PMC8769447_01
(Patient 1). (a) Serial upside-down sagittal views of HASTE sequence (slice thickness 3 mm) performed at 33+3 weeks of gestation show severe dorsal bending of the cord and deviation to the sac out of the spinal canal. No hydrocephalus or Chiari malformation is observed. (b) Photograph at birth showing a saccular lesion at the upper lumbar region. A cleft and skin erosion are noted on the surface. (c) Sagittal views of 3D-hT2WI (slice thickness, 0.45 mm) (c-1) and variable flip-angle 3D-T1WI (slice thickness, 0.45 mm) (c-2) at birth confirm that the cord shows severe dorsal bending and deviation to the sac out of the spinal canal at the L1-L2 vertebral level while the sac is collapsed. (d, e, f) Schematic drawing (d) and microscopic view of the intraoperative findings (e), and IONM (f). (d, e-1) Opening the sac, a thick stalk and tethered cord, measuring 15 mm in length together, emerge from the orifice of the spinal canal and attaches to the inner wall of the sac. (e-2) A skin erosion is observed on the outer surface of the sac where the stalk is attached. The border between spinal cord and the stalk cannot be distinguished, whereas nerve root-like structures are found near the orifice of the spinal canal. This border is neurophysiologically determined by tracing the evoked CMAPs of the hamstring with direct stimulation with 2 mA intensity starting from the functional cord and continuing to the non-functional stalk (f). CMAPs are obtained following stimulation at 0-5 mm from the orifice of spinal canal; no CMAPs are evoked following the distal stimulation at 10 mm or more. The stalk is severed at 10 mm from the orifice. Numbers indicated in e-2 and f represent the distance (mm) from the orifice of the cord. (g) Sagittal view of 3D-hT2WI (slice thickness, 0.45 mm), performed on postoperative 25th day, demonstrates marked improvement in dorsal bending of the cord, although 5.3 mm of the stalk persists. (h, i) Histopathologically, the resected stalk includes a fibrocollagenous tissue embedded with GFAP-immunopositive neuroglial tissues. The sac is covered with finely jagged squamous epithelium, except for the attachment of stalk (black arrows). Original magnification x12.5. 3D-TIWI: three-dimensional turbo spin-echo T1-weighted images, 3D-hT2WI: three-dimensional heavily T2-weighted imaging, CMAPs: compound muscle action potentials, GFAP: glial fibrillary acidic protein, HASTE: half-Fourier acquisition single-shot turbo spin-echo, IONM: intraoperative neurophysiological mapping.
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F1
The spinal cord bent approximately at right angles and ran dorsally to attach to the inner wall of the sac before running ventrally back into the spinal canal (Fig. 1a). Physical examination revealed a dorsal midline sac measuring 42 x 35 mm in the upper lumbar region, which was torn during delivery (Fig. 1b). T2-weighted imaging (3D-hT2WI) confirmed a severe dorsal bending and deviation of the cord to the sac, and out of the spinal canal, at the L1-L2 vertebral level (Fig. 1c) while the sac was collapsed. The bending cord and stalk were united, similar to the findings of prenatal MRI. Opening the sac with a widening of the tear, a thick stalk and tethered cord, which measured 8-9 mm in diameter and 15 mm in length together, emerged from the orifice of the spinal canal and attached to the wall of the sac (Fig. 1d, e-1). The border between the spinal cord and stalk could not be distinguished, and nerve root-like structures were found near the orifice of the spinal canal (Fig. 1e-2). The CMAPs were evoked following stimulation at 0-5 mm from the orifice of the spinal canal; no CMAPs were evoked following stimulation at 10 mm or more peripheral from the orifice (Fig. 1f). MRI performed on the postoperative 25th day demonstrated that the dorsal bending of the cord markedly improved due to the successful untethering of the cord, although 5 mm of the stalk persisted (Fig. 1g). Histopathologically, the resected stalk included a fibrocollagenous tissue embedded with GFAP-immunopositive neuroglial tissues (Fig. 1h and 1i).
