Usefulness of three-dimensional T1-weighted spoiled gradient-recalled echo and three-dimensional heavily T2-weighted images in preoperative evaluation of spinal dysraphism

Diagnostic Utility of 3D Gradient-Echo MR Imaging Sequences through the Filum Compared with Spin-Echo T1 in Children with Concern for Tethered Cord

BACKGROUND AND PURPOSE

Fatty intrathecal lesions are a cause of tethered cord, and detection of these on spinal MR imaging is paramount. Conventional T1 FSE sequences are the mainstay of detecting fatty elements; however, 3D gradient-echo MR images, volumetric interpolated breath-hold examination/liver acquisition with volume acceleration (VIBE/LAVA), are popular, given the increased motion resistance. We sought to evaluate the diagnostic accuracy of VIBE/LAVA compared with T1 FSE for detection of fatty intrathecal lesions.

MATERIALS AND METHODS

In this retrospective, institutional review board-approved study, 479 consecutive pediatric spine MRIs obtained to evaluate cord tethering between January 2016 and April 2022 were reviewed. Inclusion criteria were patients who were 20 years of age or younger who underwent spine MRIs containing both axial T1 FSE and VIBE/LAVA sequences of the lumbar spine. The presence or absence of fatty intrathecal lesions was recorded for each sequence. If fatty intrathecal lesions were present, anterior-posterior and transverse dimensions were recorded. VIBE/LAVA and T1 FSE sequences were evaluated on 2 separate occasions (VIBE/LAVAs first followed by T1 FSE several weeks later) to minimize bias. Basic descriptive statistics compared fatty intrathecal lesion sizes on T1 FSEs and VIBE/LAVAs. Receiver operating characteristic curves were used to determine minimal fatty intrathecal lesion size detectable by VIBE/LAVA.

RESULTS

Sixty-six patients were included, with 22 having fatty intrathecal lesions (mean age, 7.2 years). T1 FSE sequences revealed fatty intrathecal lesions in 21/22 cases (95%); however, fatty intrathecal lesions on VIBE/LAVA were detected in 12/22 patients (55%). Mean anterior-posterior and transverse dimensions of fatty intrathecal lesions measured larger on T1 FSE compared with VIBE/LAVA sequences (5.4 × 5.0 mm versus 1.5 × 1.6 mm, respectively; P values = .039 anterior-posterior; .027 transverse).

CONCLUSIONS

While T1 3D gradient-echo MR images may have decreased the acquisition time and are more motion-resistant than conventional T1 FSE sequences, they are less sensitive and may miss small fatty intrathecal lesions.

Refractory CSF leakage following untethering surgery performed 10 months after birth for enlarging terminal myelocystocele associated with OEIS complex

Background:

Terminal myelocystocele (TMC) is an occult spinal dysraphism characterized by cystic dilatation of the terminal spinal cord in the shape of a trumpet (myelocystocele) filled with cerebrospinal fluid (CSF), which herniates into the extraspinal subcutaneous region. The extraspinal CSF-filled portion of the TMC, consisting of the myelocystocele and the surrounding subarachnoid space, may progressively enlarge, leading to neurological deterioration, and early untethering surgery is recommended.

Case Description:

We report a case of a patient with TMC associated with OEIS complex consisting of omphalocele (O), exstrophy of the cloaca (E), imperforate anus (I), and spinal deformity (S). The untethering surgery for TMC had to be deferred until 10 months after birth because of the delayed healing of the giant omphalocele and the respiration instability due to hypoplastic thorax and increased intra-abdominal pressure. The TMC, predominantly the surrounding subarachnoid space, enlarged during the waiting period, resulting in the expansion of the caudal part of the dural sac. Although untethering surgery for the TMC was uneventfully performed with conventional duraplasty, postoperative CSF leakage occurred, and it took three surgical interventions to repair it. External CSF drainage, reduction of the size of the caudal part of the dural sac and use of gluteus muscle flaps and collagen matrix worked together for the CSF leakage.

Conclusion:

Preoperative enlargement of the TMC, together with the surrounding subarachnoid space, can cause the refractory CSF leakage after untethering surgery because the expanded dural sac possibly increases its own tensile strength and impedes healing of the duraplasty. Early untethering surgery is recommended after recovery from the life-threatening conditions associated with OEIS complex.

