Postural stability in blepharospasm: the effects of dual-tasking and botulinum toxin therapy

Abstract

Background Blepharospasm is a focal dystonia that presents as involuntary, intermittent, continuous contractions of the eyelids. Abnormal eyelid contractions in blepharospasm are expected to cause balance problems, but there is no clear information.Objective This study was designed to evaluate the effect of blepharospasm on postural stability (PS) in patients with blepharospasm. As a secondary endpoint, the efficacy of botulinum toxin type-A (BoNT-A) treatment on static balance in patients with blepharospasm was investigated.Methods Twenty-four patients with blepharospasm receiving regular BoNT-A injections and 20 age-matched and sex-matched healthy controls were included in the study. All subjects were evaluated on a static posturography force platform performing four tasks (eyes open (EO), eyes closed (EC), tandem Romberg (TR) and verbal cognitive task (COGT)). Evaluations of the patients were repeated 4 weeks after the injection.Results Pretreatment lateral and anterior–posterior sways, sway area and velocities of the sways were significantly higher in patients than controls during the COGT and TR (p<0.05). In the patient group, with EO and EC, a few parameters improved after BoNT-A injection. On the other hand, in the TR and COGT, most of the sway parameters and velocities improved significantly after treatment (p<0.05).Conclusions Blepharospasm may cause functional blindness in patients. This study demonstrated that PS worsens in patients with blepharospasm under dual-task conditions. BoNT-A injection treats the disease itself and, thus, markedly improves PS under dual-task conditions in blepharospasm.