Posterior circulation infarct

Case contributed by Shu Su


Woke up with right sided tinnitus, ataxia, dizziness, facial droop and dysarthria.

Patient Data

Age: 40 years
Gender: Male

CT Stroke Protocol (CT Brain / CTA COW / CT Perfusion)

Non contrast CT brain, intravenous contrast enhanced CT angiogram of the head and neck and CT perfusion.

Brain: No intracranial hemorrhage or collection. Grey-white matter differentiation is preserved. Dense basilar tip noted. The midline and posterior fossa structures are otherwise normal. 

CTA COW: Acute thrombotic occlusion at the basilar tip with hyperdense thrombus extending into the proximal portions of the bilateral superior cerebellar arteries (SCA). The thrombus also involves the origins of the posterior cerebral arteries (PCA), which demonstrate normal distal opacification, with patent bilateral posterior communicating arteries noted. The remainder of the circle of Willis opacifies normally.

CT Perfusion: Diffuse mild elevation in T-max within the right superior cerebellar hemisphere. There is no associated reduction in cerebral blood flow or volume to suggest core infarct. Estimated ischemic penumbra based on RAPID assessment measures 11 ml.

Conclusion: Acute thrombotic occlusion of the basilar tip, with involvement of the bilateral proximal posterior cerebral arteries and superior cerebellar arteries. Evidence of right superior cerebellar ischemic penumbra on CT perfusion, with no demonstrable core infarct. No features of evolving infarct on non contrast imaging.

The basilar tip thrombus was treated with thrombolysis using tenecteplase, with subsequent improvement in posterior fossa ischemic symptoms. However, later the same evening, the patient developed new symptoms of left homonymous hemianopia, and parasthesia of the left upper and lower limbs; a repeat CT stroke series was performed. 

CT Stroke Protocol (CT Brain / CTA COW / CT Perfusion) 

Noncontrast CT brain. CT angiogram circle of Willis arch to vertex. CT brain perfusion. Comparison to CT brain from earlier today 26/11/20 11:25 a.m.

Brain: No intracranial hemorrhage or mass lesions. Ventricular size and sulcal patterns are age-appropriate. Grey-white matter differentiation is preserved. 

CTA COW:  Previous basilar tip thrombus has resolved. Origins of the P1 segments of both PCAs and SCAs bilaterally now opacify. New occlusion of the mid right P2 segment, with relative paucity of arterial branches in the right PCA territory distal to this.

Perfusion: New elevated T-max in the right occipital and posterior temporal lobe (PCA territory) in keeping with ischemic penumbra (44 mL). No associated reduction in cerebral blood flow or volume to suggest core infarct. Previous increased T-max in the right cerebellar hemisphere has resolved, and is compatible with recanalization of the right SCA seen on CTA COW.

Conclusion: Previous basilar tip thrombus has resolved, with recanalization of the right SCA and resolution of previous right superior cerebellar hemisphere ischemic penumbra. New right P2 occlusion resulting in ischemic penumbra involving the right occipital and posterior temporal lobes (44 mL). No infarct core or established changes on non-contrast CT brain. 


Stroke MRI (Quick DWI protocol) 

Abnormal diffusion restriction in the right posterior cerebral and right superior cerebellar artery distribution in keeping with acute infarct. Further punctate area of diffusion restriction in the left superior frontal gyrus in keeping with a small focal infarct. 

Case Discussion

This case demonstrates a basilar tip occlusion, which resolved following thrombolysis using tenecteplase. Occlusion of the P2 segment of the right posterior cerebral artery later the same day, may represent migration of the previous basilar artery thrombus, or alternatively a new embolus from a central cause. In fact, the patient was eventually found to have left lower limb deep venous thrombosis and patent foramen ovale, which likely precipitated his strokes. 

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