Spinal cord deformity with aggravation of tethering in saccular limited dorsal myeloschisis during the first 2 months of life

Background

Although the optimal timing of prophylactic untethering surgery for limited dorsal myeloschisis (LDM) with intact or subtle neurological findings diagnosed at birth remains undetermined, intentional delayed surgery is commonly used for flat and tail-like LDM. Conversely, for saccular LDM, early surgery is indicated during the postnatal period because it prevents rupture of the sac. We treated a saccular LDM patient, in whom intentional delayed surgery was selected because the sac was thickly covered with normal skin. We describe the clinical course of the case and discuss the optimal timing of the surgery.

Case Description

The patient had a dorsal midline sac in the upper lumbar region. Initial magnetic resonance imaging (MRI) after birth revealed a tethering tract that began at the dome of the sac and joined the lumbar cord. Dorsal bending of the cord at the stalk-cord union and invagination of the cord into the sac were noted. At 2 months, he was neurologically normal; however, the second MRI examination revealed that the cord tethering was aggravated. The cord was markedly displaced dorsally and to the left, with deviation of the cord to the sac out of the spinal canal. Following untethering surgery, the spinal cord deformity markedly improved.

Conclusion

Early surgery may be recommended for saccular LDM when tethering is present, including dorsal bending of the cord at the stalk-cord union and invagination of the cord into the sac observed on detailed MRI examination, even if the sac has no risk of rupture.

Surgical histopathology of a filar anomaly as an additional tethering element associated with closed spinal dysraphism of primary neurulation failure

Background:

Closed spinal dysraphism of primary neurulation failure could be associated with filar anomalies, such as filar lipoma or thickened and tight filum terminale (TFT), resulting from impaired secondary neurulation. Retained medullary cord (RMC) is a remnant of the cavitary medullary cord originating from the secondary neurulation failure. Some filar lipomas are known to contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissues (E-LC w/NGT), that is, a characteristic histopathology of RMC. To clarify the embryological background of these filar anomalies, we evaluated the histopathological findings.

Methods:

Among 41 patients with lesions of primary neurulation failure who underwent initial untethering surgery, the filum including cord-like structure (C-LS) was additionally resected in 10 patients (five dorsal and transitional lipomas; five limited dorsal myeloschisis). We retrospectively analyzed the clinical, neuroradiological, intraoperative, and histopathological findings.

Results:

Among 10 patients, two patients were diagnosed with RMC based on morphological features and intraoperative neurophysiological monitoring. The diagnosis of filar lipoma was made in six patients, since various amounts of fibroadipose tissue were histopathologically noted in the filum. Two patients were diagnosed with TFT, since the filum was composed solely of fibrocollagenous tissue. E-LC w/NGT was noted not only in both C-LSs of RMCs but also in two out of six fila both with filar lipomas and fila with TFTs.

Conclusion:

These findings provide further evidence for the idea that entities, such as filar lipoma, TFT, and RMC, can be considered consequences of a continuum of regression failure occurring during late secondary neurulation.

Saccular Limited Dorsal Myeloschisis with Spinal Cord Deviation out of the Spinal Canal to the Sac

Saccular limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the saccular skin lesion to the underlying spinal cord. Since untethering surgery during the early postnatal period is often indicated to prevent sac rupture, saccular LDM should be distinguished from myelomeningocele (MMC) during the perinatal period. We treated two patients with the spinal cord deviation from the spinal canal to the sac, which mimicked a prolapse of the neural placode into the MMC sac. In patient 1, pre- and postnatal magnetic resonance imaging (MRI) revealed that the spinal cord was strongly tethered to the thick stalk. During surgery, the dorsally bent cord and stalk were united, and the border between these two was determined with intraoperative neurophysiological mapping (IONM). In patient 2, the spinal cord was tethered to two slender stalks close to each other, which was visible with the combined use of sagittal and axial postnatal three-dimensional heavily T2-weighted imaging (3D-hT2WI). The preoperative MRI hallmark of saccular LDM is the visualization of a stalk that links the bending cord and sac. Complete untethering surgery to return the cord into the spinal canal and correct its dorsal bending is recommended.

Two Cases of Large Filar Cyst Associated with Terminal Lipoma: Relationship with Retained Medullary Cord

BACKGROUND

A small, incidental filar cyst associated with terminal lipoma is thought to be caused by failure of secondary neurulation; however, the precise embryologic background is not fully understood. Retained medullary cord (RMC) also originates from late arrest of secondary neurulation. The central feature of RMC histopathology is a central canal-like ependyma-lined lumen with surrounding neuroglial core.

