Botulinum toxin (BTX), a neurotoxin produced by the bacterium Clostridium (C.) botulinum, is used as a prophylactic or acute treatment for chronic or recurrent headaches. The theoretical basis of its action is that BTX relieves muscle tension by blocking the release of the neurotransmitter acetylcholine at the neuromuscular junction, thereby interfering with nerve transmission and blocking subsequent muscle contraction.