Introduction
It is clearly important for the patient to have been thoroughly examined by a urologist or gynaecologist and local pelvic pathology excluded. Once a structural cause has been eliminated, a neurological opinion is often sought, with the prime aim of the neurologist being to exclude any form of conus or sacral root pathology. Magnetic resonance imaging (MRI) is the investigation of choice to show both neural tissue and surrounding structures.
If all examinations and investigations fail to reveal an abnormality, the diagnosis is likely to be one of the focal pain syndromes. These are persistent or recurrent or episodic pains referred to specific pelvic organs in the proven absence of infection, malignancy or other obvious pathology.
Pudendal Nerve Entrapment
Chronic compression of the pudendal nerve in the ischiorectal fossa may result in a perineal pain located either anteriorly in the vagina or vulval region, or posteriorly in the anorectal region. The International Continence Society (ICS) has used the following definition, 'perineal pain is felt: in the female, between the posterior fourchette (posterior lip of the introitus) and the anus, and in the male, between the scrotum and the anus'.
The pain may include unpleasant sensations of numbness or a burning sensation, and may be exacerbated by sitting and relieved by standing. Neurological examination of the perineum is often normal. If tested, the sacral reflexes are often present and anal sphincter tone is normal. Neurophysiological examination is said to be helpful is some cases; sacral reflex latency (using electrical stimulation of the dorsal nerve of the clitoris and recording muscle activity in the perineum) and the pudendal nerve distal motor latency using the St. Mark's Stimulator has been recommended. These investigations require specialist neurophysiological expertise and may be normal in the absence of clinically proven sensory changes.
Pudendal nerve neuropathy is likely to be a probable diagnosis if the pain is unilateral, has a burning quality and is exacerbated by unilateral rectal palpation of the ischial spine, with delayed pudendal motor latency on that side only. However, such cases account for only a small proportion of all those presenting with perineal pain. Proof of diagnosis rests on pain relief following local anaesthetic nerve blocks or decompression of the nerve in Alcock's canal, but long term pain relief is rarely achieved. The value of the clinical neurophysiological investigations is debatable; some centres in Europe claim that the investigations have great sensitivity, while other centres, which also have a specialized interest in pelvic floor neurophysiology, have not identified any cases. Further information may be gained by differential diagnostic nerve block or MRI investigation.
Other Neurogenic Conditions
Other pelvic floor clinical neurophysiological investigations are more helpful in identifying changes of denervation and re-innervation. Lesions causing such disorders are usually associated with bladder and/or sexual dysfunction rather than isolated urogenital pain.
