26 - Vertebrobasilar Disease

Abstract

Large artery atherothrombosis, cardiac embolism, and small artery disease are the important mechanisms of infarction in vertebrobasilar artery territory. In lateral medullary infarction, clinical manifestations vary according to rostro-caudal and ventrodorsal topography. Rostral-ventral infarcts are associated with severe dysphagia, dysarthria, and contralateral trigeminal sensory involvement, whereas caudal-lateral lesions are characterized by severe gait ataxia, absent dysphagia, and sensory symptoms worse in the lower extremities. Medial medullary infarction occurs mostly in the rostral medulla, and presents with unilateral motor, sensory, and ocular motor disturbances depending on ventrodorsal topographic involvement. Branch occlusion associated with intracranial vertebral artery disease is the most important cause of medullary infarction. Unilateral paramedian infarction is the most common pattern of pontine infarction. Basal involvement is associated with motor syndromes such as pure motor stroke, ataxic hemiparesis, and dysarthria clumsy hand, while tegmental lesions produce sensory symptoms and/or ocular motor disturbances, notably internuclear ophthalmoplegia. Bilateral pontine infarcts result in quadriparesis, horizontal gaze palsy, and locked in syndrome, and are usually associated with significant basilar artery thrombotic occlusion. The most common topographic pattern of midbrain infarction is anteromedial followed by anterolateral; the former is characterized by ocular motor dysfunction (the 3rd nerve palsy or internuclear ophthalmoplegia) whereas the latter lesions produce various motor syndromes. Cerebellar infarcts generally follow the topography of three major arteries: posterior inferior cerebellar artery, superior cerebellar artery, and anterior inferior cerebellar artery. Basilar top occlusion is mostly embolic and results in peculiar syndromes associated with paramedian midbrain, and diencephalic infarctions, with occasional involvement of the occipital and cerebellar regions.