Fibromuscular Dysplasia

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Learning objectives

  • What is Fibromuscular Dysplasia ?
  • What are the typical signs and symptoms
  • Appropriate investigations
  • Managing the patient with Fibromuscular Dysplasia

Introduction

  • Fibromuscular dysplasia is a non inflammatory and non arteriosclerotic disease
  • It tends to affect the distal extracranial portion of the carotid artery
  • It can also affect the vertebral and renal and coronary arteries.
  • It appears to be commonest in young and middle-aged females aged 20-60. *The female to male incidence is reported as being about 3:1.
  • Incidence of stroke due to dissection or aneurysmal rupture is less than 5%

Aetiology

  • FMD has been found in 1% of carotid arteries at post mortem.
  • Alternating areas of thickening of the arterial media with variable involvement of the intima and adventitial layer.
  • An intimal form can result in web like obstruction.
  • There is a typical angiographic appearance described below.
  • Subclinical disease may be found in other locations e.g. renal arteries.

Clinical Presentations

  • There are several different presentations depending on which vessels are involved.
  • Carotid or vertebrobasilar stenosis, infarction or dissection
  • Renal Artery Stenosis causing refractory hypertension
  • Rarely coronary and pulmonary arteries with dissection, beading and narrowing
  • Subarachnoid haemorrhage due to aneurysmal rupture

Differentials

  • Ehlers Danlos syndrome
  • Neurofibromatosis I
  • Cervical Dissection

Investigations

  • Standard stroke investigations.
  • CT/MRI in the most severe cases may show cerebral or brainstem or cerebellar infarction or even SAH
  • MR/CT/DS Angiography: Classically vessel narrowing with tortuosity, stenosis and "string of beads" like narrowing and then dilatation of the artery may be seen on both renal and cerebral angiography. There may also be arterial dissections and aneurysmal formation.
  • Post mortem vascular histology shows increased collagen within the intima and media. The media may be thinned and there may be beading.

Management

Manage cerebral infarction largely as per normal Ischaemic stroke and the role for antiplatelets and statins must be assessed on a case by case basis depending on the existence of likely atherosclerosis and associated risk factors and evidence of aneurysmal formation and the likelihood of bleeding. If dissection found then manage as for Dissection with either antiplatelets e.g. Aspirin or Clopidogrel or anticoagulation for 3-6 months. The role of antiplatelets in asymptomatic disease is unclear. The long-term prognosis has been traditionally been estimated as good but a recent French study shows some progressions over time of arterial disease (2). Those with renovascular disease require strict pharmacological BP control as well as considerations for percutaneous angioplasty for any renal artery stenosis. *Long-term BP screening and management should be established and screening for RAS as indicated. A recent paper (3) has recommended that every patient with FMD undergo one-time cross-sectional imaging from head to pelvis with computed tomographic angiography or magnetic resonance angiography. Certainly, renal imaging should be considered in those with a cervical arterial presentation and vice-versa as the disease often coexists.

References

  • (1) Plouin PF et al. Fibromuscular dysplasia (review). Orphanet Journal of Rare Diseases 2007, 2:28 doi:10.1186/1750-1172-2-28
  • (2)Pasquini M et al. Fibromuscular dysplasia of cervicocephalic arteries: Prevalence of multisite involvement and prognosis. Doi : 10.1016/j.neurol.2015.02.011
  • (3) Kadian-Dodov D et al. Dissection and Aneurysm in Patients With Fibromuscular Dysplasia: Findings From the U.S. Registry for FMD. J Am Coll Cardiol. 2016 Jul 12;68(2):176-85. doi: 10.1016/j.jacc.2016.04.044.