The local cord lesion in neurospinal dysraphism (meningomyelocele)

Dorsal bony spur in pediatric split cord malformations: eight-year experience from a tertiary care hospital

INTRODUCTION

Dorsal spurs in Type I split cord malformations (SCM-I) are infrequent findings. The pathogenesis of the same is debatable. The objective of this study is to analyze our experience with SCM-I patients having dorsal bony spurs.

METHODOLOGY

Retrospective analysis of SCM patients operated from 2010 to 2017 was performed. Their demographic profile, clinic-radiological features, operative findings, and outcome following surgery were recorded.

RESULTS

Twenty-four cases of Type I SCM harboring dorsal bony spurs were identified with mean age of 4.96 years. The commonest split site was lumbar, documented in 62.5%. Scoliosis was observed in 58.3%. Pre-operative neurological deficits were seen in 66.6% cases with asymmetric weakness of limbs seen in 16.6%. There was no new neurological deficit observed post-operatively.

CONCLUSIONS

This is the largest series of dorsal spurs occurring in SCM, reported in literature so far. Meticulous pre-operative evaluation and imaging are important to identify dorsal spurs for appropriate management and good clinical outcome. Differentiating dorsal spur from ventral spur is important as it has a bearing on surgical approach.

Systematic Classification of Spina Bifida

Spina bifida (SB) is an umbrella term for multiple conditions characterized by misclosure of vertebral arches. Neuropathologic findings in SB cases are often reported with imprecise and overlapping terminology. In view of the increasing identification of SB-associated genes and pathomechanisms, the precise description of SB subtypes is highly important. In particular, the term "myelomeningocele" is applied to various and divergent SB subtypes. We reevaluated 90 cases with SB (58 prenatal; 32 postnatal). The most frequent SB phenotype in our cohort was myeloschisis, which is characterized by an open neural plate with exposed ependyma (n = 28; 31.1%). An open neural plate was initially described in only in two-thirds of the myeloschisis cases. An additional 21 cases (23.3%) had myelomeningocele; 2 cases (2.2%) had a meningocele; and 21 cases (23.3%) had an unspecified SB aperta (SBA) subtype. Overall, the SB phenotype was corrected in about one-third of the cases. Our findings highlight that "myelomeningocele" and "SB aperta" cannot be used as synonymous terms and that myeloschisis is an underreported SB phenotype. Based on our findings and a review of literature we propose a classification of SB subtypes in SB occulta and the 3 SBA subtypes, meningocele, myelomeningocele, and myeloschisis.

Myelomeningocele Closure: An Embryological Perspective

Myelomeningoceles (MMCs) represent a localized failure of primary neurulation during the fourth week of embryonic development. There are a number of misconceptions concerning the proper identification, classification, and surgical repair of these lesions. To provide surgeons with a working knowledge of early neural embryology as it relates to MMC closure as a localized failure of primary neurulation. We review the embryology of early neural development as a means of providing neurosurgeons with a better understanding of MMC closure techniques. Early neural development predicts the anatomy of MMC and knowledge of embryology helps guide repair. Repair of MMC is enhanced by knowing early neural development.

Early Treadmill Practice in Infants Born With Myelomeningocele: A Pilot Study

PURPOSE

To determine the feasibility of an early treadmill training program for infants with myelomeningocele (MMC) and to measure changes in overt infant motor development and control, including mechanisms underlying the overt changes.

METHODS

Ten infants with MMC were initially enrolled: 8 infants completed 12 consecutive months of training, and 2 completed 6 months of training. Training consisted primarily of home-based, parent-administered treadmill stepping practice 5 days per week, 10 minutes per day starting within 6 months postbirth. We measured motor milestones, treadmill steps, spinal-level reflexes, and body composition.

RESULTS

Infants showed earlier acquisition of gross motor skills than previously reported. The number of alternating steps performed increased, indicating more complex neuromotor control and strength. Integrity of monosynaptic pathways and body composition were improved after controlling for chronological age.

CONCLUSIONS

This study demonstrates the feasibility of using early, home-based treadmill training for infants with MMC starting within 6 months postbirth.

Overview on neural tube defects: From development to physical characteristics

Neural tube defects (NTDs) are the second most common congenital malformations in humans affecting the development of the central nervous system. Although NTD pathogenesis has not yet been fully elucidated, many risk factors, both genetic and environmental, have been extensively reported. Classically divided in two main sub-groups (open and closed defects) NTDs present extremely variable prognosis mainly depending on the site of the lesion. Herein, we review the literature on the histological and pathological features, epidemiology, prenatal diagnosis, and prognosis, based on the type of defect, with the aim of providing important information based on NTDs classification for clinicians and scientists.

Characteristics and Clinical Relevance of the Osseous Spur in Patients with Congenital Scoliosis and Split Spinal Cord Malformation

BACKGROUND

The natural history of split spinal cord malformation (SCM) is still unclear. Knowledge of the characteristics of the osseous spur and its relationship with the spinal deformity may allow early identification of patients with a higher risk of a neurological deficit and enhance surgical decision-making.

METHODS

Eighty-five consecutive patients with congenital scoliosis and type-I SCM who had undergone surgical treatment at our hospital from May 2000 to December 2013 were identified retrospectively. There were 22 male and 63 female patients with an average age of 13.9 years at the time of surgery. Preoperative clinical and radiographic data were collected to investigate the characteristics of the scoliosis and the osseous spur. Two groups were identified on the basis of whether the patients had intact neurological function (Group A) or a neurological deficit (Group B).

RESULTS

There were 52 patients (61%) in Group A (intact neurological function) and 33 patients (39%) in Group B (neurological deficit). There were no significant differences in the demographic distribution, curve magnitude, or length and thickness of the osseous spur between the 2 groups. In Group A, the location of the osseous spur relative to the apex of the major curve was proximal in 13 patients (25%), distal in 28 (54%), and central in 11 (21%). In Group B, the osseous spur was proximal in 7 (21%), distal in 8 (24%), and central in 18 (55%). The 2 groups differed significantly with respect to the location of the osseous spur (chi square = 10.898, p = 0.004). Group-B patients had a higher proportion of patients with kyphotic deformity (42%) than Group A (10%). The ratio of the diameters of the hemicords (concave side divided by convex side) differed significantly between the 2 groups (0.98 for Group A versus 0.89 for Group B, p = 0.030).

