Pudendal neuralgia is a recent identified pathology, extremely invalidating, related to chronic pelvic entrapment. Nowadays, pudendal neuralgia can be treated with:

• neuropathic pains treatment
• specific kinesitherapy
• Alcock's canal and sacrospinal ligament infiltrations under scan
• with diagnostic block
• local steroids injections
• and surgical decompression of pudendal nerve with transrectal approach.

Only surgery was validated after a randomised protocol studying surgery versus abstention, performed and published by the CHU de Nantes. Many techniques have been proposed for realization of pudendal nerve infiltrations. The results of these infiltrations have never been published, and no randomised study had ever evaluated those results, even at short-run. Very few randomized studies have validated steroids infiltrations techniques in canal syndrome neuropathies.

The primary objective of the investigators phase IV trial is to evaluate the efficacy of three different types of pudendal nerve infiltrations in Alcock's canal and sacrospinal ligament:

• group A: only local anesthetic (control arm)
• group B: local anesthetics associated with local steroids
• group C: local anesthetics associated with local steroids and important volumes of physiological serum

Inclusion Criteria:

• Patient presenting the four indispensable clinical criteria for pudendal neuralgia (Nantes' criteria)
• Man or woman aged more than 18 years old
• Suffering from pudendal neuralgia since more than six months
• Without previous infiltration identical to the one proposed by the protocol
• Without previous surgery of pudendal nerve
• Without any hemorrhagic risk factor
• No contra-indication to Lidocaïne, Depo-medrol or contrast-product injections
• Pain intensity with an average > or = 40/100 (measured by scales during the fifteen days before infiltration)

Exclusion Criteria:

• Patient presenting one of the four exclusion clinical criterium for pudendal neuralgia (Nantes' criteria)
• Patient who has filled his "pain note book" during less than 5 days over the 15 days before the infiltration
• Pregnancy
• Depression (Beck scale > 16/39)