Midbrain infarction: associations and aetiologies in the New England Medical Center Posterior Circulation Registry

Most reports of midbrain infarction have describedclinicoanatomical correlations rather than associations andaetiologies. Thirty nine patients with midbrain infarction (9.4%) aredescribed out of a series of 415 patients with vertebrobasilarischaemic lesions in the New England Medical Center PosteriorCirculation Registry. Patients were categorised according to therostral-caudal extent of infarction. The "proximal" vertebrobasilarterritory includes the medulla and posterior inferior cerebellar artery territory. The "middle" territory includes the pons and anterior inferior cerebellar artery territory. The "distal" territoryincludes the rostral midbrain, thalami, superior cerebellum, and medial temporal and occipital lobes. Midbrain infarction was accompanied 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 ortemporal lobe infarcts. Only three patients had isolated midbraininfarcts. Cardioembolism (n=11), in situ thrombosis (n=9), large artery to artery embolism (n=7), and intrinsic branch penetrator disease (n=5)were the most common aetiologies. Bilateral infarction and accompanyingpontine infarction were associated with the most extensivevertebrobasilar occlusive disease. Midbrain infarction was 10-fold morelikely to be accompanied by ischaemia of neighbouring structures thanit was to occur in isolation. Recognition of the different patterns ofinfarction may act as a guide to the underlying aetiology and vascular lesions.