Blinking Parameters Do Not Normalize After Botulinum Toxin Therapy in Blepharospasm and Hemifacial Spasm Patients

Little is known regarding changes induced by botulinum toxin injections on blinking parameters in blepharospasm (BSP) and hemifacial spasm (HFS) patients. The purpose of this study was to investigate objective changes induced by botulinum toxin (BoNT) injections on blinking parameters in BSP and HFS patients.

Thirty-seven patients with BSP and HFS were evaluated before and 30 days after receiving onabotulinumtoxinA injections. Twelve age-matched control subjects were also assessed. Pretreatment and post-treatment parameters were assessed and compared with normal controls. A high-speed camera and microlight-emitting diodes were used to register the blinking in patients and control groups. Outcomes were blinking frequency, amplitude, and maximum velocity of eyelid closure.

BoNT injections led to a significant reduction in all parameters, compared with baseline, in BSP and on the affected side in HFS, respectively: 22% ( P < 0.001) and 20% ( P = 0.015) in amplitude; 21% ( P = 0.04) and 39% in frequency ( P = 0.002); and 41% ( P < 0.001) and 26% ( P = 0.005) in maximum closing velocity. Blinking amplitude ( P = 0.017 and P = 0.019) and velocity ( P < 0.001 for both groups) were significantly lower at 30 days on BSP and on the affected HFS side, when compared with controls. BSP and HFS patients presented a significantly lower velocity of eyelid closure, even before BoNT, compared with controls ( P = 0.004. and P < 0.001, respectively).

Although blinking frequency became close to normal, amplitude and velocity after BoNT applications were significantly lower in BSP and on the affected side of HFS patients when compared with age-matched normal controls, demonstrating that blinking parameters do not normalize after treatment. The velocity of eyelid closure was shown to be significantly lower, even before BoNT treatment, when compared with control subjects.