Dynamic magnetic resonance imaging parameters for objective assessment of the magnitude of tethered cord syndrome in patients with spinal dysraphism

• Published in: Acta neurochirurgica 2019-01, Vol.161 (1), p.147-159
• Main Authors: Singh, Suyash, Behari, Sanjay, Singh, Vivek, Bhaisora, Kamlesh S., Haldar, Rudrashish, Krishna Kumar G., Mishra, Prabhakar, Phadke, Rajendra V.
• Format: Article
• Language: English
• Subjects: Adult; Cauda Equina - diagnostic imaging; Congenital defects; Female; Humans; Interventional Radiology; Lumbosacral Region - diagnostic imaging; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Magnetic Resonance Imaging - standards; Male; Medicine; Medicine & Public Health; Minimally Invasive Surgery; Neural tube defects; Neurological diseases; Neurology; Neuroradiology; Neurosurgery; NMR; Nuclear magnetic resonance; Original Article - Spine - Other; Prone Position; Resonance; Spinal cord; Spinal Cord - diagnostic imaging; Spinal Dysraphism - diagnostic imaging; Spine; Spine (lumbar); Spine - Other; Statistical analysis; Surgical Orthopedics; Vertebrae
• ISSN: 0001-6268; 0942-0940
• DOI: 10.1007/s00701-018-3721-7

Background Dynamic magnetic resonance imaging (MRI)-based criteria for diagnosing magnitude of tethered cord syndrome (TCS) in occult spinal dysraphism are proposed. Methods 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 (Δ BA ), 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. Results 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). Conclusion 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.