Although no statistically significant benefit of botulinum toxin type A over placebo was demonstrated in this study, the high incidence of patients who were asymptomatic after a second injection suggests that further research is needed to determine whether higher dosages and sequential injections in a larger cohort might show a botulinum toxin type A effect.

No abstract

Voluntary muscle is the largest human organ system. The musculotendinous contractual unit sustains posture against gravity and actuates movement against inertia. Muscular injury can occur when soft tissues are exposed to single or recurrent episodes of biomechanical overloading. Muscular pain is often attributed to a myofascial pain disorder, a condition originally described by Drs Janet Travell and David Simons. Among patients seeking treatment from a variety of medical specialists, myofascial pain has been reported to vary from 30% to 93% depending on the subspecialty practice and setting. Forty-four million Americans are estimated to have myofascial pain; however, controversy exists between medical specialists regarding the diagnostic criteria for myofascial pain disorders and their existence as a pathological entity. Muscles with activity or injury-related pain are usually abnormally shortened with increased tone and tension. In addition, myofascial pain disorders are characterised by the presence of tender, firm nodules called trigger points. Within each trigger point is a hyperirritable spot, the 'taut-band', which is composed of hypercontracted extrafusal muscle fibres. Palpation of this spot within the trigger point provokes radiating, aching-type pain into localised reference zones. Research suggests that myofascial pain and dysfunction with characteristic trigger points and taut-bands are a spinal reflex disorder caused by a reverberating circuit of sustained neural activity in a specific spinal cord segment. The treatment of myofascial pain disorders requires that symptomatic trigger points and muscles are identified as primary or ancillary pain generators. Mechanical, thermal and chemical treatments, which neurophysiologically or physically denervate the neural loop of the trigger point, can result in reduced pain and temporary resolution of muscular overcontraction. Most experts believe that appropriate treatment should be directed at the trigger point to restore normal muscle length and proper biomechanical orientation of myofascial elements, followed by treatment that includes strengthening and stretching of the affected muscle. Chronic myofascial pain is usually a product of both physical and psychosocial influences that complicate convalescence.

Pericranial muscle tension may contribute to the development of facial discomfort, chronic daily headache, and migraine-type headache. Elimination of pericranial muscle tension may reduce associated myalgia and counteract influences that can trigger secondary headaches which fall within the migraine continuum. Four patients with chronic, predominantly tension-type headaches and associated pericranial muscle tension failed prolonged conventional treatment and, therefore, symptomatic areas were treated with botulinum toxin A. This alleviated myalgia and reduced the severity and frequency of migraine-type headaches with a concomitant reduction in subsequent medical and physical therapy interventions. Judicious use of botulinum toxin A into defined areas of pericranial muscle tension may be useful for reducing primary myalgia and secondary headache.