Occult tight filum terminale syndrome: results of surgical untethering.

The entity of an occult tight filum terminale syndrome, characterized by clinical findings consistent with a tethered cord syndrome, but with the conus ending in a normal position, has been recognized recently. The indications for sectioning the filum terminale in this situation are not well characterized and are controversial. We report a retrospective review of a consecutive series of 60 children (ages 3-18 years) with a diagnosis of occult tight filum terminale syndrome who underwent section of the filum and were followed for more than 6 months (mean 13.9 months). The criteria for surgical intervention were (1) spina bifida occulta, (2) progressive bladder instability unresponsive to conservative measures, (3) urological/nephrological evaluation to confirm or rule out nonneurogenic etiology, and (4) two or more of the following: (a) bowel involvement (fecal incontinence or chronic constipation), (b) lower extremity weakness, (c) gait changes, (d) reflex/tone abnormalities, (e) sensory disturbances, (f) back/leg pain, (g) orthopedic abnormalities/limb length discrepancy, (h) scoliosis/lordosis, (i) recurrent urinary tract infections, (j) abnormal voiding cystourethrogram/ultrasound, (k) syringomyelia, and (l) neurocutaneous stigmata. Postoperatively, urinary incontinence/retention showed complete resolution in 52%, marked improvement (>95% resolution) in 35%, moderate improvement (>75%) in 6%, minimal improvement (> 50%) in 6%, and no improvement (<50%) in 2%. Fecal incontinence completely resolved in 56%, improved in 41%, and was unchanged in 3%. Weakness, sensory abnormalities, and pain improved or resolved in all patients.