Illustrations from Hélène Fournié, created under the direction of Dr. Alexandre Kreisler (Lille University) for a medical publication: botulinum toxin injections are the first-line treatment for cervical focal dystonia. In this article, we presented the functional anatomy of the deep posterior neck muscles, their relationships with the arterial system and nerve trunks (which can be damaged during botulinum toxin injections), as well as the method for ultrasound-guided injections into these muscles.