Long‐term botulinum toxin efficacy, safety, and immunogenicity

To determine the long‐term efficacy of botulinum toxin (BTX) treatments, we analyzed longitudinal follow‐up data on 45 patients (32 women; mean age, 68.8 years) currently followed in the Baylor College of Medicine Movement Disorders Clinic, who have received BTX treatments continuously for at least 12 years (mean 15.8 ± 1.5 years). Their mean response rating after the last injection, based one a previously described scale 0‐to‐4 scale (0 = no effect; 4 = marked improvement) was 3.7 ± 0.6 and the mean total duration of response was 15.4 ± 3.4 weeks. Although the latency and total duration of the response to treatment have not changed over time, the peak duration of response ( P < 0.005) and dose per visit ( P < 0.0001) have increased since the initial visit. Furthermore, global rating ( P < 0.02) and peak effect ( P < 0.05) have improved. In total, 20 adverse events occurred in 16 of 45 (35.6%) patients after their initial visit and 11 adverse events in 10 of 45 (22.2%) patients at their most recent injection visit. Antibody (Ab) testing was carried out in 22 patients due to nonresponsiveness; blocking Abs were confirmed by the mouse protection assay in 4 of 22 (18%) patients. Of the Ab‐negative patients, 16 resumed responsiveness after dose adjustments and2 persisted as nonrespondents. Except for 1 patient, the 4 Ab‐positive and the 2 clinical nonresponders are being treated with BTX‐B. This longest reported follow‐up of BTX injections confirms the long‐term efficacy and safety of this treatment. © 2005 Movement Disorder Society