International Consensus Statement on the Radiological Evaluation of Dysraphic Malformations of the Spine and Spinal Cord.

Dysraphic malformations of the spine and spinal cord (DMSSC) represent a spectrum of common congenital anomalies typically (though not exclusively) affecting the lower spinal segments. These may be responsible for varying degrees of neurologic, orthopedic, and urologic morbidity. With advances in neuroimaging, it is now possible to better diagnose and evaluate these disorders both prenatally and postnatally. Neuroimaging, performed at the right time and with technique optimization, is integral in guiding clinical management. However, the terminology used to describe these lesions has become increasingly confusing, and there is a lack of consensus regarding the essential radiologic features and their clinical weighting. This variability in radiologic practice risks unstructured decision making and increases the likelihood of suboptimal, less informed clinical management. In this manuscript, the first of a series of consensus statements, we outline a standardized international consensus statement for the radiologic evaluation of children with suspected DMSSC derived from a critical review of the literature, and the collective clinical experience of a multinational group of experts. We provide recommendations for plain radiography, sonography, CT, and MR imaging in the evaluation of DMSSC with an emphasis on technique of imaging and imaging protocols.

Limited exposure to preserve stability and achieve complete excision of limited dorsal myeloschisis - the "Skip-Hop Laminectomy" technique: a technical note.

OBJECTIVE: The fibroneural stalk of an LDM has variable thickness, complexity, and length, which can span 5 to 6 vertebral segments from its skin attachment to its "merge point" with the dorsal spinal cord. Therefore, complete resection may require extensive multi-level laminotomies. In this technical note, a modification of the procedure is presented that avoids long segment laminectomies while ensuring complete excision of long LDM stalks. RESULTS: An illustrative case of resection of LDM is presented using skip laminectomies. The technique ensures complete removal of the stalk, thus reducing the risk of future intradural dermoid development, while at the same time minimizes the risk for delayed kyphotic deformity. CONCLUSIONS: A technique of "skip-hop" proximal and distal short segment laminectomies in cases of LDM optimizes the objectives of complete stalk resection with preservation of spinal integrity.

A New Surgical Paradigm for Postnatal Repair of Open Neural Tube Defects Using Intraoperative Neurophysiology Monitoring.

An open neural tube defect (ONTD) features an exposed, unclosed neural plate in the form of an expanded and frequently hefty neural placode. Traditional philosophy of ONTD repair aims at preserving the placode at any cost, which often means stuffing the entire thick and unwieldy but non-functional tissue into a tight dural sac, increasing the likelihood of future tethering of the spinal cord. The same philosophy of attempting to save the whole perimetry of the placode also sometimes leads to inadvertent inclusion of parts of the squamous epithelial membrane surrounding the placode into the reconstructed product, only to form inclusion dermoid cyst causing further injury to the neural tissues. Lastly, unsuccessful neurulation of the caudal primary neural tube almost always adversely affects junctional and secondary neurulation resulting in a defective conus, often with a locally active sacral micturition centre that is isolated from and therefore lacking suprasegmental inhibitory moderation. This frequently leads to the development of a spastic, hyperactive, low-compliance and high-pressure bladder predisposing to upstream kidney damage, without benefits of normal bladder function. We are introducing a new surgical technique designed to minimise or eliminate these three undesirable complications of conventional ONTD closure.

Focal Spinal Nondisjunctional Disorders: Including a Discussion on the Embryogenesis of Cranial Focal Nondisjunctional Lesions.

The publication of a comprehensive report on limited dorsal myeloschisis by the senior author (DP) in 2010 has brought full attention to the concept of limited myeloschisis that he first formulated in 1992 and ignited interests in the whole spectrum of focal spinal nondisjunctional disorders. Now that focal nondisjunctional disorders have become well known, new clinical reports on these conditions or relevant subjects are frequently seen. Here we present an updated review on the full spectrum of focal spinal nondisjunctional disorders and extend the scope to include a discussion on the embryogenesis of cranial focal nondisjunctional malformations.

Junctional Neural Tube Defect (JNTD): A Rare and Relatively New Spinal Dysraphic Malformation.

