PMC8492443_01
(a) A dorsal midline sac measuring 30x30x10 mm in the upper lumbar region. (b and c) Sagittal views of 3D-T1WI (b) and T2WI (c) demonstrate a tethering tract that began at the dome of the meningocele sac, ran caudally in the inner wall of the sac, and joined the lumbar cord at the L3 vertebral level. The attachment of the stalk to the dome contained a small syrinx cavity (blue arrows). The stalks comprising the anterior wall of the syrinx cavity were almost isointense on 3D-T1WI (red arrows). (d and e) Parallel coronal views of 3D-hT2WI with fat suppression (d) and parallel axial views of T2WI (e) also show that the attachment of the stalk to the dome. The spinal cord slightly deviated into the dome and was stuck at the entrance of the dome, which measured 15x 10 mm (yellow arrows in (d and e)).
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F1
Physical examination revealed a dorsal midline sac in the upper lumbar region measuring 30x30x10 mm in length x width x height that was thickly covered with normal skin [Figure 1a]. T1-weighted spoiled gradient-recalled echo imaging (3D-T1WI) and three-dimensional heavily T2-weighted imaging (3D-hT2WI), was performed 3 days after birth and demonstrated a tethering tract that began at the dome of the meningocele sac, ran caudally in the inner wall of the sac, and joined the lumbar cord at the L3 vertebral level [Figure 1b-e]. The attachment of the stalk to the dome was wide based and contained a small syrinx cavity.
(a) The dome grew to 50x40x15 mm by 2 months of age. (b and c) Parallel sagittal views of T1WI (b), parallel coronal views of 3D-hT2WI with fat suppression (c), and parallel axial views of 3D-hT2WI with fat suppression (d) revealed that cord tethering was aggravated. With the deviation of the cord to the sac out of the spinal canal (yellow arrows in (c and d)), the cord was displaced dorsally and to the left. The stalk comprising the anterior wall (red arrows) of the syrinx cavity (blue arrows) became lipomatous tissue. (e-k) Schematic drawing (e) and microscopic view of the intraoperative findings (f and h-k), and intraoperative neurophysiological monitoring (g). (e and f) The cord emerged from the orifice of the spinal canal. The border between the spinal cord and stalk could be distinguished and nerve roots were found on the cord. (g) This border was neurophysiologically confirmed by tracing the evoked compound muscle action potentials (CMAPs) of the hamstring with direct stimulation with 3 mA intensity starting from the functional cord and continuing to the nonfunctional stalk. The CMAPs were evoked following stimulation at the cord (1-2); no CMAPs were evoked following stimulation at the stalk (3-8). (h) The stalk was severed just distal to the border; the syrinx cavity was opened. (i) The cord was untethered from the stalk. (j) The severed edge was approximated with a pial suture and returned to the spinal canal. (k) The orifice of the cord was tightly closed.
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F2
The lumbar sac had grown to 50x40x15 mm [Figure 2a]. The cord was markedly displaced dorsally and to the left, with the deviation of the cord to the sac out of the spinal canal [Figure 2b-d]. On opening the sac, the cord emerged from the orifice of the spinal canal, which was 15 mm in diameter, with the tethering of the stalk spread widely on the inner wall of the sac [Figure 2e and f]. This border was neurophysiologically confirmed by tracing the evoked compound muscle action potentials of the external anal sphincter, hamstring, and gastrocnemius muscles with direct stimulation starting from the functional cord and continuing to the nonfunctional stalk [Figure 2g]. The stalk was severed immediately distal to the border, the syrinx cavity was opened [Figure 2h], and the cord was untethered from the stalk [Figure 2i]. The severed edge was approximated with a pial suture and returned to the spinal canal [Figure 2j]. The orifice of the cord was tightly closed [Figure 2k] and covered with a flap of the paravertebral muscle.
PMC8492443_02
(a and b) Sagittal view of T1WI (a) and coronal image of 3D-hT2WI with fat suppression (b) performed on the postoperative 14th day demonstrated that the spinal cord deformity markedly improved, although a minor hemorrhage was noted at the severed edge of the stalk. (c-f) Histopathological examination of the resected stalk stained with hematoxylin and eosin (c, d) and immunostained for glial fibrillary acidic protein (GFAP) (e and f). Higher magnification view of the area indicated by the dotted square in (c) is shown in (d and e). A central canal (CC)-like lumen lined by ependymal cells (Epen) and surrounding GFAP-immunopositive neuroglial tissues and fibrocollagenous tissue embedded with smooth muscle (SM) fibers was noted in the fibroadipose tissue (FAT). The sac was covered with finely jagged squamous epithelium (blue arrow in (c)). (f) The wall facing the syrinx cavity was composed of GFAP-immunopositive neuroglial tissue including neuronal cells and had no ependymal lining.
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F3
MRI performed on the 14th day postoperatively demonstrated that the spinal cord deformity markedly improved due to the successful untethering of the cord, although minor hemorrhage was noted at the severed edge of the stalk [Figure 3a and b]. Surrounding glial fibrillary acidic protein (GFAP)-immunopositive neuroglial tissues and fibrocollagenous tissues embedded with smooth muscle fibers in the fibroadipose tissue were also present [Figure 3c-e]. The wall facing the syrinx cavity was also composed of GFAP-immunopositive neuroglial tissue, including neuronal cells, with no ependymal lining [Figure 3f].