Background and purpose: Thalamic infarcts have traditionally been classified into 4 territories: anterior, paramedian, inferolateral, and posterior. The purpose of this study was to review this classical versus variant distribution in patients with thalamic stroke.
Methods: We reviewed all patients with a first clinical stroke included in the Lausanne Stroke Registry between 1990 and 2002. Among 71 patients with an acute stroke isolated to the thalamus confirmed by MRI, we selected all patients with lesions outside the classical territories and studied their clinical, etiological, and radiological features.
Results: A total of 21 patients (30% of all thalamic stroke patients) showed infarction outside the classical territories, allowing us to delineate 3 variant distributions: (1) Anteromedian territory (9 patients [13%]) involving anterior and paramedian territories, with predominantly cognitive impairment, including executive dysfunction, anterograde amnesia, and aphasia in left-sided or bilateral lesions. The most frequent stroke mechanism was cardiac embolism. (2) Central territory (4 patients [6%]), with lesions on the central part of the thalamus, resulting in a variety of neurological and neuropsychological signs, reflecting the involvement of several adjacent structures. Microangiopathy was the most frequent etiology. (3) Posterolateral territory (8 patients [11%]), involving inferolateral and posterior territories, with hemihypesthesia as the most frequent manifestation, followed by hemiataxia, executive dysfunction, and aphasia in left-sided lesions. Artery-to-artery embolism and microangiopathy were the main stroke mechanisms.
Conclusions: We describe 3 variant topographic patterns of thalamic infarction with distinct manifestations and etiologies. We postulate that these infarcts are the result of a variation in thalamic arterial supply or reflect borderzone ischemia.