Junctional neurulation completes the sequential embryological processes of primary and secondary neurulation as the intermediary step linking the end of primary neurulation and the beginning of secondary neurulation. Its exact molecular process is a matter of ongoing scientific debate. Abnormality of junctional neurulation-junctional neural tube defect (JNTD)-was first described in 2017 based on a series of three patients who displayed a well-formed secondary neural tube, the conus, that is physically separated by a fair distance from its companion primary neural tube and functionally disconnected from rostral corticospinal control. Several other cases conforming to this bizarre neural tube arrangement have since appeared in the literature, reinforcing the validity of this entity. The clinical, neuroimaging, and electrophysiological features of JNTD, as well as the hypothesis of its embryogenetic mechanism, will be described in this chapter.

Secondary Neurulation Defect: Terminal Myelocystocele, a Biological Leviathan.

Terminal myelocystocele (TMC) has been a puzzling entity of spinal dysraphism. It is found in the sacrococcygeal region usually forming a subcutaneous hump of various sizes. The wide variation of its morphology has been clarified by defining the essential and nonessential features as described in this chapter. Although it is not a common entity, TMC is attractive in that a highly plausible hypothesis on its pathoembryogenesis has been proposed based on observations on the secondary neurulation of the chick embryo. In this chapter, the embryology will be described, followed by the surgical strategy in accordance with the embryogenesis. The clinical features and prognosis will also be presented in detail.

The Current Status of the Surgical Management of Complex Spinal Cord Lipomas: Still Navigating the Labyrinth?

This review summarises the classification, anatomy and embryogenesis of complex spinal cord lipomas and describes in some detail the technique of total lipoma resection and radical reconstruction of the affected neural placode. Its specific mission is to tackle two main issues surrounding the management of complex dysraphic lipomas: whether total resection confers better long-term benefits than partial resection and whether total resection does better than conservative treatment, i.e. no surgery, for asymptomatic lipomas. Accordingly, the 24-year progression-free survival data of the senior author and colleagues' series of over 300 cases of total resection are compared with historical data from multiple series (including our own) of partial resection, and total resection data specifically for asymptomatic lesions are compared with the two known series of non-surgical treatment of equivalent patients. These comparisons so far amply support the author's recommendation of total resection for most complex lipomas, with or without symptoms. The notable exception is the asymptomatic chaotic lipoma, whose peculiar anatomical relationship with the neural tissue defies even our aggressive surgical approach, and consequently projects worse results (admittedly of small number of cases) than for the other two lipoma subtypes of dorsal and transitional lesions. Prophylactic resection of asymptomatic chaotic lipomas is therefore not currently endorsed. We have also recently found that some dorsal lipomas with clear outline of the conus on preoperative imaging had a significantly better long-term prognosis of preserving neurourological functions without surgery. Whether this subset of lipomas should be managed conservatively until symptoms arise is now an open question awaiting a longer follow-up of a larger cohort of such patients.

Limited dorsal myeloschisis involving one hemicord of a split cord malformation - a "hemi-LDM".

This is a case report of an exceedingly rare case of a limited dorsal myeloschisis (LDM) with its stalk inserted on the midline dorsal surface of one of a pair of hemicords in a type II split cord malformation. This entity, literally a "hemi-LDM," has been seen only once by the senior author in his catalogue of over 200 cases of LDM (Pang et al., 2020), nor has it been reported elsewhere before. We postulate that here the mechanism of focal nondisjunction of the hemi-neural plate during primary neurulation, which produces LDMs, occurs at the cusp of the consecutive developmental stages of gastrulation and primary neurulation, right after the appearance of the hemi-neural plates and hemi-notochords caused by the endomesenchymal tract. This child also had a terminal lipoma attached to the end of the conus, indicating that disruption of all three tandem stages of neural tube formation, namely, gastrulation, primary neurulation, and secondary neurulation, can occur in the same individual.

Radical resection of lumbosacral lipomas in children: the Great Ormond Street Hospital experience.

