Management of tight filum terminale syndrome with special emphasis on normal level conus medullaris (NLCM)

BACKGROUND Tethered cord syndrome is classically defined as having the tip of the conus medullaris below the body of L2, instead of at the normal L1-2 disc space level. The syndrome presents most commonly with urinary incontinence. In a patient with urinary incontinence and a low-lying conus medullaris, tethered cord syndrome can be diagnosed without difficulty. However, in a patient with urinary incontinence and a hyperreflexive type of neurogenic bladder, in whom the conus medullaris is found to be at the normal level on magnetic resonance imaging, diagnosing a tethered cord can be challenging. We hypothesized that patients with hyperreflexive neurogenic bladders have a neurologic basis for their bladder dysfunction, probably secondary to tethering by a tight filum terminale, despite having a normally positioned conus medullaris. METHODS We investigated 13 patients with tethered cord syndrome with urinary incontinence. All patients underwent urodynamic tests, somatosensory-evoked potentials (SSEPs), and magnetic resonance imaging. All had normal neurologic exams including lower extremity motor, sensory, and reflex functions. To minimize disturbance of the normal anatomy, we used a flavotomy approach and transected the tight filum terminale to release the tethered conus medullaris. RESULTS We show that urodynamic studies appear to be more predictive of a tight filum terminale than SSEPs. However, pathological SSEP results seem to correlate with poor surgical outcomes. Ninety-three percent of operated patients were continent by the first post-surgical day. However, disappointingly, almost half lost continence within the first month after surgery. CONCLUSION In cases of incontinence with a normal level conus medullaris, but urodynamic studies showing a hyperreflexic neurogenic bladder, we believe that sectioning of the filum terminale often improves continence. (C) 1998 by Elsevier Science Inc.