A stroke occurs when blood flow to a part of the brain is disrupted, leading to the rapid death of brain cells due to lack of oxygen. Anterior circulation stroke is a specific type of stroke that impacts the front portion of the brain. This form of stroke accounts for a significant majority of ischemic stroke cases.
Understanding Anterior Circulation Stroke
The brain receives its blood supply from two main arterial systems: the anterior and posterior circulations. The anterior circulation, which supplies about 70% of the brain’s blood, originates from the internal carotid arteries (ICAs). These ICAs branch into major arteries, including the anterior cerebral artery (ACA) and the middle cerebral artery (MCA). The MCA is involved in about 90% of anterior circulation strokes.
The ACA supplies the medial surfaces of the frontal and parietal lobes, the corpus callosum, and parts of the frontobasal cerebral cortex. These regions are responsible for lower limb movement, sensation, and speech production. The MCA supplies most of the lateral surface of the cerebrum, including areas involved in motor control, sensation, and language. Anterior circulation strokes are most commonly caused by an ischemic event, where a blood clot or plaque blocks one of these arteries. Atherosclerosis, a condition where fatty deposits build up in artery walls, is a frequent underlying cause, but clots originating in the heart (cardioembolism) or arterial dissections can also lead to blockages.
Identifying the Symptoms
Symptoms of an anterior circulation stroke appear suddenly and can vary. These include:
Weakness or paralysis on one side of the body (hemiparesis or hemiplegia), often affecting the face, arm, or leg.
Sensory changes or numbness on one side of the body.
Speech difficulties, such as aphasia (trouble speaking or understanding language) or dysarthria (slurred speech).
Visual field deficits, where a person loses part of their vision in both eyes (homonymous hemianopia).
Cognitive changes, including confusion, disorientation, or difficulty comprehending.
The “FAST” acronym helps recognize stroke symptoms: Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services.
Medical Diagnosis
When a stroke is suspected, medical professionals begin with an initial assessment, which includes reviewing the patient’s medical history and performing a neurological examination. Blood tests are also conducted to check glucose levels, coagulation profiles, and electrolyte levels.
Imaging tests are then performed to confirm the diagnosis and identify the type of stroke. A noncontrast computed tomography (CT) scan of the brain is typically the first imaging test to quickly rule out a hemorrhagic stroke (bleeding in the brain). Magnetic resonance imaging (MRI), particularly diffusion-weighted imaging (DWI), offers a more detailed view of ischemic lesions and can detect them within minutes of stroke onset. Additionally, CT angiography (CTA) or MR angiography (MRA) can visualize the blood vessels to pinpoint blockages or abnormalities.
Emergency Treatment and Management
Timely intervention is crucial in treating an anterior circulation stroke, as brain cells can be damaged within minutes of blood flow disruption. For ischemic strokes, acute treatments aim to restore blood flow to the affected brain tissue. Intravenous tissue plasminogen activator (IV tPA), a clot-busting medication, is recommended for eligible patients within 4.5 hours of symptom onset.
For patients with a large vessel occlusion in the anterior circulation, mechanical thrombectomy, a procedure to physically remove the blood clot, is a treatment option. This procedure can be performed within 6 to 16 hours of symptom onset. Supportive care in the acute phase involves managing blood pressure and blood sugar levels to optimize brain function and prevent further damage.
Rehabilitation and Long-Term Recovery
Recovery from an anterior circulation stroke is a highly individualized process. Rehabilitation typically begins as soon as 24 to 48 hours after the stroke, while the patient is still in the hospital, to maximize the potential for regaining lost abilities. The most significant improvements often occur within the first three months following the stroke.
A multidisciplinary rehabilitation team, including physical therapists, occupational therapists, and speech-language pathologists, works with patients to address their specific deficits. Physical therapy focuses on motor skill exercises to improve muscle strength, coordination, and mobility, including walking and balance. Occupational therapy helps patients regain independence in daily activities like bathing and dressing. Speech therapy addresses communication difficulties such as aphasia and dysarthria. Rehabilitation also addresses cognitive changes, emotional well-being, and provides guidance for lifestyle modifications to prevent future stroke events.