One occipital nerve block for the short-term prevention of migraine?

I would like to commend Dilli et al. for their work to further elucidate the role of greater occipital nerve blocks (GONBs) in migraine and congratulate them and Cephalalgia’s editors for publishing this “negative” trial (1). However, this study raises multiple questions/concerns, including but not limited to the following: primary endpoint (unrealistic?), patient selection, placebo, procedure frequency, possibly drug/anesthetic concentration and agent(s) used, and concomitant or associated procedures such as trigger point injections (TPIs) or other peripheral nerve blocks (PNBs).

Primary endpoint

The primary endpoint of this study combined with its design may beg the question who would expect one GONB in episodic migraine to produce a substantial preventive benefit at four weeks? I’m unaware of any short-term preventive that is remarkably effective after four weeks when taken or performed only once for the prevention of episodic or chronic migraine. OnabotulinumtoxinA, the only Food and Drug Administration (FDA)-approved (in the United States (US)) preventive for chronic migraine, has demonstrated increased benefit after multiple injections (2). Perhaps the expectation of prevention from a one-time dose whether medication or minimally invasive procedure is currently unrealistic for migraine disorders.

Patient selection

Patients were injected whether or not they had a headache. This may play a role in the outcome of the study as the authors suggested and may not represent what is seen clinically, as patients often present for PNB while in pain.

Placebo

Dilli et al. explore the difficulty in designing a placebo-controlled trial to assess the efficacy of GONBs; however, they never proved the placebo was inactive. Perhaps the “placebo” was not truly a placebo.

Procedure frequency

A recent study of repetitive sphenopalatine ganglia blocks by Cady et al. demonstrated promise as an acute treatment for headaches in some individuals with chronic migraine (3). Repetitive blocks to the supraorbital and infraorbital nerves showed benefit to migraine patients after a six-month clinical follow-up (4). Expert consensus suggests repetitive or serial nerve blocks may be used as “clinically indicated” as soon as two to four weeks in select cases (5). Does the frequency of GONBs have an important role in migraine prevention? Duration?

Drug/anesthetic concentration and agent(s) used

Prior study results using corticosteroids in GONBs are mixed. There was no difference between the use of local anesthetics with or without corticosteroids in GONBs for transformed migraine. Expert consensus indicates 20 mg–120 mg as the range of methylprednisolone “commonly” used (as reviewed in the literature) (5). It is not clear why the authors chose the lowest dose of the range. It is conceivable the dose of methylprednisolone may not have been optimized. In my clinical practice, combination anesthetics (lidocaine 2% with bupivacaine 0.5% or ropivacaine 0.5%) are generally used in GONBs for migrainous disorders while GONBs with corticosteroids are reserved for cluster headache disorders. Dilli et al. mention volume as possibly being an important variable to consider; however, agent used and concentration or strength (not just volume) may have importance equal or greater to that of volume.

Concomitant or associated procedures

Anecdotally, GONBs are often performed in combination with other PNBs (e.g. trigeminal branches) or TPIs. The success of GONBs alone may be limited in headache disorders barring occipital neuralgia and cervicogenic headache. The work by Dilli et al. demonstrates a single GONB is not a quick fix for migraine prevention. Many providers who perform GONBs and other PNBs for patients with migraine disorders have witnessed the remarkable benefit patients experience minutes after the procedure(s) and its value within a comprehensive headache treatment plan. It is challenging to believe a study design would not capture the immediate response to PNBs including GONBs (that occurs in many patients) and the duration of response.