By: Seethal Sara Thomas, FNP-BC
The blood supply of the brain can be divided into anterior and posterior circulation. The circle of Willis is a group of anastomosing arteries that provides collateral oxygenated blood to the forebrain and hindbrain brain. The anterior circulation includes the bilateral internal carotid arteries, middle cerebral arteries, and anterior cerebral arteries and these are usually the largest vessels of the cerebral vasculature. The posterior circulation generally has smaller arteries than the anterior, but larger arteries of the posterior circulation are the vertebral arteries, the basilar artery, and the posterior cerebral arteries. The most common artery to have an ischemic occlusion is the middle cerebral artery (MCA) and an introduction to stroke and the MCA can be read here: https://www.medreport.foundation/post/introduction-to-stroke-and-signs-of-the-most-common-infarct. Though the incidence of stroke in other arteries is less common, recognizing these stroke syndromes and rapid workup and treatment corresponds to better health outcomes.
smart servier medical art. (n.d.). BRAIN ARTERIES. Smart Servier Medical Art. https://smart.servier.com/smart_image/smart-brain-arteries/
The anterior cerebral artery (ACA) strokes make up about 0.3-4.4% of stroke cases. The ACA supplies the superior and medial part of the parietal and frontal lobe as well as some of the basal ganglia (Matos Casano, Tadi, & Ciofoaia, 2023). ACA strokes are rare because there is collateral circulation provided by the anterior communicating artery (ACoA). The ACA divides itself into five segments and it begins from the anterior clinoid segment of the internal carotid artery (Matos Casano, Tadi, & Ciofoaia, 2023). The presenting symptoms of this stroke will be varied by the size of the infarct and which branch is affected. Most commonly, the ACA stroke syndrome presentation includes contralateral motor and sensory deficits of the lower extremities. If the paracentral lobule is affected, presenting symptoms include urinary and fecal incontinence. If the prefrontal cortex is affected, changes in mood and behavior may occur such as agitation and emotional lability. If the anterior cingulate cortex is affected, changes to memory can be seen such as abulia and akinetic mutism. If the anterior and superior frontal lobe are affected, the presentation may include transcortical motor aphasia where there is non-fluent speech, but comprehension is intact. In transcortical motor aphasia, the patient should be able to repeat sentences. ACA symptoms include neuropsychologic features, lower motor, and sensory deficits (Matos Casano, Tadi, & Ciofoaia, 2023).
The posterior circulation is supplied by the bilateral vertebral arteries which fuse to form the basilar artery. In most cases, the basilar artery divides into the posterior cerebral arteries (PCAs). The incidence of PCA strokes is between 5%-10% of all strokes (Kuybu, Tadi, & Dossani, 2023). The PCA mainly supplies the occipital lobe, but it can restrict blood flow to several regions including the inferomedial temporal lobe, parts of the thalamus, upper brainstem, and midbrain. There are four segments of the PCA. PCA stroke syndromes may have many presenting symptoms, but with acute, sudden vision deficits, PCA involvement should be considered. If the primary visual cortex and association cortex are affected then contralateral homonymous hemianopia, alexia without agraphia, anomia, and Anton syndrome can occur. Anton syndrome is cortical blindness where the patient cannot see, but the patient is unaware of the blindness and often the patient insists that they can see. Contralateral hemiparesis, sensory loss, ataxia, transcortical aphasia, and ipsilateral oculomotor palsies can result from PCA infarcts. Contralateral hyperalgesia and decreased arousal can present in PCA infarcts affecting the thalamus. PCA supplies the thalamus which receives and sends stimuli to all lobes of the brain; therefore, the patient presentation may vary, and some sometimes may resemble middle cerebral artery syndrome. Astute neurologic exam and assessment are important to give information to localize the stroke. For patients with visual impairments and cognitive deficits, PCA stroke should be on the differential (Kuybu, Tadi, & Dossani, 2023).
The ability to triage stroke syndromes is important for assessment and treatment considerations. With ACA and PCA strokes, some of the deficits may be more subtle than with full blown MCA syndrome. Describing exactly what symptoms are present is vital for accurate diagnosis.
References
Kuybu O, Tadi P, Dossani RH. Posterior Cerebral Artery Stroke. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532296/
Matos Casano HA, Tadi P, Ciofoaia GA. Anterior Cerebral Artery Stroke. [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537333/ Assessed and Endorsed by the MedReport Medical Review Board
Bình luận