[Anal tone: Physiology, clinical and instrumental characteristics]. / Tonus anal : déterminant physiologique, évaluation clinique et paraclinique, caractéristique pathologique.

INTRODUCTION: The anal tone allows the maintenance of anorectal continence. Its regulation depends on spinal segmental mechanisms under supra-sacral control. MATERIAL AND METHODS: A systematic review was performed using Medline database, according to PRISMA methodology, using following keywords anal tone ; anal sphincter ; anorectal function ; reflex ; digital rectal examination. RESULTS: Anal hypertonia is an increase in the muscle's resistance to passive stretching. Muscular hypotonia is a decrease in muscle tone. It is associated with a decrease in resistance to passive mobilization. It is not possible to quantify the prevalence of anal tone alterations in the general population and in specific pathological conditions (urinary disorders, neurogenic or non-neurogenic anorectal disorders). In case of hypotonia, most often due to a lower motor neuron lesion, fecal incontinence may occur. Hypertonia (anal sphincter overactivity) is not always due to perineal spasticity. Indeed, in the majority of the cases, the cause of this anal hypertonia in a neurologic context, can be secondary to an upper motor neuron disease due to spinal or encephalic lesion, leading to recto-anal dyssynergia, giving distal constipation. In another way, this anal hypertonia can be purely behavioral, with no direct pathological significance. The evaluation of anal tone is clinical with validated scores but whose sensitivity is not absolute, and instrumental with, on the one hand, the measurement of anal pressure in manometry and, on the other hand, electrophysiological testing which still require validation in this indication. CONCLUSION: Anal tone assessment is of interest in clinical practice because it gives diagnostic arguments for the neurological lesion and its level, in the presence of urinary or anorectal symptoms.

Assessment of sacral spinal excitability using stimulus-response curves of the bulbocavernosus reflex.

OBJECTIVE: To analyze and quantify sacral spinal excitability through bulbocavernosus reflex (BCR) stimulus-response curves. METHODS: Thirty subjects with upper motor neuron lesions (UMN) and nine controls were included in this prospective, monocentric study. Sacral spinal excitability was assessed using stimulus-response curves of the BCR, modeled at different bladder filling volumes relative to the desire to void (as defined by the International Continence Society) during a cystometry. Variations in α (i.e. the slope of the stimulus-response curve) were considered as an indicator of the modulation of sacral spinal excitability. RESULTS: In all subjects, α increased during bladder filling suggesting the modulation of spinal sacral excitability during the filling phase. This increase was over 30% in 96.7% of neurological subjects and 88.9% of controls. The increase was higher before the first sensation to void in the neurological population (163.15%), compared to controls, (29.91%), p < 0.001. CONCLUSIONS: We showed the possibility of using BCR stimulus-response curves to characterize sacral spinal response with an amplification of this response during bladder filling as well as a difference in this response amplification in patients with UMN in comparison with a control group. SIGNIFICANCE: BCR, through stimulus-response curves, might be an indicator of pelvic-perineal exaggerated reflex response and possibly a tool for evaluating treatment effectiveness.