Subdural spread of injected local anesthetic in a selective transforaminal cervical nerve root block: a case report

INTRODUCTION: Although uncommon, selective cervical nerve root blocks can have serious complications. The most serious complications that have been reported include cerebral infarction, spinal cord infarction, transient quadriplegia and death. CASE PRESENTATION: A 40-year-old Japanese woman with a history of severe right-sided cervical radicular pain was scheduled to undergo a right-sided C6 selective cervical nerve root block using a transforaminal approach under fluoroscopic guidance. An anterior oblique view of the C5-C6 intervertebral foramen was obtained, and a 23-gauge spinal needle, connected to the normal extension tube with a syringe filled with contrast medium, was introduced into the posterior-caudal aspect of the C5-C6 intervertebral foramen on the right side. In the anteroposterior view, the placement of the needle was considered satisfactory when it was placed no more medial than halfway across the width of the articular pillar. Although the spread of the contrast medium along the C6 nerve root was observed with right-sided C6 radiculography, the subdural flow of the contrast medium was not observed with real-time fluoroscopy. The extension tube used for the radiculography was removed from the spinal needle and a normal extension tube with a syringe filled with lidocaine connected in its place. We performed a negative aspiration test and then injected 1.5 mL of 1.0% lidocaine slowly around the C6 nerve root. Immediately after the injection of the local anesthetic, our patient developed acute flaccid paralysis, complained of breathing difficulties and became unresponsive; her respiratory pattern was uncoordinated. After 20 minutes, she regained consciousness and became alert, and her muscle strength in all four limbs returned to normal without any sensory deficits after receiving emergent cardiorespiratory support. CONCLUSIONS: We believe that confirming maintenance of the appropriate needle position in the anteroposterior view by injecting local anesthetic is important for preventing central needle movement. Because the potential risk of serious complications cannot be completely eliminated during the use of any established selective cervical nerve root block procedure, preparation for an emergency airway, ventilation and cardiovascular support is indispensable in cases of high spinal cord anesthesia.