A population-based and cross-sectional study of the long-term prognosis in multifocal motor neuropathy.

A population-based, cross-sectional study of patients referred to the Danish hospital system between 1985 and 2006 was conducted to evaluate the long-term outcome in Danish patients treated for multifocal motor neuropathy (MMN). Thirty-four MMN patients were identified, three had died of unrelated diseases, 10 were excluded, one did not reply to study request and 20 were included. The median disease duration was 24 years (interquartile range: 18.5-31.0). Compared to 24 healthy matched control subjects, the Rasch-built Overall Disability Scale for Multifocal Motor Neuropathy was reduced by 9%, the Neuropathy Impairment Score showed a 3-fold increase, the isokinetic strength was reduced by 29%, the grip strength by 56%, the Timed 25-Foot Walk was prolonged by 13% and the EQ-5D-5 L-Index value was impaired by 20%. The isokinetic strength was significantly more impaired at the wrist and ankle as compared to the elbow and knee, and one patient had lost ambulation because of instability at the ankle. Patients were considerably more fatigued and had substantially impaired hand dexterity, while mood, aerobic capacity, social adjustment, and working capacity were not affected. Regression analysis showed that lag-time until start of initial therapy lead to impaired long-term outcome without any effect of disease duration. Long-term prognosis in treated MMN is characterized by moderate to severe impairment primarily affecting dexterity and stability at the ankle. Our observations support previous observations that the long-term impairment in MMN might be improved following earlier start of therapy and that an effect of disease duration cannot be demonstrated.