MIDBRAIN INFARCTION - ASSOCIATIONS AND ETIOLOGIES IN THE NEW-ENGLAND MEDICAL-CENTER POSTERIOR CIRCULATION REGISTRY

Most reports of midbrain infarction have described clinicoanatomical c orrelations rather than associations and aetiologies. Thirty nine pati ents with midbrain infarction (9.4%) are described out of a series of 415 patients with vertebrobasilar ischaemic lesions in the New England Medical Center Posterior Circulation Registry. Patients were categori sed according to the rostral-caudal extent of infarction. The ''proxim al'' vertebrobasilar territory includes the medulla and posterior infe rior cerebellar artery territory. The ''middle'' territory includes th e pens and anterior inferior cerebellar artery territory. The ''distal '' territory includes the rostral midbrain, thalami, superior cerebell um, and medial temporal and occipital lobes. Midbrain infarction was a ccompanied by ''proximal'' territory infarcts in four patients, and by ''middle'' territory infarction in 19 patients. Thirteen patients had associated ''distal'' territory infarcts, three of whom had occipital or temporal lobe infarcts. Only three patients had isolated midbrain infarcts. Cardioembolism (n=11), in situ thrombosis (n=9), large arter y to artery embolism (n=7), and intrinsic branch penetrator disease (n =5) were the most common aetiologies. Bilateral infarction and accompa nying pontine infarction were associated with the most extensive verte brobasilar occlusive disease. Midbrain infarction was 10-fold more Lik ely to be accompanied by ischaemia of neighbouring structures than it was to occur in isolation. Recognition of the different patterns of in farction may act as a guide to the underlying aetiology and vascular l esions.