PURPOSE: In 2009, Pang described a radical resection technique for congenital lumbosacral lipomas, with lower long-term symptomatic re-tethering rates compared with partial resections and conservative management, and low surgical morbidity. We adopted this technique in 2011, and aim to describe our first results. METHODS: In this monocentric retrospective audit, we included dorsal, transitional, chaotic, and caudal-type lumbosacral lipomas. Exclusion criteria were previously operated lipomas, pure filar lipomas, and concomitant major congenital anatomical urogenital/gastrointestinal abnormalities. Neuro-uro-orthopaedic status at presentation and at three months, one year and last postoperative follow-up, intraoperative electrophysiology, and extent of resection were collected. RESULTS: From January 2011 to September 2019, 91 patients were operated (median age 2y2m; 63 transitional; 14 caudal; 8 dorsal; 6 chaotic). Preoperatively, 67% were symptomatic. Preoperative and one-year postoperative rates of impaired ambulation (44% to 43%), hypoesthesia (8% to 5%), urodynamic/uroradiological abnormalities (49% to 37%), and foot/ankle deformities (8% to 5%) were comparable, whilst pain improved (25% to 5%) but catheterisation rates increased (21% to 36%). 23/92 (25%) suffered wound-related complications. 2/91 (2%) developed symptomatic re-tethering requiring second surgery. Mean cord/sac ratio was 0.47. 43% had > 20 mm3 residual fat, which improved with increasing surgical experience. CONCLUSION: Radical lipoma resection, guided by intraoperative neuromonitoring, with reconstruction of the neural placode and expansion duraplasty is technically feasible and results in low rates of late deterioration and re-tethering. Lipoma-type and pre-operative status are important outcome predictors. Operative risks are not insignificant. Future studies need to determine appropriate selection criteria for surgery.

Focal Spinal Nondisjunction in Primary Neurulation : Limited Dorsal Myeloschisis and Congenital Spinal Dermal Sinus Tract.

Spinal dysraphic lesions due to focal nondisjunction in primary neurulation are commonly encountered in paediatric neurosurgery, but the "fog-of-war" on these conditions was only gradually dispersed in the past 10 years by the works of the groups led by the senior author and Prof. Kyu-Chang Wang. It is now clear that limited dorsal myeloschisis and congenital spinal dermal sinus tract are conditions at the two ends of a spectrum; and mixed lesions of them with various configurations exist. This review article summarizes the current understanding of these conditions' embryogenetic mechanisms, pathological anatomy and clinical manifestations, and their management strategy and surgical techniques.

Intracranial infantile hemangioma - rare entity and common pitfalls: A comprehensive multidisciplinary approach from Neurosurgery, Neurooncology and Neuropathology.

OBJECTIVE: To review the rare entity of pediatric intracranial hemangiomas and discuss surgical pitfalls and pathophysiology in regard to cerebral edema formation. MATERIALS AND METHODS: We describe an extremely rare case of intracranial infantile hemangioma in a neonate with massive cerebral edema, surgically resected urgently because of acute herniation. We review the literature of 46 other pediatric cases of intracranial hemangioma, including congenital capillary hemangiomas. We analyze the data on age, sex distribution, tumor location, growth pattern, edema formation, histopathology, treatment, and outcome. RESULTS: Isolated intracranial infantile hemangiomas in the neonatal period are extremely rare. Some but not all hemangiomas can be treated pharmacologically. Extensive cerebral edema is a frequent finding and can become an enormous problem at surgical resection. The pathogenesis of the edema formation in hemangiomas is complex and is yet not well understood. CONCLUSION: Surgical resection of intracranial hemangiomas is associated with a high morbidity, and pharmacological treatment should, if possible, always be considered first, at least for preoperative optimization. The severity of cerebral edema varies among intracranial hemangiomas, which may be an indicator of different molecular properties of the individual lesions. This implies that further sub-classification of intracranial hemangiomas may be necessary.

New surgical paradigm for open neural tube defects.

