title: Duration of migraine is a predictor for response to botulinum toxin type A.
abstract: OBJECTIVE
  To identify the clinical characteristics and/or injection parameters that predict a favorable response to botulinum toxin type A in patients with episodic and chronic migraine.
  
  
  BACKGROUND
  There is emerging scientific and clinical evidence to support the utility of botulinum toxin type A (BoNT-A) in the prophylaxis of episodic and chronic migraine headache. However, the patient characteristics and injection strategies that predict a favorable treatment response are unknown.
  
  
  METHODS
  We conducted a prospective, open-label study on 74 patients from our clinic receiving BoNT-A for episodic or chronic migraine. For all patients, migraine-related disability (Migraine Disability Assesment [MIDAS]), headache frequency, and average headache intensity were obtained at baseline and at 3 months post-BoNT-A. Information regarding demographic characteristics and injection parameters was also collected.
  
  
  RESULTS
  Sixty-one patients met the study criteria and were available for 3-month follow-up. At the 3-month follow-up visit, the mean MIDAS scores of the 61 qualified study patients had decreased from 102 at baseline to 49 (52% decrease, P<.001). The mean number of headache days was reduced from 60 to 39 (P<.001), and the mean headache intensity decreased from 7.6 at baseline to 5.9 (P<.001). Frequency of migraine attacks, presence of analgesic overuse, total BoNT-A dose, and presence of underlying muscle tenderness were not predictive of treatment response. Age and duration of migraine were the only clinical factors significantly predictive of treatment response. Age likely was a predictor only as a consequence of duration of illness as subjects with migraine duration greater than 30 years were significantly less likely to respond to treatment with BoNT-A.
  
  
  CONCLUSIONS
  BoNT-A may be effective in decreasing headache frequency, headache intensity, and headache-related disability in episodic and chronic migraine patients. Duration of illness emerged as a predictor of treatment response. Randomized controlled studies should evaluate headache-related disability as a primary endpoint in patients with episodic and chronic headache.
authors.affiliation: Mayo Clinic College of Medicine, Mayo Clinic Scottsdale, AZ 85259, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Eross
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Gladstone
authors.forename: Susan
authors.initials: S
authors.lastname: Lewis
authors.forename: Robert
authors.initials: R
authors.lastname: Rogers
authors.forename: David W
authors.initials: DW
authors.lastname: Dodick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D002908:Chronic Disease; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000517:prevention & control*; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A