Ultrasound-guided cervical nerve root block: spread of solution and clinical effect.

Objectives: We investigated the clinical effects and accuracy of ultrasound-guided cervical nerve root block. Additionally, spinal level and spread of injected solution were confirmed by anatomic dissection of fresh cadavers. DESIGN SETTING, PATIENTS, AND INTERVENTIONS: Twelve patients diagnosed with mono-radiculopathy between C5-7 underwent ultrasound-guided nerve root block. An insulated needle was advanced with an in-plane approach using nerve stimulation and 2 mL of 0.375% ropivacaine with 4 mg of dexamethasone was injected using nerve stimulation. Ultrasound-guided C5-7 nerve root block was also performed in ten fresh cadavers. Blue dye (2 mL) was injected onto each nerve root and anatomic dissection was performed to confirm the exact spinal level and spread pattern of the dye.

Results:   Pain score before the procedure (65 [46-80], median [interquartile range]) was decreased to 25 [3-31] at 24 hours (P = 0.003) and 40 [28-66] at 30 days (P = 0.02) after the root block. Obvious side effects were not seen. All target nerve roots in patients and cadavers were correctly identified by ultrasound imaging. The needle tip did not reach the pedicle of the vertebral arch in the anteroposterior view of fluoroscopy, and spread pattern of contrast medium was extraforaminal and extraneural.

Conclusions: This study suggests that injected solution by ultrasound-guided cervical nerve root block mainly spreads to the extraforaminal direction compared with conventional fluoroscopic technique. Therefore, present clinical study involves possibility of safer selective nerve root block with sufficient analgesic effects by ultrasound guidance, despite the absence of intraforaminal epidural spread of solution.