The significance of hindbrain herniation reversal following prenatal repair of neural tube defects

OBJECTIVE

The aim of this study was to determine whether reversal of hindbrain herniation (HBH) on MRI following prenatal repair of neural tube defects (NTDs) is associated with reduced rates of ventriculoperitoneal (VP) shunt placement or endoscopic third ventriculostomy (ETV) within the 1st year of life.

METHODS

This is a secondary analysis of prospectively collected data from all patients who had prenatal open repair of a fetal NTD at a single tertiary care center between 2012 and 2020. Patients were offered surgery according to inclusion criteria from the Management of Myelomeningocele Study (MOMS). Patients were excluded if they were lost to follow-up, did not undergo postnatal MRI, or underwent postnatal MRI without a report assessing hindbrain status. Patients with HBH reversal were compared with those without HBH reversal. The primary outcome assessed was surgical CSF diversion (i.e., VP shunt or ETV) within the first 12 months of life. Secondary outcomes included CSF leakage, repair dehiscence, CSF diversion prior to discharge from the neonatal intensive care unit (NICU), and composite neonatal morbidity. Demographic, prenatal sonographic, and operative characteristics as well as outcomes were assessed using standard univariate statistical methods. Multivariate logistic regression models were fit to assess for independent contributions to the primary and secondary outcomes.

RESULTS

Following exclusions, 78 patients were available for analysis. Of these patients, 38 (48.7%) had HBH reversal and 40 (51.3%) had persistent HBH on postnatal MRI. Baseline demographic and preoperative ultrasound characteristics were similar between groups. The primary outcome of CSF diversion within the 1st year of life was similar between the two groups (42.1% vs 57.5%, p = 0.17). All secondary outcomes were also similar between groups. Patients who had occurrence of the primary outcome had greater presurgical lateral ventricle width than those who did not (16.1 vs 12.1 mm, p = 0.02) when HBH was reversed, but not when HBH was persistent (12.5 vs 10.7 mm, p = 0.49). In multivariate analysis, presurgical lateral ventricle width was associated with increased rates of CSF diversion before 12 months of life (adjusted OR 1.18, 95% CI 1.03-1.35) and CSF diversion prior to NICU discharge (adjusted OR 1.18, 95% CI 1.02-1.37).

CONCLUSIONS

HBH reversal was not associated with decreased rates of CSF diversion in this cohort. Predictive accuracy of the anticipated benefits of prenatal NTD repair may not be augmented by the observation of HBH reversal on MRI.

In Utero Restoration of Hindbrain Herniation in Fetal Myelomeningocele as Part of Prenatal Regenerative Therapy Program at Mayo Clinic

OBJECTIVE

To assess our initial experience with prenatal restoration of hindbrain herniation following in utero repair of myelomeningocele (MMC).

PATIENTS AND METHODS

Three consecutive patients with prenatally diagnosed MMC (between January 1, 2018 and September 30, 2018) were managed with open in utero surgery. As per institutional review board approval and following a protocol designed at the Mayo Clinic Maternal & Fetal Center, fetal intervention was offered between 19 0/7 and 25 6/7 weeks of gestation. Prenatal improvement of hindbrain herniation was the declared restorative end point. Obstetrical and perinatal outcomes were also assessed.

RESULTS

Diagnosis of MMC was confirmed upon referral between 20 and 21 weeks' gestation by using fetal ultrasound and magnetic resonance imaging. In all cases reported here, the spinal defect was lumbosacral with evidence of hindbrain herniation. Open in utero MMC repair was performed between 24 and 25 weeks' gestation with no notable perioperative complications. Postprocedure fetal magnetic resonance imaging performed 6 weeks after in utero repair documented improvement of hindbrain herniation. Deliveries were at 37 weeks by cesarean section without complications. Most recent postnatal follow-ups were unremarkable at both 11 months (baby 1) and 3 months of age (baby 2), with mild ventriculomegaly. Antenatal and postnatal follow-up of baby 3 at 1 month of age was also unremarkable.

