The odontoid process in Morquio-Brailsford's disease. The effects of occipitocervical fusion

Spinal Manifestations of Skeletal Dysplasia: A Practical Guide for Clinical Diagnosis

Skeletal dysplasias are a group of genetic conditions defined by atypical bone or cartilage growth and development. Skeletal abnormalities include short stature, limb deformity, joint contracture, and spinal deformity. Over 90% of disorders have a known genetic mutation that can definitively determine the diagnosis. As patients may present with a primary spinal concern, a careful clinical and radiographic evaluation can allow the physician to develop a working diagnosis to guide additional evaluation. Spinal manifestations include scoliosis and kyphoscoliosis, cervical instability, cervical kyphosis, thoracolumbar kyphosis, spinal stenosis, and atypical vertebral body morphology. An understanding of the affected conditions, prevalence, and natural history of these radiographic findings aids the orthopaedic surgeon in establishing a diagnosis and guides appropriate orthopaedic care.

Functional and radiological outcomes following craniovertebral junction surgery

Background

Craniovertebral junction (CVJ) pathologies include atlantoaxial instability/deformities resulting in myelopathy, respiratory failure, and even death. Here, we describe the indications, preoperative planning, and intra-operative/postoperative complications following surgical management of CVJ anomalies.

Methods

A prospective analysis of 34 patients with CVJ pathology was evaluated between 2015 and 2022. Their various etiologies included atlantoaxial instability, trauma, tuberculosis, Down's syndrome, Morquio syndrome, os odontoideum, and atlantoaxial abnormalities. Clinical outcomes were assessed using the American spinal injury association (ASIA) impairment scale score and Benzel's modified Japanese Orthopedic Association (mJOA) score. Surgical assessments included length of hospital stay, operative time, blood loss, and intraoperative postoperative complications. Radiological parameters included fusion (i.e., implant loosening/implant failure), preoperative/ postoperative atlanto-dens interval (ADI), clivus canal angle (CCA), and space available for cord (SAC).

Results

Five patients were managed conservatively, while 29 patients had surgery. Operations included occipitocervical fusion (14 patients), C1-2 fusion (10 patients), C1-2 transarticular screw fixation (four patients), and one patient underwent anterior corpectomy decompression/fusion. Seven patients had vertebral artery anomalies, and 13 patients had atlantoaxial abnormalities. At the final follow-up, atlantoaxial instability (i.e., mean preoperative ADI of 6.6 ± 2.3 mm) was restored to 4.2 ± 0.6 mm, significant cord compression (i.e., with mean SAC of 8.3 ± 2.9 mm) was relieved to 17.2 ± 1.6 mm, and the mean preoperative CCA (i.e., 130.2 ± 15.3) was improved to 143.3 ± 8.3°. There was also a statistically significant improvement in the ASIA scale and mJOA score.

Conclusion

Surgical management of CVJ abnormalities requires expertise and meticulous planning to avoid devastating complications such as wound dehiscence and catastrophic vertebral artery injury.

MR documented craniocervical ligamentous injury at age 18 months: delayed formation of OS odontoideum. Complex management issues. Case-based review

OBJECTIVE

There are two separate theories regarding the genesis of os odontoideum: congenital and post-traumatic. Trauma documentation in the past has been the presence of a normal odontoid process at the time of initial childhood injury and subsequent development of the os odontoideum. True MR documentation of craniocervical injury in early childhood and subsequent os odontoideum formation has been very rare.

METHODS

An 18-month-old sustained craniocervical ligamentous injury documented on MRI with transient neurological deficit. Chiari I abnormality was also recorded. Subsequent serial imaging of craniocervical region showed the formation of os odontoideum and instability. He became symptomatic from the os odontoideum and the Chiari I abnormality. The patient underwent decompression and intradural procedure for Chiari I abnormality and occipitocervical fusion. Postoperative course was complicated by the failure of fusion and redo. He later required transoral ventral medullary decompression. He recovered.

RESULTS

This is an MR documented craniocervical ligamentous injury with sequential formation of os odontoideum with accompanying changes in the atlas. Despite a subsequent successful dorsal occipitocervical fusion, he became symptomatic requiring transoral decompression.

CONCLUSIONS

Os odontoideum here is recognized as a traumatic origin with the presence of congenital Chiari I abnormality as a separate entity. The changes of the anterior arch of C1 as well as the os formation were serially documented and give credence to blood supply changes in the os and atlas as a result of the trauma. The recognized treatment of dorsal occipitocervical fusion failed in this case requiring also a ventral decompression of the medulla.

A pictorial review of the radiographic skeletal findings in Morquio syndrome (mucopolysaccharidosis type IV)

Morquio syndrome, also known as Morquio-Brailsford syndrome or mucopolysaccharidosis type IV (MPS IV), is a subgroup of mucopolysaccharidosis. It is an autosomal recessive lysosomal storage disorder. Two subtypes of Morquio syndrome have been identified. In MPS IVA, a deficiency in N-acetylgalactosamine-6-sulfate sulfatase interrupts the normal metabolic pathway of degrading glycosaminoglycans. Accumulated undigested glycosaminoglycans in the tissue and bones result in complications leading to severe skeletal deformity. In MPS IVB, a deficiency in beta-galactosidase results in a milder phenotype than in MPS IVA. Morquio syndrome presents a variety of clinical manifestations in a spectrum of mild to severe. It classically has been considered a skeletal dysplasia with significant skeletal involvement. However, the extraskeletal features can also provide valuable information to guide further work-up to assess the possibility of the disorder. Although the disease involves almost all parts of the body, it most commonly affects the axial skeleton, specifically the vertebrae. The characteristic radiologic findings in MPS IV, such as paddle-shaped ribs, odontoid hypoplasia, vertebral deformity, metaphyseal and epiphyseal bone dysplasia, and steep acetabula, are encompassed in the term "dysostosis multiplex," which is a common feature among other types of MPS and storage disorders. Myelopathy due to spinal cord compression and respiratory airway obstruction are the most critical complications related to mortality and morbidity. The variety of clinical features, as well as overlapping of radiological findings with other disorders, make diagnosis challenging, and delays in diagnosis and treatment may lead to critical complications. Timely imaging and radiologic expertise are important components for diagnosis. Gene therapies may provide robust treatment, particularly if genetic variations can be screened in utero.

Burden of Surgical Treatment for the Management of Cervical Myelopathy in Mucopolysaccharidoses: A Systematic Review

Mucopolysaccharidoses (MPSs) are a rare group of heterogeneous genetic and metabolic disorders, caused by loss of functions of several enzymes that are involved in glycosaminoglycan catabolism. Their progressive accumulations in cells, tissues, and consequently, organs lead to several clinical manifestations, such as musculoskeletal involvement. Indeed, the most common manifestation in the central nervous system is represented by cervical spinal stenosis due to bony alterations or dural thickening. Cervical involvement can commonly cause myelopathy and instability exerting severe symptoms. A prompt diagnosis and treatment of the aforementioned conditions is mandatory to ensure a better quality of life in patients with such debilitating disorders. Nevertheless, a clear consensus about their management (i.e., surgical or not) is still lacking, leading to an inevitable delay. This review aims to investigate and discuss the main causes of myelopathy in patients with mucopolysaccharidoses, available therapeutic strategies, and the impact and role of surgery on the neurological outcome.

