Autonomic dysfunction in multiple sclerosis: cervical spinal cord atrophy correlates

Autonomic dysfunction has rarely been studied in patients suffering from multiple sclerosis (MS). Some hypotheses have concerned the pathophysiology, especially with regard to a possible spinal cord origin. However, there have been no previous studies on autonomic dysfunction in MS and spinal cord lesions. This study assessed the frequency of autonomic dysfunction (AD) in MS and the correlation to spinal cord magnetic resonance imaging (MRI) findings. We prospectively studied 75 MS patients (25 with relapsing-remitting forms, 25 with secondary progressive forms and 25 with primary progressive forms). We performed sympathetic skin response, R-R interval variability and orthostatic hypotension testing. Spinal cord MRI was performed to detect demyelinating lesions (sagittal and axial plane) or spinal cord atrophy. Clinical and laboratory evidence of AD was found in 84% and 56% of MS patients, respectively. The correlation of the latter with disability was evaluated using the Extended Disability Status Scale. AD was more frequent in primary progressive MS than in the other two forms. AD was correlated with spinal cord cross-sectional area reduction but not with spinal cord hyperintensities. This study confirms that the frequency of AD in MS, especially in primary progressive forms, has until now been underestimated. Furthermore, AD appears to be more closely related to axonal loss, as demonstrated by spinal cord atrophy, than to demyelinating lesions.