Objectives: To investigate whether inclusion of lesions in the symptomatic region influences the performance of dissemination in space (DIS) criteria for a diagnosis of clinically definite multiple sclerosis (CDMS) in patients with a clinically isolated syndrome (CIS).

Methods: We studied 30 patients with CIS with brainstem/cerebellar and spinal cord syndromes who had MRI scans at the time of CIS and were followed up for the development of CDMS. We retrospectively applied the McDonald 2010 DIS criteria (excluding all lesions in the symptomatic region) to baseline MRI scans and 2 modified DIS criteria: (1) the inclusion of asymptomatic lesions in the symptomatic region in DIS, and (2) the inclusion of any lesion in the symptomatic region in DIS. The performance of the McDonald 2010 DIS criteria and the 2 modified criteria for the development of CDMS was compared.

Results: The sensitivity, specificity, and accuracy of the DIS criteria was, respectively, 73%, 73%, and 73% for the McDonald 2010 criteria, 80%, 73%, and 77% when asymptomatic lesions in the symptomatic region were included, and 87%, 73%, and 80% when any lesion in the symptomatic region was included in DIS.

Conclusions: Including lesions in the symptomatic region in DIS increases the sensitivity of MRI criteria for diagnosing multiple sclerosis without compromising specificity. These findings may help inform future revisions of the diagnostic criteria for multiple sclerosis.

Classification of evidence: This study provides Class II evidence that for patients with CIS, including lesions in the symptomatic region as part of the criteria for DIS does not significantly increase the accuracy for predicting the development of CDMS. The study lacks the precision to detect an important change in accuracy.