Cervical Paravertebral Nerve Blocks
Cervical paravertebral nerve blocks can be useful diagnostically and therapeutically for patients with cervical disc displacement, cervical foraminal steno-sis, or cancer-related pain originating from the cer-vical spine or shoulder.
The cervical spinal nerves lie in the sulcus of the transverse process of their respective vertebral lev-els. As noted earlier, unlike thoracic and lumbar nerve roots, those in the cervical spine exit the foramina above the vertebral bodies for which they are named.
The lateral approach is most commonly used to block C2–C7 (Figure 47–12). Patients are asked to turn the head to the opposite side while in a sitting or supine position. A line is then drawn between the mastoid process and Chassaignac’s tubercle (the tubercle of the C6 transverse process). A series of injections are made with a 5-cm 22-gauge needle along a second parallel line 0.5 cm posterior to the first line. In the case of diagnostic blocks, a smaller injectate volume may be helpful in order to minimize local anesthetic spread to adjacent structures and thereby increase block specificity. Because the transverse process of C2 is usually difficult to palpate, the injection for this level is placed 1.5 cm beneath the mastoid process. The other transverse processes are usually inter-spaced 1.5 cm apart and are 2.5–3 cm deep. Fluoros-copy is useful in identifying specific vertebral levels during diagnostic blocks. This procedure may also be performed with ultrasound guidance.
Unintentional intrathecal or epidural anesthe-sia at this level rapidly causes respiratory paralysis and hypotension. Injection of even small volumes of local anesthetic into the vertebral artery causes unconsciousness and seizures. Other complications include Horner’s syndrome, as well as blockade of the recurrent laryngeal and phrenic nerves.
Embolic cerebrovascular and spinal cord com-plications have resulted from injection of particulate steroid with this block. Particulate steroid should not be used with cervical paravertebral nerve blocks because of possible anomalous vertebral artery anat-omy in this region.