Managing Neurological Complications in Pediatric Spinal Deformity Surgery

Peer Reviewed

Risk severity stratification, experience/self-reflection, intraoperative monitoring, and responding to neuromonitoring alerts in a uniform fashion can help improve neurological outcomes in spinal deformity surgery, said Baron S. Lonner, MD, during his presentation on avoiding and managing neurological complications in pediatric spinal deformity surgery at the American Academy of Orthopaedic Surgeons 2018 Annual Meeting held March 6-10 in New Orleans, Louisiana.
surgeons in operating room with stats graphics.Responding to neuromonitoring alerts in a uniform fashion can help improve neurological outcomes in pediatric spinal deformity surgery.When assessing surgical risk, surgeons must understand the nature of the disease and consider their own level of training and experience, said Dr. Lonner, who is Professor of Orthopaedics at the Icahn School of Medicine at Mount Sinai, New York, NY. He emphasized the need to conduct self-audits and compare individual infection and neurological complication rates with those reported in the literature. Research indicates that neurologic complications from adolescent spinal deformity surgery are significantly less common among higher volume surgeons as well as among those with active membership in the Scoliosis Research Society versus candidate membership.1,2

“You can quote the literature on the risk associated with a spinal procedure, but if you have a 10% rate of neurological complications versus 0.5% in the literature, then obviously the patient and their family needs to know that,” Dr. Lonner said.

Surgeons, around the world, also should consider whether their hospital has the appropriate resources (eg, intraoperative spinal cord monitoring and experienced teams) to ensure optimal outcomes in pediatric spinal deformity surgery, Dr. Lonner said.

Risk Stratification by Pathology and Procedure
Neurologic deficit resulting from scoliosis or other spinal deformity surgery is of greatest concern to both patients with adolescent idiopathic scoliosis and their parents.3 Rates of neurological deficit associated with scoliosis surgery (0.99%) are lower than that for spondylolisthesis (5.93%), and kyphosis (3.54%).2 Rates are even lower for surgery to correct idiopathic scoliosis, the most common form of pediatric scoliosis (0.73%) than for surgery to address congenital scoliosis (2.00%).2

A number of other risk assessment measures have been proposed, including FOCOS level and deformity angular ratio.4,5 In addition, studies suggest that combined anterior and posterior fusion and instrumentation has double the complication rate of either anterior or posterior instrumentation and fusion alone.6 Additionally, osteotomy is linked to a higher risk for neurologic complications, with more aggressive osteotomies being associated with progressively higher complication rates.4,7 Furthermore, vertebral column resection (VCR) performed for complex congenital cases is associated with a higher rate of neurologic deficit compared with hemivertebrae excision (17% vs 8%).8

Mitigating the Risk of Neurological Deficit
Fortunately, there are ways to mitigate the complexity of the procedure, Dr. Lonner said. For example, use of halo-gravity traction for severe deformities can decrease the spinal deformity, primarily within the first 3 to 4 weeks, and possibly allow surgeons to perform a lower grade osteotomy or reduce the need for vertebral column resection.8,9

In addition, surgeons can improve their proficiency with spinal deformity surgery through didactic sessions, increased training using hands on courses with cadaver labs, mentored surgery, and working with an assistant who is more experienced.

Dr. Lonner suggested perfecting surgical techniques by gradually mastering procedures with increasing complexity over time, such as starting with posterior spinal fusion and progressing to posterior column osteotomy, hemivertebrae excision, pedicle subtraction osteotomy, and vertebral column resection.

Pre-operative evaluation should include magnetic resonance imaging (MRI) screening for presence of neurologic deficit (gross deficit, asymmetrical abdominal reflexes, abnormal ankle clonus and Babinski), calf asymmetry or cavus foot, congenital deformities, Scheuermann’s kyphosis, and early-onset scoliosis (<10 years of age). In adolescent idiopathic scoliosis, “funny-looking curves”, left thoracic curves, and rapid progression of curves should be assessed for syrinx, Chiari malformation, tethered cord, or intraspinal lipoma with MRI, Dr. Lonner said.

Intraoperative Monitoring for Spinal Deformity Surgery
Dr. Lonner emphasized the importance of baseline monitoring before the start of the operation and intraoperative multimodal monitoring, including transcranial motor evoked potentials, somatosensory evoked potentials (SSEPs), and electromyography (free running and evoked).

He noted that inhalational anesthesia affects the quality of the intraoperative monitoring data, so that total intravenous anesthesia (TIVA) is used. Muscle relaxants can also be used during exposure of the spine, except if the patient is neurologically labile pre-operatively, to help decrease blood loss, tissue trauma, and surgeon fatigue. Muscle relaxants must be stopped and be inactive in order for motor-evoked and EMG monitoring to be performed.

Dr. Lonner said that SSEPs should not be used alone for intraoperative monitoring as there is a possibility of false-negative findings.10

“We like to use a lower mean arterial pressure (65 to 75 mmHg) during exposure, and then raise it to 80 mmHg or more, except if the patient is neurologically labile, in which case pressures will be maintained above 80 mm Hg throughout the procedure,” Dr. Lonner noted. “If there is a precipitous change in blood pressure during a surgical maneuver, that patient may have just had a spinal cord injury,” he added.

In order to confirm pedicle screw placement, the screw tracts should be palpated, evoked-EMG testing of each screw should be performed, and use fluoroscopic imaging or advanced imaging (O-arm) utilized with special attention to screws with low EMG responses below 7 mAmps, Dr. Lonner said.

“The goals of intraoperative monitoring are to prevent neurological injury via timely detection and reversal of impending neurological insult, and to reduce the effects of neurological injury with early detection and appropriate treatment,” Dr. Lonner told the audience.

Best Practices in Intraoperative Monitoring
Dr. Lonner highlighted a checklist for response to intraoperative neuromonitoring,11 and summarized that if a motor or sensory alert arises during surgery first look for technical issues, check the leads and temperature, and establish if the deficit is unilateral, which is more worrisome than all 4s. Raise the blood pressure to a mean arterial pressure of >80 mmHg and give blood to raise the hemoglobin if necessary. Next steps are described in the Table.11
Table. Next Steps in Patients With Intraoperative Neuromonitoring AlertsNext steps in patients with intraoperative neuromonitoring alerts.“If you have a true unilateral or bilateral problem that is acute, undo the last maneuver (eg, screw placement) to release the correction, check the canal for hemostatic agent or sponge,” Dr. Lonner said. “If you closed a VCR and saw neuromonitoring change, release the correction slightly, undercut the lamina, and check the alignment. If the VCR is not closed, you may have a cord under stretch, and need to compress (close) to take tension off of the cord.”

Dr. Lonner concluded that delayed neurological deficits are not common, but spine surgeons should remain vigilant post-operatively nonetheless, he said.14

Disclosures
Dr. Lonner has no relevant disclosures.

Updated on: 03/28/18
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Adolescent Idiopathic Scoliosis Study, Skeletal Maturity and Surgical Considerations
Baron S. Lonner, MD
Professor of Orthopaedic Surgery
Icahn School of Medicine at Mount Sinai
New York, NY
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