Sympathetic skin responses (SSRs) in monofocal brain lesions: topographical aspects of central sympathetic pathways

Lesions of the central sympathetic pathways are likely to be of clinical relevance. In patients with acute stroke, in particular, they may be responsible for the partially deleterious cardiac arrhythmia. There is little knowledge of the central organization of sympathetic pathways above the brainstem level for both cardio-efferent and sudomotor fibers. We studied the sympathetic skin response (SSR) in 29 patients with brainstem stroke or infarction in the territory of the middle cerebral artery (MCA) in order to evaluate the pathways mediating emotional sweating. In 24 patients (82.8%) the SSR was pathological. These abnormalities were bilateral with no clear asymmetry in 10 patients (34.5%), bilateral with marked contralateral pathology in 8 patients (27.6%), purely contralateral in 5 patients (17.2%) and purely ipsilateral in one patient (3.5%). Bilateral abnormalities were more frequent and more marked in brainstem than in MCA stroke. This is probably indicative of a more generalized sympathetic dysfunction. In contrast, contralateral abnormalities were more pronounced in MCA than in brainstem infarcts. Our results show that sympathetic skin responses are suppressed in the majority of stroke patients. Asymmetric responses may indicate that sudomotor fibers mediating emotional sweating have their origin or receive input from the contralateral MCA territory.