CONCLUSION

Our study highlights the prenatal restoration of hindbrain herniation following in utero MMC repair in all cases presented here as an example of a prenatal regenerative therapy program in our institution.

Coagulation in hindbrain membrane meningioma patients treated with different injections using acute hypervolemic hemodilution

The aim of this study was to analyze the changes in coagulation in meningioma patients treated with different injections using the method of acute hypervolemic hemodilution (AHH). One hundred fifty hindbrain membrane meningioma patients were randomly divided into 5 groups, 30 per group. The first group were injected 40ml/time with Danhong after anesthesia induction; the second group were injected with 40ml~60ml/time Kangai and combined with interventional chemotherapy and embolization procedure; the third group of AHH were injected with polygeline 15ml/kg; the fourth group were injected with hydroxyethyl starch (130/0.4) sodium chloride in doses of 15ml/kg; the control group underwent basic treatment for lowering blood pressure and lowering blood fat. The changes of coagulation index were recorded before and after surgery and before and after the injection of different medications. Compared to the control group, for the first group of AHH, after being treated for 10 days and 30 days, the concentrations of bone specific alkaline phosphatase (BALP), bone Gla protein (BGP) and pro-collagen carboxy-terminal propeptide (PICP) were higher than that of the control group, the levels of endotoxin (ET) and C-reactive protein (CRP) were decreased compared to the control group (p less than 0.05); for the second group of AHH, after being treated for 10 days, the index of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (Fg) were not significantly changed, but the related level of vascular endothelial growth factor (VEGF) significantly decreased (p less than 0.05). Comparing the coagulation function index after surgery in the third and fourth groups, there were no significant changes in mean arterial pressure (MAP) level, heart rate (HR) value presented a low decrease, central venous pressure (CVP) level increased and the level of interleukin IL-6 showed a steady state after increasing. Analyzing the levels of interleukin IL-8 and tumor necrosis factor-α (TNF-α) after surgery, it was seen that in the third group they increased and in the fourth group they decreased (p less than 0.05). Danhong injection improved the coagulation function and microcirculation of patients, Kangai injection and interventional chemotherapy and embolization restrained the appearance of tumor angiogenesis, AHH operation with polygeline injection and hydroxyethyl starch (130/0.4) sodium chloride kept blood flow in normal parameters.

Morphometric analysis of foramen magnum dimensions and intracranial volume in pediatric Chiari I malformation

PURPOSE

Foramen magnum dimensions and intracranial volume in Chiari I malformations in children were studied, and the statistical relationship between patient demographics, radiological features and foramen magnum morphometry was investigated.

METHODS

Linear measurements were used to calculate the intracranial volume using preoperative magnetic resonance images and computed tomogram images. The area of the foramen magnum was obtained independently using computer imaging software and a regression formula. The result of 21 pediatric patients was compared with a matched control group.

RESULTS

The area of the foramen magnum was within the range of the expected value deduced using a formula based on the intracranial volume. There was no statistical difference in the area and linear dimensions of the foramen magnum in the study and control groups. Six patients (28%) had a foramen magnum in close proximity to a spherical shape.

CONCLUSION

The authors provide a simple, accurate and reproducible method of estimating foramen magnum area in the pediatric Chiari I group. The irregular shape of the foramen magnum is accentuated by developmental bony and soft tissue anomalies at the cranio-vertebral junction in Chiari malformation. Consequently, an individualized cross-sectional assessment of the foramen magnum in relation to the hindbrain tissue in the same plane is required to study the initiation and propagation of the Chiari I symptomatology.

Endoscopic diagnosis and treatment of far distal obstructive hydrocephalus

PURPOSE

Obstruction of the CSF circulation distal to the fourth ventricle is a rare cause of noncommunicating hydrocephalus. Endoscopic third ventriculostomy (ETV) represents one of the treatment options, but reports of results are rare.

METHODS

Between March 1997 and June 2008, 20 ETVs in 20 patients (mean 32.4 years, range 1 month-79 years) for noncommunicating hydrocephalus distal to the fourth ventricle were undertaken. All patients suffered from severe internal hydrocephalus and typical clinical symptoms. In addition to the standard ETV, a transaqueductal inspection of the posterior fossa with a flexible scope was performed. All patients were prospectively followed.

