Posterior cerebral artery syndrome

Overview

Posterior cerebral artery (PCA) syndrome is a neurological condition that occurs due to obstruction or occlusion of the posterior cerebral artery, which supplies blood to important areas of the brain, including the occipital lobe, inferior temporal lobe, thalamus, and midbrain. The resulting ischemia (reduced blood flow) can lead to a range of symptoms, most commonly visual disturbances, but also including sensory and cognitive deficits depending on the location and extent of the affected brain tissue.

PCA syndrome is considered a type of ischemic stroke and accounts for approximately 5–10% of all cerebral infarctions. Early recognition and prompt management are critical to minimizing permanent neurological damage and improving outcomes.

Causes

Posterior cerebral artery syndrome is caused by an interruption of blood flow through the PCA. Common underlying causes include:

• Embolism: The most frequent cause, where a clot (often cardiac in origin) travels to and blocks the PCA.

• Thrombosis: Local formation of a clot in the PCA, often due to atherosclerosis or hypercoagulable states.

• Vasculitis: Inflammation of the blood vessels, such as in autoimmune diseases, may lead to PCA occlusion.

• Arterial dissection: A tear in the wall of an artery leading to clot formation and occlusion.

• Vertebrobasilar insufficiency: Inadequate blood flow in the vertebrobasilar system that supplies the PCA.

• Trauma: Head or neck injuries that disrupt blood supply to the PCA region.

Risk factors include hypertension, diabetes, atrial fibrillation, smoking, hyperlipidemia, and previous cerebrovascular disease.

Symptoms

The symptoms of posterior cerebral artery syndrome vary depending on the specific brain regions affected. The most common and characteristic symptom is visual disturbance due to occipital lobe involvement. Other symptoms may include:

Visual Symptoms

• Contralateral homonymous hemianopia: Loss of vision in the same half of the visual field in both eyes, opposite to the side of the lesion.

• Cortical blindness: Total vision loss with preserved pupillary reflexes (in bilateral PCA infarction).

• Visual agnosia: Inability to recognize objects or faces (prosopagnosia), especially if the temporal lobe is involved.

Sensory and Cognitive Symptoms

• Thalamic syndrome: Contralateral sensory loss (pain, temperature, touch) due to infarction of the thalamus.

• Dyslexia without agraphia: Inability to read despite preserved writing ability (typically from left PCA infarction involving the splenium of the corpus callosum).

• Memory impairment: When the hippocampus is affected, particularly in bilateral infarctions.

Motor and Brainstem Symptoms

• Contralateral hemiparesis: Mild weakness on one side of the body, less common than in anterior circulation strokes.

• Oculomotor nerve palsy: Eye movement abnormalities, ptosis, and pupil dilation if the midbrain is involved.

Symptoms can range from mild visual loss to profound deficits depending on the size and location of the infarct.

Diagnosis

Prompt diagnosis of posterior cerebral artery syndrome is essential for effective treatment. A combination of clinical evaluation and imaging studies is used:

• Neurological examination: Assessment of visual fields, sensory function, and cognitive status.

• CT scan: Often used initially to rule out hemorrhagic stroke, but may miss early PCA infarcts.

• MRI of the brain: Preferred imaging modality, especially diffusion-weighted imaging (DWI), to detect acute ischemic changes in PCA territory.

• Magnetic Resonance Angiography (MRA) or CT Angiography (CTA): To visualize blood vessels and detect occlusion of the PCA.

• Carotid and vertebral artery Doppler ultrasound: To evaluate extracranial and vertebrobasilar circulation.

• Echocardiography: To identify cardiac sources of embolism, especially in younger patients or those with atrial fibrillation.

• Blood tests: Including coagulation profile, lipid panel, and inflammatory markers for identifying underlying risk factors or causes.

Treatment

Treatment of PCA syndrome follows standard ischemic stroke protocols and focuses on restoring blood flow, minimizing brain damage, and preventing recurrence.

Acute Management

• Intravenous thrombolysis: Tissue plasminogen activator (tPA) may be administered within 4.5 hours of symptom onset if no contraindications exist.

• Mechanical thrombectomy: Considered in selected patients with large vessel occlusion within 6–24 hours of onset.

• Antiplatelet therapy: Aspirin is typically started once bleeding is ruled out.

• Management of risk factors: Control of hypertension, diabetes, atrial fibrillation, and hyperlipidemia.

Rehabilitation and Supportive Care

• Vision rehabilitation: Includes strategies for compensating for visual field loss and improving functional independence.

• Occupational and physical therapy: For improving strength, coordination, and daily functioning.

• Cognitive therapy: To address memory, attention, or recognition issues.

Long-term care also includes lifestyle changes, medication adherence, and regular follow-up to prevent recurrent stroke.

Prognosis

The prognosis of posterior cerebral artery syndrome varies depending on the extent of the infarction, the speed of diagnosis and treatment, and the affected regions of the brain. Many individuals with small or moderate infarctions recover well, especially if treatment is initiated promptly. Visual deficits may persist, but with rehabilitation, patients can often adapt and maintain independence.

Key factors influencing prognosis include:

• Size and location of the infarct

• Time to treatment initiation

• Presence of bilateral infarction

• Underlying comorbidities and stroke risk factors

With comprehensive care, many patients achieve functional recovery, though some may experience permanent visual or cognitive impairments requiring ongoing support.