A 31-year-old man with a history of pain from cervical degenerative disc disease was seen at an outside institution for a right selective cervical nerve root block at C7. He reported intermittent stabbing pain in the back and right side of his neck, and 4 years earlier he had undergone the same procedure without complication. During the current cervical procedure, he received a 6-mL injection consisting of 40 mg Kenalog in 0.25% Marcaine. On awakening from anesthesia his radicular pain had resolved, but he noted a droopy right upper eyelid. Two months later, he was seen in The Methodist Hospital neuro-ophthalmology clinic. Vision was 20/20 in each eye, and the remainder of the examination was normal except for pupil size and eyelid position. In darkness, pupils measured 3 mm on the right eye and 4 mm on the left eye (Fig. 1), and the right pupil showed dilation lag. There was 1 mm of right ptosis. Topical apraclonidine drops confirmed the diagnosis of a right Horner syndrome (Fig. 2). Contrast-enhanced MRI of the head and neck was normal, and MRA of the neck showed no evidence of carotid or vertebral dissection.
Selective nerve root block (SNRB) is an increasingly utilized procedure for both confirmation of diagnosis and treatment of radicular pain (1). It is being used to empirically help define the etiology of pain in patients and to deliver local therapeutics. The procedure typically involves injecting 1-2 mL of a combination of a local anesthetic and steroid. Fluoroscopic guidance is used first to achieve appropriate positioning, and then contrast is injected to anticipate where the medication will be delivered.
In a review of 4,612 patients undergoing a cervical SNRB, the only neurological complication involved one patient who had a seizure (2). In a prospective review of 799 SNRBs, 5 patients had transient sympathetic blockade leading to ptosis and miosis, but these all resolved (3). There are 3 reported cases of vertebral artery dissection following fluoroscopically guided cervical SNRB, but Horner syndrome was not noted in any of these cases (4,5).
Other reported complications of SNRB include direct damage to the nerve or the nearby radicular artery; transient extremity paresis; cerebral, cerebellar, or spinal cord infarction; cardiac arrhythmia; meningitis; syncope; dural puncture; and death (4). Some may be due to the physical trauma of the injection, others from particulate emboli of the injected steroid preparation, and yet others from the inadvertent injection of the anesthetic agent into the radicular artery, which usually results in motor weakness (6).
In our patient, the cause of Horner syndrome was most likely damage to the second-order neuron of the oculosympathetic pathway. The operative record noted that a 22-gauge needle was inserted near the right seventh cervical nerve root under fluoroscopic guidance. While transient sympathetic blockade is possible from local absorption of the injected anesthetic, our patient's symptoms were present 2 months following SNRB, arguing against a medication-related neuropathy. The needle could have perforated the vertebral artery. The MRI and MRA revealed no such pathology; however, a dissection could potentially have already healed. The most likely possibility is direct damage from the needle to the second-order sympathetic neurons as they ascend to the superior cervical ganglion.
Although Horner syndrome is well recognized following stellate ganglion block, we found no other reports of a permanent Horner syndrome following a selective cervical nerve root block. Physicians involved with selective nerve blocks should be aware of this potential complication and consider including this during discussion of informed consent with the patient.
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© 2011 Lippincott Williams & Wilkins, Inc.
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