CASE DESCRIPTION

We surgically treated 2 patients with a large cyst in the rostral part of the filum and lipoma in the caudal filum. At cord untethering surgery, the filum was severed at the caudal part of the cyst. Histopathologically, the filar cyst was the cystic dilatation of the central canal-like structure at the marginal part of the lipoma. The central canal-like structure was continuous caudally in the lipoma, and its size decreased toward the caudal side.

CONCLUSIONS

The present findings support the idea raised by Pang et al that entities such as filar cyst, terminal lipomas, and RMC can all be considered consequences of a continuum of regression failure occurring during late secondary neurulation.

Terminal syringomyelia associated with lumbar limited dorsal myeloschisis

PURPOSE

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural tethering stalk linking the skin lesion to the underlying spinal cord. Terminal syringomyelia, which is located at the lower third of the cord, is often associated with a tethered cord caused by various spinal dysraphisms; however, terminal syringomyelia has not been documented in LDM. The purpose of this study was to clarify the pathophysiological mechanisms of syringomyelia in LDM.

METHODS

In our 16 patients with lumbar LDM, three patients had terminal syringomyelia. We retrospectively analyzed the clinical, neuroradiological, intraoperative, and histopathological findings for these patients, with particular attention to the clinical course of the syrinx.

RESULTS

Patient 1 had a saccular skin lesion and patients 2 and 3 had flat lesions. In all patients, the syringomyelic cavity was located in the lower thoracolumbar cord, immediately rostral to the stalk-cord attachment at the lumbar level. The caudal pole of the syrinx extended to the thickened stalk at the attachment instead of at the caudal cord. Patient 3 had another syrinx in the stalk itself. The longitudinal axis of the syrinx and central canal coincided with the traveling angle of the LDM stalk at the stalk-cord attachment. In patient 1, histology revealed an ependyma-lined central canal in both the LDM stalk and meningocele sac. Patients 1 and 2 underwent syringostomy, but long-term effects were not obtained. Preoperative spontaneous resolution occurred in patient 3.

CONCLUSIONS

The histological findings in patient 1 supported the idea that segmental myelocystocele is involved in the development of saccular LDM. The hydromyelic central canal herniates and distends the stalk, resulting in the formation of the myelocystocele. It is possible that the hydromyelic central canal also distends the stalk of flat LDM lesions. The syrinx in patient 3 differed from that in patients 1 and 2, in that the syrinx resolved spontaneously. Further studies are needed to clarify the outcomes of syrinxes associated with LDM stalks.

Retained medullary cord with sacral subcutaneous meningocele and congenital dermal sinus

BACKGROUND

A retained medullary cord (RMC) is a rare closed spinal dysraphism with a robust elongated cord-like structure extending continuously from the conus medullaris to the dural cul-de-sac that is caused by late arrest of secondary neurulation. Five patients with RMC extending to an associated sacral subcutaneous meningocele have been reported.

CASE PRESENTATION

We report an additional patient with RMC, in whom a congenital dermal sinus (CDS) was found in the caudal portion of the RMC. At the age of 3 days, the patient underwent surgery consisting of meningocele excision and cord untethering, and CDS was noted histologically in the proximal cut end of the RMC. During a second surgery at the age of 5 months, after determining the exact border of the nonfunctional RMC and the true conus by neurophysiological mapping, we removed the entire length of the remnant RMC, including newly developed epidermoid cysts in the CDS.

CONCLUSION

Although the exact pathoembryogenesis of concurrent RMC and CDS is unknown, an associated subcutaneous meningocele, caused by failure of primary neurulation, could be involved. Surgeons should be aware of the possibility of the coexistence of CDS when dealing with RMCs that extend out to the extradural space.

Neurosurgical Pathology and Management of Limited Dorsal Myeloschisis Associated with Congenital Dermal Sinus in Infancy

BACKGROUND

Because of the shared origin of limited dorsal myeloschisis (LDM) and congenital dermal sinus (CDS), CDS elements may be found within the fibroneural LDM stalk. When part of the CDS invested in the intradural stalk is left during untethering surgery, inclusion tumors such as dermoid cysts may develop. However, the most appropriate surgical strategy for LDM with CDS is still under debate.

METHODS

Of 19 patients with LDM, 3 (15.8%) had histologically verified CDS elements. We retrospectively analyzed the clinicopathological findings of these patients.