RESULTS

An ETV was achieved in all patients. It was clinically successful in 15 of 20 patients (75%) with an improvement of 50% (three out of six) of the pediatric and of 83% (12 out of 14) of the adult population. A reduction of ventricle size was found in ten (50%). Five patients (25%) received ventriculoperitoneal shunting. A transaqueductal inspection of the posterior fossa cerebrospinal fluid (CSF) pathways was performed in 16. In the remaining four patients, no inspection with the flexible scope was done. One clinically silent fornix contusion and one CSF fistula which was treated conservatively occurred. There was no permanent morbidity.

CONCLUSIONS

ETV is a successful treatment option in CSF pathway obstructions distal to the fourth ventricle. Although the success rate particularly of the pediatric population appears to be lower than with other indications of obstructive hydrocephalus, a relevant part of the patient population improves after ventriculostomy and shunting can be avoided.

Long-term survival in a child with a brain stem dermoid cyst

BACKGROUND

Brain stem dermoid cysts are very rare lesions, and in most, the outcome has been very poor. Because of the dangers of dissecting the cyst wall away from the brain stem parenchyma, some authors have advocated not to attempt a radical resection.

METHODS

We describe a child in whom the brain stem dermoid cyst recurred rapidly after a conservative approach. We therefore attempted a radical removal.

RESULTS

During surgery, the almost complete resection of the cyst wall was not very difficult, leading to an apparent cure after 4 years.

CONCLUSION

In exceptional cases, it may be possible to remove a brain stem dermoid cyst without prohibitive morbidity and with long-term cure.

Significant scoliosis regression following syringomyelia decompression: case report

We present the case of a 5-year-old boy presenting with a 54-degree scoliosis secondary to a Chiari I malformation with a holocord syringomyelia extending from C1 to T10. Neurosurgical treatment involved posterior fossa craniectomy with decompression, and partial C1 laminectomy. At follow-up 7 years later, at age 12, radiographs revealed only a 4-degree scoliosis, and follow-up MRI revealed a deflated syrinx. We report this case to reveal the most significant scoliosis regression seen in our experience that may occur in younger patients after neurosurgical syringomyelia decompression for Chiari I hindbrain herniation.

Hox gene misexpression and cell-specific lesions reveal functionality of homeotically transformed neurons

Hox genes are critical for establishing the segmental pattern of the vertebrate hindbrain. Changes in their expression can alter neural organization of hindbrain segments and may be a mechanism for brain evolution. To test the hypothesis that neurons induced through changes in Hox gene expression can integrate into functional neural circuits, we examined the roles of ectopic Mauthner cells (M-cells) in the escape response of larval zebrafish. The activity of the paired Mauthner cells in rhombomere 4 (r4) has been shown to be critical for generating a high-performance startle behavior in response to stimulation of the tail (Liu and Fetcho, 1999). Previous studies have found that misexpression of particular Hox genes causes ectopic M-cells to be generated in r2 in addition to the r4 cells (Alexandre et al., 1996; McClintock et al., 2001). With calcium imaging, we found that the homeotically transformed neurons respond to startle stimuli. To determine the roles of ectopic and endogenous M-cells in the behavior, we lesioned the r2, r4, or both M-cells with cell-specific laser lesion and examined the effect on startle performance. Lesion of the normal M-cells did not decrease escape performance when the ectopic cells were present. These results indicate that the homeotically transformed Mauthner cells are fully functional in the escape circuit and are functionally redundant with normal M-cells. We suggest that such functional redundancy between neurons may provide a substrate for evolution of neural circuits.

Surgical prognosis in hindbrain related syringomyelia

OBJECTIVES

The recommended operative treatment against hindbrain related syringomyelia is suboccipital decompression. The aim of the study was to define prognostic factors for surgical outcome in this disease.

