OnabotulinumtoxinA Safe, Provides Symptomatic Relief in Primary Trochlear Headache
Therapeutic effects were noticeable within 15–20 days post-injection, with five of six patients achieving complete pain relief.
Alex Jaimes, MD
Data from a small-scale study published in Headache showed that the use of onabotulinumtoxinA (BoNTA) injections was safe and resulted in substantial pain relief among patients with primary trochlear headache (PRTH). To the authors knowledge, this was the first report of successful treatment of PRTH with BoNTA.1
Six patients, aged between 29 and 74 years, diagnosed with PRTH according to the International Classification of Headache Disorders, 3rd edition criteria and treated with BoNTA, were included. Most were female (n = 5), none had bilateral symptoms, and 4 cases presented with left eye symptoms. One month after the initial injection, 5 patients achieved complete pain relief, while 1 patient experienced a partial response, reducing pain intensity from 10 to 4 on the visual analog scale, even after the second infiltration.
Led by Alex Jaimes, MD, a neurologist at Fundación Jiménez Diaz University Hospital, all patients in the trial received medical therapy, beginning with oral nonsteroidal anti-inflammatory drugs, prior to BoNTA. Other therapies such as amitriptyline, carbamazepine, gabapentin, and indomethacin all showed limited and inconsistent effectiveness. Three patients received anesthetic and corticoid infiltrations; however, treatment impacts were limited, and lasted for 3-4 months. Subsequent infiltrations resulted in similar outcomes, with pain recurrence after 12 weeks.
Following the recurrence of pain, each patient received 20 units of BoNTA, distributed as 5 units per corrugator muscle and 10 units in the procerus muscle divided into 2 points. As mentioned, almost all patients achieved complete pain relief, with effects that were seen as early as 15-20 days post-injection. End-dose effects lasted around 3 months, which promoted subsequent injections. To date, 4 patients received 3 or more infiltrations, with BoNTA continuing to be effective. While patients were on BoNTA or the symptomatic therapies beforehand, there were no adverse events reported.
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All patients entered the trial with localized trochlear pain, with 3 cases having additional radiating pain involving the SON and STC innervation regions. Three out of the 6 cases had a different type of primary headache, 2 had migraine, and 1 had tension-type headache. Migraine-like features such as photophobia or nausea were not present during pain exacerbations. Investigators noted that while pain may not be consistent with migraine, there remains a possibility that trochleodynia could be secondary to a sensitization process. “Although this phenomenon is more common in chronic migraine than in episodic migraine, it cannot be completely ruled out," Jaimes et al wrote.
The study was limited by the fact that it did not include a control group nor did it have data on potential long-term treatment outcomes. Importantly, patients were not concurrently receiving other pharmacological treatments, excluding the possibility of improvement because of other drugs. Of note, the retrospective nature of the study may have introduced information bias.
"Since the pathophysiology of PRTH remains puzzling and the analgesic mechanism of BoNTA is complex, it is challenging to establish why this treatment proved effective; however, exploring proposed hypotheses might shed light," the study authors wrote. "This hypothesis is supported by a reported case of superior oblique (SO) muscle myokymia preceding the onset of trochleodynia. Additionally, the neuromuscular hypothesis posits that myofascial trigger points in the SO muscle increase nociceptive input from the SON or STN to the spinal trigeminal nucleus caudalis. In both scenarios, pain relief may result from the blockade of the release of algogenic neuropeptides such as substance P, neurokinin A, and calcitonin gene-related peptide."