RESULTS

In patient 1, the entire stalk including a tiny dermoid cyst at the intradural stalk could be resected through two-level laminectomy during untethering at 6 months of age. In patients 2 and 3, the stalk appeared to be a typical LDM stalk during the initial surgery at 18 and 7 days, respectively; however, CDS was histologically diagnosed in the proximal severed end of the stalk. Postoperative three-dimensional heavily T2-weighted imaging demonstrated spherical enlargement of the remnant stalk, and the entire length of the remnant stalk including newly developed dermoid was resected during the second surgery at 3 years 11 months and 11 months, respectively. Histopathologically, glial fibrillary acidic protein-immunopositive neuroglial tissues and CDS elements were mainly located at the proximal and distal sites of the stalk, respectively, supporting the "dragging down and pulling up" theory. In patients 2 and 3, however, the proximal head of the dermoid cyst passed the distal head of the neuroglial tissues and located at the stalk-cord attachment.

CONCLUSION

Surgeons should be aware of the approximately 10% possibility of the coexistence of CDS when managing infant LDM. However, the recommendation for excision of the entire length of the LDM stalk in all patients should be more carefully made because such a strategy may result in an unnecessary extent of laminotomy/laminectomy for most patients with pure LDM. However, once the postoperative histological examination reveals coexistence of CDS in the resected proximal part of the stalk, the entire length of the remnant stalk should be excised as soon as possible.

Human tail-like cutaneous appendage with a contiguous stalk of limited dorsal myeloschisis

PURPOSE

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the skin lesion to the underlying spinal cord. On account of the external skin lesion, all LDMs are either flat (nonsaccular) or saccular, and a human tail-like cutaneous appendage has not been reported.

METHODS

In our 14 LDM patients, 2 had tail-like appendages. We retrospectively analyzed the relationship between the appendage and the LDM tract from the clinicopathological findings of these 2 patients.

RESULTS

Preoperative magnetic resonance imaging including three-dimensional heavily T2-weighted images demonstrated an intradural tethering tract, but failed to reveal the precise communication with the appendage. However, surgery revealed the extradural and intradural slender stalk, starting at the base of appendage and running through the myofascial defect. Histological examination demonstrated that there was a tight anatomical relationship between the fibroadipose tissue of the appendage and the fibrocollagenous LDM stalk.

CONCLUSION

When there is potential for an LDM stalk in patients with an appendage, a meticulous exploration of the stalk leading from an appendage is required. Clinicians should be aware of possible morphological variations of skin lesions associated with LDM.

Surgical histopathology of limited dorsal myeloschisis with flat skin lesion

PURPOSE

Limited dorsal myeloschisis (LDM) is characterized by two invariable features: a focal closed neural tube defect and a fibroneural stalk linking the skin lesion to the underlying spinal cord. Although detailed histopathological findings of the LDM stalk were originally described by Pang et al., the precise relationship between the histopathological findings and clinical manifestations including intraoperative findings has not been fully determined.

METHODS

We retrospectively analyzed the histopathological findings of the almost entire stalk and their relevance to the clinical manifestations in six Japanese LDM patients with flat skin lesions.

RESULTS

Glial fibrillary acidic protein (GFAP)-immunopositive neuroglial tissues were observed in three of the six patients. Unlike neuroglial tissues, peripheral nerve fibers were observed in every stalk. In four patients, dermal melanocytosis, "Mongolian spot," was seen surrounding the cigarette-burn lesion. In three of these four patients, numerous melanocytes were distributed linearly along the long axis of the LDM stalk, which might represent migration of melanocytes from trunk neural crest cells during formation of the LDM stalk.

CONCLUSION

Immunopositivity for GFAP in the LDM stalk was observed in as few as 50% of our patients, despite the relatively extensive histopathological examination. We confirm that the clinical diagnosis of LDM should be made based on comprehensive histopathological examination as well as clinical manifestations. The profuse network of peripheral nerve fibers in every stalk and the high incidence of melanocyte accumulation associated with dermal melanocytosis might assist the histopathological diagnosis of LDM.

