Value of electrophysiological assessment after surgical treatment of spinal dysraphism

This study was conducted in children treated surgically for spinal dysraphism between 1994 and 2000 to determine the value of electrophysiological parameters for followup in comparison with clinical, radiological and urodynamic findings.

Electrophysiological examination was performed based on electromyographic detection of perineal muscle activity with evaluation of the sacral reflexes and measurement of lower limb and perineal evoked potentials. Clinical and radiological assessment consisted of physical examination, kidney ultrasonography and retrograde cystouretrography. Urodynamic assessment included determination of urethral pressure profile, bladder activity, compliance, voiding pressure and sphincter synergy. A total of 45 children were included in the study. In 28 cases electrophysiological assessment was performed routinely in 20 children (group 1) before and after (6 months and annually thereafter) surgical treatment (mean followup 30 months) and in 8 children (group 2) only after surgical treatment (mean followup 65 months). Electrophysiological findings were correlated with the urodynamic and clinical findings. Sensitivity, specificity and positive and negative predictive values were calculated. In 17 children (group 3) electrophysiological assessment was performed only once either before or after surgery.

Electrophysiological assessment with combined electromyographic detection and perineal evoked potentials was highly sensitive in predicting urodynamic impairment, particularly vesico-sphincter dyssynergia (sensitivity 100%) or bladder dysmotility (sensitivity 86%). Specificity of perineal evoked potentials for detecting urodynamic dysfunction was 90%. Electromyographic detection and perineal evoked potentials also demonstrated satisfactory sensitivity in confirming urological impairment (sensitivity 79%, negative predictive value 90%).

Electromyographic detection and perineal evoked potentials are valuable for assessment of patients after surgical treatment of spinal dysraphism. Because these techniques are minimally invasive and highly reproducible, they are suitable for baseline assessment in most cases (tethered cord, lipoma, syringomyelic cavities). Urodynamic assessment should be reserved for patients at high risk for secondary neurogenic bladder dysfunction such as myelomeningocele or sacral agenesis.