Botulinum toxin A in the therapy of headache disorders and pericranial pain syndromes

For 20 years botulinum toxin A has been used for the treatment of a variety of disorders characterised by pathologically increased muscle contraction. Recently, treatment of tension headache, migraine, cluster headache, and m yofascial pain syndromes of neck, shoulder girdle, and back with botulinum toxin A has become a rapidly expanding new field of research. Several modes of action are discussed for these indications. The blockade of cholinergic innervation reduces muscular hyperactivity for 3 to 6 months. Degenerative changes in the musculoskeletal system of the head and neck are prevented. Nociceptive afferences and blood vessels of the pericranial muscles are dec ompressed and muscular trigger points and tender points are resolved. The n ormalisation of muscle spindle activity leads to a normalisation of muscle tone and central control mechanisms of muscle activity. Oromandibular dysfu nction is eliminated and muscular stress removed. However, the effect of bo tulinum toxin A cannot be explained by muscular actions only. Its retrograd e uptake into the central nervous system modulates the expression of substa nce P and enkephalins in the spinal cord and nucleus raphe. Recent findings suggest an inhibition of sterile inflammation which may lead to a blockade of the neurogenic inflammation believed to be the pathophysiological subst rate of primary headache disorders. The efficacy of botulinum toxin A in th e treatment of pain disorders is being investigated in several studies at t he moment. The results and experiences obtained so far present new alternat ives in the treatment of chronic pain disorders. The practical use of botul inum toxin A is demonstrated.