MATERIALS AND METHODS

Between 1990 and 1997, 31 patients with hindbrain related syringomyelia were treated. All patients underwent craniovertebral decompression by suboccipital craniectomy and laminectomy of C1 or C1 and C2, respectively. Additionally, in nearly half of the cases, the tonsils were treated by bipolar coagulation. Mean post-operative observation period was 35 months including clinical and radiological (MRI) examination.

RESULTS

Neither there was correlation between clinical outcome and age nor correlation between clinical outcome and duration of preoperative symptoms. There was good correlation between clinical outcome and result of post-operative MRI: 63% of patients with a sufficient post-operative MRI demonstrated a significant clinical improvement, whereby only 17% of patients with insufficient MRI did so (P < 0.05). None of the patients with coagulation of the tonsils showed clinical improvement. In contrast, 77% of patients without tonsillar manipulation demonstrated clinical improvement (P < 0.01). Additionally, 88% of the patients with dorsal-tenting duraplasty experienced neurological improvement (P < 0.01), too.

CONCLUSIONS

The results give evidence for the prognostic importance of creating an adequate artificial cisterna magna. Dorsal-tenting of the duraplasty is an advantageous means against scarring and adhesions, whereby intradural applications such as extensive bipolar coagulation of the cerebellar tonsils should be avoided.

Surgical treatment of Chiari I malformation: indications and approaches

Chiari I malformation is a well-described entity characterized by hindbrain herniation through the foramen magnum. Although the exact origin of congenital Chiari I malformation is unknown, it appears to be caused by a mismatch between the volume of the posterior fossa neural elements and the posterior fossa cranial content. Several theories have been proposed to describe the resultant pathophysiology of this mismatch. It is clear, however, that abnormal cerebrospinal fluid flow and velocity play a role in the symptoms and signs associated with this disorder. The authors will review the pathophysiology, clinical presentation, and treatment options for patients with Chiari I malformation.

Rapid lesioning of large numbers of identified vertebrate neurons: applications in zebrafish

Establishing a causal role between the activity of specific individual nerve cells and the behaviors they produce (or the neural computations they execute) is made difficult in vertebrate animals because of the large numbers of neurons involved. Traditional techniques for establishing causal roles, such as tract cutting and electrolytic lesions, are limited because they produce damage that affects a variety of different cell types, invariably intermingled, and often of uncertain identity. We propose here an alternative lesioning technique in which large numbers of neurons are lesioned, but the lesioned neurons are specifically identified by fluorescent labeling. We use the locomotor control system of the larval zebrafish to illustrate this approach. In this example, the technique involves injection of fluorescent dextrans into far-rostral spinal cord to label descending nerve fibers. Such injections appear to interrupt the descending nerve fibers, and therefore their accompanying locomotor control signals. This protocol is shown to produce significant behavioral deficits. Because the CNS of the larval zebrafish is transparent, the entire population of lesioned cells can be imaged in vivo and reconstructed using confocal microscopy. This large-scale lesioning technique is important, even in this relatively 'simple' vertebrate animal, because the ablation of smaller numbers of neurons, using more precise laser-ablation techniques, often fails to produce observable behavioral deficits. While this technique is most readily applied in simpler and transparent vertebrate animals, the approach is general in nature and might, in principle, be applied to any vertebrate nerve tract.

Can hindbrain decompression for syringomyelia lead to regression of scoliosis?

Scoliosis in childhood develops secondary to syringomyelia in some children. The existing literature does not provide a clear answer as to whether surgical treatment of the syrinx can allow subsequent improvement of the spinal deformity, thus preventing the need for scoliosis surgery. This series comprised 16 patients with syringomyelia who presented with significant scoliosis in the absence of major neurological deficit. All underwent a hindbrain decompression, and follow-up ranged from 1 to 6 years (mean 2.5 years). Subsequent deformity surgery was necessary in eight cases, but the scoliosis was seen to improve or arrest its progression in six (37.5%). Improvement was found to be statistically more likely in children of younger age at the time of syrinx surgery and in those with left thoracic curves. Improvement occurred in 71.4% of those under the age of 10 at the time of hindbrain decompression.

