Are initial demyelinating event recovery and time to second event under differential control?

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Abstract
Relapsing-remitting multiple sclerosis (RRMS) begins with an initial demyelinating event (IDE) that can be monosymptomatic, polysymptomatic, or polyregional. Failure to recover from the IDE is a known predictor of later development of disability. Factors that predict IDE recovery (outside optic neuritis) and time to second event are relatively unknown. The authors speculate that IDE recovery and time to second event are under separate biologic or genetic control, and as such, their clinical predictors are different. Data on all UCSF MS clinic patients are entered prospectively into an ACCESS database. The authors identified all patients seen at the UCSF clinic within 1 year of their IDE. Expanded Disability Status Scale scores, functional system scores, and visual acuity were used to define IDE severity and recovery. The cohort included 186 patients (127 women, 59 men) with an average onset age of 34 +/- 10 years with 150 whites (non-Hispanic), 15 African Americans, 11 Hispanics, eight Asians, and two unknown/unreported. Worse onset severity predicted worse IDE recovery (23.1% of the patients with severe onset vs 32.9% with moderate severity vs 56.4% with mild onset recovered completely, p < 0.001). Polyregional onset predicted poor recovery compared to monoregional onset (46.2% vs 14.4%, p < 0.001). Nonwhite patients were 2.48 times more likely than whites to experience a second episode within 1 year from onset (95% CI: 1.45 to 4.23, p < 0.001). Similarly, age younger than 30 years predicted higher risk of a second exacerbation (hazard ratio 1.92, 95% CI: 1.17 to 3.15, p = 0.010). Initial demyelinating event recovery and time to second event may have distinct predictors. These findings suggest that recovery and time to second event might be under separate biologic control.