CONCLUSIONS

The neurological status in patients with congenital scoliosis and type-I SCM appears to be closely related to the location of the osseous spur relative to the congenital scoliosis. An osseous spur at the apex of the scoliosis may be related to a higher risk of developing a neurological deficit, especially in patients with kyphotic deformity. Asymmetric splitting of the spinal cord may contribute to neurological deficits.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Cellular Profiles and Molecular Mediators of Lesion Cascades in the Placode in Human Open Spinal Neural Tube Defects

Myelomeningoceles (mmc) are clinically challenging CNS malformations. Although improvement in their management has been achieved with respect to antenatal diagnosis, prevention, and fetal surgery, the cellular mechanisms of damage in the neural placode are poorly understood. We aimed to identify cellular and molecular factors in lesion amplifying cascades in mmc placodes. Seventeen mmc specimens obtained during reconstructive surgery that harbored sufficient neuroepithelial tissue were investigated. Normal adult and stillborn spinal cord tissue served as controls. Placodes exhibited similar cellular profiles with consistent neuronal marker expression, elevated GFAP-/vimentin immunoreactivity in all, and CD3/CD11b/CD68-immunolabeling in some cases. Increased expression of pro-inflammatory (tumor necrosis factor, interleukin-1β [Il-1β]/IL-1 receptor type 1 [IL-R1]) and neuroprotective erythropoietin/erythropoietin receptor (Epo/EpoR) cytokines was detected by immunohistochemistry, double-fluorescence labeling, and real-time RT-PCR. In all cases, there was a multi-cellular induction of IL-1β and IL1-R1. EpoR and Epo immunoreactivity was elevated in some cases with neuronal expression patterns. Epo was further co-expressed with HIF-1/-2α, which paralleled Epo induction in the corresponding placodes. These observations confirm the induction of cellular and molecular alterations in human mmc placodes that resemble the secondary lesion cascades induced by spinal cord injury. The pro-inflammatory and neuroprotective cytokine expression in mmc placodes may represent new targets for the treatment of open neural tube defects.

Trans-amniotic stem cell therapy (TRASCET) minimizes Chiari-II malformation in experimental spina bifida

PURPOSE

We sought to study the impact of trans-amniotic stem cell therapy (TRASCET) in the Chiari-II malformation in experimental spina bifida.

METHODS

Sprague-Dawley fetuses (n=62) exposed to retinoic acid were divided into three groups at term (21-22 days gestation): untreated isolated spina bifida (n=21), isolated spina bifida treated with intra-amniotic injection of concentrated, syngeneic, labeled amniotic fluid mesenchymal stem cells (afMSCs) on gestational day 17 (n=28), and normal controls (n=13). Analyses included measurements of brainstem and cerebellar placement on high resolution MRI and histology. Statistical comparisons included ANOVA.

RESULTS

In parallel to the expected induced coverage of the spina bifida in the afMSC-treated group (P<0.001), there were statistically significant differences in brainstem displacement across the groups (P<0.001), with the highest caudal displacement in the untreated group. Significant differences in cerebellar displacement were also noted, albeit less pronounced. Pairwise comparisons were statistically significant, with P=0.014 between treated and normal controls in caudal brainstem displacement and P<0.001 for all other comparisons. Labeled afMSCs were identified in 71% of treated fetuses.

CONCLUSIONS

Induced coverage of spina bifida by TRASCET minimizes the Chiari-II malformation in the retinoic acid rodent model, further suggesting it as a practical alternative for the prenatal management of spina bifida.

Fetal syringomyelia

We explored the prevalence of syringomyelia in a series of 113 cases of fetal dysraphism and hindbrain crowding, of gestational age ranging from 17.5 to 34 weeks with the vast majority less than 26 weeks gestational age. We found syringomyelia in 13 cases of Chiari II malformations, 5 cases of Omphalocele/Exostrophy/Imperforate anus/Spinal abnormality (OEIS), 2 cases of Meckel Gruber syndrome and in a single pair of pyopagus conjoined twins. Secondary injury was not uncommon, with vernicomyelia in Chiari malformations, infarct like histology, or old hemorrhage in 8 cases of syringomyelia. Vernicomyelia did not occur in the absence of syrinx formation. The syringes extended from the sites of dysraphism, in ascending or descending patterns. The syringes were usually in a major proportion anatomically distinct from a dilated or denuded central canal and tended to be dorsal and paramedian or median. We suggest that fetal syringomyelia in Chiari II malformation and other dysraphic states is often established prior to midgestation, has contributions from the primary malformation as well as from secondary in utero injury and is anatomically and pathophysiologically distinct from post natal syringomyelia secondary to hindbrain crowding.

Split cord malformation types I and II: a personal series of 131 patients

PURPOSE

A personal series of 131 patients with split cord malformation (SCM) operated on is presented.

METHODS

Age, gender, symptoms and signs, radiological and operative findings, complications, associated anomalies, outcome, and pathological specimens were analyzed.

RESULTS

There were 88 girls (73 %) and 43 boys (27 %). The female predominance was slightly more remarkable in type I SCMs than in type II SCMs. The presenting symptoms can be summarized as skin lesions, spina bifida aperta, scoliosis or kyphoscoliosis, sphincter disturbance, foot deformities and weakness, and/or atrophy in the lower extremities. The ages of patients with neurological deficits and orthopedic deformities were significantly older than those without deficits (P = 0.030). The duration of symptoms was longer in the patients with neurological deficits and orthopedic deformities than that in those without deficits (P = 0.00095). In six patients, composite SCMs were present. Only one patient with a type II SCM did not have an associated spinal cord lesion. A type I SCM was more frequently encountered in patients with spina bifida (P < 0.0005). Transient postoperative complications were seen in 29 patients (22 %). There was no permanent complication. Retethered cord syndrome developed in five patients with a type I SCM.

CONCLUSIONS

The risk of neurological and orthopedic deficits increases with the age of the patient. The risk of permanent deficit after surgery is very low. The whole spine must be examined for additional lesions. All patients should be surgically treated when diagnosed, especially before the development of orthopedic and neurological manifestations, and all associated lesions should also be treated at the same session.

Sensory tract abnormality in the chick model of spina bifida

Spina bifida aperta (SBA) is an open neural tube defect that occurs during the embryonic period. We created SBA chicks by incising the roof plate of the neural tube in the embryo. The area of the dorsal funiculus was smaller in the SBA chicks than in the normal controls. Additionally, the SBA group had fewer nerve fibres in the dorsal funiculus than the normal controls. The pathway of the ascending sensory nerves was revealed by tracing the degenerated nerve fibres using osmification. We cut the sciatic nerve (L5) of the control and SBA chicks at the central end of the dorsal root ganglion 1 day after hatching and fixed the tissue 3 days later. Degenerated sensory nerve fibres were observed in the ipsilateral dorsal funiculus in the control chicks. In contrast, degenerated sensory nerve fibres were observed in the ipsilateral and contralateral dorsal, ventral and lateral funiculi of the spinal cord in the SBA chicks. Consequently, fewer sensory nerve fibres ascended to the thoracic dorsal funiculus in the SBA chicks than in the normal controls. This is the first report of abnormal changes in the ascending sensory nerve fibres in SBA.

