The usefulness of the somatosensory evoked potentials of the pudendal nerve in diagnosis of probable multiple sclerosis.

STUDY DESIGN: The aim of the study was to evaluate the sensitivity of pSEP in patients affected by probable MS. OBJECTIVES: Bladder dysfunction is the presenting symptom in 2% of patients affected by multiple sclerosis (MS) and may be present in up to 78% of them. Abnormalities of somatosensory evoked potentials of the pudendal nerve (pSEP) have been found by many authors in patients affected by clinically defined MS, but little is known of diagnostic reliability of pSEP in early stage of MS. METHODS: Sixteen patients, eleven females and five males, aged between 18 and 45 years old (mean age 28.9), affected by clinically probable MS, were studied. Six of them reported retention or urge incontinence. pSEP with P1 (P40) scalp wave was analyzed. All patients also underwent visual evoked potentials (VEP), SEP of median and tibial nerves (mSEP, tSEP), brainstem acoustic evoked potentials (BAEPs), MRI of the brain and cerebrospinal fluid (CSF) evaluation. Urodynamic study with simultaneous measurement of intravesical, intraurethral and abdominal pressures with external sphincter electromyography was performed. RESULTS: Abnormalities of the evoked potentials were found in all patients. Abnormalities of the pSEP were observed in all the symptomatic cases and in eight of the remaining ten patients; ten showed no responses from the scalp and four showed P1 increased latency. Urodynamic abnormalities were found in 12 patients and MRI showed demyelinating lesions in 13 patients and oligoclonal bands were found in eight of them. CONCLUSION: pSEP can be worthwhile as part of the initial diagnostic evaluation in patients affected by MS. It provides information of diagnostic relevance and plays a role in screening patients for urodynamic testing, which, however, is more specific for detecting urethrovesical dysfunctions and preventing urological complications.