RESUMEN
PURPOSE: Intraoperative neurophysiological monitoring using somatosensory evoked potentials has been linked to a reduction in the incidence of neurological deficits during corrective surgery. Nonetheless, quantitative assessments of somatosensory evoked potential waveforms are often difficult to evaluate, because they are affected by anesthesia, injury, and noise. Here, we discuss a novel method that integrates somatosensory evoked potential signals into a single metric by calculating the area under the curve (AUC). METHODOLOGY: Thirty-two Sprague-Dawley rats underwent a laminectomy procedure and were then randomly assigned to a control group or to receive a contusive spinal cord injury ranging from 100 to 200 kilodynes. Neurophysiological testing was completed at various points perioperatively and postoperatively. Somatosensory evoked potential traces obtained were processed and the AUC metric was calculated. RESULTS: The AUC significantly decreased to 11% of its baseline value after impact and remained at 25% baseline after 1 hour for the 200-kdyn cohort. Postimpact, AUC for the control versus the 150-kdyn and 200-kdyn groups, and the 150-kdyn versus 200-kdyn groups were significantly higher (P < 0.01, P < 0.001, and P < 0.05, respectively). Across days, the only significant parameter accounting for AUC variability was impact force, P < 0.0001 (subject parameters and number of days were not significant). CONCLUSIONS: The AUC metric can detect an iatrogenic contusive spinal cord injury immediately after its occurrence. Moreover, this metric can detect different iatrogenic injury impact force levels and identify injury in the postoperative period. The AUC integrates multiple Intraoperative neurophysiological monitoring measures into a single metric and thus has the potential to help clinicians and investigators evaluate spinal cord impact injury status.
Asunto(s)
Electrodiagnóstico , Potenciales Evocados Somatosensoriales , Traumatismos de la Médula Espinal/diagnóstico , Animales , Área Bajo la Curva , Modelos Animales de Enfermedad , Complicaciones Intraoperatorias/diagnóstico , Complicaciones Intraoperatorias/fisiopatología , Monitorización Neurofisiológica Intraoperatoria , Laminectomía , Distribución Aleatoria , Ratas Sprague-Dawley , Procesamiento de Señales Asistido por Computador , Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/fisiopatologíaRESUMEN
OBJECTIVE: Neurotransplantation has focused on disorders that involve subcortical brain targets. We evaluated the concepts of epileptic focus repair and changes in animal behavior through replacement of lost hippocampal neurons. The safety of hippocampal neurotransplantation was assessed in the rat kainic acid (KA) epilepsy model. METHODS: Sixty-three rats were studied and classified into six groups: KA plus 40,000 LBS-Neurons (Layton BioScience, Sunnyvale, CA; n = 13); KA plus 80,000 cells (n = 12); KA plus media (n = 9); no-KA plus 40,000 cells (n = 12); no-KA plus 80,000 cells (n = 12); and no-KA plus media (n = 5). Clinical observation (2 h daily) and electroencephalogram recording (3 h every other week) were performed to check for seizures until Week 11 after KA injection. On Week 12, the Morris water maze test was performed to assess spatial learning and memory. RESULTS: Four rats were excluded because of intracranial hematoma or abscess. In the clinical observation of seizures, the no-KA plus media group had significantly fewer seizures than rats that received KA followed by injection of 40,000 cells, 80,000 cells, or media (P = 0.001, 0.0004, and 0.004, respectively). On electroencephalographic analysis, there was no significant difference between any of the groups. Transplanted rats with KA-induced epilepsy did not have an increased number of seizures. In the Morris water maze test, the hidden platform task showed that the KA plus 80,000 cell group had significantly longer swim latencies than groups with no-KA plus 40,000 cells (P = 0.035) or no-KA plus 80,000 cells (P = 0.015), demonstrating the behavioral deficits caused by KA injection. The probe trial showed no significant difference for the percentage of time in the target quadrant between any of the groups. Histological studies showed that 26 (59%) of 44 transplanted rats had evidence of graft survival. CONCLUSION: The safety of cortical neurotransplantation was demonstrated, even in an animal model predisposed to epilepsy. We did not find evidence for cessation of seizures or improvement in behavior using this model.