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J Neurol Neurosurg Psychiatry 2001;71:732-740 ( December )

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

Y Hu, K D K Luk, W W Lu, A Holmes, J C Y Leong

Department of Orthopaedic Surgery, Duchess of Kent Children's Hospital, The University of Hong Kong, 12 Sandy Bay Road, Hong Kong

Correspondence to: Dr Y Hu yhud{at}hkusua.hku.hk

Received 11 August 2000 and in revised form 27 March 2001; Accepted 23 July 2001

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.


Keywords: time frequency analysis; evoked potential; spinal cord injury

© 2001 by Journal of Neurology, Neurosurgery, and Psychiatry


This article has been cited by other articles:


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Y Hu, K D K Luk, W W Lu, and J C Y Leong
Application of time-frequency analysis to somatosensory evoked potential for intraoperative spinal cord monitoring
J. Neurol. Neurosurg. Psychiatry, January 1, 2003; 74(1): 82 - 87.
[Abstract] [Full Text] [PDF]


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