CORTICAL EVOKED-POTENTIALS BY STIMULATION OF THE VESICOURETHRAL JUNCTION - CLINICAL-VALUE AND NEUROPHYSIOLOGICAL CONSIDERATIONS

In 21 healthy volunteers and 42 patients with either neurogenic bladder dysfunction (24), partial peripheral denervation of the bladder (12) or nonneurogenic bladder dysfunction (6) scalp-derived evoked potentials after stimulation of the vesicourethral junction (cortical evoked potentials) were recorded. In addition, evoked potentials from the posterior tibial nerve (tibial somatosensory evoked potentials) and from the pudendal nerve (pudendal somatosensory evoked potentials) were evaluated. The results obtained in normal subjects were reproducible and comparable to those reported in previous studies. Cortical evoked potentials of vesicourethral junction consisted of a prominent negativity with a mean latency of 95 msec. Tibial and pudendal somatosensory evoked potentials were similar and showed a typical W-shaped complex. In normal subjects stimulation of the vesicourethral junction was described as a stimulus-synchronous pulsation combined with a continuous burning feeling and sometimes with a desire to void. In 4 normal subjects no cortical evoked potentials of the vesicourethral junction could be obtained because of a decreased pain threshold. In regard to clinical value, the results demonstrate that in patients with lesions of the central nervous system (in the group with cauda equina and conus medullaris lesions, and in the group with suprasacral spinal cord lesions) the results of cortical evoked potentials of the vesicourethral junction and pudendal somatosensory evoked potentials widely correlate due to similar afferent nervous pathways within the central nervous system. However, in patients with partial peripheral denervation of the bladder with suspected additional secondary local detrusor damage the results of cortical evoked potentials obtained by stimulation of the vesicourethral junction differ mostly from the results of somatosensory evoked potentials obtained by stimulation of the pudendal nerve. The pattern obtained (increased sensory and pain threshold, normal cortical evoked potentials of the vesicourethral junction with normal latencies and normal or increased amplitude) is indicative of local detrusor damage. In 21 patients the ability to detect cortical evoked potentials of the vesicourethral junction was combined with the sensation of stimulus-synchronous pulsation, whereas in the other 21 patients the absence of this sensation during stimulation was combined with the absence of cortical evoked potentials. On the other hand, no correlation was found between the ability of obtaining cortical evoked potentials of the vesicourethral junction and the stimulus-induced sensation of pain and/or desire to void. Therefore, we conclude that afferent fibers conducting the perception of stimulus-synchronous pulsation and the vague feeling of abdominal fullness also represent the nervous pathways responsible for cortical evoked potentials of the vesicourethral junction, which reach the central nervous system via the dorsal columns of the spinal cord.