Paradoxical enhancement of spinal-cord-evoked potentials rostral and caudal to the site of progressive cord compression in the cat.
METHODS
Analysis of the sequential waveform changes of the spinal-cord-evoked potentials (SCEPs) associated with progressive cord compression in the cat.


OBJECTIVE
To document the phenomenon of paradoxical enhancement of SCEPs despite conduction abnormalities and to evaluate its possible significance.


METHODS
Kochi Medical School, Kochi, Japan.


METHODS
SCEPs were recorded simultaneously at four serial intervertebral levels, from T6-7 to T9-10 caudal to, and at three serial levels from T2-3 to T4-5 rostral to the compression site at T5-6 following epidural stimulation at L6 in 14 cats.


RESULTS
Caudal to the compression site, the area of negative peak significantly increased toward maximal values of 277+/-36 (mean+/-SE), 151+/-9 and 110+/-4% as compared to the baseline precompression values (100%) at T6-7, T7-8, and T8-9, respectively. Rostral to the compression site, the area of negative peak significantly increased before subsequent deterioration and reached 105+/-2, 106+/-2, and 104+/-2% at T4-5, T3-4, and T2-3, respectively. The onset of negative peak enhancement, recorded either caudal or rostral to the compression site, showed a close temporal correlation (r>0.8, P&<0.001) with that of the prolongation in latency of SCEPs at T2-3.


CONCLUSIONS
A progressive focal conduction block induced by compression of the spinal cord can paradoxically enhance the ascending SCEPs both caudally and, though less consistently, rostrally, representing a warning of the impending risk of paraplegia.
Kishimoto
H
H
Department of Orthopaedic Surgery, Kochi Medical School, Kohasu Oko-cho, Nankoku City, Kochi, Japan.
Tani
T
T
Ueta
E
E
Ushida
T
T
Taniguchi
S
S
Zinchuk
V S
VS
Yamamoto
H
H
D000818:Animals; D002415:Cats; D004195:Disease Models, Animal; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D009431:Neural Conduction / Q000502:physiology*; D013117:Spinal Cord Compression / Q000503:physiopathology*; D013126:Spinal Nerve Roots / Q000473:pathology / Q000503:physiopathology