The feasibility of detecting motor and sensory potentials in a sheep model

To investigate the characteristics of motor, sensory and sensory-evoked potentials (SEPs) of thoracic and lumbar roots, and demonstrate the feasibility of assessing axonal regrowth after the neurotization procedure in a sheep model. Six adult sheep were anaesthetized and placed in a sternal position. The thoracic and lumbar roots from T11 to L5 were identified at their emergence from the vertebral foramen and stimulated. Motor and sensory responses were monitored. Thoracic and lumbar roots were easily identified in all cases. Motor potentials were detected for each stimulated nerve without difficulty. The amplitudes were quite variable, ranging from 100 to 5300 microV. Sensory and SEPs were satisfactorily recorded in only three of the six animals. Sensory amplitudes also varied greatly, ranging from 25 to 120 microV. In three cases, SEPs could not be identified due to motor artefacts. The motor pathway after axonal regrowth in neurotized lumbar roots might easily be explored by proximal electric stimulation of the root, close to the sutured area. Detection of sensory and spinal cord evoked potentials might be improved by the use of curve summation techniques. Specific axonal tracing holds promise of being a useful technique for examining sensory and motor pathway recovery after neurotization in the sheep model.