Identifying Intraoperative Spinal Cord Injury Location from Somatosensory Evoked Potentials' Time-Frequency Components.

Excessive distraction in corrective spine surgery can lead to iatrogenic distraction spinal cord injury. Diagnosis of the location of the spinal cord injury helps in early removal of the injury source. The time-frequency components of the somatosensory evoked potential have been reported to provide information on the location of spinal cord injury, but most studies have focused on contusion injuries of the cervical spine. In this study, we established 19 rat models of distraction spinal cord injury at different levels and collected the somatosensory evoked potentials of the hindlimb and extracted their time-frequency components. Subsequently, we used k-medoid clustering and naive Bayes to classify spinal cord injury at the C5 and C6 level, as well as spinal cord injury at the cervical, thoracic, and lumbar spine, respectively. The results showed that there was a significant delay in the latency of the time-frequency components distributed between 15 and 30 ms and 50 and 150 Hz in all spinal cord injury groups. The overall classification accuracy was 88.28% and 84.87%. The results demonstrate that the k-medoid clustering and naive Bayes methods are capable of extracting the time-frequency component information depending on the spinal cord injury location and suggest that the somatosensory evoked potential has the potential to diagnose the location of a spinal cord injury.

Identification of injury type using somatosensory and motor evoked potentials in a rat spinal cord injury model.

The spinal cord is at risk of injury during spinal surgery. If intraoperative spinal cord injury is identified early, irreversible impairment or loss of neurological function can be prevented. Different types of spinal cord injury result in damage to different spinal cord regions, which may cause different somatosensory and motor evoked potential signal responses. In this study, we examined electrophysiological and histopathological changes between contusion, distraction, and dislocation spinal cord injuries in a rat model. We found that contusion led to the most severe dorsal white matter injury and caused considerable attenuation of both somatosensory and motor evoked potentials. Dislocation resulted in loss of myelinated axons in the lateral region of the injured spinal cord along the rostrocaudal axis. The amplitude of attenuation in motor evoked potential responses caused by dislocation was greater than that caused by contusion. After distraction injury, extracellular spaces were slightly but not significantly enlarged; somatosensory evoked potential responses slightly decreased and motor evoked potential responses were lost. Correlation analysis showed that histological and electrophysiological findings were significantly correlated and related to injury type. Intraoperative monitoring of both somatosensory and motor evoked potentials has the potential to identify iatrogenic spinal cord injury type during surgery.

Low Back Pain Assessment Based on Alpha Oscillation Changes in Spontaneous Electroencephalogram (EEG).

Objectively and accurately assessing pain in clinical settings is challenging. Previous studies showed that alpha oscillations of electroencephalogram data are correlated with subjective perceived pain. Based on this finding, this study is aimed at assessing chronic low back pain based on alpha oscillations. Multichannel electroencephalogram data were recorded from 27 subjects with chronic low back pain under the simple conditions of closing eyes or opening eyes. Spectral analyses were conducted to extract the alpha band responses, and the alpha powers were calculated for the two conditions, respectively. Normalized alpha power was calculated by subtracting the alpha power in the eyes-open condition from that in the eyes-closed condition. The correlation between the alpha power and the subjective pain intensity was evaluated in frontal, central, and posterior regions. The normalized alpha power in the central region was negatively correlated with the subjective pain intensity (R = -0.50, P = 0.01), with the strongest correlation occurring at the Cz electrode (R = -0.59, P = 0.04). The correlation analysis results demonstrated the possibility of using the differences of alpha spectral power between eyes-closed and eyes-open conditions as a measure for assessing chronic low back pain. The findings suggest that the normalized alpha power in the central region may be used as a measurable and quantitative indicator of chronic pain for clinical applications.

Effect of brain alpha oscillation on the performance in laparoscopic skills simulator training.

BACKGROUND: Laparoscopic skill involves sensory processing and motor control, which is associated with high-level alpha oscillation of the brain. Neurofeedback (NF) has been reported effective in enhancing alpha oscillation. Our objectives were to assess the alpha oscillation during laparoscopic skills training, and to verify the usefulness of NF in improving the learning efficacy. METHODS: Sixty medical students without laparoscopic experience were recruited. Multi-channel electroencephalography (EEG) signals were recorded during training of peg transfer task. Training performance was assessed based on the task completion time. All subjects participated in the first experiment comprising eight training blocks and one testing block. Subjects were ranked based on performance: the top 20 subjects were classified as the good performance group and the bottom 20 subjects as the fair performance group. In the second experiment, the fair performance group were randomly divided into the NF and control groups. Spectral analysis of EEG signals was used to calculate alpha power and alpha band coherence. Training performance and EEG alpha powers were compared between the NF and control groups. RESULTS: In the first experiment, the completion time was significantly faster in the good performance group (62.5 ± 2.8 s) compared with the fair performance group (75.0 ± 5.6 s) (P < 0.05). EEG oscillations showed strong alpha power and alpha coherence in the posterior electrode clusters in the good performance group. In the second experiment, the NF group showed much stronger alpha activity power and coherence compared with the control group. Furthermore, the NF training led to a significant performance improvement from 75.1 ± 5.9 s in the first experiment to 64.3 ± 4.9 s in the second experiment (P = 0.003). CONCLUSIONS: The learning performance of laparoscopic skills varies among individuals. Subjects with good performance results had high alpha power and strong alpha coherence. The alpha enhancement NF increased alpha oscillations, leading to improved learning efficacy.

Utility of Trial-to-Trial Latency Variability of Somatosensory Evoked Potentials for Diagnosis of Spinal Cord Demyelination.

Traditional measurement of somatosensory evoked potentials (SEPs) depends on averaging of many recordings, which introduces loss of dynamic variability. Single trial extraction provides a new measurement of SEP latency variability for evaluation of the neurodynamic status of the somatosensory pathway. The aim of this study was to apply a single trial SEP to diagnose the severity of demyelination in a chronical spinal cord injury model. The severity of demyelination was measured by myelin area and staining intensity at the ventral column (VC), lateral column (LC), and dorsal column (DC) by histological examination with Luxol fast blue staining. Results showed that there was a strong negative correlation of the latency variability of trial-to-trial SEP with the myelin area in three columns (DC: r=-0.90, p<0.05; VC: r=-0.91, p<0.05; LC: r=-0.89, p<0.05), and the staining intensity in three columns (DC: r=-0.95, p<0.05; VC: r=-0.94, p<0.05; LC: r=-0.93, p<0.05). These data suggest that single trial SEP can provide a dynamic indicator of spinal cord demyelination.