Presentation
Decreased level of consciousness, with impaired horizontal gaze
Patient Data
Unenhanced axial CT scan shows rounded areas of low attenuation, bilaterally in the medial thalami and midbrain.
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Axial T2 FLAIR stack - Foci of abnormal signal intensity is shown in the ventral - medial margins of the bilateral thalamus extending into the medial margins of mid-brain appearing hyperintense on long TR sequences, (represented by these FLAIR images).
Hyperintense on Diffusion-Weighted Images (DWI) and hypointense on Apparent Diffusion Co-efficient images (ADC) in keeping with acute infarction. Note : DWI iamges include B = 0, 500. 1000.
Axial Time of Flight (TOF) MR angiogram showing a fetal origin of the left Posterior Cerebral Artery (PCA). At the level of the basilar tip, the origin of a tiny unpaired artery is noted which was presumed to be the occluded Artery of Percheron.
Similar finding is demonstrated in the 3D rendering.
This is an illustrative drawing.
The right side image shows the prevalent anatomy wherein the multiple perforator branches of the basilar artery the medial thalami and the ventral midbrain, corresponding to a particular peculiar zone.
The left side image shows an Artery of Percheron (AOP), wherein the perforator arteries are either absent altogether or are severely hypoplastic and the above-said areas of the thalamus and midbrain are supplied by small perforator branches which arise from a solitary artery which usually arises from the P1 segment of the Posterior Cerebral Artery (PCA).
It has been reported that a right AOP is more common than the left side origin.
Case Discussion
The AOP is a vascular anomaly wherein a single arterial branch arises from the PCA circulation to supply the midbrain and thalamus.
The AOP was first described by the French medical scientist Gerald Percheron in 1973.
The multiple perforator branches which usually arise from the basilar artery are replaced by branches from this singleton branch of the posterior cerebral artery. Occlusion of this branch leads to a particular type of brain stem infarction with characteristic imaging findings as described.
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