INTRODUCTION: An open neural tube defect (ONTD) features an exposed, unclosed neural plate in the form of an expanded, flat, and frequently hefty neural placode. Traditional philosophy of ONTD repair aims at preserving function at any cost, which often means stuffing the entire thick and unwieldy but non-functional placode into a tight dural sac, increasing the likelihood of future tethering of the spinal cord. The same philosophy of attempting to save the whole perimetry of the placode also sometimes leads to inadvertent inclusion of parts of the squamous epithelial membrane surrounding the placode into the reconstructed product, only to form inclusion dermoid cyst causing further injury to the neural tissues. Lastly, defective closure of the caudal primary neural tube usually results in abolition of secondary and junctional neurulation, leaving a defective conus and sacral nerve roots, clinically presenting in most cases with neurogenic bladder and bowel dysfunction. Preserving this trapped but locally active sacral micturition center, isolated from suprasegmental inhibitory moderation, leads to a spastic, hyperactive, low compliance, and high-pressure bladder predisposing to upstream kidney damage, without benefits of normal bladder function. METHOD AND MATERIAL: We report the post-natal surgical treatment of 8 newborn infants with ONTD, in which we resected the non-functional portion of the neural placode identified as such by direct spinal cord/placode and nerve root stimulation, as well as by transcortical evoked motor responses to check for suprasegmental corticospinal connectivity. Any part of the placode without local function or upstream connections was resected, and the small caudal spinal cord stump closed with pia-to-pia microsutures. The patients were followed for pre- and post-operative neuro-urological status and with serial magnetic resonance imaging (MRI) at 3 weeks, 6 months, and 2 years post-repair. Follow-up period ranged from birth to 3 years (mean of 24 months). RESULTS: Of the 8 patients analyzed, 7 had a terminal and one a segmental ONTD. Pre-operative neurological level ranged from L4 to S2. Applying our new surgical paradigm, we found no neurological worsening post-operatively. All patients had a neurogenic bladder and bowel dysfunction but none had a high-pressure bladder on urodynamics studies. Early and late MRIs all showed a loose and capacious neural placode to dural sac relationship. None had an inclusion dermoid cyst. CONCLUSION: We propose a new paradigm for the surgical repair of open neural tube defects with intraoperative neuromonitoring and introduce a safe and reliable technique of placode debulking.

Surgical Management of Complex Spinal Cord Lipomas : A New Perspective.

This review summarises the classification, anatomy and embryogenesis of complex spinal cord lipomas, and describes in some detail the new technique of total lipoma resection and radical reconstruction of the affected neural placode. Its specific mission is to tackle two main issues surrounding the management of complex dysraphic lipomas : whether total resection confers better long term benefits than partial resection, and whether total resection does better than conservative treatment, i.e., no surgery, for asymptomatic lipomas. Accordingly, the 24 years progression-free survival data of the author and colleagues' series of over 350 cases of total resection are compared with historical data from multiple series (including our own) of partial resection, and total resection data specifically for asymptomatic lesions are compared with the two known series of non-surgical treatment of equivalent patients. These comparisons amply support the author's recommendation of total resection for most complex lipomas, with or without symptoms. The notable exception is the asymptomatic chaotic lipoma, whose peculiar anatomical relationship with the neural tissue defies even our aggressive surgical approach, and consequently projects worse results (admittedly of small number of cases) than for the other two lipoma subtypes of dorsal and transitional lesions. Prophylactic resection of asymptomatic chaotic lipomas is therefore not currently endorsed.

Perspectives on Spinal Dysraphism : Past, Present, and Future.

This article recounts the author's personal views and recollections of the history, conception of embryogenetic theories, application of intraoperative electrophysiology, and development of prospective treatment recommendations of several important spinal dysraphic malformations, including limited dorsal myeloschisis, dermal sinus tract, retained medullary cord, terminal myelocystocoele, and complex spinal cord lipomas.

Junctional Neural Tube Defect.

Junctional neurulation represents the most recent adjunct to the well-known sequential embryological processes of primary and secondary neurulation. While its exact molecular processes, occurring at the end of primary and the beginning of secondary neurulation, are still being actively investigated, its pathological counterpart -junctional neural tube defect (JNTD)- had been described in 2017 based on three patients whose well-formed secondary neural tube, the conus, is widely separated from its corresponding primary neural tube and functionally disconnected from corticospinal control from above. Several other cases conforming to this bizarre neural tube arrangement have since appeared in the literature, reinforcing the validity of this entity. The cardinal clinical, neuroimaging, and electrophysiological features of JNTD, and the hypothesis of its embryogenetic mechanism, form part of this review.

Surgical management of complex spinal cord lipomas: how, why, and when to operate. A review.