Developmental delay in islet-1-positive motor neurons in chick spina bifida

Spina bifida aperta (SBA) is a congenital malformation of the spinal cord with complications such as spinal ataxia and bowel and bladder dysfunction. We have developed a chick model with surgery-induced SBA that shows spinal ataxia after hatching. In the present study, motor neurons in the early stages in chicks with and without SBA were observed by immunohistochemical staining with a monoclonal antibody against Islet-1, a motor neuron marker. Delay in migration and maturation of motor neurons was observed in SBA. Although the final numbers of Islet-1-positive neurons in these two groups were not different, a defect in the production and elimination of excess motor neurons in the early developmental stages in the SBA group may be involved in the pathological mechanism of the motor complications of this disease.

The embryogenesis of trypan-blue induced spina bifida aperta and short tail in the rat

The study of litters from 140 Wistar-derived rats injected with trypan blue during gestation leads to conclusion that a myelocele can result from faulty closure of the neural plate and that this is accompanied in many cases by blebs in the paraxial mesoderm. Haematomata usually underlie the open neural plate at an early stage and they form by extravasation of blood from the dorsal aortae into the blebs. Local ventral deflection of the notochord beneath a myelocele probably results from delayed separation of the notochord from the hindgut. Complete failure of separation and abnormality induced in the tail-bud could result in sacral agenesis and/or a short tail. All these malformations may result from varying severity of the action of the trypan blue at different developmental stages.

Heterotopic dorsal-root ganglion cells around the spinal cord in children with spina bifida aperta

Sixty-three of 95 cords from children with spina bifida aperta had associated heterotopic ganglion cells, usually located in dorsal nerve roots posterior or lateral to the cord. Heterotopic cells were more common in cords with complete or partial diplomyelia, and the largest number was found in the upper sacral region. It is proposed that the heterotopic position of the cells is due to abnormal and delayed migration of neural crest cells during primary neurogenesis. The findings lend support to the concept that in children with myelomeningocele the cord lesion is not due to secondary rupture.

Split cord malformation associated with myelomeningocele

OBJECT

The coexistence of split cord malformations (SCMs) and myelomeningoceles (MMCs) can be misdiagnosed or ignored and can cause spinal cord tethering. The authors investigated cases involving the coexistence of SCMs and MMCs in patients from the Children's Hospital Medical Center in Tehran.

METHODS

Of the 330 patients with MMCs who underwent operations at the Children's Hospital Medical Center between January 2001 and June 2005, 33 (10%) had an associated SCM. These 33 cases were retrospectively reviewed.

RESULTS

Eighteen patients (55%) were female, and the mean age of the patients at presentation was 2.9 months. In 17 of the 33 patients, the SCM occurred at the level of the neural placode. A Type I SCM was found in 26 children. Two patients had hypertrichosis. Eight patients had unilateral leg paresis. The MMC sac was located in the lumbar region in 14 cases. Two patients had double spinal dysraphism with meningoceles at the thoracic level. All patients underwent simultaneous repair of both lesions at the time of surgery.

CONCLUSIONS

Patients with MMCs, especially those with unusual manifestations such as unilateral paresis or skin lesions, should undergo a preoperative clinical examination to check for the presence of an SCM. Use of spinal magnetic resonance imaging can help in identifying the associated abnormalities. The neural placode and the rostral and caudal spinal cord segments should be carefully inspected for dysraphic lesions such as SCMs during the operation to repair the MMC. In this paper, the authors hope to show the wisdom of identifying these anomalies at the time of the initial repair of the MMC.

Diastematomyelia in children: treatment outcome and natural history of associated syringomyelia

OBJECTIVE

To quantify the long-term outcome of children with diastematomyelia and the implication of syringomyelia in the natural history.

MATERIALS

Retrospective study of 17 children (nine girls and eight boys) with diastematomyelia operated during 1989-2004. Mean age at diagnosis was 3.4 years (range 5 days-12 years), mean follow-up was 5 years; 14 had excision of spur and cord untethering, 3 had excision of spur alone.

RESULTS

The bony spur was in the lumbar region in 12 and thoracic in 5 patients. Syringomyelia was present in eight (47%), associated with bony spur between L1 and 4 (p=0.088), spina bifida occulta in ten (58.8%), and spinal lipoma in one (6%). Preoperative Necker Enfants Malades (NEM) scores were 17 in eight patients, 16 in four, 15 in three, 13 in one, and 12 in one patient. Presenting neurological deficits were motor in eight, sensory deficits in three, and anal incontinence in one patient. There was improvement of NEM scores postoperatively in five patients only, but still with residual deficit. Repeat spur excision and cord untethering was performed in three patients for neurological deterioration 1-4 years after first operation. On postoperative MRI scans syringomyelia remained unchanged in all eight patients. There were one skin infection, one transient motor deterioration, and one patient with sensory deficit after surgery.

CONCLUSION

Prophylactic operations were associated with the best clinical outcome. Despite improvement, all patients with established preoperative deficit still had residual neurological deficits at their last follow-up. The associated syringomyelia remained unchanged after surgery, indicating that it does not contribute to the neurological syndrome.

A case of split cord malformation associated with myeloschisis

INTRODUCTION

Split cord malformation (SCM) associated with myeloschisis is a very rare form of spinal dysraphism. We encountered a case of SCM associated with myeloschisis showing split neural placodes (hemicords) in the upper lumbar region.

RESULTS

Radiological examinations, including prenatal MRI and postnatal CT scan, clearly demonstrated a bony spur between the two hemicords as well as myeloschisis, which facilitated a precise preoperative diagnosis of this complex anomaly. Resection of the spur, closure of the myeloschisis, and untethering of the thickened filum terminale were successfully accomplished in one stage. The presence of SCM associated with myeloschisis is consistent with the hypothesis of an ontogenic basis of neural development, and we emphasize the importance of early imaging including prenatal MRI for diagnosing this complex anomaly.

Outcome of meningomyelocele/lipomeningomyelocele in children of northern India

OBJECTIVE

To evaluate the clinical profile, associated anomalies and surgical outcome of children with meningomyelocele (MMC)/lipomeningomyelocele.

METHODS

Out of a total of 181 cases of spinal dysraphism treated at our Institute between 1996 and 2004, 102 (56.35%) cases of MMC/lipomeningomyelocele were analyzed retrospectively and prospectively. The clinical profile and radiological findings of these children were recorded. Craniospinal MRI was the essential investigation and was done as a management protocol at our Institute for these children. Eighty-two out of 102 (80.3%) cases had pure MMC/lipomeningomyelocele and 20/102 (19.6%) had associated split cord malformation (SCM; complex spina bifida). All these children underwent surgery for their primary and associated malformations as indicated. They were clinically assessed over a mean follow-up period of 3.6 years ranging from 1.5 months to 8 years. No urodynamic or evoked potential studies were done to assess the sphincteric outcome following surgery.

