Spinal cord injury is the most feared complication of spinal surgery. Even when the spinal cord is not exposed, it is at risk for injury during reduction of deformities and during ligation of segmental vessels, which could precipitate an ischemic spinal cord event. Decreased blood flow in the anterior spinal artery can result in infarction of a significant portion of the spinal cord. Disruption of blood flow in the artery of Adamkiewicz often has been implicated in this phenomenon. Cadaveric investigations suggests that the anterior spinal artery typically appears to be a continuous structure.
However, because of the wide range in luminal size there may be functional discontinuities in anterior spinal artery blood flow. Because of the changes in diameter (0.23 to 0.94 mm), variability in resistance to flow is likely. This resistance to flow may be as high as 278 times normal in vessels with narrow lumens, resulting in regions of functional hypoperfusion of the spinal cord.
Three major neurologic patterns can emerge during an anterior spinal cord artery ischemic event:
1 - Spinal Cord transient ischemic attacks manifested by transient motor deficit
2 - Reversible spinal cord ischemia with significant neurologic symptoms that slowly resolve leaving minor residual neurologic deficits
3 - Complete spinal cord injury with flaccid paralysis and complete sphincter dysfunction
Waters and associates reported the variability of spinal cord recovery after ischemia in five patients with at least partial spinal cord injury after surgery. All patients underwent surgical maniupulation of the aorta for trauma, tumour or aneurysm. Three patients with no lower extremity motor function postoperatively remained paralyzed, whereas two patients with partial mkotor paralysis had significant recovery at 1 year. One patient eventually regained the ability to ambulate independently with reciprocal gait using lower extremity orthoses.
Postoperative lumbar epidural anesthesia for pain control has been blamed for paralysis in several patients. The question remains, however, di the epidural cause the paraplegia or just mask the symptoms of a devloping spinal cord ischemic event?
Linz and associates reported the case of a patient with bilateral lower extremity weakness on the first postoperative day. These neurologic symptoms were attributed to the effect of the epidural local anaesthetics. The epidural medications were discontinued. On the second postoperative day, the patient still had motor weakness diffusely from L1 to S1. The symptoms gradually improved, and the patient regained bowel and bladder control and functional use ofn his left leg. The right hand side, however, remained essentially paralyzed.
American Academy of Orthopaedic Surgeons