Background: Benign essential blepharospasm (BEB) is a common form of focal dystonia. Besides pathology in the basal ganglia, accumulating evidence suggests pathologic changes in the anterior cingulate cortex (ACC).
Methods: This is a randomized, sham-controlled, observer-blinded prospective study. In 12 patients with BEB, we evaluated the effects of a 15-minute session of low-frequency (0.2 Hz) repetitive transcranial magnetic stimulation (rTMS) over the ACC with stimulation intensities at 100% active motor threshold with 3 stimulation coils: a conventional circular coil (C-coil), a sham coil (S-coil), and a Hesed coil (H-coil, which allows stimulation of deeper brain regions. Primary outcome was the clinical effects on BEB (blink rate, number of spasms rated by a blinded physician and patient rating before, immediately after, and 1 hour after stimulation); secondary outcome was the blink reflex recovery curve.
Results: Subjective stimulation comfort was similar for each coil with no stimulation-associated adverse events. Stimulation with the H- and C-coils resulted in a significant improvement in all 3 outcome measures and was still detectable in physician rating and patient rating 1 hour after stimulation. S-coil stimulation had no effects. The active motor threshold was significantly lower for the H-coil compared to the other 2 coils.
Conclusions: rTMS could be used as a therapeutic tool in BEB. Further studies will be necessary to show whether repeated stimulation applications result in lasting clinical effects.
Classification of evidence: This study provides Class II evidence that for patients with BEB, H- and C-coil rTMS is safe and improves clinical symptoms of BEB immediately and 1 hour after stimulation.