Clinical study of 16 patients with thalamic infarction

Background: The pathophysiology of sensory impairment in thalamic infarction is unclear. Aim: The association between extents of lesions in the ventroposterior nucleus (VP) and distributions of sensory impairments after thalamic infarction was studied. Methods: Neurological symptoms and locations of lesions in 16 patients with thalamic infarction were analyzed. Locations of lesions were grouped into the four regions (region 1–4) in the front to back direction. Results: The lateral part of the region3 within the intermediate to caudal levels where the VP exists was frequently involved. Subjective superficial sensory impairments were noted in eight patients. The other six patients showed objective sensory impairment alone. The most frequent type was the face/arm in 6 patients. In these six patients, sensory impairments were distributed to the distal part of the arm and the mouth surrounding in five patients each. Sensory impairments were distributed to the half of the body in four patients, the face/trunk/arm in one patient, the face/arm/leg in two patients, and the arm in one patient. Conclusions: The principal inferolateral branch supplies the VP and has no anastomosis. In ischemic conditions, blood flow can be decreased in the inside part of the VP, which corresponds to the field of the hand and the mouth surrounding. The detection threshold of superficial sensations for hand and mouth is low. These phenomena were associated with frequent involvement limited to the face/arm. Distributions of sensory impairments were considered to depend on the detection threshold and the lower blood flow in the inside part.