be female (79.4% vs 48.3%, p<0.001). The median NIHSS was 1.5 (IQR:1-4). The most frequent pattern of vascular involvement was extracranial proximal internal carotid artery with involvement of multiple vascular beds. Twenty-seven (81.8%) FMD cases had tortuous vessels on CT angiogram. Concomitant intracranial or extracranial aneurysms were detected in 9.1% (Table 2). 5year mortality following the index event was 29.4% and recurrent IS or TIA occurred in 23.5% of the patients by 5 years; this was not significantly higher than patients without FMD (aOR=1.7 95%CI:0.8-3.9).
Conclusions
cFMD is a rare finding in patients with IS/TIA and mostly affects females and the extracranial proximal ICA. Whereas these patients had substantial rates of recurrent IS/TIA and mortality, this was not significantly higher than patients without FMD. Our findings merit further validation in larger cohorts of FMD.