ABSTRACT
OBJECTIVES: Intraoperative neuromonitoring (IONM) is a common practice in spinal surgery, mostly during pedicle screw placement. However, there is not enough information about the factors that can interfere with IONM data. One of these factors may be existing damage of the nerve root whose function must be preserved. The main purpose of the present study is to evaluate the effect of chronic compression in lumbar nerve roots in terms of stimulation thresholds during direct nerve stimulation. PATIENTS AND METHODS: Direct electrical stimulation was performed in 201 lumbar nerve roots during lumbar spinal procedures under general anaesthesia in 80 patients with different lumbar spinal pathologies. Clinical and radiological data were reviewed in order to establish the presence of chronic compression. RESULTS: Chronically compressed nerve roots showed a higher stimulation threshold than non compressed nerve roots (11.93 mA vs. 4.33 mA). This difference was confirmed with intra-subject comparison (paired sample t test, p=0.012). No other clinical factors were associated with this higher stimulation threshold in lumbar nerve roots. CONCLUSION: A higher stimulation threshold is present in compressed lumbar nerve roots than non compressed roots. This needs to be taken into consideration during pedicle screw placement, where intraoperative neurophysiological monitoring is being used.
Subject(s)
Electric Stimulation , Intraoperative Neurophysiological Monitoring/methods , Lumbar Vertebrae/surgery , Radiculopathy/physiopathology , Spinal Diseases/surgery , Spinal Nerve Roots/physiopathology , Adult , Aged , Chronic Disease , Cohort Studies , False Negative Reactions , Female , Humans , Intervertebral Disc Displacement , Lumbar Vertebrae/injuries , Male , Middle Aged , Pedicle Screws , Prospective Studies , Scoliosis/surgery , Spinal Fractures/surgery , Spinal Neoplasms/surgery , Spinal Stenosis/surgery , Spondylolisthesis/surgeryABSTRACT
OBJECTIVE: To determine the use of multimodal intraoperative neurophysiological monitoring (IONM) during positioning procedures in cervical spine surgery. METHODS: IONM data was collected from 75 patients from the onset of positioning to the end of the surgical procedure. These included: transcranial motor evoked potentials (TcMEP), somatosensory evoked potentials (SEP) and free running electromyography (EMG) recordings. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (PNV) were calculated. RESULTS: IONM warnings were given in 5 cases during neck positioning. These consisted of the disappearance of TcMEP in all the cases, while two cases showed a loss of SEPs as well. Four of these patients presented a complete recovery of TcMEP and SEPs after neck repositioning. The patient in which this recovery was not present, woke up with new postoperative neurological deficits. Sensitivity, specificity, PPV and NPV of TcMEP during cervical positioning were all 100%. Sensitivity of SEPs was 40%; specificity and PPV were 100%; and the NPV of SEPs was 95.9%. CONCLUSION: Multimodal IONM is a useful method to prevent spinal cord injury during neck positioning in cervical spine surgical procedures. TcMEPs showed the highest sensitivity in detecting injuries to cervical spine related to neck positioning. SIGNIFICANCE: Multimodal IONM should not only be considered for detecting intra-operative warnings, but also during positioning.
