Multiple sclerosis (MS) is the leading non-traumatic cause of severe acquired disability in young people. The disease is defined by relapses, which can affect all neurological functions depending on the location of the new inflammatory lesion(s). The disease can thus manifest itself through bladder and bowel disorders (BWS), which affect approximately 80% of MS patients in all stages. Lower urinary tract dysfunction has a significant negative impact on the quality of life of patients and places a significant burden on the healthcare system in terms of resource allocation. In addition, there is a risk of long-term chronic renal failure, an infectious risk (recurrent cystitis and/or pyelonephritis, sometimes life-threatening) and a lithiasis risk. The most frequently observed urinary symptoms are: urinary frequency, urgency with or without urinary incontinence, dysuria and chronic retention of urine. These disorders most often combine bladder hyperactivity and dysuria. This dysuria may be responsible for recurrent urinary tract infections, lithiasis, alteration of renal function. The only therapeutic class currently used to treat dysuria in MS is alpha-blockers. Tamsulosin, alfusozin and doxazosin induce relaxation of the urethral smooth sphincter and prostatic urethral muscle fibers, facilitating the removal of subvesical obstruction and bladder emptying. The study investigators hypothesize that treatment with tamsulosin 0.4 mg daily in adult MS patients with dysuria will result in symptom improvement as assessed by the International Prostate Symptom Score (IPSS) and Urinary Symptom Profile (USP) scores, a decrease in post-void residual, and an improvement in urine flow and quality of life.