RESULTS

Forty-six (45.1%) of children with MMC had other associated tethering lesions, including the presence of SCM. Craniospinal axis screening remained an important tool to understand the associated tethering lesions and malformations. Only 58.8% of children had hydrocephalus; thus the incidence was much lower compared with reports from the western literature (80-96%). 63.3% of children with overt hydrocephalus required shunt surgery prior to the definitive surgery; however, 23.3% of cases required a shunt after the MMC has been closed. Improvement in clinical profile following microneurosurgery was observed in 42.8% of cases with motor involvement, 46.8% of cases with sensory dysfunction and 39.5% of cases with sphincteric involvement. Motor improvement was seen in 43.6% of cases of pure MMC/lipomeningomyelocele as compared to only 40.0% of cases of complex spina bifida. Sensory improvement was also better in pure MMC/lipomeningomyelocele group being seen in 48.0% of cases as compared to only 42.9% of cases of complex spina bifida.

CONCLUSION

Presence of SCM with MMC is referred to as complex spina bifida and is seen in a significant proportion (19.6%) of all cases of MMC. Thorough assessment of the craniospinal imaging needs to be done to look for the presence of multiple tethering lesions which could be present in the same case. Not all children with spinal dysraphism with hydrocephalus required shunt surgery or CSF diversion but a constant and vigilant follow up could avoid it in 13.3% of cases. Improvement in motor and sensory dysfunction was better in the pure MMC/lipomeningomyelocele group than in the complex spina bifida group. Improvement in sphincteric dysfunction, although seen in significant cases, was less compared with improvement in motor and sensory dysfunction. This probably represents a lack of definitive objective criteria for urodynamic improvement and a lack of proper rehabilitation. Electromyographic studies and uroflowmetry are required to asses the true sphincteric outcome following surgery.

Basicranial diplomyelia: an extension of the split cord malformation theory. Case report

Basicranial diastematomyelia is an extremely rare congenital disorder. A review of the literature indicates only one reported case of basicranial diastematomyelia in which an osseous peg divided the brainstem in two. The authors present the first reported case of basicranial diplomyelia split by a fibrous band and correlate its pathogenesis with that of split cord malformation (SCM). The patient described in the present report had a fibrous stalk dividing the brainstem, and therefore the condition was categorized as a diplomyelia, or SCM Type II. Because the occipital dermatomes behave similarly to the spinal dermatomes early in development, they may be subject to the same embryonic error that results in SCM. The authors propose that the mechanism leading to SCM is the same as that found in basicranial split malformations and that the theory explaining it be modified to include the posterior fossa.

Leg dysfunctions in a hatched chick model of spina bifida aperta

We created chicks with spina bifida aperta (SBA) by incising the roof plate of the neural tube of embryos at Hamburger and Hamilton stage 18 or 19. Incision over the length of three somites caused spina bifida occulta (SBO)-like malformation in 47% of the hatchlings. Incision over the length of five and seven somites caused SBA-like malformation in 100% of the hatchlings. The SBO chicks exhibited no symptoms, whereas the SBA chicks exhibited paralysis of a leg muscle and imbalance between an agonist and an antagonist leg muscles. Lesions in these SBA chicks were located in the spinal segments that give rise to motor neurons that innervated the dysfunctional muscles. Histological analysis revealed that there were fewer small spinal neurons (interneurons) at the site of the lesion in SBA chicks than in the normal chicks and that there was no such difference in the number of the large spinal neurons (motor neurons). Leg dysfunctions in this model of SBA may be attributable to the smaller number of interneurons in the spinal segments that contain motor neurons that innervate the dysfunctional muscle. This model may facilitate studies of the pathological mechanisms that lead to leg dysfunctions in SBA chicks.

Fetal magnetic resonance imaging enhances detection of spinal cord anomalies in patients with sonographically detected bony anomalies of the spine

OBJECTIVE

Although fetal magnetic resonance imaging (MRI) is being increasingly used to evaluate sonographically suspected abnormalities, its utility in the evaluation of the spinal canal is not well studied. Because it is not susceptible to the limitations of fetal position, oligohydramnios, and shadowing from bony structures, we hypothesize that fetal MRI is better suited to assess the contents of the spinal canal compared with prenatal sonography. The purpose of this investigation was to determine whether fetal MRI could detect spinal abnormalities in cases in which they had not been originally suspected on prenatal sonography.

METHODS

Fetal spine MR images were retrospectively reviewed over a 42-month period. Corresponding sonographic images were then rereviewed to determine whether there were findings in retrospect that might have suggested the cord abnormalities. Cases of myelomeningocele were counted as a spinal cord abnormality only if fetal MRI showed a cord anomaly other than the myelomeningocele.

RESULTS

Of 33 cases referred for bony anomalies of the spine, fetal MRI showed additional abnormalities involving the spinal cord in 3 patients. These included diastematomyelia in 2 cases and segmental spinal dysgenesis in the third case. One case of diastematomyelia occurred in association with a lumbosacral myelomeningocele. The spinal cord anomalies were not visible on any of the prenatal sonograms, even in retrospect.

CONCLUSIONS

Additional spinal cord anomalies were detected in 10% of cases reviewed. Fetal MRI can be useful in assessing the spinal cord in fetuses with bony spinal anomalies. Our findings suggest that fetuses with sonographically diagnosed bony abnormalities of the spine may benefit from further evaluation with fetal MRI.

Pre- and post-operative hydromyelia in spinal dysraphism

BACKGROUND AND PURPOSE

There has been limited description of hydromyelia after surgery for spinal dysraphism. The opportunity to compare pre- and post-operative hydromyelia in patients with spinal dysraphism has been possible in two groups of patients using MRI. Post-operative assessment and possible relationship of hydromyelia to clinical findings has been made during a 7- to 14-year period.

METHODS

A total of 38 patients with congenital lumbar or sacral lipomas and 20 with diastematomyelia were studied pre-operatively with a 1.5-T MRI. Most patients in each group were examined with surveillance MRI (1.5 T) post-operatively. Clinical correlations were carried out with each examination.

RESULTS

Of the 38 dorsal or terminal lipoma post-operative patients, hydromyelia increased in 3 and was a new finding in 4. One symptomatic patient in the latter group had extensive septated lumbar hydromyelia. In 8 of 20 diastematomyelia patients, pre-operative hydromyelia was unchanged post-operatively. Hemicord hydromyelia developed in 1.

CONCLUSION

Hydromyelia of varying degree was found in almost one-third of post-operative dorsal or terminal lipoma patients and nearly one-half of diastematomyelia patients. In five post-operative lipoma and two diastematomyelia patients, significant neurological findings remained. One of the six post-operative lipomas had new extensive lumbar hydromyelia that may have been responsible for the patient's symptoms. In the remaining symptomatic patients, hydromyelia was absent or modest.

Comparative study of complex spina bifida and split cord malformation

OBJECTIVE

To see the difference in clinical profiles, radiological findings and surgical outcome of the group 1 split cord malformation and meningomyelocele (SCM with MMC) from group 2 (SCM without MMC).