How did intraoperative neuromonitorization prevent tetraplegia?

Patients with mucopolysaccharidosis type IVA (MPS IVA) have many risk factors for myelopathy and paresis. These are spinal cord compression, bone stenosis, and soft tissue thickening with ligament laxity, deformity, odontoid hypoplasia, and atlantoaxial instability. Although most patients with MPS IVA appear generally healthy at birth, patients often show skeletal deformities within a few years. Surgical indications are difficult to determine. Historically, many physicians have used prophylactic decompression and fusion in young, asymptomatic MPS IVA patients to prevent cord compression. Although spinal cord decompression is usually required at the craniocervical junction in patients with MPS IVA, decompression may be required at other spinal cord levels as well. There is a risk of developing neurological damage during surgery. The most common causes are ischemia secondary to cardiac output deteriorated in the prone position or due to artery damage, and local trauma due to neck movements or traction while bringing the patient to the prone position. Neurophysiological monitoring is very important during surgery to reduce the risk of neurological damage in spinal cord surgery. In this case report, a case with loss of lower extremity neuromonitorization motor evoked potential (MEP) responses in the early period of surgery without any intervention to the craniocervical junction after prone positioning will be presented.

Os odontoideum: A comprehensive review

Os odontoideum (OO) is a rare craniocervical anomaly that is characterized by a round ossicle separated from the C2 vertebral body. With a controversial etiology and unknown prevalence in the population, OO may be asymptomatic or present in patients with myelopathic and neurological symptoms. In this literature review, we aimed to investigate epidemiology, embryology, pathophysiology, clinical presentation, and the role of diagnostic radiography in OO. By providing an overview of different management strategies, surgical complications, and postoperative considerations for OO, our findings may guide neurosurgeons in providing proper diagnosis and treatment for OO patients. A literature review was conducted using the PubMed, EMBASE, and Scopus databases. A search using the query "os odontoideum" yielded 4319 results, of which 112 articles were chosen and analyzed for insights on factors such as etiology, clinical presentation, and management of OO. The presentation of OO varies widely from asymptomatic cases to severe neurological deficits. Asymptomatic patients can be managed either conservatively or surgically, while symptomatic patients should undergo operative stabilization. Although multiple studies show different techniques for surgical management involving posterior fusion, the diversity of such cases illustrates how treatment must be tailored to the individual patient to prevent complications. Conflicting studies and the paucity of current literature on OO highlight poor comprehension of the condition. Further understanding of the natural history of OO is critical to form evidence-based guidelines for the management of OO patients. More large-center studies are thus needed to promote accurate management of OO patients with optimal outcomes.

The surgical management of spinal disorders in lysosomal storage diseases: a systematic review

BACKGROUND

The skeletal manifestations of lysosomal storage diseases (LSDs) are largely refractory to available therapeutic modalities. Consequently, there is an increasing need to manage their spinal deformities. The aim was to perform a systematic review to answer the questions, "What are the reported indications for surgery for spinal deformity in patients with LSDs?" and "what are the published surgical management strategies?".

METHODS

Articles that made reference to at least one LSD, a spinal abnormality and surgical management were included. Extracted study data included: study type, sample size, methodology and year of publication. The following clinical information was collected: demographics, spinal abnormalities, and surgical indications, details and outcomes.

RESULTS

Thirty-seven articles were included, with 23 describing surgical management of craniocervical manifestations seen in mucopolysaccharidosis. Radiological evidence of myelopathy at the craniocervical junction and/or progressive clinical neurological compromise were accepted as surgical indications. Prophylactic surgery was proposed by some authors. The recommended surgical technique and whether to stabilise and/or decompress varied between articles and LSD types. Twenty-one articles discussed thoracolumbar pathology, including thoracolumbar kyphosis and scoliosis. Radiological severity, progression of deformity, and presence of neurological deterioration were discussed as surgical indications. Most papers recommended circumferential arthrodesis via combined anterior and posterior approaches.

CONCLUSION

The surgical management of spinal disorders in LSDs remains controversial. Centres managing these patients should be encouraged to have a standardised system of reporting outcomes, to facilitate recommendations for management of the spinal manifestations.

Bone Biomarkers in Mucopolysaccharidoses

The accumulation of glycosaminoglycans (GAGs) in bone and cartilage leads to progressive damage in cartilage that, in turn, reduces bone growth by the destruction of the growth plate, incomplete ossification, and growth imbalance. The mechanisms of pathophysiology related to bone metabolism in mucopolysaccharidoses (MPS) include impaired chondrocyte function and the failure of endochondral ossification, which leads to the release of inflammatory cytokines via the activation of Toll-like receptors by GAGs. Although improvements in the daily living of patients with MPS have been achieved with enzyme replacement, treatment for the bone disorder is limited. There is an increasing need to identify biomarkers related to bone and cartilage to evaluate the progressive status and to monitor the treatment of MPS. Recently, new analysis methods, such as proteomic analysis, have identified new biomarkers in MPS. This review summarizes advances in clinical bone metabolism and bone biomarkers.

Clinical outcomes of laminoplasty for patients with lysosomal storage disease including mucopolysaccharidosis and mucolipidoses: a retrospective cohort study

Background

Although the clinical efficacy of laminoplasty in adult cervical spondylotic myelopathy or ossification of posterior longitudinal ligament has been frequently reported, there are only few reports of laminoplasty for patients with lysosome storage diseases (LSDs). Therefore, this study aimed to report the midterm clinical and radiological outcomes of patients with LSDs after cervical laminoplasty.

Methods

Six patients with LSD who underwent laminoplasty with/without C1 laminectomy for cervical myelopathy were enrolled. Clinical evaluations, including the cervical Japanese Orthopedic Association (cJOA) score and visual analog scale (VAS) scores for upper extremity numbness, and radiographic parameters, including C2–C7 lordotic angle, atlanto-dens interval (ADI), and ⊿ADI, were evaluated preoperatively, at 2 years postoperatively, and at the final follow-up.

Results

Five patients had mucopolysaccharidoses (type I: n = 1, II: n = 3, VII: n = 1) and one patient had mucolipidoses type III. The mean age of patients at surgery was 27.5 years, and the mean postoperative follow-up period was 61 months. All mucopolysaccharidoses cases required C1 posterior arch resection with C2–C7 laminoplasty. No critical complications were observed postoperatively. There were no significant differences in C2–C7 angle (p = 0.724) and ⊿ADI (p = 0.592) between the preoperative and final follow-ups. The cJOA score and VAS for numbness significantly improved at the final follow-up (p = 0.004 and p = 0.007, respectively).

