title: Predictors of response to botulinum toxin type A (BoNTA) in chronic daily headache.
abstract: OBJECTIVE
  To evaluate predictors of response to botulinum toxin type A (BoNTA; BOTOX, Allergan Inc., Irvine, CA, USA) in patients with chronic daily headache (CDH).
  
  
  BACKGROUND
  Chronic migraine (CM) and chronic tension-type headache (CTTH) form the majority of CDH disorders. Controlled trials indicate that BoNTAis effective in reducing the frequency of headache and number of headache days in patients with CDH disorders. A recent migraine study found that patients with imploding or ocular types of headaches were responders to BoNTA, whereas those with exploding headaches were not. To date, there are no data on factors that might predict response to BoNTA in patients with CDH.
  
  
  METHODS
  A total of 71 patients with CM and 11 patients with CTTH were treated with 100 units BoNTA. Every patient received at least 2 sets of injections at intervals of 12-15 weeks; fixed sites, fixed dose, and "follow-the-pain" approaches were used for the injections. A detailed medical history was taken for each patient in addition to recording Migraine Disability Assessment Scale (MIDAS) scores at baseline and every 3 months after each set of injections. Headache frequency was assessed throughout the study from baseline to weeks 24-27. Patients recorded the frequency, severity, and duration of headaches in Headache Diaries. Patients were divided into responders (> or = 50% reduction in both headache frequency and MIDAS scores compared with baseline) and nonresponders (< 50% reduction in either of the above variables). Variables analyzed for predictors of response include headache that is predominantly unilateral or bilateral in location, presence of cutaneous allodynia (scalp allodynia), and presence of pericranial muscle tenderness (also referred to as muscle allodynia). Chi-square analysis was used for parallel-group comparisons (proportion of CM responders vs proportion of CM nonresponders and proportion of CTTH responders vs proportion of CTTH nonresponders).
  
  
  RESULTS
  In the CM group, 76.1% (54 /71) of patients were responders to BoNTA, of which 68.5% (37/54) had headache that was predominantly unilateral in location and the remaining 31.5% (17/54) had headache that was predominantly bilateral in location (both P < .01 vs CM nonresponders). Of the 23.9% (17/71) CM nonresponders, 76.5% (13/17) reported predominantly bilateral headache and in the remaining 23.5% (4/17) the headache was unilateral. In the CM responders group, 81.5% (44/54) had clinically detectable scalp allodynia, while pericranial muscle tenderness was present in 61.1% (33/54) (both P < .01 vs CM nonresponders). The presence of scalp allodynia and pericranial muscle tenderness in the CM nonresponders was 11.8% (2/17) and 17.6% (3/17), respectively. In the CTTH group where all patients (100%, 11/11) had bilateral headache, 36.4% (4/11) of patients were responders to BoNTA. All of those CTTH responders (100%, 4/4) had pericranial muscle tenderness (P < .05 vs CTTH nonresponders). None of the CTTH nonresponders had pericranial muscle tenderness. No clinically significant serious adverse events (AEs) were reported. Mild AEs, eg, injection-site pain that persisted for 1-9 days, were reported in 11 patients. One patient had transient brow ptosis.
  
  
  CONCLUSIONS
  A greater percentage of patients with CM responded to BoNTA than patients with CTTH. Headaches that were predominantly unilateral in location, presence of scalp allodynia, and pericranial muscle tenderness appear to be predictors of response to BoNTA in CM, whereas in CTTH, pericranial muscle tenderness may be a predictor of response.
authors.affiliation: Houston Headache Clinic, Houston, TX 77004, USA.
authors.forename: Ninan T
authors.initials: NT
authors.lastname: Mathew
authors.forename: Jayasree
authors.initials: J
authors.lastname: Kailasam
authors.forename: Lori
authors.initials: L
authors.lastname: Meadors
mesh_terms: D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D004185:Disability Evaluation; D004334:Drug Administration Schedule; D005260:Female; D020773:Headache Disorders / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement; D011237:Predictive Value of Tests; D018781:Tension-Type Headache / Q000188:drug therapy*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A