A 45-year-old gentleman was brought to emergency department with dizziness and diplopia within stroke window period. On examination, he had ocular movement abnormalities and hypersomnolence. Brain computed tomography (CT), as well as magnetic resonance imaging (MRI) brain [Figure 1a and b screening sequence] on arrival, were interpreted as normal. On CT angiography, Long-segment thrombosis of the left vertebral artery-V2 segment and nonfilling of the right P1 segment of posterior cerebral artery (PCA) was noted. Within 24 h, there was a significant drop in sensorium, extraocular involvement restriction with vertical gaze palsy, bilateral ptosis, anisocoria without motor weakness, and there was high index suspicion of thalamus and midbrain involvement. Hence, repeat MRI brain was done, [Figure 1c–e] which showed features of an artery of Percheron involvement (bilateral thalamus and midbrain) and confirmed the clinical findings.
Figure 1.
Magnetic resonance imaging (diffusion-weighted imaging) on the 1st May figure (a and b) and 2nd-day figure (c-e). Showing artery of Percheron infarcts involving bilateral thalamus and midbrain, in addition acute infarcts were noted on the right occipital area
Early imaging of the brain including MRI diffusion-weighted imaging may still not show the lesions as in our case. The artery of Percheron is rarely visualized with conventional angiography, and only four other authors have successfully demonstrated this variant [Figure 2].[1,2] We have shown the origin of Artery of percheron (AOP) from different patient and be the 5th demonstrated case [Figure 3]. It is also too small to be visualized by CT angiography or magnetic resonance angiography. Performing conventional angiography may not be indicated because lack of visualization of the artery does not exclude its presence (because it is occluded)[3] In our patient, the hyperdense P1 segment of the left PCA indicative of thrombosis possibly the site of origin of an artery of Percheron must have occluded hence not visualized. The imaging differential of bithalamic lesions is broad and includes arterial and venous occlusion, infiltrative neoplasm, infectious, and inflammatory.
Figure 2.
Four variants of paramedian thalamomesencephalic artery supply for thalamus and midbrain
Figure 3.
Catheter angiography (different patient) left vertebral injection showing origin of artery of Percheron
Learning points
In an emergency setting, sudden dip in sensorium with localizing neurology findings to midbrain and thalamus (e.g., coma and vertical gaze palsy) could be due to multiple causes. Embolic occlusion of the proximal artery of Percheron should be one of the differentials. Anytime the initial imaging is normal, perform a follow-up head CT or MRI as early, to make the correct diagnosis. If the diagnosis was made within stroke window period, thrombolytic therapy could still be done, and the outcome can be fairly good.[4]
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgment
The authors would like to thank Srikanth londe DM, interventional radiologist.
REFERENCES
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