Blepharospasm is the most frequent cranial dystonia and consists of involuntary, symmetric, tonic or clonic bilateral contractions of the orbicularis oculi muscle, resulting in partial or complete eye closure. Blepharospasm can be primary (idiopathic), secondary or psychogenic. Primary blepharospasm is an adult-onset focal dystonia, manifesting with forceful eyelid closures. Rarely, blepharospasm is secondary to structural brain lesions, drug-induced or other neurodegenerative conditions like atypical parkinsonism. Blepharospasm’s severity may range from increased blinking frequency (only causing minor discomfort) to a persistent and forceful eyelid closure, leading to functional blindness

The orbicularis oculi muscle is the most frequently involved muscle; other involved muscles may include the corrugator supercilii, the procerus and the frontalis. Botulinum neurotoxin (BoNT) is considered the first-line treatment for blepharospasm. Typically, four injections are administered in the orbital or preseptal portion of the orbicularis oculi muscle, but the number of injections can be increased to include the lateral canthus and the pretarsal component of the orbicularis oculi. This chapter diagrams typical injection sites, tabulates dose ranges for different preparations of neurotoxin and lists frequencies of common adverse events.