Dynamic magnetic resonance imaging parameters for objective assessment of the magnitude of tethered cord syndrome in patients with spinal dysraphism
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Dynamic magnetic resonance imaging (MRI)-based criteria for diagnosing magnitude of tethered cord syndrome (TCS) in occult spinal dysraphism are proposed.
In this prospective, case-control design study, MRI lumbosacral spine was performed in 51 subjects [pilot group (n = 10) without TCS (for defining radiological parameters), control group (n = 10) without TCS (for baseline assessment), and study group (n = 31) with spinal dysraphism (thick filum terminale [n = 12], lumbar/lumbosacral meningomyelocoele [n = 6], and lipomyelomeningocoele [n = 13])]. The parameters compared in control and study groups included oscillatory frequency (OF), difference in ratio, in supine/prone position, of distance between posterior margin of vertebral body and anterior margin of spinal cord (oscillatory distance [OD]), with canal diameter, at the level of conus as well as superior border of contiguous two vertebrae above that level; delta bending angle (ΔBA), difference, in supine/prone position, of angle between longitudinal axis of conus and that of lower spinal cord; and sagittal and axial root angles, subtended between exiting ventral nerve roots and longitudinal axis of cord. An outcome assessment at follow-up was also done.
In the study group (cord tethered), significantly less movement at the level of conus (OF0, p = 0.013) and one level above (OF1, p = 0.03) and significant difference in ΔBA (p = 0.0) were observed in supine and prone positions, compared to controls. Ventral nerve root stretching resulted in sagittal/axial root angle changes. Median OF (0.04) in the lipomyelomeningocoele group was significantly less than that in control group (0.23). Median OF was also lesser in patients with thick filum terminale or meningomyelocele. Difference in median sagittal and axial root angles among the study and control groups was statistically significant (p = 0.00).
New dynamic MRI-based parameters to establish the presence and magnitude of TCS have been defined. OF measured the extent of loss of translational cord displacement in supine and prone positions; ΔBA defined the relative angulation of conus with lower spinal cord, and sagittal and axial root angles represented ventral nerve root stretching. The difference in OF or ΔBA was minimum in the group with thick filum terminale and progressively increased in the groups with lipomyelomeningocele and meningomyelocele.
KeywordsSpinal dysraphism Tethered cord syndrome Magnetic resonance imaging Thick filum terminale Meningomyelocoele Lipomyelomeningocoele
No funding was received for this research.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
Additional informed consent was obtained from all individual participants for whom identifying information is included in this article.
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