Relevance of sonography for botulinum toxin treatment of cervical dystonia: an expert statement

Abstract

Botulinum neurotoxin A (BoNT A) is the first-line treatment for cervical dystonia. However, although BoNT A has a favorable safety profile and is effective in the majority of patients, in some cases the treatment outcome is disappointing or side effects occur when higher doses are used. It is likely that in such cases either the target muscles were not injected accurately or unintended weakness of non-target muscles occurred. It has been demonstrated in clinical trials for spastic movement disorders that sonography-guided BoNT A injections could improve treatment outcome. As the published evidence for a benefit of sonography-guided BoNT injection in patients with cervical dystonia is scarce, it is the aim of this review to discuss the relevance of sonography in this indication and provide a statement from clinical experts for its use. The clear advantage of sonography-guided injections is non-invasive, real-time visualization of the targeted muscle, thus improving the precision of injections and potentially the treatment outcomes as well as avoiding adverse effects. Other imaging techniques are of limited value due to high costs, radiation exposure or non-availability in clinical routine. In the hands of a trained injector, sonography is a quick and non-invasive imaging technique. Novel treatment concepts of cervical dystonia considering the differential contributions of distinct cranial and cervical muscles can reliably be implemented only by use of imaging-guided injection protocols.

Keywords: Botulinum toxin; Cervical dystonia; Sonography; Ultrasound.

Fig. 1

Sonographic appearance of frequently injected muscles (mainly a, b) and more difficult accessible, small, or deeper located muscles (mainly c, d, e). Muscles: IH infrahyoid, SCM sternocleidomastoideus, SA scalenus anterior, SMP scalenus medius posterior, LEV levator scapulae, TRA trapezius, SEM semispinalis capitis, SPL splenius capitis, OCI obliquus capitis inferior, LC longissimus capitis, LCo longus colli, LCa longus capitis, RMi rectus capitis posterior minor, RMa rectus capitis posterior major, and OCS obliquus capitis superior. Others are CA carotid artery, BP brachial plexus, VC5 vertebra C5, RC5 root C5, and VN vagus nerve