Posterior Circulation Infarcts and Carotid Disease. Is There a Correlation?

Abstract

Case report: A 66 year old man presented with a sudden right Hemianopia and right facial weakness. Initial Brain CT scan demonstrated low attenuation in the left cerebral hemisphere[Fig 1] and MRI confirmed areas of infarction affecting Left MCA and Left PCA circulation [Fig 1]. The etiology was presumed to be Cardioembolic. Echocardiography proved to be normal and prolonged cardiac monitoring demonstrated Sinus Rhythm. Carotid imaging demonstrated a moderate Left Internal Carotid Artery [ICA] Stenosis at 50-59%. This was initially thought to be a coincidental finding as Posterior Circulation Infarcts could not be normally explained with Carotid Stenosis. A CTA demonstrated a large ruptured plaque in the Left ICA [Fig 1]. These findings were associated with a dominant Left Posterior Communicating Artery [PCOM] [Fig 1] and thereby explaining the fact that the plaque present in the Left ICA was able to seed the Left Middle Cerebral and the Left Posterior Cerebral circulation. It became clear that the multi-territory infarcts demonstrated were not Cardio-Embolic rather, related to the underlying Carotid disease. The patient underwent a successful Left Carotid Endarterectomy and made a good functional recovery. Discussion: Foetal variant PCOM is the commonest anatomical variant of the Posterior circulation of the Circle of Willis. It is related to hypoplasia or absence of the PI segment of the PCA. It occurs in up to 29% of the adult population and is more commonly found unilaterally [1]. CT Angiography has been shown to be both a sensitive and specific tool in identifying Foetal variant PCOM. It must be noted that the Foetal variant PCOM does not per se increase the incidence of PCA territory ischaemic stroke[2]. However, in patients with anterior and posterior circulation territory ischaemic stroke with ipsilateral Carotid disease, consideration must always be given to further imaging to determine if the Foetal variant PCOM exists. Our case demonstrates symptomatic Carotid Artery Disease resulting in both MCA and PCA territory strokes due to a Foetal variant PCOM [3]. We highlight the fact that patients presenting with isolated PCA territory stroke or mixed PCA and MCA territory strokes and ipsilateral ICA stenosis, should have a low threshold to be assessed with CT or MR Brain Angiography to determine if variants in Cerebral Circulation exist.