What is the risk of permanent disability from a multiple sclerosis relapse?

To determine how often patients with relapsing-remitting multiple sclerosis (MS) develop severe (Expanded Disability Status Scale [EDSS] > or =6.0) sustained (greater than 6 months) disability due to an acute relapse.

We analyzed our database of all patients with MS followed up at the Marshfield Multiple Sclerosis Center.

Among the 1,078 patients, there were 2,587 relapses (mean of 2.4 per patient, with a range of 1-11 attacks over 1-15 years). Only 7 patients had a relapse resulting in EDSS > or =6 that did not recover. Genetic analysis showed no difference in HLA-DR or NOS2A loci between these patients and other MS populations, nor were there any clinical factors that identified high risk. Two of these patients were on interferon treatment at the time of their disabling attack.

The fear of a sudden irreversible disability should not influence therapeutic decisions because such attacks are very rare and can occur whether or not patients are treated with interferons.