Paramedian thalamic and midbrain infarct: clinical and neuropathological study.

The clinical and neuropathological findings in 28 cases of paramedian thalamic and midbrain infarcts are reported. The 4 instances of unilateral paramedian thalamic infarct were characterized by mood and behavioral changes, limitation of the infarct to the center of the anatomical paramedian territory, and symmetrical configuration of the paramedian thalamic arteries. Basilar artery occlusion was found in 1 patient. The 5 cases of bilateral paramedian thalamic infarcts were characterized by disturbances of consciousness and behavior, extension of the infarct (to the mammillothalamic tracts in 4 cases, the red nuclei in 3, and the hypothalamus in 2), and a variable paramedian thalamic arterial pattern. The arterial pattern was symmetrical in 2 cases, asymmetrical in 1, and unilateral in 1. The basilar artery was occluded in 1 case, the basilar communicating and posterior cerebral arteries in 1, and a third patient had occlusion involving an aneurysm of the basilar artery. The 19 patients with paramedian thalamopeduncular infarcts had marked disturbances of consciousness (hypersomnia, deep coma, akinetic mutism) associated with ocular motility changes. Later, abnormal movements--always delayed--and memory disturbances were observed in some. Thalamic changes were restricted to beh paramedian territory in only 3 cases. The arterial pattern was symmetrical in 5. The basilar and posterior cerebral arteries were occluded in 4 patients each. Paramedian infarcts were rarely found as isolated lesions and were always bilateral when there was only one arterial pedicle. The paramedian thalamic pedicle can supply the polar thalamic territory.