METHODS

46 patients of SCM were selected from a total of 138 cases of spinal dysraphism. They were divided into two groups, based on presence or absence of MMC. Group I (SCM with MMC) n =19 patients and Group II (SCM without MMC) n=27 patients. A detail clinical evaluation and MR screening of whole spine of all cases was performed. All patients underwent surgical detethering of cord. After an average follow-up of 1.7 years, the operative results were clinically assessed and statistical significance was calculated.

RESULTS

Male to female ratio was 1:09. Mean age of presentation was 3.6 years. Cutaneous markers like tuft of hair, cutaneous haemangioma, etc, had a higher incidence in group II in comparison to group I (50% vs 10.5%). The incidence of motor deficits was significant in group I in comparison to group II (63% vs 40%). The incidences of sensory loss, trophic ulcers, sphincteric dysfunction and muscle atrophy were relatively more common in group I patients, while neuro-orthopedic deformities such as congenital telepes equinovarus (CTEV), scoliosis and limb shortening were more frequent (67%) in group II children as compared to group I (53%). Type I SCM has higher incidence in group I children. Low lying conus were found in 47% patient of group I, while in group II it was noticed in 69%. The associated cranial anomalies like hydrocephalus, ACM and syrinx, were slightly higher in group I patients. At surgery, dysgenetic nerve roots, neural placode, arachnoid bands and atrophic cord were seen mainly in group I. Postoperative complications like, CSF leak, pseudomeningocele and meningitis were more commonly encountered in group I patients. The patients of group II showed better operative outcome compared to group I cases.

CONCLUSION

Incidence of SCM with MMC amount to 41% of total SCM cases. Progressive neurological deficit was higher in this group (SCM with MMC) in comparison to the group harboring SCM without MMC. In view of a significant association of SCM in MMC cases, associated with other craniospinal anomalies, a thorough screening of neuraxis (by MRI) is recommended to treat all treatable anomalies simultaneously for desired outcome.

Correction of hindbrain herniation and anatomy of the vermis after in utero repair of myelomeningocele in sheep

BACKGROUND/PURPOSE

In utero repair of myelomeningocele (MMC) in humans spares distal neurologic function, reverses the hindbrain herniation component of the Arnold-Chiari II malformation (ACM), and reduces the rate of postnatal shunt placement. The authors hypothesized that extravasation of cerebrospinal fluid (CSF) from the lumbar spinal cord results in herniation. This hypothesis was tested by assessing the impact of a spinal cord myelotomy on hindbrain anatomy in fetal sheep.

METHODS

A MMC lesion was created surgically in 34 fetal sheep at 75 days' gestation by excision of the L1-L5 lamina, the exposed dura, and surrounding tissues. A lumbar level myelotomy was performed in 28 of the 34 fetuses to open the central canal of the spinal cord to enhance egress of CSF through the MMC defect and potentially induce hindbrain herniation. At 102 days' gestation, a repair of the MMC lesion was performed in 14 fetuses with a myelotomy. Fetuses underwent autopsy at 102, 114, 120, or 140 days' gestation. Control animals underwent 2 unrelated fetal surgical procedures at approximately 70 and 110 days' gestation. The incidence of hindbrain herniation, ventricular size, biparietal diameter, brain weight, and brain anatomy were compared between the different animal groups.

RESULTS

After MMC creation, significant cerebellar tonsillar herniation was observed in 85% of fetuses that underwent creation of a myelotomy; none of the lambs without a myelotomy (n = 6) had hindbrain herniation. At autopsy, cerebellar tonsillar herniation was present at the time of MMC repair (102 days' gestation), 2 weeks after MMC repair, but was reversed 3 weeks post-MMC repair. At birth, tonsillar herniation was absent, and hindbrain anatomy was restored in 88% of the fetuses with a myelotomy that underwent fetal MMC repair. No significant differences in brain weight and ventricular size was observed between animals with and without MMC repair.

CONCLUSIONS

Adding a myelotomy to the sheep model of MMC leads to hindbrain herniation that is similar to that observed in the human ACM. These experiments support the hypothesis that leakage of CSF through the exposed central canal alters the normal CSF hydrodynamics, resulting in cerebellar tonsillar herniation. Fetal MMC repair reverses hindbrain herniation and restores gross anatomy of the vermis.

Split spinal cord malformations: report of 22 cases and review of the literature

OBJECT

The aims of this study were to describe the embryological changes that drive the formation of a split spinal cord malformation, analyse the forms of presentation, evaluate the diagnostic procedures and discuss the indications for the different forms of therapy for each case.

METHODS

Clinical and radiological features of 22 cases of split spinal cord malformations (SSCM) are reported. Three groups of patients are considered: group a, patients with signs of tethered cord or scoliosis; group b, patients with midline cutaneous stigmata and group c, patients with a meningocele or meningomyelocele.

CONCLUSION

While CT scan is particularly useful for the evaluation of vertebral bodies and posterior arch abnormalities and spur characteristics in SSCM, MRI gives complementary information on the anatomy of spinal cord, dural sac, conus and filum terminale and permits the exclusion of associated lesions such as hydro-syringomyelia, dermal sinus or dermoid and epidermoid cysts. Surgery should be considered indicated in all cases of SSCM, even the asymptomatic ones, except in very badly handicapped meningomyelocele patients with nonprogressive disability and type II SSCM.

Homocysteine modifies development of neurulation and dorsal root ganglia in chick embryos

BACKGROUND

The formation of the neural tube (neurulation) involves two mechanisms: primary and secondary neurulation. In chicks, there is also an overlap zone, where both mechanisms work together. Homocysteine (Hcy) may have an important teratogenic role in neural tube defects (NTD) when folic acid levels are considered normal. Recently, Hcy capability to generate NTD and modify neural crest cell migration has been demonstrated in chick embryos. This study was aimed to evaluate the effects of Hcy on neurulation and the development of the dorsal root ganglia (DRG).

METHODS

Chick embryos were treated with L-Hcy thiolactone 20 micromol to produce the highest rate of survival with embryos carrying neural tube defect (NTD) in the spine. Embryos at stages (st) 3-10 were treated and harvested at st 18-23. Only externally normal embryos or those carrying spinal NTD embryos were considered.

RESULTS

Histological sections of Hcy-treated embryos showed: open spina bifida (39% of embryos), more than one tube forming the spinal cord (26%), disorganized spinal cord (26%), always affecting lumbosacral regions, probably in the overlap zone. Additionally, 32% of embryos had small and continuous DRG, associated with a slimmed roof plate. Three-dimensional reconstruction showed unsegmented DRG until the C8 ganglion level. There was a 75% reduction of C3 DRG cells in treated embryos in comparison to untreated ganglia.

CONCLUSION

Hcy teratogenicity in avian embryos affected the neural tube in the overlap zone, secondary neurulation and the cervical DRG.