Slender Stalk with Combined Features of Saccular Limited Dorsal Myeloschisis and Congenital Dermal Sinus in a Neonate

Limited dorsal myeloschisis (LDM) and congenital dermal sinus (CDS) originate from incomplete disjunction between the cutaneous and neural ectoderms. Some LDM stalks have been found to have elements of a CDS or dermoid cyst. We surgically treated a saccular lesion in the lumbosacral region of a 7-day-old male neonate. Although fetal magnetic resonance imaging (MRI) failed to reveal a stalk, postnatal MRI including three-dimensional heavily T2-weighted imaging demonstrated a stalk originating from the lumbar cord and extending caudally to enter the lumbosacral meningocele sac. During untethering surgery, we found that the stalk was slender, with a diameter of 0.7-0.8 mm, but otherwise appeared to be a typical LDM stalk. Histopathological examination revealed that the fibrocollagenous stalk contained glial fibrillary acidic protein-immunopositive neuroglial tissues and stratified squamous epithelium. The present report describes the first documented case of a stalk with combined features of saccular LDM and CDS in a neonate. Since cutaneous ectodermal tissue is likely to remain in the remnant stalk, this patient requires careful monitoring to detect the potential development of a dermoid cyst.

Limited dorsal myeloschisis with no extradural stalk linking to a flat skin lesion: a case report

BACKGROUND

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the skin lesion to the underlying spinal cord. CASE PRESENTATION : A 7-month-old girl with a lumbosacral "cigarette-burn" flat skin lesion underwent untethering surgery. The intradural tethering stalk appeared to originate at the dural wall and join the cord with no extradural stalk linking to the skin lesion. Histological examination of the intradural stalk revealed glial fibrillary acidic protein-immunopositive neuroglial tissues in the fibrocollagenous band, which is the central histopathological feature of an LDM stalk.

CONCLUSION

It is conceivable that the LDM stalk in our patient was originally linked to the skin lesion and subsequently regressed and was replaced by mature adipose tissue. We should be mindful of possible variations in the morphological features of LDM.

Enlargement of sacral subcutaneous meningocele associated with retained medullary cord

BACKGROUND

A retained medullary cord (RMC) is a rare closed spinal dysraphism with a robust elongated neural structure continuous from the conus and extending to the dural cul-de-sac. Four cases of RMC extending down to the base of an associated subcutaneous meningocele at the sacral level have been reported.

CLINICAL PRESENTATION

We report an additional case of RMC, in whom serial MRI examination revealed an enlargement of the meningocele associated with RMC over a 3-month period between 8 and 11 months of age, when he began to stand. At the age of 12 months, untethering of the cord was performed. Histologically, the presence of ependyma-lined central canals in the dense neuroglial cores was noted in all cord-like structures in the intradural and intrameningocele sacs and at the attachment to the meningocele.

CONCLUSION

It is conceivable that the hydrodynamic pressure with standing position and the check valve phenomenon were involved in meningocele enlargement. We should be mindful of these potential morphological changes.

Retained medullary cord extending to a sacral subcutaneous meningocele

BACKGROUND

A retained medullary cord (RMC) is a rare closed spinal dysraphism with a robust elongated neural structure continuous from the conus and extending to the dural cul-de-sac. One case extending down to the base of a subcutaneous meningocele at the sacral level has been reported.

CLINICAL PRESENTATION

We report on three cases of closed spinal dysraphism, in which a spinal cord-like tethering structure extended out from the dural cul-de-sac and terminated at a skin-covered meningocele sac in the sacrococcygeal region, which was well delineated in curvilinear coronal reconstructed images of 3D-heavily T2-weighted images (3D-hT2WI). Intraoperative neurophysiology revealed the spinal cord-like tethering structure was nonfunctional, and histopathology showed that it consisted of central nervous system tissue, consistent with RMC. The tethering structure histologically contained a glioneuronal core with an ependymal-like lumen and smooth muscle, which may indicate developmental failure during secondary neurulation.

CONCLUSIONS

When the RMC extending to a meningocele is demonstrated with the detailed magnet resonance imaging including 3D-hT2WI, decision to cut the cord-like structure for untethering of the nervous tissue should be made under careful intraoperative neurophysiological monitoring.

Neurosurgical pathology of limited dorsal myeloschisis

PURPOSE

The term limited dorsal myeloschisis (LDM) was used by Pang et al. (2010) to describe a distinct clinicopathological entity. LDMs are characterized by two invariable features: a focal-closed neural tube defect and a fibroneural stalk that links the skin lesion to the underlying spinal cord.

METHODS

We retrospectively analyzed the neurosurgical pathologic findings of four LDM patients.

