IN BRIEF

Optimized Neurophysiologic Intraoperative Monitoring Provides Real-Time Clinical and Diagnostic Benefits in Patients With Polyneuropathy

May 8, 2020

New study reports that optimizing NIOM parameters can provide actionable, real-time data to protect the nervous system during surgery and facilitate diagnosis of previously unrecognized polyneuropathies.

Neurophysiologic intraoperative monitoring (NIOM) provides a multimodal approach to evaluating the nervous system’s functional integrity. Components of NIOM include sensory evoked potentials (SEP), which monitor the dorsal column sensory pathway, transcranial electrical motor evoked potentials (MEP), which monitor the motor pathway, and electromyography.

“Having an underlying neuromuscular disorder, such as a hereditary polyneuropathy, significantly increases the risk of developing scoliosis,” says Jennifer McKinney, MD, an attending pediatric neurologist at Nationwide Children’s Hospital. NIOM provides real-time data for surgeons during pediatric scoliosis surgery.

In a recent publication in Child’s Nervous System, Dr. McKinney and her research team reported findings of a retrospective evaluation of NIOM data in six pediatric patients with scoliosis and underlying polyneuropathy. Study results, says Dr. McKinney, not only demonstrate NIOM’s usefulness in real-time monitoring and nervous system protection but also point to its potential diagnostic utility in identifying previously undiagnosed neuropathies.

For pediatric scoliosis surgery, pre-surgical baseline data on nervous system functioning are collected. During surgery, SEPs are evoked by stimulating peripheral nerves in the hand or foot, and MEPs are evoked by stimulating the motor cortex. These data are then used to alert surgeons to possible nervous system stress or injury, allowing surgeons to make modifications to protect nervous system structures.

After monitoring a posterior spinal fusion case in which the patient’s baseline NIOM data revealed a previously undiagnosed neuropathy, Dr. McKinney and her research team decided to examine NIOM data from pediatric scoliosis patients with known polyneuropathy. They sought to analyze electrophysiologic changes in the data and assess how NIOM parameters were adjusted in real-time to achieve optimal monitoring results.

Adjustments for improving SEP stimulation, she explains, include slowing the stimulation rate to allow more time for signal transmission and using a needle electrode instead of a surface patch electrode. For MEP stimulation, train parameters can be altered to improve the motor responses.

The patients included in the study had a range of polyneuropathies. Although no single specific NIOM pattern is representative of all polyneuropathies, some general patterns in the electrophysiologic data exist. For example, Dr. McKinney says: “Primary demyelinating neuropathies cause delays in the response latencies due to conduction slowing.”

The retrospective data analysis revealed that some patients with absent SEPs had MEPs, highlighting the importance of multimodal monitoring; if only the SEPs had been monitored in these patients, evidence of injury would have been missed. In patients with absent MEPs, the SEPs were also absent.

“This study serves as a resource for NIOM teams, regarding monitoring modifications for patients with peripheral neuropathy to increase the likelihood of obtaining useful and monitorable electrophysiologic data,” Dr. McKinney says. “Clinically, optimal NIOM can improve clinical vigilance and signal the need for post-operative testing if suspicions arise for a possible pre-existing condition.”

 

Reference

McKinney JL, Islam MP. Neurophysiologic intraoperative monitoring (NIOM) in pediatric patients with polyneuropathy. Child’s Nervous System. 2020 Mar 26.  

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