Abstract
Botulinum toxin type-A (BTX-A) injection for treating chronic migraine (CM) has developed into a new technique covering distinct injection points in the head and neck regions. The postulated analgesic mechanism implies that the injection should be administered to sensory nerves rather than to muscles. This study aimed to determine the topographical site of the auriculotemporal nerve (ATN) and to propose the effective injection points for treating CM. ATNs were investigated on 36 sides of 25 Korean cadavers. The anatomical structures of the ATN were investigated focusing on the temporal region. A right-angle ruler was positioned based on two clearly identifiable orthogonal reference lines based on the canthus and tragus as landmarks, and photographs were taken. The ATN appeared superficially in the anterosuperior region of the tragus. The nerve is located deeper than the superficial temporal artery. And it runs between the artery and the superficial temporal vein. In the superficial layer, it is divided into anterior and posterior divisions. The anterior division runs in a superior direction, while the posterior division runs in front of the ear and the several branches are distributed to the skin. We suggest that the optimal BTX-A injection points for CM are in the temporal region. The first point is about 2 cm anterior and 3 cm superior to two orthogonal reference lines defined based on the tragus and canthus, and the second point is about 4 cm superior to the first point. The third and fourth points are recommended about 2 cm superior to the first point, but respectively 1 cm anterior and posterior to it.
Highlights
Chronic migraine (CM) is a disabling neurologic disorder that affects 1.4–2.2% of the general population [1]
The anterior division runs in a superior direction, while the posterior division runs in front of the ear and the several branches are distributed to the skin
We proposed the injection points into temporal region, based on the topographic anatomy of the auriculotemporal nerve (ATN)
Summary
Chronic migraine (CM) is a disabling neurologic disorder that affects 1.4–2.2% of the general population [1]. Toxins 2020, 12, 214 months, with the features of migraine headache occurring on at least 8 days per month [2]. The analgesic effects of botulinum toxin type-A (BTX-A) were first reported in 1985, based on a pilot study of BTX-A treatment for cervical dystonia, which is characterized by abnormal and involuntary neck and shoulder muscle contractions that often result in significant and disabling musculoskeletal pain [3]. The results from several studies suggest that muscle relaxation effects do not directly coincide with the relief of pain, implying that other mechanisms underlie the analgesic effects of BTX-A [12]; for example, the analgesic effect of the toxin often occurs earlier and lasts longer than its effect on muscle tone. It can be proposed that the analgesic effects of BTX-A is related to inhibition of pain transmission in sensory neurons, rather than its effects in motor neurons
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