Intermediate cervical plexus block
Transducer position: Transverse over the lateral aspect of the neck, overlying the sternocleidomastoid muscle (SCM) at the midpoint between the mastoid process and clavicle (approximately the level of the thyroid cartilage).
Scanning: Position the posterior edge of the SCM in the middle of the screen and slide the transducer in a craneo-caudal way to identify the superficial branches of the cervical plexus as a small collection of hypoechoic nodules located between the scalene muscles and the SCM as they travel posteriorly and superficially.
Insert the needle through the skin, platysma, and investing layer of the deep cervical fascia, and place the tip adjacent to the plexus behind the posterior border of the SCM muscle.
Inject 1–2 mL of local anesthetic to confirm proper distribution over and in between the fascial layers where the cervical branches are positioned. Complete the block with 5–8 mL.
An alternative longitudinal technique may be used placing the transducer in the coronal plane over the SCM.
How? Advance the needle in-plane, behind the SCM, and direct the tip to lie in the space between the muscle and the prevertebral fascia, alongside the posterior border of the SCM.
Inject 1-2 mL of local anesthetic to confirm needle position and complete the block with a volume of 5–10 mL. The spread should occur between the SCM and the underlying prevertebral fascia.