Pudendal Neuralgia Due to Pudendal Nerve Entrapment: Warning Signs Observed in Two Cases and Review of the Literature

Abstract

Pudendal neuralgia is a chronic neuropathic pelvic pain that is often misdiagnosed and inappropriately treated. The Nantes criteria provide a basis for the diagnosis of pudendal neuralgia due to pudendal nerve entrapment. The 5 essential diagnostic criteria are pain situated in the anatomical territory of the pudendal nerve, worsened by sitting, the patient is not woken at night by the pain, and no objective sensory loss is detected on clinical examination. The fifth criterion is a positive pudendal nerve block. We have also clarified a number of complementary diagnostic criteria and several exclusion criteria that make the diagnosis unlikely. When pudendal neuralgia due to pudendal nerve entrapment is diagnosed according to the Nantes criteria, no further investigation is required and medical or surgical treatment can be proposed. Nevertheless, a number of warning signs suggesting other possible causes of pudendal neuralgia must not be overlooked. These warning signs (red flags) are waking up at night, excessively neuropathic nature of the pain (for example, associated with hypoesthesia), specifically pinpointed pain, which can suggest neuroma and pain associated with neurological deficit. In these atypical presentations, the diagnosis of pain due to pudendal nerve entrapment should be reconsidered and a radiological examination should be performed. The 2 cases described in this report (tumor compression of the pudendal nerve) illustrate the need to recognize atypical pudendal neuralgia and clarify the role of pelvic magnetic resonance imaging (MRI), as MRI provides very valuable information for the evaluation of diseases involving the ischiorectal fossa. The presence of red flags must be investigated in all cases of pudendal neuralgia to avoid missing pudendal neuralgia secondary to a mechanism other than nerve entrapment. Key words: Pudendal nerve, pudendal neuralgia, Nantes criteria, pelvic pain, pudendal canal, perineal pain