Anterocollis posture and deep cervical muscle injections

Dr Laxman Bahroo (Georgetown University Medical Center, USA) talked about anterocaput, a head flexion of the skull base on the cervical spine, as well as anterocollis, a forward flexion of the neck and head that involves the cervical vertebrae and the skull, which remains undertreated. Anterocollis represents approximately 6.8% of the abnormal posture seen in cervical dystonia and presents several challenges to the neurotoxin injector.

Anterocollis is more common in females (67%) than in males. Aetiologies include neuroleptic exposure and parkinsonism syndromes. Dr Bahroo stressed the importance to differentiate this distinct abnormal posture from other similar looking postures such as anterocaput. In anterocollis posture, various muscles are involved, i.e. the scalenes, the longus capitus, and the longus colli muscle. Accurate distinction is important as the various postures involve different combinations of muscles.

Injections with botulinum toxin under various guidance modalities resulted in improvement of posture with mild side effects (mild dysphagia). However, anterocollis is often excluded from pivotal trials studying botulinum toxins. Moreover, botulinum toxin treatment may be limited by the occurrence of dysphagia. In addition, doses are not well known because these muscles are not commonly injected. Depending on the targeted muscles and the botulinum toxin that is injected, dose may vary considerably (Table 1).

Table 1 Botulinum toxin dose, depending on the muscle and the drug that is used

Dr Bahroo reported that the sternocleidomastoid and the scalene muscles are commonly injected in anterocollis but may not provide significant benefit [1]. Case reports of failure indicated that the sternocleidomastoid and/or the scalene anterior muscle were the only muscles that had been injected. If posture does not respond to standard sternocleidomastoid/scalene injections, Dr Bahroo recommended that the lower sternocleidomastoid should also be targeted. He mentioned two case reports describing injections targeting the lower sternocleidomastoid in "refractory" anterocollis patients who had had a limited response to upper sternocleidomastoid injections after 3 injection cycles. In these patients, when the lower sternocleidomastoid (i.e. sternal and clavicular heads) was injected under EMG guidance, posture improved without side effects [2].

A literature review indicated that refractory anterocollis involves the deep cervical muscles (i.e. the longus colli and longus capitus muscles). If posture is refractory, one should consider targeting the longus capitus muscle/longus colli muscle with guidance, Dr Bahroo added. Thus, he advised that consideration is given to injections in these muscles in cases of anterocollis that do not improve with sternocleidomastoid and scalene injections. With injections targeting the longus capitus muscle and the longus colli muscle, sustained improvement was demonstrated in “refractory” anterocollis neck posture in several case reports. Yet, the deep cervical muscles are located in the retropharyngeal space presenting an additional challenge in accurate and successful injection of these muscles. Nonetheless, they may be successfully targeted using several guidance methods including EMG, CT, ultrasound, and fluoroscopy, with sustained benefit over several treatment cycles [3-7].

Guidance necessary to reach deep cervical muscles

According to Dr Bahroo, reasons for potential anterocollis treatment failures are incorrect characterisation of posture, lack of appropriate muscle identification, incorrect targeting of muscles, and issues with guidance. Guidance is important given the deep location of muscles, and there are various ways to target deep cervical muscles. There is no consensus, however, on which technique is best in terms of accuracy since there is no comparison.

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   1. Marion M-H, et al. Pract Neurol. 2016 Aug;16(4):288-95.
   2. Peng-Chen Z, et al. Neurologist. 2016 Mar;21(2):30-1.
   3. Herting B, et al. Mov Disord. 2004 May;19(5):588-90.
   4. Ulzheimer JC, et al. Klin Neurophysiol 2007; 38-P67.
   5. Allison SK, Odderson R. Ultrasound Q. 2016 Sep;32(3):302-6.
   6. Glass GA, et al. Parkinsonism Relat Disord. 2009 Sep;15(8):610-3.
   7. Bhidayasiri R. Parkinsonism Relat Disord. 2011 Nov;17 Suppl 1:S20-4.

Posted on 15 March 201924 March 2021