Atraumatic Spine Distraction Induces Metabolic Distress in Spinal Motor Neurons.

Corrective forces during spine deformity surgery, including distraction, impart significant stresses to the spinal cord that may result in permanent injury. Intraoperative neuromonitoring is commonly used by surgeons to recognize possible damage to the spinal cord in cases of evident traumatic or vascular damage to the spinal cord. However, mild insult to the spinal cord that does not result in obvious trauma or electrophysiological changes present a major clinical challenge as the mechanisms of this type of spinal cord injury (SCI) remain largely unknown, and thus preventive strategies are lacking. We used a sustained bidirectional spinal distraction animal model to determine the role of stretch-induced hypoxia in mild SCI. Direct measurement of intraparenchymal oxygen revealed an immediate decrease in partial pressure (47.08 ± 5.79% pO2) distal to the injury site following a 5-mm distraction. This hypoxic insult induced mitochondrial dysfunction as evidenced by an acute increase (216%) in protein oxidation 30 min post-injury, as well as a 37% decrease in perikaryal size and a 42% decrease in nuclear area (pyknosis) in ventral motor neurons at the injury site. These results indicate that hypoxic events during mild spine distraction may lead to cellular metabolic impairments and permanent functional deficits. The development of strategies targeting the prevention of hypoxic injury during spine distraction may be useful in protecting the cellular metabolic damage that may occur during spine surgery in the absence of overt mechanical or vascular SCI.

A wireless system for monitoring transcranial motor evoked potentials.

Intraoperative neurophysiological monitoring (IONM) is commonly used as an attempt to minimize neurological morbidity from operative manipulations. The goal of IONM is to identify changes in the central and peripheral nervous system function prior to irreversible damage. Intraoperative monitoring also has been effective in localizing anatomical structures, including peripheral nerves and sensorimotor cortex, which helps guide the surgeon during dissection. As part of IONM, transcranial motor evoked potentials (TcMEPs), and somatosensory evoked potentials (SSEPs) are routinely monitored. However, current wired systems are cumbersome as the wires contribute to the crowded conditions in the operating room and in doing so not only it limits the maneuverability of the surgeon and assistants, but also places certain demand in the total anesthesia required during surgery, due to setup preoperative time needed for proper electrode placement, due to the number and length of the wires, and critical identification of the lead wires needed for stimulation and recording. To address these limitations, we have developed a wireless TcMEP IONM system as a first step toward a multimodality IONM system. Bench-top and animal experiments in rodents demonstrated that the wireless method reproduced with high fidelity, and even increased the frequency bandwidth of the TcMEP signals, compared to wired systems. This wireless system will reduce the preoperative time required for IONM setup, add convenience for surgical staff, and reduce wire-related risks for patients during the operation.