The effect of interferon beta-1b on size of short-lived enhancing lesions in patients with multiple sclerosis.

Background: Contrast enhancing lesions (CELs) in MRI represent inflammatory events in multiple sclerosis (MS). IFN-beta-1b decreases the formation of CELs. However, the ability of IFN-beta-1b to reduce the size of CELs arising during therapy has not been extensively investigated. Methods: Thirty patients with relapsing-remitting (RR) MS were followed for a 3-month pre-therapy phase then for a 6-month therapy phase during which treatment with IFN-beta-1b at a dosage of 250 mu g subcutaneously injected every other day was employed. Each patient underwent monthly clinical and MRI examinations. For all patients, CELs were identified on postcontrast T1-weighted MRIs. CEL number, size, and volume were computed using Medx software. Results: The average number and total lesion volume of CELs visible during the therapy phase were significantly lower than the number and total lesion volume of CELs observed in the pre-therapy phase. However, there was no significant reduction between pre-therapy and therapy phases in the mean size of individual lesions arising during the respective phases. Conclusions: Since size of CELs has been related to severity of tissue damage, the lack of size decrease during therapy suggested a limited therapeutic effect of IFN-beta-1b if a blood-brain barrier breakdown has occurred.