Evaluation of Myobloc ™ (Botulinim Toxin Type B) in Patients with Post-Whiplash Headaches
Background:BoNT-B is a new botulinum toxin serotype antigenically distinct from the type A toxin. It acts to block the release of acetylcholine at the neuromuscular junction, resulting in a localized paralysis when minute doses are injected. Studies in patients with cervical dystonia have shown that BoNT-B effectively reduces symptoms including pain associated with this disorder, and suggest that it may be effective in alleviating other painful syndromes, such as chronic headaches.
Design/Methods:Thirty-one patients were enrolled in the study. These patients were status post-whiplash after 6 months, had headaches that were disabling after 4 weeks of injury, and were complaining of deep head pain that was radiating from the occipital to the orbital and lasting for more than 5-months duration. Patients had restriction of head flexion, rotation, and/or side bending at the top of the neck. The numeric rating scale (0–10) was used to rate the severity of symptoms. Pre-injection, most patients were at 10 on the NRS; none were below 8. Patients were injected with 1 cc BoNT-B (5000 U) divided among the suboccipital muscles (recti capitis posteriors major and minor, obliqui capitis inferior and superior).
Results:Of the 31 patients, 22 (71%) reported improvements in their headache intensity and severity, and neck motion. Mean pain score on the NRS decreased by 6.5 at 4 weeks after injection. Adverse effects were minor, consisting mainly of dry mouth (40%) and pain at the injection site lasting for only a few days.
Conclusions:The results of our study suggest that BoNT-B may be an effective agent for the treatment of post-whiplash headaches, and support further studies with BoNT-B in this condition.
(1) Whiplash-associated headache is related to trigger points in the associated musculature and increased pain with function.
(2) Interventions such as mobilization, manipulation, and exercises are beneficial for pain and dysfunction, but on a time-limited basis.
(3) Pharmacologic treatment with oral muscle relaxants is limited by unfavorable side effects.
Botulinum Toxin Type B
(1) Myobloc is a liquid formulation of botulinum toxin type B (BoNT-B). It is
antigenically distinct from the type A serotype, and is FDA approved (in December
2000) for the treatment of cervical dystonia.
(2) Clinical trials have shown that BoNT-B is effective in alleviating symptoms, including the pain, associated with cervical dystonia.1,2
(3) BoNT-B causes dose-dependent weakness or paralysis by blocking the Ca++-mediated release of acetylcholine from motor nerve endings.
(4) The mechanism by which BoNT-B provides pain relief is unclear at this time and may not be due solely to its muscle relaxant properties.
We investigated whether BoNT-B trigger point injections improve pain, range of motion, and function in patients with chronic post-whiplash headaches.
Methods
(1) This is a prospective, open-label study evaluating 31 patients with
postwhiplash headaches
(Table 1).
(2) Patients were status post-whiplash after 6 months, had headaches that were disabling after 4 weeks of injury, and were complaining of deep head pain that was radiating from the occipital to the orbital and lasting for > 5 months (Figure 1). Patients had restriction of head flexion, rotation, and/or side bending at the top of the neck.
(3) Patients were injected with 1 cc BoNT-B (5000 U) divided among the suboccipital muscles (recti capitis posteriors major and minor, obliqui capitis inferior and superior).
(4) Efficacy was determined by change from baseline in pain severity, which was based on a numeric rating scale (0–10); and change from baseline in headache frequency. Patients were assessed at baseline, Week 4, and Week 12.
Table 1. Patient Characteristics and Dose
No. of patients . . . . . . . . . . . . . . . . . . . . . . . . 31
Mean age, y . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Gender (F/M) . . . . . . . . . . . . . . . . . . . . . . . . . 3:1
BoNT-B dose . . . . . . . . . 5000 U divided among the suboccipital muscles
Figure 1. Headache frequencies at baseline
Results
(1) Of the 31 patients, 22 (71%) reported improvements in their headache intensity and severity, and neck motion.
(2) There was a significant reduction in mean pain score from baseline to Week 4 (-6.5; p<0.001) and benefits were generally maintained through Week 12 (-4.1; p<0.001) (Figure 2).
(3) Overall the number of headaches/month decreased at Week 4 and Week 12 compared with baseline (Table 2)
(4) Adverse effects were minor, consisting mainly of dry mouth (40%) and pain at the injection site lasting for only a few days.
Figure 2. Mean pain score pre- and post-injection
Table 2. Results of headache frequency
|
Patients, n |
|||
|
Headaches/month |
Baseline |
Week 4 |
Week 12* |
|
0-4 |
2 (12.9%) |
14 (45.2%) |
13 (41.9%) |
|
5-9 |
13 (41.9%) |
11 (35.5%) |
11 (35.5%) |
|
10-14 |
8 (25.8%) |
5 (16.1%) |
5 (16.1%) |
|
³ 15 |
6 (19.4%) |
1 (3.2%) |
1 (3.2%) |
* One patient lost to follow-up
Summary
(1) The results of our study suggest that BoNT-B may be an effective
agent for the treatment of post-whiplash headaches.
(2) Overall, headache pain and frequency were decreased, and neck motion was improved.
(3) Further studies evaluating BoNT-B in chronic pain syndromes, including headaches, are warranted.
References
1. Brashear A, Lew MF, Dykstra DD, et al. Safety and efficacy of NeuroBloc
(botulinum toxin type B) in type A responsive cervical dystonia. Neurology.
1999;53:1439–1446.
2. Brin MF, Lew MF, Adler CH, et al. Safety and efficacy of NeuroBloc (botulinum toxin type B) in type A-resistant cervical dystonia. Neurology. 1999;53:1431–1438.