(Patient 2). (a) Sagittal view of HASTE image (slice thickness 5 mm) performed at 31+1 weeks of gestation shows a dorsal tenting of the spinal subarachnoid space continuous with the sac, but it fails to reveal the exact anatomical relationship involving the cord, stalk and sac. Sagittal (b) and axial images (c) of cranial HASTE images (slice thickness 5 mm) show hydrocephalus and Chiari malformation. (d) Photograph showing a saccular skin lesion at the lower thoracic region. (e) Serial sagittal images of 3D-hT2WI (slice thickness 1.25 mm) demonstrates a severe dorsal bending and deviation of the lumbar cord to the sac out of the spinal canal at the T8-T10 vertebral level but does not reveal the stalk. (f) Serial axial images of 3D-hT2WI (slice thickness 1.25 mm) show that the stalk is attached to the rostral part of the sac (f-1, yellow arrow) and the tethered cord deviates to the sac (f-2, 3, 4). The existence of another slender stalk is suspected (f-5, red arrow) and the caudal cord returns to the spinal canal. (g) Axial view of T2WI (slice thickness 4 mm) shows a narrow slit, indicating a type II SCM, at the caudal cord to the dorsally bending site. Axial T1-weighted image of the head (slice thickness 4 mm) (h) and sagittal T2WI of the craniovertebral junction (slice thickness 3 mm) (i) show ventriculomegaly with subependymal nodular heterotopias on both sides and Chiari malformation, respectively. (j, k) Microscopic view (j) and schematic drawing of the intraoperative findings (k). Opening the sac shows two stalks linking between the cord, protruding from the orifice of the spinal canal, and inner wall of the sac, are observed. Each stalk is severed at the attachment with the cord, and the cord is returned to the spinal canal. (l, m) Sagittal (l) and serial axial views of 3D-hT2WI (slice thickness 1.25 mm), performed on postoperative 39th day, demonstrate that the cord has been returned to the spinal canal with the successful untethering surgery. The dorsal bending of the cord improves to some extent, but it persists. Hydromyelic central canal is observed at the attachment of the stalk. Epidural fluid collection is observed. 3D-hT2WI: three-dimensional heavily T2-weighted imaging, HASTE: half-Fourier acquisition single-shot turbo spin-echo, SCM: split cord malformation, T2WI: T2-weighted image.
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F2
Prenatal MRI at 31+1 weeks did not reveal the anatomical relationship involving the cord, stalk, and sac, although the dorsal tenting of the subarachnoid space continuous with the sac was demonstrated (Fig. 2a). Hydrocephalus and Chiari malformation were also observed (Fig. 2b and 2c). Physical examination revealed a dorsal midline sac measuring 42 x 33 mm, with small blood vessels on the surface at the lower thoracic level (Fig. 2d). Sagittal 3D-hT2WI images showed severe dorsal bending and deviation of the spinal cord to the sac out of the spinal canal at the T8-T10 vertebral levels, but it did not show the stalk (Fig. 2e). The existence of another slender stalk was suspected (Fig. 2f-5), and the caudal cord returned to the spinal canal (Fig. 2f-4, 5, 6). Type II split cord malformation (SCM) was observed at the caudal cord to the dorsally bending site (Fig. 2g). Cranial MRI showed ventriculomegaly with subependymal nodular heterotopias on the both sides (Fig. 2h) and Chiari malformation (Fig. 2i). Ommaya's reservoir, untethering and repair surgery for the sac were performed. Opening the sac (Fig. 2d), two stalks linking the bending cord, protruding from the orifice of the spinal canal, and inner wall of the sac were observed after dissecting the surrounding connective tissue (Fig. 2j and k).
