Background: Recently, lateral differences in body surface temperature (BST) have been reported as a symptom of Wallenberg syndrome (WS), resulting from disturbances in the sympathetic nerve pathway. This study aimed to investigate the relationship between the laterality of BST and brain magnetic resonance imaging (MRI) findings in 12 patients with WS.Methods: BST was measured using an infrared thermal camera at 7±3 days and 90±30 days after symptom onset. The MRI findings were categorized as rostral, middle, and caudal medulla rostrocaudally and typical, ventral, large, dorsal, and lateral types in the horizontal direction.Results: MRI revealed medullary lesions on the right in five patients and on the left in seven patients. Two patients without lateralized BST had lateral caudal medullary infarction, and one patient had a dorsal middle medullary infarction. One patient with lateralized BST had a rostral medullary infarction and the other had a typical or large middle medulla infarction. Lateralized BST in patients with WS may disturb the sympathetic nervous system pathway that descends from the rostral ventrolateral medulla oblongata. Deficits in sweating and skin blood flow may cause BST laterality.Conclusion: This study showed that lateralized BST in patients with WS may be associated with disturbances in the sympathetic nervous pathway descending from the rostral ventrolateral medulla. These results support the assumption that autonomic dysfunction may be related to abnormal sensory symptoms in patients with WS.