CT Case 083

Non-contrast CT demonstrates a hyperdense thrombosed basilar artery seen as a hyperdense dot.

Corresponding angiogram images demonstrates lack of enhancement of the basilar artery confirming thrombosis. Distal reformation of the basilar tip is seen, via collaterals from the anterior circulation.

The perfusion map demonstrates acute ischemia with a large penumbra of 256ml, 94%, and core infarct of 15ml, 6%.

Acute basilar artery occlusion (BAO) is a rare condition accounting for 1% of all ischaemic strokes and 5% of large vessel occlusion (LVO) strokes.

The basilar artery provides blood supply to the brainstem, cerebellum, thalamus, and occipital cortex.

Due to the structures supplied by the basilar artery, BAO often has a catastrophic outcome.  Up to 68% of the patients with acute BAO die or remain severely disabled. Survivors have multisystem dysfunction (eg, quadriplegia or hemiplegia, ataxia, dysphagia, dysarthria, gaze abnormalities, cranial neuropathies).

Patients with a BAO will present with sudden and rapidly progressive neurological impairment. The clinical features are initially often stuttering, and variable (due to the anatomical areas involved), resulting in delay in initial diagnosis.

The neurological deficit will depend on the exact location of occlusion and can include;

• Sudden death
• Sudden loss of consciousness
• ‘top of basilar syndrome’ ischaemia to bilateral thalami – causing visual, oculomotor and behaviour abnormalities, without motor dysfunction
• ‘locked in syndrome’ when the proximal and mid portions of the basilar artery are involved causing ischaemic to the ventral pons – resulting in quadriplegia with preserved consciousness
• Ataxia
• Hemiparesis
• Visual and oculomotor deficits

It has been proposed that the brainstem and cerebellum are more resistant to ischaemia than structures supplied by the anterior cerebral circulation.

Hence basilar artery stroke has a longer time window in which reperfusion therapy might be attempted compared with anterior circulation strokes.

This patient was taken for urgent endovascular clot retrieval (ECR). The procedure involved clot aspiration and basilar artery stent insertion.

Unfortunately, over the following days, this patient’s GCS did not improve, he remained off sedation in ICU with a GCS of 3. Repeat CTs over the next 48 hours demonstrated interval development of infarction involving the pons, as well as the right peripheral and left central cerebellum.

He was extubated and passed away 7 days after presentation.

• Warren CR. Vertebrobasilar Artery Occlusion. WestJEM
• Writing Group for the BASILAR Group. Assessment of Endovascular Treatment for Acute Basilar Artery Occlusion via a Nationwide Prospective Registry. JAMA Neurol. 2020 May 1;77(5):561-573. 
• Jovin TGet al; BAOCHE Investigators. Trial of Thrombectomy 6 to 24 Hours after Stroke Due to Basilar-Artery Occlusion. N Engl J Med. 2022 Oct 13;387(15):1373-1384.