a novel dosing regimen for the administration of botulinum toxin based on the pattern , quantity , and location of neuromuscular junctions in the target tissue . because the number of neuromuscular junctions in a target tissue remains generally stable throughout life and because the pharmacological effect of botulinum toxin is localized at the neuromuscular junction , dosing efficacy is unaffected by muscle mass , age of the patient , or body weight .