[Effects of attention and desire to void on sensory evoked cortical potentials following perineal stimulation]

Cortical somatosensory evoked potentials (SEP) are usually used to test the integrity of lemniscal pathways and thus provide arguments for the neurogenic etiology of sensory symptoms. For example, PES by perineal stimulation (SEP-P) has been shown to be altered in incontinence or neurogenic sexual dysfunction. We wanted to verify the integrity, structure and amplitude of far-field responses of PES-P in two conditions, the first without feeling the need to urinate (S0), the second with urgency (US).

SEP-P were recorded in ten patients without neurological pathology in both conditions S0 and US after stimulation of the dorsal nerve of the penis/clitoris. Three consecutive responses each averaged over 1000 passages at a frequency of 3Hz were recorded.

Seven men and 3 women were included. All patients had normal SEP-P in terms of amplitude and latency of the P40 complex and fully reproducible especially for late responses. These early P40 responses were identical in both S0 and US states. Conversely, the far-field potentials, i.e. the late responses, were different in the two states, with a significant decrease (P<0.008 paired T-test) in the amplitude of cortical responses in the US state.

We observe that the late components of SEP-P were altered by the need to urinate urgently with sustained and selective attention to this need. These late components of SEP-P could be useful to better specify the attentional mechanisms involved in the continence-voiding cycle and to specify pathological sensory dysfunctions (urgency, painful bladder, frequency…).

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