Acute myelopathy characterized by crus spasm and periodic foot bounce after cervical epidural anesthesia

Sir, Cervical epidural anesthesia (CEA) has been employed in a number of surgical settings and in pain management (1—4). However, attention should be drawn to the potential risks in its performance. We treated a patient suffering post-operatively from acute myelopathy, mainly characterized by crus spasm and periodic bilateral foot bounce, after CEA. To our knowledge, this manifestation is clinically distinct from all other previously reported cases related to epidural manipulations (5—10). A 52-year-old patient was admitted to the Department of General Surgery for thyroid adenoma. As ultrasound detection showed the tumor body crossing and stretching 2—3 cm beyond the outer margin of the right sternocleidomastoid muscle, CEA was selected. CEA was induced with a 22-gauge Tuohy needle passed through the C6—C7 interspace. Initially, we observed a small amount of blood reflux through the puncture needle by syringe test, which disappeared after washing with 2 ml of saline. Afterwards, a transient paresthesia of the right upper limb was felt during catheter placement, followed by block level formation 5 min after infusion of 5 ml of 1.2% lidocaine containing nephridine (1:2 10). Another 10 ml of 1.2% lidocaine was infused after no other side reactions were observed. Six hours after the completion of the operation, the patient complained of a burning pain in the skin area of his right forelimb on the ulnar side. More notably, the patient experienced uncontrollable bilateral crus spasm with his feet bouncing from the bed to a height of 5—10 cm at 15—30-min intervals. The bouncing feet appeared to be concurrent with the worsening of the burning pain. Neurologic examination demonstrated a well-balanced myodynamia (Grade V) of both upper and lower extremities, with a slight sthenic knee jerk. Computed tomography (CT) scan, in the absence of magnetic resonance imaging (MRI), provided no obvious signs of congestion in the lower and upper chest vertebral tubes. As no improvement was observed in the aforementioned symptoms on the second day after the operation, intravenous mannitol was administered (20%, 250 ml twice daily), together with an intramuscular injection of dexamethasone (10 mg/day), oral vitamins B1 and B12 and dibazole, with auxiliary oral Valium before sleep. Five days after the operation, the burning pain, bilateral crus spasm and foot bounce had disappeared, so that mannitol and dexamethasone were discontinued. Seven days after the operation, the patient was discharged with a slight decrease in dermal sensation on the ulnar side of his right elbow. Normal movement and myodynamia were evident. He discontinued oral drugs 1 month after discharge and regained normal sensation 3 months later. To our knowledge, the symptoms described here have not been recorded previously in the literature. Firstly, the blood outflow after needle withdrawal suggested that the tip of the needle might have scraped the regional vasal plexus, resulting in an epidural hematoma, although the damage was minimal and the bleeding ceased after saline washing. During the process of saline washing, saline may possibly have dispersed into the epidural space corresponding to the bilateral cervical spinal lateral cable, where the cortico-spinal-lateral bundle controlling skeletal muscle movement is located. Anatomically, the cortico-spinal-lateral bundle contains the motor fibers controlling the muscular movement of the lower limbs. These are arranged marginally, raising the possibility that the hematoma or dispersed saline may have indirectly influenced the lower limb muscles, especially the quadriceps femoris. This stimulation may also have triggered hyperfunction of the spinal anterior horn cells, manifesting as bilateral crus spasm and foot bounce. Secondly, the paresthesia felt during catheter placement suggested an injury to the C7 and C8 nerve roots. The paresthesia was quickly blocked by lidocaine, whose effect faded 6 h after the operation, leading to the burning pain, possibly caused by edema of the nerve roots. Notably, the bewildering periodic occurrence of foot bounce concurrent with the worsening of burning pain remained investigatable, which cannot be fully explained by anatomic or pathophysiologic knowledge now available. We hypothesized the existence of periodic discharging neurons intermediate between the sensory neurons in the back spinal root and the spinal anterior horn cells, which were activated by stimulation through puncture or pressure damage. The tip depth and injection speed should be critical considerations in CEA in view of the narrow separation between the cervical skin and the epidural space. The body weight and body mass index should also be considered when a cervical epidural manipulation is indicated (11). In addition, CT or MRI data should be included if necessary. Dexamethasone (10 mg/ day) and vitamins B1 and B12 administered through a catheter may exert a preventive effect on root edema if paresthesia of the upper limb occurs, which is sometimes unavoidable.