Therefore, a local anesthetic used in cervical ESP can potentially reach the roots of the brachial plexus within and throughout the prevertebral compartment. The fascia of the neck can determine the spread pattern of the local anesthetic (LA) in the neck. Concept of perivertebral space: all contents inside the perivertebral fascia can access the LA if the injection is inside that compartment. Those neck compartments act like a conduit for the LA to spread to the cervical nerve roots, roots of the brachial plexus, and caudally in the upper thoracic area into the space deep to the erector spinae and rhomboid muscles. The needle is inserted through the trapezius, levator scapulae, and deep cervical muscles (i.e., erector spinae muscles) until it contacts the posterior tubercle of the C6 or C7 transverse process and can be used for shoulder pain, cervical spondylosis, facet arthropathy, occipital pain and headaches, cervical postlaminectomy, and myofascial pain in the upper thoracic and cervical area. Current evidence illustrates that cervical ESP injections resulted in the involvement of the ventral rami of C5 to C7 (i.e., brachial plexus), less incidence of phrenic nerve involvement also consistently spread to the posterior aspect of the erector spinae muscles, and the dorsal rami.