Fibromuscular dysplasia unraveled: the pulsation-induced microtrauma and reactive hyperplasia theory

Fibromuscular dysplasia (FMD) is a relatively uncommon, non-inflammatory, non-atherosclerotic vascular condition of unknown etiology. There have been no major advancements in understanding FMD in the past 30-40yrs. We hypothesize that the vascular changes seen in FMD are a direct result of recurrent mechanical trauma in susceptible vessels and reflect a compensatory response to recurrent pulsation-induced mechanical trauma.

Radiology records at a large tertiary care medical center were queried for cases of cervical carotid FMD. Cases with viewable sequential angiographic evidence of FMD were selected and analyzed for degree of vessel tortuosity, FMD type, degree of vessel movement, and association with the FMD lesion. Images were independently analyzed by 1 neurologist and 2 neuroradiologists.

Twenty-four carotid vessels in fourteen patients were identified to have FMD, 100% of patients were female, average age was 58.43±8.72yrs (range 45-73), 35.7% were black, 35.7% had HTN, 7.14% had CKD and 7.14% used tobacco in the past year. Associated findings included aneurysms and dissections. All but 1 patient had at least mild vessel tortuosity, and 28.6% were moderate or severe. All but 1 patient had at least "some" pulsation-like vessel movement, 16.7% had "significant" movement, and all movement was focally associated with the FMD abnormality.

Pulsatile vascular movements were observed in high frequency and in high association with FMD. We propose a theoretical connection between the pulsation-induced movement and a process of reactive vascular hyperplasia and fibrosis responsible for the FMD phenotype and is consistent with previous findings.