T2 hypointense rims and ring-enhancing lesions in MS

Hypointense rims peripherally on T2-weighted MRI (rim lesions) have been associated with gadolinium ring-enhancing lesions in multiple sclerosis (MS) in pathological studies. However, little is known about their frequency, we analyzed clinical significance in a cohort of MS sufferers according to routine clinical practice.

We retrospectively reviewed all available MRI scans performed on our MS patients between 2000 and 2009. A total of 580 MRI scans from 257 patients were analyzed. The presence of rim lesions and ring enhancement was assessed and counted blind. Furthermore, the correlation between both patterns, and with clinical characteristics, was evaluated.

Thirty-five rim lesions were identified and 9% (24/257) of the patients showed at least one of these lesions. Forty ring-enhancing lesions were counted and 12% (29/245) of the patients who had undergone gadolinium MRI presented at least one such lesion. Thirteen lesions co-localized both patterns (40% of the rim lesions and 33% of the ring-enhancing lesions). Rim lesions and ring-enhancing lesions were observed in patients with clinically isolated syndrome (7%, 7%), relapsing-remitting (11%, 15%) and secondary progressive (13%, 9%) but none with primary progressive MS. Presence of ring-enhancing lesions was significantly associated with a shorter time to reach EDSS (Expanded Disability Status Scale) 4.0 and 6.0 (hazard ratio 7.6, 95% confidence interval 2.3-24.6).

Rim lesions and ring-enhancing lesions are present in close to 10% of patients with MS, and frequently both lesions appear independently one to the other. The association of ring enhancement with worst prognosis needs to be confirmed in prospective studies.