Acute basilar artery occlusion

Dr Owen Kang and Dr Donna D'Souza et al.

Acute occlusion of the basilar artery may cause brainstem or thalamic ischaemia or infarction. It is a true neuro-interventional emergency and, if not treated early, brainstem infarction results in rapid deterioration in the level of consciousness and ultimately death.

Occlusions of the posterior circulation arteries are related to a fifth of all strokes, and basilar artery occlusion is rare (~1% of all strokes) 9.

Patients with acute occlusion of the basilar artery will present with sudden and dramatic neurological impairment, the exact characteristics of which will depend on the site of occlusion:

  • sudden death/loss of consciousness
  • top of the basilar syndrome
    • visual and oculomotor deficits
    • behavioural abnormalities
    • somnolence, hallucinations and dream-like behaviour
    • motor dysfunction is often absent
  • proximal and mid portions of the basilar artery (pons) can result in patients being 'locked in' 7-8
    • complete loss of movement (quadriparesis and lower cranial dysfunction)
    • preserved consciousness
    • preserved ocular movements (often only vertical gaze) 8

Acute occlusion of the basilar artery can be due to either thromboembolism,  atherosclerosis or propagation of intracranial dissection. Although these may occur anywhere, each of these have predilections for different segments of the basilar artery:

  • vertebrobasilar junction
    • thromboembolism (e.g. cardioembolic)
    • atherosclerosis with thrombosis
    • propagation of vertebral arterial dissection (rare)
  • midsegment
    • atherosclerosis with thrombosis
  • distal third or basilar tip

Remains the gold standard for the diagnosis of basilar artery occlusion. However, DSA is used only after non-invasive imaging for therapeutic recanalisation 9 (see case 1). Images demonstrate a filling defect within the vessel.

  • transcranial Doppler
    • absence of signal in the basilar artery
    • indirect signs such as abnormal waveforms in the vertebral arteries and collateral flow
  • non-contrast CT
    • hyperdense basilar artery (the basilar artery equivalent of the hyperdense MCA sign), present in ~65% 9
    • a high index of suspicion is needed in the correct clinical setting as the diagnosis can easily be missed (often only present on 1 or 2 slices); additionally it is well recognised that acute clots are of lower attenuation than chronic clots 5-6
    • hypoattenuation delineates tissue with ischaemic damage (limitations due beam-hardening artifacts limit the visualization of the brainstem on CT)
  • contrast CT
  • loss of flow void within the basilar artery on spin-echo and FLAIR images
  • DWI: restricted diffusion within infarcted tissue
  • FLAIR/T2: hyperintense signal within infarcted tissue

Acute occlusion of the basilar artery is a life threatening event, which carries a terrible prognosis: ~ 90% mortality depending on the location, and high morbidity in the survivors 3.

Treatment usually involves catheter-directed intra-arterial thrombolysis and intravenous heparin, which carries a risk of haemorrhage of up to 15%. Mechanical embolectomy with a clot retrieval device has been used in selected cases.

Stroke and intracranial haemorrhage
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Article information

rID: 971
Section: Gamuts
Synonyms or Alternate Spellings:
  • Basilar artery occlusion
  • Thrombosis of basilar artery
  • Thrombosis of the basilar artery
  • Basilar arterial thrombosis
  • Basilar artery thrombosis

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Cases and figures

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    Figure 1: vascular territories
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    Case 1
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    CT of brainstem i...
    Case 2
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    MRI of posterior ...
    Case 3
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    Case 4
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    Case 5: with stent retriever placement
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    Case 6
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    Case 7
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    MIP
    Case 8
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    Case 9: NECT hyperdense artery
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    Case 10
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