A new look at myelomeningoceles: functional level, vertebral level, shunting, and the implications for fetal intervention

OBJECTIVE

Previous reports have suggested that 80% to 85% of patients who have a myelomeningocele (MMC) and undergo surgical repair after birth develop hydrocephalus and require the placement of a ventricular shunt. However, the rate of shunting as a function of spinal level is not well established. We sought to determine the distribution of postnatally repaired MMC lesions as characterized by both functional and radiologic assessment, as well as the incidence of shunting when patients were categorized according to these 2 methods.

METHODS

A retrospective chart review of 297 patients who were born with open MMCs and followed in the spina bifida clinic at the Children's Hospital of Philadelphia was performed. The presence or absence of a shunt was determined for each patient. Functional spinal level was determined by the best-recorded neurologic examination and vertebral level by spine radiographs.

RESULTS

The overall rate of ventricular shunting was 81%. The level of the lesion significantly affected the incidence of shunting, with more cephalad lesions correlating with higher rates. This was true both for functional and radiologic categorizations. A significantly higher shunt rate was found among patients with sacral lesions when categorized by radiologic rather than functional criteria. In 86% of patients, the functional level was found to be equal to or higher (worse) than the radiologic level.

CONCLUSIONS

This study describes the natural history of ventricular shunting in MMC patients with relation to both radiologic and functional criteria. Fetal MMC closure is being performed in some centers in an attempt to decrease the incidence of shunting and to improve leg function in selected patients. The present data may serve as a comparison group and aid in the design and analysis of a prospective trial to assess the efficacy of this new procedure.

Fetal surgery for myelomeningocele

Myelomeningocele is a common birth defect that is associated with significant lifelong morbidity. Despite improvements in technology and overall patient care, little progress has been made in the postnatal surgical management of the child with spina bifida. Postnatal surgery is aimed at covering the exposed spinal cord and preventing infection. Numerous interventions for ventricular shunts, tethered cord, scoliosis, incontinence, urologic complications, and extremity anomalies are frequently required. Although myelomeningocele is a nonlethal fetal anomaly, the limitations with current postnatal treatment strategies has led to extensive investigation of prenatal treatment options. This article outlines the rationale for fetal intervention and discusses the preliminary experience with human fetal myelomeningocele surgery.

Urodynamic predictors of upper tract deterioration in children with myelodysplasia

The clinical and urodynamic data of 62 children with myelodysplasia without previous urological treatment were tested statistically for the ability to predict upper tract deterioration. This was done by comparing these data among 26 children with dilated upper tracts and 36 children with normal upper tracts. Vesicoureteric reflux had a strong positive correlation with upper tract dilation but the maximum cystometric capacity, detrusor instability, compliance, maximum urethral closure pressure and peak flow rate all had no predictive value. Residual urine is sensitive and negatively predictive and leak pressure is specific and positively predictive; detrusor pressure at peak flow, opening pressure, pressure at least flow and the detrusor-adjusted mean passive urethral resistance relation factor (DAMPF) are sensitive and specific with high positive and negative predictive values.

Split spinal cord malformations in children

OBJECT

The authors reviewed and analyzed information on 74 patients with split spinal cord malformations (SSCMs) treated between January 1, 1980 and December 31, 1996 at their institution with the aim of defining and classifying the malformations according to the method of Pang, et al.

METHODS

Computerized tomography myelography was superior to other radiological tools in defining the type of SSCM. There were 46 girls (62%) and 28 boys (38%) ranging in age from less than 1 day to 12 years (mean 33.08 months). The mean age (43.2 months) of the patients who exhibited neurological deficits and orthopedic deformities was significantly older than those (8.2 months) without deficits (p = 0.003). Fifty-two patients had a single Type I and 18 patients a single Type II SSCM; four patients had composite SSCMs. Sixty-two patients had at least one associated spinal lesion that could lead to spinal cord tethering. After surgery, the majority of the patients remained stable and clinical improvement was observed in 18 patients.

CONCLUSIONS

The classification of SSCMs proposed by Pang, et al., will eliminate the current chaos in terminology. In all SSCMs, either a rigid or a fibrous septum was found to transfix the spinal cord. There was at least one unrelated lesion that caused tethering of the spinal cord in 85% of the patients. The risk of neurological deficits resulting from SSCMs increases with the age of the patient; therefore, all patients should be surgically treated when diagnosed, especially before the development of orthopedic and neurological manifestations.

The spinal cord lesion in human fetuses with myelomeningocele: implications for fetal surgery

Recently produced experimental evidence suggests that secondary traumatic injury and degenerative changes, acquired in utero, to the openly exposed neural tissue may be primarily responsible for the massive neurological deficit associated with myelomeningocele (MMC). The goal of this study was to examine the morphology of human fetuses with MMC to determine if acquired trauma to the spinal cord could be identified. The MMC lesions with surrounding tissues from 10 human fetuses ranging in gestational age between 19 and 23 weeks were prepared with serial histological sections. The MMC lesions were characterized by an open vertebral arch, an open dura mater fused laterally to the dermis, and an open pia mater fused laterally to the epidermis. The spinal cord was exposed, without any meningeal, bony, or cutaneous covering, and was resting on the dorsal aspect of the abnormal arachnoid sac created by the fusion of the meninges to the cutaneous tissues. The exposed neural tissue had undergone varying degrees of recent traumatic injury as a result of its exposed position, ranging from nearly complete preservation of neural elements in four cases to nearly complete loss in two cases. The neural tissue remaining in the MMC with partial loss contained hemorrhages and abrasions from recent injury, suggesting that injury occurred during passage through the birth canal. The presence of dorsal and ventral parts of the cord with nerve roots and ganglia demonstrated that these structures had formed during development and that the loss of tissue by injury was a secondary change. The results support the concept that performing in utero surgery could protect the exposed but initially well-developed and uninjured cord, prevent secondary neural injury, and preserve neural function in the human fetus with myelomeningocele.

Diastematomyelia and spina bifida can be caused by the intraspinal grafting of somites in early avian embryos

OBJECTIVE

In this experimental study, an embryological model was created to reproduce diastematomyelia and spina bifida and to investigate new aspects of the origin of spinal cord malformations.

METHODS

A somite was implanted from a donor quail embryo into the neural tube of a 2-day-old chick embryo. The somite was chosen because the septum that characteristically separates the two hemicords consists exclusively of mesodermal derivatives.

RESULTS

After 2 days of reincubation, diastematomyelia, spina bifida, or a normal embryo without a graft was observed. If the graft persisted in the neural tube, it formed a septum between the floor and roof plates but never made contact with the lateral walls of the tube. Otherwise, the graft was extruded from the neural tube. In this case, the quail cells often were found in dorsal or dorsolateral positions in the surrounding tissue. Sometimes, the wall of the neural tube formed an extrusion in the direction of the eliminated graft. On many occasions, however, spina bifida aperta was produced and no quail cells could be found in the host.

CONCLUSION

The results suggest that diastematomyelia may be the result of abnormal mesodermal invasion of the neural tube. The development of a septum in the neural tube after implantation of a somite may mimic the process during spontaneous diastematomyelia formation, which could be the consequence of abnormal gastrulation, the process by which the two early germ layers of the blastodisc are converted into the three definitive germ layers.

