Evaluation of the Analgesic Effect of Intramyometrial Botulinum Toxin Injection Via Hysteroscopy in Pelvic Pain Suggestive of Dysmenorrhea

The objective of the study is to evaluate the global impression of improvement at 3 months following intramyometrial botulinum toxin injections via hysteroscopy in women with severe primary dysmenorrhea who have failed first-line medical treatment, compared to intramyometrial placebo injections.

Inclusion Criteria: * Adult women who are not menopausal, * Presenting with: * Either severe primary dysmenorrhea, defined by an average pain intensity (VAS) ≥ 6/10 over the last 3 months at the inclusion visit, * Or, in cases of amenorrhea under hormonal treatment, severe chronic pelvic pain (average VAS ≥ 6/10 over the last 3 months), described as cramp-like, localized in the pelvic region, and similar to the initial dysmenorrhea pain. * Having failed optimal first-line medical treatment combining hormonal therapy and appropriate analgesics (Level I and II analgesics, and NSAIDs), * Having undergone a pelvic MRI within 1 year prior to the randomization visit that shows no evidence of deep infiltrating endometriosis or endometrioma, following systematic review by radiologists from the expert center managing the patient (if the pelvic MRI is deemed of insufficient quality for interpretation, a new MRI will be performed at the center), * Using a highly effective method of contraception (failure rate \