Conclusions

The cervical myelopathy in patients with LSD could be safely and effectively treated with laminoplasty with/without C1 posterior arch resection after excluding patients with atlantoaxial instability. Atlantoaxial stability and symptom improvement could be maintained at an average of 5 years postoperatively.

Adult Morquio syndrome requiring occipito-thoracic fusion

Morquio syndrome is a relatively rare entity that is often associated with atlantoaxial instability from early childhood due to odontoid dysplasia based on a mucopolysaccharoidal disorder. Here, we present the case of a 55-year-old male patient with Morquio syndrome who developed cervical myelopathy, which is an extremely rare condition in the older population. Myelopathy developed gradually with upper-limb paresthesia and clumsiness of both hands. The patient had a characteristic "gargoyle-like" coarse face with a trunk shortening-type short stature. Imaging of the cervical spine demonstrated several problems, including diminutive structures called platyspondyly with small pedicles and fragile bone quality, hypoplasia of the C1 posterior arch that migrated into the spinal canal, and os odontoideum with atlantoaxial instability. With intraoperative navigation guidance, posterior decompression of C1 followed by occipito-cervico-thoracic spinal fusion was successfully performed in this complicated case. Clinical and radiographic outcomes were both excellent and have been maintained for 2 years postoperatively.

Lessons learned from surgical management of craniovertebral instability in Morquio syndrome: A series of four unusual cases

Morquio syndrome (MS) is an autosomal recessive defect caused by the deficiency of N-acetylgalactosamine-6-sulfatase. Odontoid hypoplasia, periodontoid soft tissue deposition, and cervical stenosis lead to myelopathy and quadriparesis in these patients. Craniovertebral junction instability in MS possesses a surgical challenge as bones are yet to completely ossify. The atlantoaxial dislocation (AAD) is reducible, and the need of transoral decompression for the soft tissue deposition ventral to odontoid is debatable. We present a series of four cases (mean age 4.3 ± 0.4 years) operated through posterior-only approach (n = 2, C1-lateral mass to C2 pars-interarticularis [Goel's technique]; n = 1 sublaminar wiring followed by C1-lateral mass to C2 pars-interarticularis; and n = 1 suboccipital plate with pars-interarticularis of C2 screw and pedicle of C3 and rod fixation). All patients had acceptable outcome and doing well at the last follow-up (12–96-follow-up). None of our patient needed transoral decompression. Patients with MS frequently manifest with spastic quadriparesis at an early age due to reducible AAD. Early surgical fixation with posterior C1–C2 screw and rod technique is recommended for the favorable surgical outcome and long-term stability of the cervical spine.

Mucopolysaccharidosis IVA: Diagnosis, Treatment, and Management

Mucopolysaccharidosis type IVA (MPS IVA, or Morquio syndrome type A) is an inherited metabolic lysosomal disease caused by the deficiency of the N-acetylglucosamine-6-sulfate sulfatase enzyme. The deficiency of this enzyme accumulates the specific glycosaminoglycans (GAG), keratan sulfate, and chondroitin-6-sulfate mainly in bone, cartilage, and its extracellular matrix. GAG accumulation in these lesions leads to unique skeletal dysplasia in MPS IVA patients. Clinical, radiographic, and biochemical tests are needed to complete the diagnosis of MPS IVA since some clinical characteristics in MPS IVA are overlapped with other disorders. Early and accurate diagnosis is vital to optimizing patient management, which provides a better quality of life and prolonged life-time in MPS IVA patients. Currently, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are available for patients with MPS IVA. However, ERT and HSCT do not have enough impact on bone and cartilage lesions in patients with MPS IVA. Penetrating the deficient enzyme into an avascular lesion remains an unmet challenge, and several innovative therapies are under development in a preclinical study. In this review article, we comprehensively describe the current diagnosis, treatment, and management for MPS IVA. We also illustrate developing future therapies focused on the improvement of skeletal dysplasia in MPS IVA.

Os Odontoideum in Children

Os odontoideum is a rare entity of the second cervical vertebra, characterized by a circumferentially corticated ossicle separated from the body of C2. The ossicle is a distinct entity from an odontoid fracture or a persistent ossiculum terminale. The diagnosis may be made incidentally on imaging obtained for the workup of neck pain or neurologic signs and symptoms. Diagnosis usually can be made with plain radiographs. MRI and CT can assess spinal cord integrity and C1-C2 instability. The etiology of os odontoideum is a topic of debate, with investigative studies supporting both congenital and traumatic origins. A wide clinical range of symptoms exists. Symptoms may present as nondescript pain or include occipital-cervical pain, myelopathy, or vertebrobasilar ischemia. Asymptomatic cases without evidence of radiologic instability are typically managed with periodic observation and serial imaging. The presence of atlantoaxial instability or neurological dysfunction necessitates surgical intervention with instrumentation and fusion for stability.

Clinical Manifestations and Surgical Management of Spinal Lesions in Patients With Mucopolysaccharidosis: A Report of 52 Cases

STUDY DESIGN

Descriptive retrospective cohort of 52 pediatric patients with mucopolysaccharidosis (MPS) and spinal cord disease and surgical outcomes in a reference hospital.

OBJECTIVES

To describe clinical manifestations and surgical management and outcomes of spinal lesions.

METHODS

All medical records of 52 patients with mucopolysaccharidosis (I, II, III, IV, and VI) diagnosed between 1992 and 2011 were identified and followed at a single spine center of a pediatric hospital. Demographic, clinical manifestations, spinal cord lesions, and surgical management were the focus of the descriptive report.

RESULTS

A total of 52 patients (32 males and 20 females), mean age at diagnosis of 8 ± 4 years (range 1-19), and with a mean follow-up of 11 ± 8 years were identified. Forty-three had cervical disease (the most frequent affection found was odontoid hypoplasia followed by atlantoaxial instability) and 14 patients had thoracolumbar kyphosis. Twenty-one patients presented neurologic compromise before surgery (quadriparesis as the most frequent manifestation), with the progression of neurologic impairment being the most common surgical indication. Surgery was performed in 38 patients (25 cervical and 13 thoracolumbar). Of the 21 patients with preoperative neurologic deficit, 6 patients showed neurologic improvement. The most common surgical complication found was proximal junctional kyphosis.

CONCLUSION

This is the largest series published of mucopolysaccharidosis pediatric patients with a surgically treated spinal condition. We recommend early spinal cord decompression in mucopolysaccharidosis spine pathology to prevent or potentially reverse neurologic impairment.

LEVEL OF EVIDENCE

Level IV.