Regeneration of isthmic tissue is the result of a specific and direct interaction between rhombomere 1 and midbrain

The midbrain-hindbrain boundary, or isthmus, is the source of signals that are responsible for regional specification of both the midbrain and anterior hindbrain. Fibroblast growth factor 8 (Fgf8) is expressed specifically at the isthmus and there is now good evidence that it forms at least part of the patterning signal. In this study, we use Fgf8 as a marker for isthmic cells to examine how interactions between midbrain and hindbrain can regenerate isthmic tissue and, thereby, gain insight into the normal formation and/or maintenance of the isthmus. We show that Fgf8-expressing tissue with properties of the isthmic organiser is generated when midbrain and rhombomere 1 tissue are juxtaposed but not when midbrain contacts any other rhombomere. The use of chick/quail chimeras shows that the isthmic tissue is largely derived from rhombomere 1. In a few cases a small proportion of the Fgf8-positive cells were of midbrain origin but this appears to be the result of a local respecification to a hindbrain phenotype, a process mimicked by ectopic FGF8. Studies in vitro show that the induction of Fgf8 is the result of a direct planar interaction between the two tissues and involves a diffusible signal.

Utility of early postoperative MRI in hindbrain-related syringomyelia. A preliminary prospective study on five patients

We report a series of five patients operated on for hindbrain-related syringomyelia with posterior fossa decompression and duraplasty. In all cases an early postoperative MRI was performed (24-36 h after surgery). These images have been compared with the preoperative ones and with those obtained, 1, 3 and 6 months after operation. Both before and after surgery there was not always a tight correlation between clinical and MRI pictures. In all but one patient the early postoperative MR images showed a reduction of syrinx size and were as to those obtained later. We discuss the results observed in our small series and analyze the role of early postoperative MRI studies in patients with hindbrain-related syringomyelia.

Autoradiographic distribution of bombesin/gastrin-releasing peptide receptors in fetal cortex transplants

Bombesin/gastrin-releasing peptide (BB/GRP) receptors were characterized in fetal cortex transplants in the rat. Using in vitro autoradiography techniques, the density of (125I-Tyr4)BB grains was low 2 weeks after transplantation but increased 4 weeks after cortex transplantation into the adult rat fourth ventricle. Densitometry analysis of the autoradiograms indicated that (125I-Tyr4)BB bound with high affinity (Kd = 5 nM) to a single class of sites in the transplant tissue. Specific (125I-Tyr4)BB binding was inhibited with high affinity by (Tyr4)BB but not by NMB (IC50 values of 3 and 100 nM, respectively). These data suggest that GRP may act as a novel growth factor and play a regulatory role in the development of fetal cortex transplants.

Surgical treatment of "hindbrain related" syringomyelia: new data for pathogenesis

52 patients with "hindbrain related" syringomyelia underwent surgical treatment. All patients underwent primary reconstructive surgery at the craniovertebral junction. Terminal ventriculostomy was performed as the secondary operation in 2 cases. The surgical treatment arrested progression of signs in 33 (63.5%), stabilized disease in 9 (17%) cases. Postoperative deterioration occurred in 8 (15%) cases. Mortality was 4% (2 patients). Percutaneous or intra-operative injection of myodil and gas into the syrinx, as well as CT, revealed the existence of communication with the 4th ventricle in 14 patients. Investigation of cerebrospinal and syrinx fluid revealed increased level of IgG, IgM or IgA in the syrinx fluid in 16 out of 22 patients. Immunohistological examination of pia mater revealed specific staining for IgG. Thus, syrinx formation may be due to synergic action of hydrodynamic and immunopathological mechanisms. Results indicate that early surgical treatment is preferable to patients with hindbrain anomalies and hydromyelia. We consider primary reconstructive operation at the posterior fossa as the preferred surgical management of "hindbrain related" syringomyelia.

Surgery for hindbrain related syringomyelia

Syringomyelia is a condition with many possible causes, the commonest of which seems to be an abnormality at the foramen magnum. Such cases may be grouped under the heading of "Hindbrain related syringomyelia" and the principles of treatment for all such cases are largely similar. The commonest of these foramen magnum region abnormalities is hindbrain herniation which may be associated with a history of birth difficulties, a small posterior fossa, segmentation abnormalities of the cervical vertebrae or the base of the skull, arachnoiditis of the subarachnoid spaces, subarachnoid pouches, hydrocephalus and intracranial tumours or tumours partly blocking the foramen magnum. Other causes of syringomyelia include conditions which could be grouped under the heading of "non-hindbrain related syringomyelia", these mostly produce blockage of the spinal subarachnoid spaces, especially spinal "arachnoiditis" or meningeal fibrosis, including that secondary to traumatic paraplegia. Intraspinal tumours are sometimes cystic and some authors have included this association under the heading of syringomyelia. Syringomyelia of all kinds is almost always a surgical condition, the destructive forces are those of fluid distending the tissues. As a principle, treatment directed against the cause of the accumulation and the intracord propagation of the fluid by normalising the CSF pathways is more likely to be successful than drainage of the cavities. Drainage operations have an inevitable failure rate and a further incidence of complications attends myelotomy and the leaving of any drainage tube within the narrow confines of the spine. Correction of craniospinal pressure dissociation and re-establishment of a cisterna magna appears to be the most successful treatment strategy and is likely to be immediately and permanently successful in correcting not only the pressure problems such as long tract involvement and syringobulbia features but also in producing satisfactory clinical and radiological improvement in the syringomyelia. The recommended technique includes radical means to gain space at the foramen magnum by creating a large artificial cisterna magna, resecting part of the tonsils, preventing the descent of the cerebellum and avoiding the use of space occupying or fibrosis producing dural grafts. Because the pathogenesis of the cavities remains in doubt, the method by which this treatment stratagem is effective is unclear. It may be that change in the closure conditions of parts of the neuraxis, i.e., alteration in the capacitance and consequent change in pulsation characteristics afforded by the decompression may be the factor which predicates success. Surgical management of hindbrain related syringomyelia is not easy, there are hazards associated with operation, hydrocephalus demands priority in it's management.(ABSTRACT TRUNCATED AT 400 WORDS)

Formation and regeneration of rhombomere boundaries in the developing chick hindbrain

Development in the chick hindbrain is founded on a segmented pattern. Groups of cells are allocated to particular segmental levels early in development, the cells of each segment (rhombomere) mixing freely with each other, but not with those of adjacent segments. After rhombomere formation, cells in the boundary regions become increasingly specialised. Rhombomeres are thus separate territories that will ultimately pursue different developmental fates. We are investigating the mechanisms that establish and maintain the pattern of rhombomeres and their boundaries. Donor-to-host transplantation experiments were used to confront tissue from different axial levels within the hindbrain. The frequency of boundary regeneration and patterning in the hindbrain was then assessed, based on gross morphology, arrangement of motor neurons and immunohistochemistry. We found that when rhombomeres from adjacent positions or positions three rhombomeres distant from one another were confronted, a normal boundary was invariably reconstructed. Juxtaposition of rhombomere 5 with 7 also yielded a new boundary. By contrast, donor and host tissue of the same positional origin combined without forming a boundary. The same result was obtained in combinations of rhombomeres 3 and 5. Confrontation of tissue from even-numbered rhombomeres 4 with 6 or 2 with 4 also failed to regenerate a boundary in the majority of cases. These results suggest that cell surface properties vary according to rhombomeric level in the hindbrain, and may support the idea of a two-segment periodicity.

Anatomical landmarks of the Rhomboid fossa (floor of the 4th ventricle), its length and its width

Described are: 1. Length and width values of the rhomboid fossa. 2. Number and development of the transverse and oblique striae in the bottom area of the fourth ventricle. 3. The course of the facial nerve inside the pons and the medulla oblongata. 4. Some fiber tracts and nuclei in the tegmentum pontis and the medulla oblongata. 5. A very thick arcuato-cerebellar tract. 6. The results of our investigations are compared with descriptions of other researchers.