1. Home>
2. Specialties>
3. Neurology>
4. Summary and Comment

Is Benign Multiple Sclerosis Truly Benign?

A diffusion tensor MRI study suggests not.

A well-known small subgroup of patients with so-called benign multiple sclerosis (BMS) do not develop substantial locomotor disability during long-term follow-up. Nonetheless, cognitive dysfunction can occur in patients with BMS. These authors used diffusion tensor (DT) MRI techniques to prospectively examine the extent of brain tissue damage and correlated the findings with measures of cognitive disability in 62 patients with BMS (disease duration, 15 years; EDSS score, 3.0). Thirty-six patients with secondary progressive MS (SPMS) and 19 healthy controls also underwent DT MRI.

Of the 62 patients with BMS, 12 (19%) had cognitive impairments. These 12 had severe structural brain disease that resembled that of the SPMS patients as detected by both conventional and DT MRI metrics. Among the BMS patients, abnormalities in mean diffusivity and in fractional anisotropy in normal-appearing white matter and gray matter on DT MRI showed significant correlations with cognitive disability. Cognitive scores did not correlate with T2 lesion volume or normalized brain volume. BMS patients without cognitive impairment had lower MRI disease burden compared with SPMS patients. The authors question the validity of the current definition of BMS, which does not take into account cognitive disability.

Comment: Clinical MS neurologists have seen, and previously published studies have confirmed, that cognitive disability can be a devastating consequence of MS, even in a setting of relatively spared motor, sensory, and cerebellar functions. This work further confirms that "benign MS" is truly benign only if neither substantial motor nor cognitive disability is present in MS patients after many years of follow-up. Moreover, these authors uniquely show that BMS patients with cognitive impairment have markedly abnormal MRI scans that are indistinguishable from those of SPMS patients. We can only speculate about particular predilections toward cognitive versus motor dysfunction in a setting of similar MRI pathology in the two groups of patients. The neurology community needs a unified definition of "benign MS." This study is yet another stepping stone in the right direction.

— Maria K. Houtchens, MD, MMSci

Dr. Houtchens is Staff Neurologist, Partners MS Center, Department of Neurology, Brigham and Women’s Hospital, Boston.

Published in Journal Watch Neurology February 3, 2009

Citation(s):

Rovaris M et al. Cognitive impairment and structural brain damage in benign multiple sclerosis. Neurology 2008 Nov 4; 71:1521.

• Original article (Subscription may be required)
• Medline abstract (Free)