An Evidence-based Approach to the Management of Children With Morquio A Syndrome Presenting With Craniocervical Pathology

STUDY DESIGN

Retrospective case series OBJECTIVE.: The aim of this study was to review clinical and radiological outcomes of craniovertebral surgery in children with Morquio A syndrome (Mucopolysaccharidosis type IVA) and develop an evidence-based management algorithm.

SUMMARY OF BACKGROUND DATA

Myelopathy secondary to craniovertebral pathology is a common cause of neurological disability in Morquio A syndrome. Previously unresolved surgical controversies include the value of surveillance, surgical indications, and operative technique.

METHODS

A retrospective case-based review of children with Morquio A syndrome and craniovertebral pathology seen in a tertiary referral pediatric center from 1992 to 2016 was performed. Patients treated nonoperatively and operatively were included. Medical records and imaging were reviewed to determine clinical and radiological findings at initial assessment, before cervical spine surgery, early postoperative period, and final follow-up. The clinical outcomes of interest were neurological status and mobility at follow-up, complications, and need for further surgery.

RESULTS

Twenty-seven patients were included. Surgical indications were radiological evidence of cervicomedullary compression alone (six cases) or with clinical evidence of myelopathy (12 cases). Eighteen patients (median age 6.2 years, range 3.5-15.9 years) underwent surgery, with median follow-up of 8.5 years. Occiput to upper cervical spine fusion with C1 decompression was performed in all cases with the addition of autologous calvarial graft in young patients (12 cases) and occipital-cervical plate fixation in older children (six cases). Neurological improvement occurred in 38% of cases but by one functional level only. Six of nine conservatively treated patients remained independent walkers.

CONCLUSION

Surgery for craniovertebral pathology is required in the majority of children with Morquio A syndrome. Close clinical and radiological surveillance is essential for timely intervention. Occiput to cervical fusion is safe and feasible even in young patients and improves clinical and radiological parameters.

LEVEL OF EVIDENCE

4.

Outcomes from 18 years of cervical spine surgery in MPS IVA: a single centre's experience

PURPOSE

This study examines the long-term outcomes of paediatric Morquio (MPS IVA) patients undergoing cervical spine surgery and evaluates the factors that impacting this.

METHODS

A retrospective review was performed on all MPS IVA patients undergoing cervical spine surgery, since the introduction of standardised neuroradiological screening. The impact of preoperative neurological status, growth, genotype and radiological status on outcome is assessed, whilst long-term surgical, radiological and neurological outcomes are documented.

RESULTS

Twenty-six of the eighty-two MPS IVA patients (31%) reviewed underwent cervical spine surgery at a median age of 6.1 years (range, 1.45 to 15.24). Preoperatively, cord signal change was seen in 11 patients with 5 being myelopathic; however, 6 clinically manifesting patients had no overt cord signal change. Postoperatively, none of the 14 preoperatively clinically asymptomatic patients followed long term progressed neurologically during a median follow-up of 77.5 months (range = 18-161). Of the ten preoperatively clinically symptomatic patients who were followed up for the same duration, seven continued to deteriorate, two initially improved and one remained stable. Radiological follow-up performed for a median duration of 7 years (range = 0.5-16) has shown a degree of stenosis at the level immediately caudal to the termination of the graft in 76% of patients, though only one has become clinically symptomatic and required revision.

CONCLUSIONS

Once clinically elicitable neurological signs become evident in patients with MPS IVA, they tend to progress despite surgical intervention. Referring clinicians should also not be falsely reassured by the lack of T2 spinal cord signal change but should consider surgical intervention in the face of new clinical symptomology or radiological signs of progressive canal stenosis or instability.

Molecular genetics and metabolism, special edition: Diagnosis, diagnosis and prognosis of Mucopolysaccharidosis IVA

Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is an autosomal recessive disorder caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to the accumulation of specific glycosaminoglycans (GAGs), chondroitin-6-sulfate (C6S) and keratan sulfate (KS), which are mainly synthesized in the cartilage. Therefore, the substrates are stored primarily in the cartilage and its extracellular matrix (ECM), leading to a direct impact on bone development and successive systemic skeletal spondylepiphyseal dysplasia. The skeletal-related symptoms for MPS IVA include short stature with short neck and trunk, odontoid hypoplasia, spinal cord compression, tracheal obstruction, obstructive airway, pectus carinatum, restrictive lung, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. The degree of imbalance of growth in bone and other organs and tissues largely contributes to unique skeletal dysplasia and clinical severity. Diagnosis of MPS IVA needs clinical, radiographic, and laboratory testing to make a complete conclusion. To diagnose MPS IVA, total urinary GAG analysis which has been used is problematic since the values overlap with those in age-matched controls. Currently, urinary and blood KS and C6S, the enzyme activity of GALNS, and GALNS molecular analysis are used for diagnosis and prognosis of clinical phenotype in MPS IVA. MPS IVA can be diagnosed with unique characters although this disorder relates closely to other disorders in some characteristics. In this review article, we comprehensively describe clinical, radiographic, biochemical, and molecular diagnosis and clinical assessment tests for MPS IVA. We also compare MPS IVA to other closely related disorders to differentiate MPS IVA. Overall, imbalance of growth in MPS IVA patients underlies unique skeletal manifestations leading to a critical indicator for diagnosis.

The mucopolysaccharidoses: advances in medical care lead to challenges in orthopaedic surgical care

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders with clinical manifestations relevant to the orthopaedic surgeon. Our aim was to review the recent advances in their management and the implications for surgical practice. The current literature about MPSs is summarised, emphasising orthopaedic complications and their management. Recent advances in the diagnosis and management of MPSs include the recognition of slowly progressive, late presenting subtypes, developments in life-prolonging systemic treatment and potentially new indications for surgical treatment. The outcomes of surgery in these patients are not yet validated and some procedures have a high rate of complications which differ from those in patients who do not have a MPS. The diagnosis of a MPS should be considered in adolescents or young adults with a previously unrecognised dysplasia of the hip. Surgeons treating patients with a MPS should report their experience and studies should include the assessment of function and quality of life to guide treatment. Cite this article: Bone Joint J 2017;99-B:1132-9.

Mucopolysaccharidosis IVA and glycosaminoglycans

Mucopolysaccharidosis IVA (MPS IVA; Morquio A: OMIM 253000) is a lysosomal storage disease with an autosomal recessive trait caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to accumulation of specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS). C6S and KS are mainly produced in the cartilage. Therefore, the undegraded substrates are stored primarily in cartilage and in its extracellular matrix (ECM), leading to a direct impact on cartilage and bone development, and successive systemic skeletal dysplasia. Chondrogenesis, the earliest phase of skeletal formation, is maintained by cellular interactions with the ECM, growth and differentiation factors, signaling pathways, and transcription factors in a temporal-spatial manner. In patients with MPS IVA, the cartilage is disrupted at birth as a consequence of abnormal chondrogenesis and/or endochondral ossification. The unique skeletal features are distinguished by a disproportional short stature, odontoid hypoplasia, spinal cord compression, tracheal obstruction, pectus carinatum, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. In spite of many descriptions of these unique clinical features, delay of diagnosis still happens. The pathogenesis and treatment of systemic skeletal dysplasia in MPS IVA remains an unmet challenge. In this review article, we comprehensively describe historical aspect, property of GAGs, diagnosis, screening, pathogenesis, and current and future therapies of MPS IVA.

Simultaneous bilateral total hip arthroplasty in Morquio syndrome

A 16-year-old girl who had Morquio syndrome presented with severe bilateral hip pain and limited mobility because of bilateral hip osteoarthritis and fixed flexion deformities. She was wheelchair bound for the previous 6 months. Cervical spine flexion-extension views showed mild subluxation (<3 mm), and there was thoracolumbar spine kyphosis. Magnetic resonance imaging of the cervical and thoracolumbar spine showed hypoplasia of the odontoid and vertebral bodies, but no spinal cord compression. Bilateral cemented total hip arthroplasty was performed through a posterior approach under general anesthesia with fiberoptic intubation. The femoral canals accepted a small-diameter stem, the right femoral head was used as a graft for superior right acetabular deficiency, and low-profile all-polyethylene acetabular cups were implanted. Follow-up at 15 years after surgery showed that the patient was fully ambulatory without pain or supports, and radiographs showed no loosening. In summary, total hip arthroplasty at a young age may be necessary in patients who have Morquio syndrome because of severe arthritis and soft tissue contractures. Extensive preoperative evaluation that includes imaging of the entire spine is mandatory because of the risk of developing spinal cord compression.

Spine malformation complex in 3 diverse syndromic entities: Case reports

RATIONALE

Clinical and radiographic phenotypic characterizations were the base line tool of diagnosis in 3 syndromic disorders in which congenital cervico-thoracic kyphosis was the major deformity.

PATIENTS CONCERNS

Directing maximal care toward the radiographic analysis is not only the axial malformation but also toward the appendicular abnormalities was our main concern. We fully documented the diversity of the spine phenotypic malformation complex via the clinical and radiographic phenotypes.

DIAGNOSES

We established the diagnosis via phenotypic/genotypic confirmation in 3 diverse syndromic entities namely acampomelic campomelic dysplasia, Larsen syndrome and Morquio syndrome type A (mucopolysaccharidosis type IV A).

INTERVENTIONS

Surgical interventions have been carried out in the Larsen syndrome and Morquio syndrome type A, resepectively.

OUTCOMES

The earliest the diagnosis is, the better the results are. The necessity to diagnose children in their first year of life has many folds, firstly the management would be in favor of the child's growth and development and secondly, the prognosis could be clearer to the family and the medical staff as well. Our current paper is to sensitize paediatricians, physicians and orthopedic surgeons regarding the necessity to detect the aetiological understanding in every child who manifests a constellation of malformation complex.

LESONS

Scoliosis and kyphosis/kyphoscoliosis are not a diagnosis in themselves. Such deformities are mostly a symptom complex correlated to dozens of types of syndromic associations. The rate curve progression and the final severity of congenital spine tilting are related to 3 factors: (a) the type of vertebral malformation present, (b) the patient's phenotype, and

Cutaneous Manifestations of Mucopolysaccharidoses

Mucopolysaccharidoses (MPSs) are a group of inherited lysosomal storage disorders characterized by deficiencies in specific enzymes involved in the catabolism of glycosaminoglycans (GAGs). These deficiencies cause excessive metabolites to accumulate in multiple organs. There are eight different MPS disorders, contributing to the wide variation in clinical presentation. Depending on the severity and subtype of the disease, some children live normal life spans, while others have a more grim prognosis. Children with MPS can present with neurologic, behavioral, skeletal, cardiovascular, gastrointestinal, or respiratory abnormalities. Cutaneous manifestations are mostly nonspecific and can include coarse facial features, thickened skin, and excessive hair growth. More specific skin findings include ivory-colored "pebbly" papules found in Hunter syndrome and extensive dermal melanocytosis found in Hurler and Hunter syndromes. Early diagnosis of MPS disorders is extremely important to minimize the progression of the disease and for early initiation of appropriate treatment.

Current therapies for Morquio A syndrome and their clinical outcomes

INTRODUCTION

Morquio A syndrome is characterized by a unique skeletal dysplasia, leading to short neck and trunk, pectus carinatum, laxity of joints, kyphoscoliosis, and tracheal obstruction. Cervical spinal cord compression/inability, a restrictive and obstructive airway, and/or bone deformity and imbalance of growth, are life-threatening to Morquio A patients, leading to a high morbidity and mortality. It is critical to review the current therapeutic approaches with respect to their efficacy and limitations.

AREAS COVERED

Patients with progressive skeletal dysplasia often need to undergo orthopedic surgical interventions in the first two decades of life. Recently, we have treated four patients with a new surgery to correct progressive tracheal obstruction. Enzyme replacement therapy (ERT) has been approved clinically. Cell-based therapies such as hematopoietic stem cell therapy (HSCT) and gene therapy are typically one-time, permanent treatments for enzyme deficiencies. We report here on four Morquio A patients treated with HSCT approved in Japan and followed for at least ten years after treatment. Gene therapy is under investigation on mouse models but not yet available as a therapeutic option.

EXPERT OPINION

ERT and HSCT in combination with surgical intervention(s) are a therapeutic option for Morquio A; however, the approach for bone and cartilage lesion remains an unmet challenge.

RESULTS OF SURGICAL TREATMENT IN THE CRANIOCERVICAL JUNCTION IN MUCOPOLYSACCHARIDOSIS

ABSTRACT Objective: Evaluate the results after decompression and stabilization of craniocervical junction in patients with mucopolysaccharidosis (MPS). Method: Retrospective study of 10 patients with MPS through the analysis of medical records and additional tests. Result: All patients with mid-term and long-term follow-up achieved consolidation of the arthrodesis and 87.5% had neurological improvement of Nurick score. Conclusion: Early diagnosis and intervention in cases of stenosis and/or craniocervical instability of patients with MPS provide patients a good recovery of neurological function, despite the great technical difficulty and risk of complications.

