Multiple sclerosis causes demyelinating lesions, which can induce multiple symptoms. If motor disorders are the most visible disability, urinary disorders are frequent, with prevalence from 32 to 86%. The first ones are due to pyramidal, cerebellar or proprioceptive lesions. The seconds are due to specific lesion in inhibitor/activator encephalic centers, or interruption on medullary conduction. It seems to be evident that walk and urinary disorders are link, because of similar anatomic ways and control process. Effect of bladder filling is well known on motoneuronal excitability. The effect of bladder filling on walk stay unknown, while medullary integration of these two functions is very close, in medullary cone.