This review summarizes the classification, anatomy, and embryogenesis of complex spinal cord lipomas, and it describes in some detail the new technique of total lipoma resection and radical reconstruction of the affected neural placode. Its specific mission is to tackle two main issues surrounding the management of complex dysraphic lipomas: whether total resection confers better long-term benefits than partial resection and whether total resection fares better than conservative treatment-i.e., no surgery-for asymptomatic lipomas. Accordingly, the 24-year progression-free survival data of the author and colleagues' series of over 300 cases of total resection are compared with historical data from multiple series (including the author and colleagues' own) of partial resection, and total resection data specifically for asymptomatic lesions are compared with the two known series of nonsurgical treatment of equivalent numbers of patients. These comparisons amply support the author's recommendation of total resection for most complex lipomas, with or without symptoms. The notable exception is the asymptomatic chaotic lipoma, whose peculiar anatomical relationship with the neural tissue defies even this aggressive surgical approach and consequently projects worse results (admittedly of a small number of cases) than for the other two lipoma subtypes of dorsal and transitional lesions. Prophylactic resection of asymptomatic chaotic lipomas is therefore not currently endorsed.

Posttraumatic Spinal Cord Injury without Radiographic Abnormality.

"Spinal Cord Injury without Radiographic Abnormality" (SCIWORA) is a term that denotes objective clinical signs of posttraumatic spinal cord injury without evidence of fracture or malalignment on plain radiographs and computed tomography (CT) of the spine. SCIWORA is most commonly seen in children with a predilection for the cervical spinal cord due to the increased mobility of the cervical spine, the inherent ligamentous laxity, and the large head-to-body ratio during childhood. However, SCIWORA can also be seen in adults and, in rare cases, the thoracolumbar spinal cord can be affected too. Magnetic resonance imaging (MRI) has become a valuable diagnostic tool in patients with SCIWORA because of its superior ability to identify soft tissue lesions such as cord edema, hematomas and transections, and discoligamentous injuries that may not be visualized in plain radiographs and CT. The mainstay of treatment in patients with SCIWORA is nonoperative management including steroid therapy, immobilization, and avoidance of activities that may increase the risk of exacerbation or recurrent injury. Although the role of operative treatment in SCIWORA can be controversial, surgical alternatives such as decompression and fusion should be considered in selected patients with clinical and MRI evidence of persistent spinal cord compression and instability.

The Pantheon Variant of the Classic Cathedral Dome Procedure for Parieto-Occipital Skull Deformities.

OBJECTIVE: To describe a new technique for the reconstruction of parieto-occipital skull deformities. METHODS AND RESULTS: The technique is a variant of the previously described "cathedral dome procedure" used for frontal skull deformities. The authors apply the same principle of remodeling by making meridional slat craniotomies surrounding the depressed dome of the posterior skull deformity, followed by "green-stick fracture-reshaping" of the meridional slats to elevate and support the excised depressed dome. The authors present an illustrative patient with a follow-up of 2 years and an excellent cosmetic result. CONCLUSION: The authors introduce a new operative technique for the reconstruction of parieto-occipital skull deformities with excellent long-term results. The freshly reconstructed occiput resembles the dome of the pantheon in Rome, Italy, whose unique features inspired us to name this procedure the "Pantheon" variant of the cathedral dome operation.

Traumatic Posterior Fossa Subdural Hygroma and Secondary Occlusive Hydrocephalus.

BACKGROUND: Infratentorial subdural hygromas causing secondary occlusive hydrocephalus are extremely rare in children. Only a handful of cases have been reported in the literature. METHODS: We present a case of a 6-month-old infant with an occipital fracture and slow enlargement of a posterior fossa subdural hygroma that culminated in obstructive hydrocephalus. We give a review of the literature on post-traumatic posterior fossa hygroma with secondary occlusive hydrocephalus and discuss its pathogenesis and the mechanism of its later resolution, as well as the available treatment options. RESULTS: A temporary external ventricular drain led to acute relief of the hydrocephalus and subsequent complete resolution of the subdural hygroma. CONCLUSION: Temporary external ventricular drain placement led to complete resolution of the subdural hygroma and hydrocephalus. We recommend close clinical follow-up, and imaging if indicated, for as long as 4 weeks after trauma with occipital skull fractures.