title: The effect of graded spinal cord injury on the extrapyramidal and pyramidal motor evoked potentials of the rat.
abstract: This study investigated the differential effects of graded spinal cord injury on the rat extrapyramidal motor evoked potential (exp-MEP) and pyramidal motor evoked potential (pyr-MEP) and the prognostic value of these effects in predicting postinjury motor performance in the rat model. In 20 rats subjected to graded spinal injury (10-100 g-cm), there was a differential injury threshold for ablation of exp-MEP and pyr-MEP. All peaks of the pyr-MEP were extinguished in the animals subjected to impact forces of 50 g-cm and above (n = 12). In contrast, the exp-MEP was completely abolished in only two animals at injuries of 80 g-cm or above. A residual exp-MEP response persisted in the remaining 18 animals. Motor performance was monitored in 16 additional animals for up to 1 week after spinal injury. The pyr-MEP was abolished in 100% of the rats subjected to a 50-g cm injury (n = 7), whereas the exp-MEP persisted up to the highest impact forces (80 g-cm). Hind leg paralysis was present in the five rats where the pyr-MEP was extinguished but with persistence of the exp-MEP. An 80% reduction in the amplitude of the pyr-MEP in four animals resulted in mild ataxia with motor improvement at the end of a week. An increase or a 70% loss in pyr-MEP peak amplitude resulted in no clinical motor deficits (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Neurosurgery, Mount Sinai Medical Center, New York, New York.
authors.forename: J S
authors.initials: JS
authors.lastname: Shiau
authors.forename: R A
authors.initials: RA
authors.lastname: Zappulla
authors.forename: J
authors.initials: J
authors.lastname: Nieves
mesh_terms: D000818:Animals; D005071:Evoked Potentials; D005116:Extrapyramidal Tracts / Q000503:physiopathology*; D005260:Female; D009044:Motor Cortex / Q000503:physiopathology*; D011712:Pyramidal Tracts / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors