Electrophysiological evaluation of the afferent spinal roots and nerves in patients with conus medullaris and cauda equina lesions.

The clinical value and practical application of the lumbosacral evoked electrospinogram (Espg) and somatosensory cerebral evoked potentials (SEP) were investigated in 52 patients with conus medullaris or cauda equina lesions. It was shown that the destruction or compression of the conus/cauda equina region by traumatic fracture and dislocation of upper lumbar vertebrae, by midline herniation of the nucleus pulposus and by tumoral mass, produced significant reduction in amplitude and delay in latency of Espg recorded just above the lesion site, and the SEP behaved in a similar way. The degree of abnormality was found to be in accord with the severity of clinical sensorimotor deficits in the legs. Tumoural compression caused more significant delay in evoked responses than traumatic injury. From the diagnostic point of view, Espg and SEP were useful in showing latent and manifest involvement of the lumbosacral sensory roots and these are discussed in relation to other electrodiagnostic tests.