Paracervical Injection for Headache in the Emergency Department

Headache is one of the most common presenting complaints in the emergency department.1 By the time patients with benign headaches present for treatment in the ED, they often have exhausted non-invasive treatments, and physicians are left with few therapeutic options.

Amongst the array of medications used by physicians to manage benign headache, dopamine antagonists have demonstrated the best efficacy in trials. A number of studies have demonstrated the efficacy of dopamine antagonists in treating migraine, tension, cluster-type, and other benign headaches2,3 Dopamine antagonists have shown superiority over opioids4, non-steroidal anti-inflammatory drugs5, triptans6, and anti-epileptics7. Prochlorperazine is probably the most studied and most commonly clinically utilized in this regard in the ED setting.

Despite the preponderance of evidence supporting the use of dopamine antagonists as first-line therapeutic agents in the ED management of benign headache, more than half of the 1.2 million patients treated in U.S. emergency departments for acute migraine are treated with opioids despite the known risks and recommendations to the contrary.12 In addition, there is tremendous variation in the medications chosen by ED physicians for managing benign headache.13 Most of these regimens involve administration of systemic medications that have considerable side effect profiles. Moreover, many of these headache cocktails require prolonged durations of treatment with sedative side effects. This results in prolonged ED lengths of stay that occupy valuable bed space in increasingly busy and crowded emergency departments.

A less well-known approach to managing benign headache is bilateral, paracervical, intramuscular injection of a long-acting anesthetic. The mechanism of action is not entirely understood, however it is postulated to involve neuronal pathways in the trigeminocervical complex thought to play a central role in headache physiology. This is similar in concept to the mechanism proposed for the occipital nerve blocks performed by neurologists.

Paracervical injection was first described by Mellick et al.8 This method has the advantage of ease of administration, favorable safety profile, lack of need for intravenous access, lack of sedative side effects, and swiftness of therapeutic response. In Mellick's case series, he treated 417 patients who presented with all manner of benign headaches with a 65% rate of complete relief of pain and a 20% rate of partial relief. Many patients had rapid relief of headache within 5 minutes and the remainder in less than 30 minutes. This study was limited by possible selection bias, given it is unclear why the specific patients enrolled were chosen for this treatment. The study was also limited by its observational nature and lack of a control group.

In recent years this procedure has gained popularity amongst emergency physicians, and it has been widely discussed in emergency medicine blogs and podcasts. Numerous online videos demonstrate the ease with which the procedure is performed by physicians and tolerated by patients. Many physicians have called for clinical trials to assess its efficacy.

The investigators therefore propose to study the use of paracervical injection as a novel approach to managing headache in the emergency department. This procedure has great potential, if efficacious, to provide a safe, rapidly effective, non-sedating treatment for headache that does not involve intravenous line placement and systemic medication administration. To date, there are no published trials that evaluate this technique in this setting. The investigators intend to compare the efficacy of paracervical injection to standard first-line therapy (intravenous prochlorperazine and diphenhydramine) for the treatment of benign headache of any etiology in the emergency department.