Cerebral Aneurysms, Fusiform

Diseases,

Subtypes:

There are two main subtypes:

  • Non-atherosclerotic fusiform cerebral aneurysms (some authors include dissecting aneurysms here)
  • Atherosclerotic fusiform cerebral aneurysms
  • These are different from saccular cerebral aneurysms

These are discussed in the two sections below:

Non-Atherosclerotic fusiform cerebral aneurysms:

Diagnosis of non-atherosclerotic fusiform aneurysms:

Catheter Angiography:

  • Long segment fusiform dilatation in absence of atherosclerosis, +ectatic vessel, +/-focal outpouching
  • Common locations:
    • Posterior circulation (BA, VA) more common than anterior (supraclinoid ICA, MCA)

MRI:

  • T1: ectatic vessel. +/-high signal with thrombus or slow flow
  • T2: Flow void. +/-low signal with thrombus
  • FLAIR: +/-hyperintense thrombus in vessel
  • DWI: restricted if associated with ischemia

MRA:

  • TOF may be inaccurate due to abnormal flow
  • Contrast enhanced dynamic MRA for accurate delineation

 

Classification & pathology:

Type 1: typical dissecting aneurysm:

  • Acute widespread disruption of the internal elastic lamina
  • Without intimal thickening
  • Rebleeds are common

Type 2: segmental ectasia:

  • Extended and/or fragmented internal elastic lamina with intimal thickening
  • Benign course

Type 3: dolichoectatic dissecting aneurysms:

  • Fragmentation of the internal elastic lamina
  • Multiple dissections of thickened intima
  • Organized thrombus in the lumen
  • Symptomatic progressive enlargement

Type 4: atypically located saccular aneurysm i.e. not at branching point e.g. lateral wall:

  • Minimally disrupted internal elastic lamina
  • Without intimal thickening
  • High rerupture risk

Associated with Ehlers-Danlos type IV, Neurofibromatosis 1, HIV associated vasculopathy, VZV associated vasculopathy, SLE

Treatment of non-atherosclerotic fusiform cerebral aneurysm:

  • Consider observation
  • If anterior circulation: endovascular therapy using flow diversion (flow diverting stent) e.g. Pipeline stent. Consider balloon-test occlusion followed by endovascular vessel sacrifice
  • If posterior circulation:
    • Vertebral artery (segment without perforators):endovascular therapy using flow diversion (flow diverting stent) e.g. Pipeline stent. Consider balloon-test occlusion followed by endovascular vessel sacrifice
    • Basilar artery (segment with perforators): observation. Consider surgical wrapping
  • Note, if Ehlers-Danlos type IV catheter angiography is contraindicated because of risk of dissection

 

Diagnosis:

Catheter Angiogram:

  • Ectatic vessel with atherosclerosis with focal out-pouching
  • Common locations:
    • Posterior circulation (BA, VA) more common than anterior (supraclinoid ICA, MCA)
    • Basilar artery

CT:

  • Hyperdense due to calcium
  • Enhancing lumen

CTA:

  • Ectatic vessel +atherosclerosis +focal outpouching/dilatation

MRI:

  • T1,T2: depend on presence of hematoma or thrombus
  • Enhancement of lumen.

MRA:

  • TOF is inadequate because slow flow in the lumen gives heterogenous signal
  • Dynamic Contrast enhanced MRA is useful
Treatment of atherosclerotic fusiform cerebral aneurysms:
  • Medical management of atheroslcerosis
  • In selected cases consider endovascular treatment

 

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