BACKGROUND: Blepharospasm is an adult-onset focal dystonia that causes 
involuntary blinking and eyelid spasms. Studies have shown the presence of 
sensory deficits associated with dystonia.
AIM: To rule out any confounding effect of muscle spasms on sensory performance 
in affected and unaffected body regions of patients with blepharospasm and with 
hemifacial spasm.
METHODS: Participants (19 patients with blepharospasm, 19 patients with 
hemifacial spasm and 19 control subjects) were asked to discriminate between two 
stimuli that were either simultaneous or sequential (temporal discrimination 
threshold, TDT). Pairs of tactile stimuli were delivered with increasing or 
decreasing inter-stimulus intervals from 0 to 400 ms (in 10-ms steps) to the 
hands or on the skin over the orbicularis oculi muscle.
RESULTS: Tactile stimuli elicited similar TDTs in control subjects and patients 
with hemifacial spasm, but significantly higher TDTs in patients with 
blepharospasm, regardless of whether stimuli were applied to the orbicularis 
muscle or the hand.
CONCLUSIONS: As TDT was abnormal in unaffected body regions of patients with 
blepharospasm, and patients with hemifacial spasm processed tactile stimuli 
normally, TDT deficits in blepharospasm depend on central rather than peripheral 
factors. This study further supports the link between focal dystonia and 
impaired temporal processing of somatosensory inputs.