In utero repair of experimental myelomeningocele saves neurological function at birth

In a previous series of fetal sheep experiments, the authors demonstrated that midgestational exposure of the normal spinal cord to the amniotic space leads to a myelomeningocele (MMC) at birth that closely resembles human MMC phenotypes in terms of morphology and functional deficit. The present study tested whether delayed in utero repair of such evolving experimental MMC lesions spares neurological function. In 12 sheep fetuses, a spina bifida-type lesion with exposure of the lumbar spinal cord was created at 75 days' gestation (full term, 150 days). Four weeks later, the developing MMC lesions were repaired in utero for seven fetuses (five fetuses died before this time). Of those that had repair, three were delivered near term by cesarean section, and four died in utero or were aborted. All survivors had healed skin wounds and near-normal neurological function. Despite mild paraparesis, they were able to stand, walk, and perform demanding motor tests. Sensory function of the hindlimbs was present clinically and confirmed electrophysiologically. No signs of incontinence were detected. Histologically, the exposed and then covered spinal cord showed significant deformation, but the anatomic hallmarks as well as the cytoarchitecture of the spinal cord essentially were preserved. These findings show that timely in utero repair of developing experimental MMC stops the otherwise ongoing process of spinal cord destruction and "rescues" neurological function by the time of birth. Because there is evidence that a similar secondary damage to the exposed neural tissue also occurs in human MMC, we propose that in utero repair of selected human fetuses might reduce the neurological disaster commonly encountered after birth.

Creation of myelomeningocele in utero: a model of functional damage from spinal cord exposure in fetal sheep

A recent study in human fetuses with myelomeningocele (MMC) suggested that the primary malformation is not neural but a failed closure of the posterior vertebral column and paraspinal soft tissue, which leads to exposure and secondary destruction of the spinal cord. The goal of this study was to test whether chronic exposure of the normal spinal cord to the amniotic space produces a lesion similar to human MMC. In fetal sheep at 75 days' gestation (group A) and 60 days' gestation (group B) (term = 150 days), the lumbar spinal cord was exposed to the amniotic cavity by excising skin and paraspinal soft tissues, and by performing a laminectomy. Some animals from both groups were fetectomized and assessed morphologically at 100 days' gestation. The remainder were delivered near term and assessed clinically, electrophysiologically, and morphologically. In group A, all animals showed MMC-type pathology. The exposed spinal cord was herniated out of the spinal canal and rested on the dorsal membranes of a cystic sac. The neural tissue was stretched and flattened out. Histologically, the hallmarks of the spinal cord were not discernable and the cytoarchitecture was lost. These changes were less severe at 100 days than at term. The three survivors in group A were paraplegic. In group B, the two survivors and two fetuses harvested at 100 days had healed skin wounds and near normal spinal cord histology. The other animal harvested at 100 days had a MMC-type lesion with less severe histological changes. The two survivors had a mild paraparesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological study of surgically induced open neural tube defect in old (14 and 21 days) chick embryos

As an experimental model for the research of open neural tube defect (NTD), the surgical model has several advantages over others, in spite of the fact that the pathogenetic mechanism is not compatible with the human intrauterine events. To make reproducible NTDs by surgery and to compare the surgically induced lesions with the human myeloschisis morphologically, we opened the neural tube for a length of 9-11 somites in Hamburger and Hamilton stage 16-19 chick embryos. Embryos which survived until the late in ovo life (total age 14 and 21 days) showed relatively reproducible open NTDs. Morphologically they are similar to human myeloschisis. This study suggests that the surgical model can be suitable for studies of open NTDs.

In utero surgery rescues neurological function at birth in sheep with spina bifida

We hypothesize that the neurologic deficit associated with open spina bifida is not directly caused by the primary defect but rather is due to chronic mechanical and chemical trauma since the unprotected neural tissue is exposed to the intrauterine environment. We report here that exposure of the normal spinal cord to the amniotic cavity in midgestational sheep fetuses leads to a human-like open spina bifida with paraplegia at birth, indicating that the exposed neural tissue is progressively destroyed during pregnancy. When open spina bifida was repaired in utero at an intermediate stage, the animals had near-normal neurologic function. The spinal cord was deformed but largely preserved. These findings suggest that secondary neural tissue destruction during pregnancy is primarily responsible for the functional loss and that timely in utero repair of open spina bifida might rescue neurologic function.

Radiographic and histological characterization of Tc/tw5 mice: an animal model of lumbosacral agenesis/myelomeningocele

Twenty-five Tc/tw5 and 12 control mice were killed at different ages and radiographically and histologically examined. In addition, histochemical analysis was performed on muscles from four mutant and one control mouse. All Tc/tw5 mice were tailless and had a fluid-filled lumbar myelomeningocele. Radiographically, most animals had six instead of 10 lumbosacral vertebrae. Vertebral anomalies were common. The spinal cord was grossly abnormal: at the level of the plaque, it was replaced by patches of neural tissue intermingled with connective tissue and muscle. Affected skeletal muscles had small myofibers with centrally placed nuclei consistent with arrest of development at the myotubular stage secondary to denervation in early embryonic life. Abnormal nerves were smaller and had fewer axons. Tc/tw5 mice show features of neural tube and notochord dysplasia. These mutant mice may be useful as animal models of lumbosacral agenesis and myelomeningocele.

Malformation of the lumbosacral spinal cord in a case of sacral agenesis

Agenesis of the sacrum is a rare anomaly that is associated with numerous visceral abnormalities, spinal cord malformation, and lower limb defects. A fatal case of sacral and lower lumbar agenesis in a 3-day-old female infant born at 38 weeks of gestation is reported. The extraneural malformations comprised an imperforate anus, a rectovaginal fistula, and musculoskeletal abnormalities, including several thoracocervical hemivertebrae and aplasia of the sacrum and the fourth and fifth lumbar vertebrae. The cervical and high thoracic spinal cord segments were normal. Disruption of secondary neurulation, possibly due to notochord dysfunction, was suggested by malformation of the ventral half of the lower thoracic spinal cord with relative preservation of the dorsal horns and, more caudally, by loss of all normal histological landmarks, including the central canal. Neither skeletal muscle nor myoblasts were found in muscle compartments that would normally have received motor innervation from the levels of the spinal cord from which anterior horn cells were absent, indicating parallel, segmental failure of myotomal differentiation in the caudal eminence.

Pathogenesis of diastematomyelia: can a surgical model in the chick embryo give some clues about the human malformation?

