Is a filum terminale with a normal appearance really normal?

Abstract

Introduction: Tethered spinal cord is defined as a condition in which the conus medullaris ends at a level below the L1-2 intervertebral space. The spinal cord is considered to be tethered when there is a thick filum terminale or low-lying conus medullaris. It has also been reported that a normal level of the conus medullaris and normal thickness of the filum terminale do not mean that there is no cord tethering. Materials and methods: In this investigation, we examined 21 fila terminalia; 5 of them were taken from cadavers, and these were used as a control group (group 1; n/n), 8 from patients with a normal appearance of the filum terminale but with clinical symptoms (incontinence) and pathologic results of a urodynamic study (group 2; n/ab), and 8 from patients with an abnormal appearance of the filum terminale and with clinical symptoms (group 3; ab/ab). Interestingly, we found that while fila terminalia in the control group were made up mainly of collagen fibers, more connective tissue with dense colla-gen fibers, some hyalinization and dilated capillaries were noticed in the fila from group 2. Results: Our results suggest that these histological features may reflect a decreased elasticity within the filum terminale, resulting in a tethering effect on the lower conus in otherwise normal physiological conditions. Conclusion: These findings lead us to reconsider sectioning of the filum terminale in incontinent patients with normal results in radiological studies, whose condition is called "nonneurogenic neurogenic bladder."

Association of Chiari malformation type I and tethered cord syndrome: preliminary results of sectioning filum terminale

“…In 1990, Khoury et al [25], reported a series of 31 children with neurogenic bladder dysfunction and normal radiographic findings in whom SFT resulted in symptomatic improvement in 72% of the patients. Subsequent surgical series in children with TCS and a normally positioned CMD have described clinical or urodynamic improvements in 71% to 100% of the patients [34,42,47,57,58,61,74,76]. Growing interest in the concept of minimal or occult TCS has required a re-examination of the criteria for diagnosis and surgical intervention [59,66,72,80].…”

“…Histological studies have suggested that fila obtained from patients with occult TCS may be more fibrotic than normal [58,61,78], lending support to the notion that a normally positionedCMD could be tethered by a tight or inelastic FT [60,66,72,78]. This hypothesis is supported by the following findings in the current report: [1] the width of the FT decreased steadily as the CMD ascended during growth and development; [2] most patients with normal position of the CMD had positive FT traction tests; [3] at surgery, the FT appeared as a thin, taut, immobile structure that was associated with lateral packing of the cauda equina and reduced regional CSF flow; and [4] immediately after SFT, there was marked distraction of the divided ends, normalized distribution and movements of the cauda equina and increased regional CSF flow (see Fig.…”

Prenatal evaluation of the position of the fetal conus medullaris

“…Although the prevalence of these defects is estimated to be 2-4 in 1000 in postnatal life 3,4 , these disorders are rarely diagnosed prenatally 5 . However, early detection is not only important to inform and prepare parents for the anomaly but also to allow pediatric neurosurgeons to develop ahead of time a well-timed surgical repair strategy to avoid irreversible neurological damage 6 .…”

Neonatal and infantile spinal sonography: A useful investigation often underutilized

“…[2615] Assessment of normal nerve root motion is even more important in older children as the conus may be normally positioned but still be tethered (tight filum syndrome). [16] …”