RESULTS

Case 1 had a saccular skin lesion with nonterminal abortive myelocystocele at T11-12. Cases 2, 3, and 4 had a non-saccular (flat) skin lesion in the lumbosacral region. The morphologic features of the lesion in case 2 were those of meningocele manque. Cases 3 and 4 had accompanying non-LDM anomalies, caudal-type lipoma and type II split-cord malformation with neurenteric cyst, respectively. At preoperative diagnosis of the LDM stalk, magnetic resonance imaging, including 3D heavily T2-weighted image was useful; however, minute findings were often missed in the complicated cases 3 and 4. All patients had a favorable outcome following untethering of the stalk from the cord. The central histopathological feature of the LDM stalk is neuroglial tissue in the fibrocollagenous band; however, the stalk in cases 2 and 4 did not have glial fibrillary acidic protein-immunopositive neuroglial tissues.

CONCLUSIONS

Therefore, the diagnosis of LDM should be made based on comprehensive evaluation of histologic and clinical findings.

Ependyma-Lined Canal with Surrounding Neuroglial Tissues in Lumbosacral Lipomatous Malformations: Relationship with Retained Medullary Cord

BACKGROUND

An ependyma-lined canal with surrounding neuroglial tissues can be present in lumbosacral lipomatous malformations; however, the precise embryological significance is still unclear.

METHOD

Six out of 50 patients with lipomatous malformations had ependymal structures. We retrospectively analyzed the clinical, neuroradiological, and histological findings of these patients to demonstrate the relationship with the embryological background of the retained medullary cord (RMC), which normally regresses, but was retained here because of late arrest of secondary neurulation.

RESULTS

Five (13.9%) of 36 patients with filar and caudal types and 1 of 3 lipomyelomeningoceles had ependymal structures, while none with dorsal and transitional types had these tissues. Histologically, the ependymal structures surrounded by neuroglial tissue and containing various amounts of adipose tissue bear a striking resemblance to the ependymal structures in RMC.

CONCLUSION

The 13.9% incidence of association between the ependymal structures and filar and caudal types is thought to be because of second ary neurulation failure with the same embryological background as that of RMC. Dorsal and transitional types, resulting from primary neurulation failure, therefore, did not have ependymal structures.

Lateral lipomyelomeningocele of the hemicord with split cord malformation type I revealed by 3D heavily T2-weighted MR imaging

BACKGROUND

Lipomyelomeningocele (LMMC) is defined by a low-lying tethered spinal cord protruding posteriorly from the spinal canal and terminating in a lipomatous mass in the subcutaneous meningeal sac. The coexistence of LMMC with split cord malformation (SCM) is rare.

CLINICAL PRESENTATION

We report on a patient with laterally protruded LMMC arising from the hemicord of SCM type I. Direct coronal and axial views (instead of sagittal views) of 3D heavily T2-weighted MR imaging (3D-hT2WI) clearly demonstrated the topographical relationship between both of the hemicords, the bony septum, and nerve roots in the right subcutaneous meningeal sac.

CONCLUSION

Combined use of axial and coronal images of 3D-hT2W is useful for visualization and surgery of such a complicated anomaly.

Sequential morphological change of Chiari malformation type II following surgical repair of myelomeningocele

PURPOSE

To document long-term morphological changes of Chiari type II malformation (CM-II) following closure of spina bifida manifesta (SBM).

METHODS

We retrospectively evaluated postnatal magnetic resonance images of the CM-II and posterior fossa (PF) in 28 consecutive cases. We measured changes in vertebral level and length of the cerebellar peg (CP), cerebrospinal fluid (CSF) spaces anterior and posterior to the cerebrospinal junction, PF area, and the anteroposterior diameters of the foramen magnum (FM) and C1 vertebra. We examined the morphological differences between the cases with and without ventriculoperitoneal (VP) shunting and derived predicted means by nonlinear mixed-effect modeling.

RESULTS

At birth, there were significant differences in CP length, PF area, and FM and C1 diameters between those who underwent VP shunting and those who did not. In cases with a CP below C1, VP shunting was required in every case but one. In those with visible CSF space at birth, VP shunts were not required. In 17 of 18 cases with a CP below C1, the vertebral level ascended by mean two vertebral levels (range 0-5 levels) within 4-6 months of delivery. In the remaining case, slowly progressive hydrocephalus and delayed CP descent required VP shunting at 8 months. Predicted mean CP length and FM and C1 diameters were greater in those who underwent VP shunting, but there was no difference in predicted mean PF area.

CONCLUSION

The morphology of CM-II and the presence of hydrocephalus influence each other in children who have undergone postnatal SBM repair.