To reproduce diastematomyelia, a sagittal incision was carried out at the level of the rhomboidal sinus of 36- to 40-h-old chick embryos. A small piece of membrane shell, a small agar screen, or a piece of quail isochronous isotopic notochord was inserted into the gap. The embryos were killed and fixed after 9 days' incubation. Diastematomyelia was obtained in several embryos treated with interposition of a membrane screen or a piece of quail notochord. Microscopic examination revealed two hemicords, each containing its own central canal; in some cases one of the cords showed hydromyelia. Absence of the rump was seen in association with experimental diastematomyelia. The interposition of a resorbable agar screen did not succeed in reproducing diastematomyelia. The results of these surgical manipulations suggest that diastematomyelia cannot be explained by a primary disorder of neurulation. It supports the theory of noninvolution of a firm midline structure (probably the neurenteric canal, rapidly surrounded by mesodermal cells originating from the notochord), which prevents the fusion of the separated parts.

Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations

Much confusion still exists concerning the pathological definitions and clinical significance of double spinal cord malformations. Traditional terms used to describe the two main forms of these rare malformations, diastematomyelia and diplomyelia, add to the confusion by their inconsistent usage, ambiguities, and implications of their dissimilar embryogenesis. Based on the detailed radiographic and surgical findings of 39 cases of double cord malformations and the autopsy data on two other cases, this study endorses a new classification for double cord malformations and proposes a unified theory of embryogenesis for all their variant forms and features. The new classification recommends the term split cord malformation (SCM) for all double spinal cords. A Type I SCM consists of two hemicords, each contained within its own dural tube and separated by a dura-sheathed rigid osseocartilaginous median septum. A Type II SCM consists of two hemicords housed in a single dural tube separated by a nonrigid, fibrous median septum. These two essential features necessary for typing, the state of the dural tube and the nature of the median septum, do not ever overlap between the two main forms and can always be demonstrated by imaging studies so that accurate preoperative typing is always possible. All other associated structures in SCM such as paramedian nerve roots, myelomeningoceles manqué, and centromedian vascular structures frequently do overlap between types and are not reliable typing criteria. The unified theory of embryogenesis proposes that all variant types of SCMs have a common embryogenetic mechanism. Basic to this mechanism is the formation of adhesions between ecto- and endoderm, leading to an accessory neurenteric canal around which condenses an endomesenchymal tract that bisects the developing notochord and causes formation of two hemineural plates. The altered state of the emerging split neural tube and the subsequent ontogenetic fates of the constituent components of the endomesenchymal tract ultimately determine the configuration and orientation of the hemicords, the nature of the median septum, the coexistence of various vascular, lipomatous, neural, and fibrous oddities within the median cleft, the high association with open myelodysplastic and cutaneous lesions, and the seemingly unlikely relationship with fore and midgut anomalies. The multiple facets of this theory are presented in increasing complexity against the background of known embryological facts and theories; the validity of each facet is tested by comparing structures and phenomena predicted by the facet with actual radiographic, surgical, and histopathological findings of these 41 cases of SCM.

Split cord malformation: Part II: Clinical syndrome

Thirty-nine patients with split cord malformations (SCM) were studied in detail with respect to their clinical, radiographic, and surgical findings as well as their outcome data. Eight patients were adults and 31 patients were children. According to the classification endorsed by Part I of the SCM study, 19 patients had Type I SCM (6 adults and 13 children), 18 patients had Type II SCM (2 adults and 16 children), and 2 patients had composite SCM with both lesion types situated in tandem. Six SCMs were cervical, 2 were thoracic, and 31 were in the lumbar region. All 8 adults had pain and progressive sensorimotor deficits at diagnosis. Only 16 of the 31 children had symptoms, and among these, 14 had progressive sensorimotor deficits, but only 6 had pain. The difference in the clinical picture between adults and children is similar to that described in the tethered cord syndrome, except for left-right functional discrepancy, which was prominent in 8 children with SCM but rarely seen in tethered cord syndrome due to other causes. Cutaneous manifestations of either occult or open dysraphic states were present in all but 3 patients; hypertrichosis was by far the best predictor of an underlying SCM, being found in 56% in the series. Neurological deterioration in SCM was independent of the lesion type: the Type I:Type II ratio for symptomatic progression was 13:11. It was also independent of the location of the lesion: 67% of patients with cervical SCMs had symptomatic progression versus 64% of patients with thoracolumbar lesions. High-resolution, thin cut, axial computed tomographic myelography using bone algorithms was more sensitive than magnetic resonance imaging in defining the anatomical details of the SCM. Radiographic classifications of the SCM, using the nature of the median septum and the number of dural tubes as criteria, was always possible without ambiguity. However, whereas every Type I bone septum was identified preoperatively, only 5 Type II fibrous septa were revealed by preoperative imaging, even though a fibrous septum and/or other fibroneurovascular bands were found tethering the hemicords in every Type II case at surgery. Complete imaging studies also showed that all lumbar SCMs had low-lying coni and at least one additional tethering lesion besides the split cords, whereas only 1 of 7 cervical and high thoracic SCMs had a low conus and a second tethering lesion. The surgical goal for SCM was release of the tethered hemicords by eliminating the bone spurs, dural sleeves, fibrous septa, or any fibroneurovascular bands (myelomeningoceles manqué) that might be transfixing the split cord. Type I cases were technically more difficult and had a slightly higher surgical morbidity than Type II cases, especially if an oblique bone septum had asymmetrically divided the cord into one larger hemicord and one smaller, hence, very delicate, hemicord.(ABSTRACT TRUNCATED AT 400 WORDS)

Hydrosyringomyelia and diastematomyelia detected by MRI in myelomeningocele

Magnetic resonance imaging of the spine in 45 patients with myelomeningocele revealed hydrosyringomyelia in 24 and diastematomyelia in two. No patient at initial imaging manifested symptoms referable to hydrosyringomyelia; both patients with diastematomyelia had flaccid lower extremities. One patient developed an upper extremity monoparesis which resolved with syringo-peritoneal shunt placement; no other patient manifested symptoms or required surgery. Ventriculoperitoneal shunt malfunction produced reversible distention of the syrinx in another patient who remained asymptomatic.

Retinoic acid-induced neural tube defects with multiple canals in the chick: immunohistochemistry with monoclonal antibodies

When retinoic acid was injected into chicken yolks before incubation, various types of neural tube defect (NTD) were induced in 38-46% of the embryos after 48-96 h of incubation. The cranial NTD consisted of a delay in closing of the neural plate in 48-h embryos and some remained as disorganized, hyperplastic masses in older embryos. In spinal NTD of 48-h embryos the posterior neuropore remained widely open. In older embryos with a closed posterior neuropore, the neural tube appeared dissociated or disorganized locally at the trunk level. The tissue consisted of a dorsally-situated, neural-plate-like structure and a ventrally-located cell mass containing multiple canals. Although the location was different, this arrangement was similar to the overlap zone which appears between primary and secondary neurulation in normal development. Immunohistochemistry was performed using monoclonal antibodies which selectively stained various components of chick tissue. Considering the similarity in neural tube formation between chick and human, this experimental NTD may provide clues to understanding the etiology of human myelomeningocele.