Mucopolysaccharidosis-like phenotype in feline Sandhoff disease and partial correction after AAV gene therapy

Sandhoff disease (SD) is a fatal neurodegenerative disease caused by a mutation in the enzyme β-N-acetylhexosaminidase. Children with infantile onset SD develop seizures, loss of motor tone and swallowing problems, eventually reaching a vegetative state with death typically by 4years of age. Other symptoms include vertebral gibbus and cardiac abnormalities strikingly similar to those of the mucopolysaccharidoses. Isolated fibroblasts from SD patients have impaired catabolism of glycosaminoglycans (GAGs). To evaluate mucopolysaccharidosis-like features of the feline SD model, we utilized radiography, MRI, echocardiography, histopathology and GAG quantification of both central nervous system and peripheral tissues/fluids. The feline SD model exhibits cardiac valvular and structural abnormalities, skeletal changes and spinal cord compression that are consistent with accumulation of GAGs, but are much less prominent than the severe neurologic disease that defines the humane endpoint (4.5±0.5months). Sixteen weeks after intracranial AAV gene therapy, GAG storage was cleared in the SD cat cerebral cortex and liver, but not in the heart, lung, skeletal muscle, kidney, spleen, pancreas, small intestine, skin, or urine. GAG storage worsens with time and therefore may become a significant source of pathology in humans whose lives are substantially lengthened by gene therapy or other novel treatments for the primary, neurologic disease.

Occipitocervical stabilization using bilateral laminar C2 screws in children with mucopolysaccharidosis IVA

PURPOSE

Mucopolysaccharidosis IVA (MPS IVA) is a multisystemic storage disorder. Patient's disability and life expectancy depends upon skeletal complications, including cervical myelopathy due to upper cervical compression or instability. Posterior decompression followed by occipitocervical fixation or C1-2 fusion are the most frequently recommended surgical interventions. The bony elements of C1 and C2 are often inadequately developed making routine screw insertion difficult. The main purpose of this work was to present novel technique of occipitocervical fixation using two C2 laminar screws.

METHODS

Four children with MPS IVA underwent decompression and C0-C2 instrumented fusion using two C2 bilateral laminar screws. The dimensions of the C2 lamina were measured. Clinical and radiological results were monitored prospectively for a minimum 3 years.

RESULTS

The mean laminar length was 24 ± 1.15 mm, width 6.15 ± 0.55 mm and height 7.4 ± 0.6 mm. Patients remained in a stable neurological condition. The mean antero-posterior diameter of the spinal canal on the pre-operative MR was 6.2 ± 0.74 mm and it was enlarged to 11.4 ± 0.8 mm after 3 years. All screws were placed adequately. In all patients, the control CT scan 2 years post-operatively revealed a stable position of the treated segments, but solid bony fusion was not registered in any patient.

CONCLUSIONS

Decompression and fusion of the upper cervical spine is a generally accepted approach to treat upper cervical spine instability and myelopathy in MPS IVA patients. The feasibility and the suitability of the technique of C0-C2 stabilization using bilateral C2 laminar screws have been presented.

Diagnostic evaluation, monitoring, and perioperative management of spinal cord compression in patients with Morquio syndrome

Mucopolysaccharidosis IVA is an autosomal recessive condition caused by mutations in the GALNS gene, which encodes N-acetylgalactosamine-6-sulfatase, also called galactosamine-6-sulfatase (GALNS). A reduction in or absence of effective GALNS leads to faulty catabolism of keratan sulfate and chondroitin-6-sulfate within the lysosome; their accumulation causes cell, tissue, and organ dysfunction. The connective tissue, cartilage, ligaments, and bone of patients with Morquio A syndrome are particularly affected. Patients with Morquio A syndrome are at high risk of neurological complications because of their skeletal abnormalities; many patients are in danger of cervical myelopathy due to odontoid hypoplasia and ligamentous laxity leading to atlantoaxial subluxation. The multisystemic involvement of patients with Morquio A syndrome requires treatment by multidisciplinary teams; not all members of these teams may be aware of the potential for subluxation and quadriparesis. A multinational, multidisciplinary panel of 10 skeletal dysplasia or Morquio A syndrome specialists convened in Miami, FL on December 7 and 8, 2012 to develop consensus recommendations for early identification and effective management of spinal cord compression, for anesthesia and surgical best practices, and for effectual cardiac and respiratory management in patients with Morquio A syndrome. The target audience for these recommendations includes any physician who may encounter a patient with Morquio A syndrome, however doctors who do not have access to the full spectrum of specialists and resources needed to support patients with Morquio A syndrome should attempt to refer patients to a center that does. Physicians who manage Morquio A syndrome or comorbid conditions within specialty centers should review these expert panel recommendations and fully understand the implications of spinal cord instability for their own practices.

A review of the diagnosis and treatment of atlantoaxial dislocations

Study Design Literature review. Objective Atlantoaxial dislocation (AAD) is a rare and potentially fatal disturbance to the normal occipital-cervical anatomy that affects some populations disproportionately, which may cause permanent neurologic deficits or sagittal deformity if not treated in a timely and appropriate manner. Currently, there is a lack of consensus among surgeons on the best approach to diagnose, characterize, and treat this condition. The objective of this review is to provide a comprehensive review of the literature to identify timely and effective diagnostic techniques and treatment modalities of AAD. Methods This review examined all articles published concerning "atlantoaxial dislocation" or "atlantoaxial subluxation" on the PubMed database. We included 112 articles published between 1966 and 2014. Results Results of these studies are summarized primarily as defining AAD, the normal anatomy, etiology of dislocation, clinical presentation, diagnostic techniques, classification, and recommendations for timely treatment modalities. Conclusions The Wang Classification System provides a practical means to diagnose and treat AAD. However, future research is required to identify the most salient intervention component or combination of components that lead to the best outcomes.

Occipitocervical fusion in skeletal dysplasia: a new surgical technique

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

This study describes clinical and radiological results of a new cable technique for occipitocervical fusion (OCF) in children with skeletal dysplasia (SD).

SUMMARY OF BACKGROUND DATA

Anatomical variability and poor bone quality make upper cervical surgery technically challenging in patients with SD. We present a new cable technique for OCF in children with SD when the posterior elements are not of a size or quality for other types of instrumentation.

METHODS

Retrospective review of 24 patients with SD (8 boys, 16 girls) who underwent OCF between 2001 and 2011. In this technique, cables provide compression across a bone graft that is prevented from entering the canal and the graft resists excessive lordosis. Demographic and radiographical data are presented. All patients were followed for initial outcomes of surgery, and 20 patients (83%) were followed for 2 years or more for mid- and long-term outcomes.

RESULTS

Mean age at surgery was 6.5 years and mean follow-up was 4.1 ± 2.4 years. This technique was used as a primary procedure in 20 and a revision procedure in 4 patients. Diagnoses included Morquio syndrome (6), spondyloepiphyseal dysplasia (9), spondyloepimetaphyseal dysplasia (5), metatropic dysplasia (3), and Kniest syndrome (1). Ten patients had upper cervical instability and features of cervical myelopathy, and the remaining 14 patients had instability and signal changes on magnetic resonance image. Fusion extended from occiput to C2 in 71% patients, and upper cervical decompression was needed in 92% patients. Postoperatively, all patients were immobilized in a halo vest for mean duration of 12 weeks. Fusion was achieved in all patients. Complications included halo pin-tract infections (7), junctional instability (2), and extension of fusion (4).

