Electrodiagnosis of human dorsal sacral nerve roots by recording afferent and efferent extracellular action potentials.

Single extracellular nerve action potentials from afferent fibres with various functions were recorded from human sacral nerve roots. It was shown that the potentials from these fibres can have different wave forms (amplitude, duration) and conduction velocities. The smaller potentials with longer durations have lower cut-off frequencies for certain identification than the larger potentials of shorter duration. The conduction velocity diagnosis covers a range of velocities with a factor of about 10. The slowest measured conduction velocities were between 4 and 10 m/sec. The identification of the functions of afferents in nerve roots is possible by calculating conduction velocities and stimulated activity increase measurements. Besides touch and pain fibres from the skin, afferents from mechano-receptors of the urinary bladder and the anal canal could be detected in dorsal sacral roots. There is evidence of motoneurons in the dorsal sacral roots supplying fatigue resistant muscle fibres. Sacral nerve root electrodiagnosis can be used in operations to identify physiologically-stimulated afferents and reflex activated motoneurons and, therefore, possibly will be useful in nerve anastomoses and nerve root stimulations in paraplegia.