PMC8769447_02
(Patient 2). (a) Sagittal view of HASTE image (slice thickness 5 mm) performed at 31+1 weeks of gestation shows a dorsal tenting of the spinal subarachnoid space continuous with the sac, but it fails to reveal the exact anatomical relationship involving the cord, stalk and sac. Sagittal (b) and axial images (c) of cranial HASTE images (slice thickness 5 mm) show hydrocephalus and Chiari malformation. (d) Photograph showing a saccular skin lesion at the lower thoracic region. (e) Serial sagittal images of 3D-hT2WI (slice thickness 1.25 mm) demonstrates a severe dorsal bending and deviation of the lumbar cord to the sac out of the spinal canal at the T8-T10 vertebral level but does not reveal the stalk. (f) Serial axial images of 3D-hT2WI (slice thickness 1.25 mm) show that the stalk is attached to the rostral part of the sac (f-1, yellow arrow) and the tethered cord deviates to the sac (f-2, 3, 4). The existence of another slender stalk is suspected (f-5, red arrow) and the caudal cord returns to the spinal canal. (g) Axial view of T2WI (slice thickness 4 mm) shows a narrow slit, indicating a type II SCM, at the caudal cord to the dorsally bending site. Axial T1-weighted image of the head (slice thickness 4 mm) (h) and sagittal T2WI of the craniovertebral junction (slice thickness 3 mm) (i) show ventriculomegaly with subependymal nodular heterotopias on both sides and Chiari malformation, respectively. (j, k) Microscopic view (j) and schematic drawing of the intraoperative findings (k). Opening the sac shows two stalks linking between the cord, protruding from the orifice of the spinal canal, and inner wall of the sac, are observed. Each stalk is severed at the attachment with the cord, and the cord is returned to the spinal canal. (l, m) Sagittal (l) and serial axial views of 3D-hT2WI (slice thickness 1.25 mm), performed on postoperative 39th day, demonstrate that the cord has been returned to the spinal canal with the successful untethering surgery. The dorsal bending of the cord improves to some extent, but it persists. Hydromyelic central canal is observed at the attachment of the stalk. Epidural fluid collection is observed. 3D-hT2WI: three-dimensional heavily T2-weighted imaging, HASTE: half-Fourier acquisition single-shot turbo spin-echo, SCM: split cord malformation, T2WI: T2-weighted image.
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F2
Prenatal MRI at 31+1 weeks did not reveal the anatomical relationship involving the cord, stalk, and sac, although the dorsal tenting of the subarachnoid space continuous with the sac was demonstrated (Fig. 2a). Hydrocephalus and Chiari malformation were also observed (Fig. 2b and 2c). Physical examination revealed a dorsal midline sac measuring 42 x 33 mm, with small blood vessels on the surface at the lower thoracic level (Fig. 2d). Sagittal 3D-hT2WI images showed severe dorsal bending and deviation of the spinal cord to the sac out of the spinal canal at the T8-T10 vertebral levels, but it did not show the stalk (Fig. 2e). The existence of another slender stalk was suspected (Fig. 2f-5), and the caudal cord returned to the spinal canal (Fig. 2f-4, 5, 6). Type II split cord malformation (SCM) was observed at the caudal cord to the dorsally bending site (Fig. 2g). Cranial MRI showed ventriculomegaly with subependymal nodular heterotopias on the both sides (Fig. 2h) and Chiari malformation (Fig. 2i). Ommaya's reservoir, untethering and repair surgery for the sac were performed. Opening the sac (Fig. 2d), two stalks linking the bending cord, protruding from the orifice of the spinal canal, and inner wall of the sac were observed after dissecting the surrounding connective tissue (Fig. 2j and k).
(Patient 2). Histopathological findings of the rostral (a, b, c) and caudal stalks (d, e, f). (a) The rostral stalk includes a fibrocollagenous tissue embedded with GFAP-immunopositive neuroglial tissues (a) containing several neurons (b, black arrows). The attachment of the rostral stalk to the sac has a partial ependymal lining (black arrows in c) and it is densely infiltrated with neutrophils (blue arrows in c). The caudal stalk has an endodermal cyst lined by bronchial epithelium, including goblet cells (black arrows in d), and ciliated columnar epithelial cells (blue arrow in d) and arachnoid villi-like structures (black arrow in e). The sac to which the caudal stalk attached is covered by keratinizing stratified squamous epithelium with angiomatous dilated blood vessels (3f). Scale bars indicate 20 musigma. GFAP: glial fibrillary acidic protein.
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F3
The existence of another slender stalk was suspected (Fig. 2f-5), and the caudal cord returned to the spinal canal (Fig. 2f-4, 5, 6). Histopathologically, the rostral stalk included a fibrocollagenous tissue embedded with GFAP- immunopositive neuroglial tissues (Fig. 3a) containing several neurons (Fig. 3b). The attachment of the rostral stalk to the sac had a partial ependymal lining and was densely infiltrated with neutrophils (Fig. 3c). The caudal stalk also included a fibrocollagenous tissue embedded with GFAP-immunopositive neuroglial tissues, an endodermal cyst lined by bronchial epithelium (Fig. 3d), peripheral nerve bundles, and arachnoid villi-like structures (Fig. 3e). The sac to which the caudal stalk attached was covered by keratinizing stratified squamous epithelium with angiomatous dilated blood vessels (Fig. 3f).