Anatomo-sonographic identification of the longissimus capitis and splenius cervicis muscles: principles for possible application to ultrasound-guided botulinum toxin injections in cervical dystonia

Abstract

Objective: The main objective of this study was to define and verify anatomo-sonographic landmarks for ultrasound-guided injection of botulinum toxin into the longissimus capitis (LC) and splenius cervicis (SC) muscles.

Methods and results: After a preliminary work of anatomical description of the LC and SC muscles, we identified these muscles on two cadavers and then on a healthy volunteer using ultrasound and magnetic resonance imaging (MRI) to establish a radio-anatomical correlation. We defined an anatomo-sonographic landmark for the injection of each of these muscles. The correct positioning of vascular glue into the LC muscle and a metal clip into the SC muscle of a fresh cadaver as verified by dissection confirmed the utility of the selected landmarks.

Discussion: For the LC muscle, the intramuscular tendon of the cranial part of the muscle appears to be a reliable anatomical landmark. The ultrasound-guided injection can be performed within the cranial portion of the muscle, between the intra-muscular tendon and insertion into the mastoid process at dens of the axis level. For the SC muscle, the surface topographic landmarks of the spinous processes of the C4-C5 vertebrae and the muscle body of the levator scapulae muscle seem to be reliable landmarks. From these, the ultrasound-guided injection can be carried out laterally by transfixing the body of the levator scapulae.

Conclusion: The study defined two cervical anatomo-sonographic landmarks for injecting the LC and SC muscles.

Keywords: Anatomic landmarks; Botulinum toxin; Cervical dystonia; Neck muscles; Ultrasound.

Fig. 1

a Dissection of the posterior cervical muscles (left side, fixed cadaver). Longissimus capitis (1), splenius cervicis (2), levator scapulae (3) semi-spinalis capitis (4), and sternocleidomastoid muscle (6). b Dissection of the posterior cervical muscles (right side, fixed cadaver). Longissimus capitis (1) with its intra-muscular tendon (arrow), levator scapulae (3), semi-spinalis capitis (4), longissimus cervicis (5). Splenius capitis has been cut

Fig. 2

a T1-weighted MRI, axial slice at level of the dens of axis. Longissimus capitis (blue). Sternocleidomastoid muscle (6), splenius capitis (7), and semi-spinalis capitis (4). b Ultrasound image at the level of the dens of axis. Longissimus capitis (blue). Sternocleidomastoid muscle (6) and splenius capitis (7)

Fig. 3

a T1-weighted MRI axial slice at the C5 vertebrae level. Splenius cervicis (blue). Levator scapulae (3) and splenius capitis (7). b Ultrasound image between C4 and C5 spinous processes. Splenius cervicis (blue). Levator scapulae (3) and splenius capitis (7)

Fig. 4

a Probe position for longissimus capitis injection. b Probe position for splenius cervicis injection

Fig. 5

Dissection of the posterior cervical muscles (left side, fresh frozen cadaver). Metal clip (circle and arrow) within the splenius cervicis. Solidified surgical glue (arrow) within the longissimus capitis (6), levator scapulae (3), semi-spinalis capitis (4), sternocleidomastoid muscle (6), and splenius capitis (7)