CONCLUSION

This new cable technique is a good alternative for OCF in patients with SD who have altered anatomy at the craniocervical junction not amenable to rigid internal fixation.

LEVEL OF EVIDENCE

4.

[Occipital-cervical instability in Morquio disease: a presentation of 2 cases and a review of the literature]

INTRODUCTION

Morquio syndrome is caused by an inherited autosomal recessive enzyme deficiency. It presents with numerous musculoskeletal anomalies, among which atlantoaxial instability is highlighted, due it being life-threatening. Occipital-cervical arthrodesis surgery (and decompression) is indicated in these cases.

OBJECTIVE

The cases of 2 patients with Morquio syndrome that required this type of surgery are presented, along with a review of the literature.

PATIENTS AND METHODS

Two patients: one boy and one girl, with Morquio syndrome and high cervical instability, with neurological signs and symptoms, who were subjected to surgery using decompression and instrumented occipital-cervical arthrodesis and followed up for 6 months and one year, respectively.

RESULTS

The neurological problems of both patients improved, and are currently having a normal life for their age.

CONCLUSION

Occipital-cervical arthrodesis with decompression provides a safe biomechanical environment that prevents neurological involvement. It should be indicated before the appearance of symptoms or mechanical instability.

Neurologic complications of craniovertebral dislocation

Craniovertebral dislocation is uncommon, but its diagnosis is important taking into account the potential severity of the neurologic complications. A number of causes are known; the most common are Down syndrome, rheumatoid arthritis, Paget's disease, other metabolic bone diseases, and craniocervical trauma. Down's syndrome is a relatively common clinical condition but craniovertebral subluxation is only observed in a small percentage of patients. About half of all cervical spine injuries affect the atlanto-occipital region and C2 vertebra. In rheumatoid arthritis, craniocervical dislocation occurs in up to 40% of patients with severe disease. In Paget's disease, involvement of the craniovertebral region occurs in about 30% of all cases. The clinical neurologic syndrome is characterized by local pain, features of upper spinal cord and medullary compression, positive Lhermitte phenomenon, syncope associated with neck flexion, vertebral artery obstruction or dissection leading to stroke, and asymmetrical lower cranial nerve palsies. Neuroimaging is essential to confirm the clinical diagnosis and to categorize severity. The treatment of this disorder is usually surgical, but traction and external immobilization is relevant in some cases. Specific conditions may require additional treatments such as radiotherapy, antibiotics, or chemotherapy.

Biomarkers of bone remodeling in children with mucopolysaccharidosis types I, II, and VI

PURPOSE

Skeletal disease causes significant morbidity in mucopolysaccharidoses (MPS), and bone remodeling processes in MPS have not been well characterized. The objective of this study was to determine if biomarkers of bone turnover are abnormal in children with specific MPS disorders (i.e. MSP-I, MPS-II, and MPS-VI) compared to healthy children.

METHODS

A cross-sectional study was performed of serum biomarkers of bone formation (bone-specific alkaline phosphatase [BSAP], osteocalcin) and urine biomarkers of bone resorption (pyridinoline, deoxypyridinoline) in MPS and healthy controls. Measures of physical function and pain were obtained using the Children's Health Questionnaire (CHQ).

RESULTS

The cohort consisted of 39 children with MPS (MPS-I=26; MPS-II=11; MPS-VI=4) and 51 healthy children. Adjusting for sex and Tanner stage group, MPS individuals had statistically significant increases for osteocalcin (p< 0.001), with trends toward higher BSAP (p=0.054) and urinary pyridinoline (p=0.084). These biomarkers were not significantly associated with CHQ bodily pain and physical-function scores.

CONCLUSION

Osteocalcin was increased in children with MPS disorders, with trends for increases in BSAP and urinary pyridinoline, suggesting that bone remodeling is altered in children with MPS. Future studies to assess the ability of these biomarkers to quantify and monitor MPS skeletal disease in response to therapy are needed.

Os odontoideum syndrome: pathogenesis, clinical patterns and indication for surgical strategies in childhood

Os odontoideum is a rare condition with a controversial pathogenesis and poorly understood natural history. Hypoplasia of the odontoid associated with an independent oval ossicle, with smooth margins widely separated from C2 and well above the superior facets of the axis, is termed "os odontoideum". The neurological manifestations arise from bulbospinal compression both at rest and during motion, due to the craniovertebral junction (CVJ) instability itself. Consequently, the surgical management of os odontoideum should aim at achieving both neural decompression and stabilization of the CVJ. The aims of this paper are to introduce the embryological steps involved in the CVJ development, to underline the updated theories propounded to interpret developmental and congenital disorders of the os odontoideum, to introduce the most updated surgical techniques and to discuss some exemplary cases selected from our personal experience.

Imaging of the craniovertebral junction anomalies in children

The craniovertebral junction (CVJ) is interposed between the unsegmented skull and the segmented spine; it is functionally unique as it allows the complex motion of the head. Because of its unique anatomy, numerous craniometric indices have been devised. Because of its complex embryology, different from that of the adjacent skull and spine, it is commonly the seat of malformations. Because of the mobility of the head, and its relative weight, the craniovertebral junction is vulnerable to trauma. Like the rest of the axial skeleton, it may be affected by many varieties of dysplasia. In addition, the bony craniovertebral junction contains the neural craniovertebral junction and its surrounding CSF: any bony instability or loss of the normal anatomic relationships may therefore compromise the neural axis. In addition, the obstruction of the meningeal spaces at this level can compromise the normal dynamics of the CSF and result in hydrocephalus and/or syringohydromyelia. To image the CVJ, plain X-rays are essentially useless. MR is optimal in depicting the soft tissues (including the neural axis) and the joints, as well as the bone itself. CT still may be important to better demonstrate the bony abnormalities.

Craniovertebral junction pathological features and their management in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are multisystemic inherited metabolic diseases caused by the deficiency of the enzymes involved in the degradation of glycosaminoglycans (GAGs), which variably involve the central nervous system, heart, lungs, and bones.Undegraded or only partly degraded GAGs accumulate in the extracellular matrix, joint fluid, and connective tissue leading to widespread tissue and organ dysfunction.The introduction of hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) has positively affected the natural history of MPS patients and their life expectancy. However, the presence of spinal abnormalities and deposition of GAGs in soft tissues remains nearly unaltered.Abnormalities of the craniovertebral junction (CVJ) and GAG deposits can result in spinal cord compression with slowly progressive myelopathy or acute posttraumatic tetraplegia.The current paper discusses neuroimaging findings in a consecutive series of 42 MPS patients followed at our Center for Metabolic Diseases and their neurosurgical issues.Current recommendations for decompression and fusion will be discussed according to our experience and review of the literature.

