10-20% of ischemic strokes involve the posterior vertebrobasilar circulation.
Characterized by poor blood flow to the posterior portion of the brain fed by two vertebral arteries that join to become the basilar artery.
Blockage of these arteries caused by atherosclerosis.
Basilar artery occlusion is associated with a high morbidity and mortality.
The vertebral arteries are branches of the subclavian arteries, arising on each side of the body, going through the vertebral column in the back of the neck, and enter the skull at the foramen magnum.
The two vertebral arteries join up to form the basilar artery at the base of the medulla oblongata.
The basilar artery supplies arterial branches to the brain stem, cerebellum and occipital lobes.
Basilar artery circulation controls the autonomic nervous system, level of conscious, coordination, balance and vision.
Many cases remain undiagnosed but vertebrobasilar stroke can be severe and some forms associated with a high death rate.
Most common causes of vertebrobasilar ischemia are embolism, large artery atherosclerosis, small artery disease and arterial dissection, with less frequent causes such associated migraine, fibromuscular dysplasia, coagulopathies and drug abuse.
Emboli may arise from the heart, aorta, and proximal vertebral and basilar arteries.
Large artery atherosclerosis is common in Caucasian men with atherosclerosis at the vertebral arteries from the subclavian arteries.
Intracranial large vessel atherosclerosis is most common among blacks, Asians and women.
Patients present with vertigo, headache, impaired vision, diplopia, ataxia, numbness, weakness, associated with clinical findings of limb weakness, oculomotor palsies, impaired balance and gait and oropharyngeal dysfunction.
The most frequent sites of arterial emboli involve the intracranial vertebral arteries which lead to cerebeller infarction, and the distal basilar artery leading to infarcts of the upper cerebellum, midbrain, thalamus, and areas of the posterior cerebral artery.
Patients with cerebeller infarction often report dizziness, vertigo, blurred vision, impaired walking, vomiting, inability to maintain posture and veer to one side, and frequently have nystagmus.
Patients with cerebeller infarcts may have arm hypotonia in the arm on the side of the lesion.
Patients with pure cerebeller infarcts do not have hemiparesis or hemisensory loss.
Embolic infarcts involving one posterior cerebral artery can lead to an occipital lobe infarct and hemianopia and sometimes hemisensory symptoms on the same side of the body and face as the hemianopia.
Risk factors include: Smoking, hypertension, advancing age, males at higher risk before 75 years ans women have a higher risk after 75 years of age, family history, hyperlipidemia, genetic factors, peripheral and coronary arterial disease.
Large infarcts of the left posterior cerebral artery can cause difficulty in reading and in identifying colors.
Right posterior cerebral artery infarct may be associated with neglect of the left visual field and disorientation to place.
Bilateral posterior cerebral infarcts may cause bilateral visual field defects, cortical blindness, inability to make new memories as well as agitation.