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

To the Editor: As one who has used nerve blocks for migraine treatment and prophylaxis for many years and seen great efficacy lasting up to six months in patients who have failed other prophylactic therapies, I was glad to see the long awaited publication of a randomized control trial (RCT) of greater occipital nerve block (GONB) migraine prophylaxis (1). I was surprised by the authors’ choice of lidocaine for placebo to ‘‘create numbness . . . but at a minimal dose and duration.’’ But, even given the low dose which may or may not reduce prophylactic efficacy (we do not know), I am truly puzzled by the lack of much efficacy in either arm. Have I have been blinded by anecdote? Perhaps. An alternative explanation for the lack of observed benefit to those mentioned by the authors in their discussion may be that neither active nor placebo injections consistently produced GONB. The cadaveric series studied by Loukas et al. (2) showed wide variation in the location of the greater occipital nerve (GON) with an average location at 22% rather than at 33% of the distance along the external occipital protuberance to mastoid line. Caputi and Firetto (3) in their series of successful GONB (and supraorbital) migraine prophylaxis used the 2 cm inferior and 2 cm lateral to the external occipital protuberance localization method, and they verified occipital anesthesia by pinprick. And, Palamar et al. (4) recently demonstrated prophylactic efficacy in patients with migraine without aura in a small-n RCT which used ultrasound-guided injection of bupivacaine in the active arm and saline for placebo. As my residents will attest, I expect them to immediately and humbly repeat the injection if they miss. Did the authors of this new study verify correct placement of the block by assessing for ipsilateral occipital anesthesia and verify only dense anesthesia to pain in the active group patients and absence of the same in the placebo group? If anesthesia was not present 5–10 minutes post-injection in the active group patients, did they repeat the injection in a new location to ensure that GON distribution anesthesia was obtained in the active group?