By Steven Karceski, MD
Assistant Professor of Neurology, Weill Cornell Medical College
Dr. Karceski reports he is on the speakers bureau for LivaNova.
SYNOPSIS: In non-complex spine surgeries (spinal decompression and spinal fusion), intraoperative neurophysiologic monitoring improved clinical outcomes and reduced the risk of neurological complications by nearly one-half (49%).
SOURCE: Ney JP, et al. Does intraoperative neurophysiologic monitoring matter in noncomplex spine surgeries? Neurology 2015;85:2151-2158.
Intraoperative neurophysiologic monitoring (IONM) is often used when the surgery might cause an injury to the nervous system. There are many neurophysiologic procedures: electroencephalography (EEG), electromyography (EMG), somatosensory evoked potentials (SEPs), and motor evoked potentials (MEPs). In spinal surgeries, SEPs, MEPs, and free-run EMG are the most commonly used modalities. Using this combination of neurophysiologic monitoring techniques allows for continuous monitoring of both spinal cord and nerve root function. A significant change that occurs on one or more of these tests informs the surgeon of a potential injury, and corrective measures can be implemented immediately.
Although this seems to be a straightforward concept, there has been much debate over how much IONM actually helps. First, complication rates are generally low in uncomplicated spine surgeries; most estimates of neurological complications are around 1%. IONM can be costly, and in an ever-increasing cost-conscious medical environment, many have questioned whether the additional cost can be justified.
Dr. Ney and his colleagues tried to answer some of these questions. They used a very large national database of all non-federal hospitals, the Nationwide Inpatient Sample. They used both surgical codes and IONM codes to identify patients who had been discharged after having spinal surgeries. Since they wanted to look at uncomplicated spinal surgeries, they excluded complicated surgical procedures, such as posterior cervical fusions, fusions involving multiple levels, and surgeries that combined an anterior and posterior approach. Between 2007 and 2012, they identified 1.1 million hospital discharges following spinal surgery.
Their first observation was that IONM was used in 4.9% of the uncomplicated spine surgeries. There was no difference in age or sex between the monitored and unmonitored patients. Interestingly, there was no difference in the rates of IONM at teaching vs non-teaching hospitals. Monitored patients tended to be “a little sicker” with three or more comorbidities, were more likely to be privately insured, and were more likely to be undergoing a fusion procedure. In addition, there was a slight preponderance of IONM in the Western United States compared to other geographical areas.
There was a significant reduction in neurologic complications in the monitored group following uncomplicated spinal surgery. The overall rates of complications were low, but in the unmonitored group, the rate of complications was 1.4% vs 0.8% in the monitored group. The use of IONM reduced the rate of neurological complications by nearly one-half (49%). Similar to other studies, there were more complications following laminectomy (2.7% in the unmonitored group vs 1.7% in the monitored group) compared to discectomy alone.
In terms of cost, the authors found that there was no significant change in the unadjusted length of stay (3 days in both groups). When adjusted for type of surgical procedure, comorbidities, and other hospital factors, there was a reduced length of stay of 0.3 days in the monitored group. As anticipated, the hospital charges in patients who underwent IONM increased by 9% after adjusting for type of surgery and comorbidities.
COMMENTARY
There were several limitations to Dr. Ney’s study. The database did not provide information about the severity or duration of the postoperative neurological dysfunction. Therefore, the “cost” of the neurological dysfunction could not be measured. Although the rates of complications may be low, the costs may be high. IONM may reduce the “cost” of the neurological complications, such as ongoing medical care, time lost from work, loss of income, and malpractice liability costs. In addition, this study could not assess the type of IONM nor the expertise of the monitoring professionals. Additional prospective studies would be helpful, but this analysis of IONM in noncomplex spine surgeries clearly shows a benefit in reducing postoperative neurological
complications.
In non-complex spine surgeries (spinal decompression and spinal fusion), intraoperative neurophysiologic monitoring improved clinical outcomes and reduced the risk of neurological complications by nearly one-half (49%).
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