Prevention of spinal cord injury with time-frequency analysis of evoked potentials: an experimental study

• Published in: Journal of neurology, neurosurgery and psychiatry Vol. 71; no. 6; pp. 732 - 740
• Main Authors: Hu, Y, Luk, K D K, Lu, W W, Holmes, A, Leong, J C Y
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.12.2001; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: Algorithms; Analysis; Analysis of Variance; Animals; Back surgery; Biological and medical sciences; Cerebral Cortex - physiopathology; Cerebrospinal fluid. Meninges. Spinal cord; Disease Models, Animal; Electrodiagnosis. Electric activity recording; evoked potential; Evoked potentials (Electrophysiology); Evoked Potentials, Motor; Evoked Potentials, Somatosensory; Fourier Analysis; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Monitoring, Intraoperative - methods; Monitoring, Intraoperative - standards; Nervous system; Nervous system (semeiology, syndromes); Neurology; Prevention; Rats; Reaction Time; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Spinal Cord - physiopathology; Spinal cord injuries; Spinal Cord Injuries - diagnosis; Spinal Cord Injuries - etiology; Spinal Cord Injuries - physiopathology; Spinal Cord Injuries - prevention & control; spinal cord injury; Studies; Surgery; Time Factors; time frequency analysis; Tropical medicine; Vertebrae; Hong Kong; Asia; China; Performance evaluation; Animal model; Nervous system diseases; Rat; Rodentia; Exploration; Experimental study; Electrodiagnosis; Somatosensory cortex; Vertebrata; Mammalia; Evoked potential; Central nervous system disease; Adult animal; Motor evoked potential; Diagnosis; Technique; Somatosensory evoked potential; Spinal cord disease
• ISSN: 0022-3050; 1468-330X
• DOI: 10.1136/jnnp.71.6.732

OBJECTIVES To verify the applicability and validity of time-frequency analysis (TFA) of evoked potential (EP) signals in detecting the integrity of spinal cord function and preventing spinal cord injury. METHODS The spinal cord was simulated during surgery in 20 mature rats by mechanically damaging the spinal cord. Cortical somatosensory evoked potential (CSEP), spinal somatosensory evoked potential (SSEP), cortical motor evoked potential (CMEP), and spinal cord evoked potential (SCEP) were used to monitor spinal cord function. Short time Fourier transform (STFT) was applied to the CSEP signal, and cone shaped distribution (CSD) was used as the TFA algorithm for SSEP, CMEP, and SCEP signals. The changes in the latency and amplitude of EP signals were measured in the time domain, and peak time, peak frequency, and peak power were measured in the time-frequency distribution (TFD). RESULTS The TFDs of EPs were found to concentrate in a certain location under normal conditions. When injury occurred, the energy decreased in peak power, and there was a greater dispersion of energy across the time-frequency range. Strong relations were found between latency and peak time, and amplitude and peak power. However, the change in peak power after injury was significantly larger than the corresponding change in amplitude (p<0.001 by ANOVA). CONCLUSIONS It was found that TFA of EPs provided an earlier and more sensitive indication of injury than time domain monitoring alone. It is suggested that TFA of EP signals should therefore be useful in preventing spinal cord injury during surgery.