Sequential imaging demonstrating os odontoideum formation after a fracture through the apical odontoid epiphysis: case report and review of the literature

INTRODUCTION

The mechanism of formation of an os odontoideum is controversial and likely multifactorial. One theory states that the apex of the odontoid separates from the body because of a fracture. The intact alar and apical ligaments pull the fractured segment superiorly. The independent vascular supply of the apex allows the fractured bone to remain viable and remodel into the smooth, corticated bone characteristic of an os odontoideum. However, there are no publications with direct radiographic evidence supporting the theory.

CASE REPORT

In this paper, the authors present a 7-year-old child with a fracture through the apical odontoid epiphysis, extending into the body of the dens. Serial imaging studies demonstrate progressive separation of the apex from the body of the odontoid. The fractured segment begins to remodel and assume the classic form of an os.

CONCLUSION

The authors consider this case to be radiographic evidence supporting an acquired/traumatic origin of os odontoideum. Further, the mechanism of fracture through a cartilaginous epiphysis may explain the formation of an os after "normal" x-ray images or following seemingly minor trauma.

Development of a Scoring System to Evaluate the Severity of Craniocervical Spinal Cord Compression in Patients with Mucopolysaccharidosis IVA (Morquio A Syndrome)

BACKGROUND

As spinal cord compression at the craniocervical junction (CCJ) is a life-threatening manifestation in patients with mucopolysaccharidosis (MPS) IVA, surgical decompression should be performed before damage becomes irreversible. We evaluated the diagnostic value of several examinations for determining the need for decompression surgery.

METHODS

We retrospectively analysed results of clinical neurological examination, somatosensory evoked potential (SEP) and magnetic resonance imaging (MRI) in 28 MPS IVA patients. A scoring system - based on the severity of findings - was used to compare results of patients with and without indication for decompression surgery. Individual test scores and two composite scores were evaluated for their potential to assess severity of CCJ impairment.

RESULTS

Sixteen patients had an indication for surgery; 12 of them had undergone surgery. Twelve patients had no indication for surgery; none had received surgery. Neurological (P = 0.004), MRI (P < 0.001) and atlantoaxial subluxation (P = 0.006) scores, but not SEP and odontoid hypoplasia scores, differed significantly between patients with and without surgical indication. Both the abbreviated CCJ score, i.e. sum of neurological and MRI scores, and the extended CCJ score, i.e. sum of abbreviated CCJ and atlantoaxial subluxation score, discriminated between patients with and without surgical indication (abbreviated: 0-2 points vs 2-5 points, P < 0.001; extended: 0-3 points vs 3-7 points; P < 0.001). Although CCJ instability plays a major role in cervical cord pathology, decompression surgery without occipito-cervical stabilisation may yield good postoperative results.

CONCLUSIONS

The abbreviated and extended CCJ scores are objective, transparent and reproducible tools for assessing the CCJ pathology and the need for surgery.

MRI morphometric characterisation of the paediatric cervical spine and spinal cord in children with MPS IVA (Morquio-Brailsford syndrome)

Nearly all children with MPS IVA develop skeletal deformities affecting the spine. At the atlanto-axial spine, odontoid hypoplasia occurs. GAG deposition around the dens, leads to peri-odontoid infiltration. Transverse/alar ligament incompetence causes instability. Atlanto-axial instability is associated with cord compression and myelopathy, leading to major morbidity and mortality. Intervention is often required. Does the presence of widened bullet shaped vertebra in platyspondily encroach on the spinal canal and cause spinal stenosis in MPS IVA? So far, there have been no standardised morphometric measurements of the paediatric MPS IVA cervical spine to evaluate whether there is pre-existing spinal stenosis predisposing to compressive myelopathy or whether this is purely an acquired process secondary to instability and compression. This study provides the first radiological quantitative analysis of the cervical spine and spinal cord in a series of affected children. MRI morphometry indicates that the MPS IVA spine is narrower at C1-2 level giving an inverted funnel shape. There is no evidence of a reduction in the Torg ratio (canal-body ratio) in the cervical spine. The spinal canal does not exceed 11 mm at any level, significantly smaller than normal historical cohorts (14 mm). The sagittal diameter and axial surface area of both spinal canal and cord are reduced. C1-2 level cord compression was evident in the canal-cord ratio but the Torg ratio was not predictive of cord compression. In MPS IVA the reduction in the space available for the cord (SAC) is multifactorial rather than due to congenital spinal stenosis.

Spinal involvement in mucopolysaccharidosis IVA (Morquio-Brailsford or Morquio A syndrome): presentation, diagnosis and management

Mucopolysaccharidosis IVA (MPS IVA), also known as Morquio-Brailsford or Morquio A syndrome, is a lysosomal storage disorder caused by a deficiency of the enzyme N-acetyl-galactosamine-6-sulphate sulphatase (GALNS). MPS IVA is multisystemic but manifests primarily as a progressive skeletal dysplasia. Spinal involvement is a major cause of morbidity and mortality in MPS IVA. Early diagnosis and timely treatment of problems involving the spine are critical in preventing or arresting neurological deterioration and loss of function. This review details the spinal manifestations of MPS IVA and describes the tools used to diagnose and monitor spinal involvement. The relative utility of radiography, computed tomography (CT) and magnetic resonance imaging (MRI) for the evaluation of cervical spine instability, stenosis, and cord compression is discussed. Surgical interventions, anaesthetic considerations, and the use of neurophysiological monitoring during procedures performed under general anaesthesia are reviewed. Recommendations for regular radiological imaging and neurologic assessments are presented, and the need for a more standardized approach for evaluating and managing spinal involvement in MPS IVA is addressed.

Prevalence and development of orthopaedic symptoms in the dutch hurler patient population after haematopoietic stem cell transplantation

Hurler syndrome (MPS-IH) is a rare autosomal recessive lysosomal storage disease. Besides a variety of other features, Hurler syndrome is characterized by a range of skeletal abnormalities known as dysostosis multiplex. Despite the successful effect of haematopoietic stem cell transplantation on the other features, dysostosis remains a disabling symptom of the disease. This study analyzed the status and development of the orthopaedic manifestations of 14 Dutch Hurler patients after stem cell transplantation.Data were obtained retrospectively by reviewing patients' charts, radiographs and MRIs. Existing methods to measure the deficiencies were modified to optimally address the dysostosis. These measurements were done by two of the authors independently. The odontoïd/body ratio, kyphotic angle, scoliotic angle and parameters for hip dysplasia and genu valgum were measured and plotted against age. The degree of progression was determined. The intraclass correlation coefficient (ICC) was calculated to determine the reliability of the measurements.All patients showed hypoplasia of the odontoïd, which significantly improved during growth. Kyphosis in the thoracolumbar area was present in 13 patients and proved to be progressive. