Ultrasound-guided cervical nerve root block: Does volume affect the spreading pattern?

Objective. Ultrasound-guided cervical nerve root block (US-CRB) is considered a safe and effective method for the treatment of radicular pain. However, previous studies on the spreading pattern of injected solution in US-CRB have reported conflicting results. The aim of this study was to investigate the spreading pattern in relation to injection volume. Design. An institutional, prospective case series. Setting. A university hospital. Subjects. Fifty-three patients diagnosed with monoradiculopathy in C5, 6, or 7. Methods. US-CRB with fluoroscopic confirmation was performed. After the cervical roots were identified in ultrasound imaging, a needle was gently introduced toward the posterior edge of the root using an in-plane approach. The spread of 1mL and 4mL contrast medium, each injected in the same needle position, was examined with anteroposterior and lateral fluoroscopic views. After contrast injection, a mixture of local anesthetic and corticosteroid was injected. Clinical outcome was assessed using a numeric rating scale before and 2 weeks after the procedure. Results. Contrast medium did not spread into the epidural space in any patients with 1mL contrast medium injection, but it did spread into the intraforaminal epidural space in 13 patients (24.5%) with 4 mL. Pain improved in all patients. There was no significant difference in pain relief according to the spreading pattern. Conclusion. The spreading pattern of injected solution in US-CRB could be partially affected by the injectant volume. However, further studies are needed to assess the importance of other factors, such as needle position and physiological effects.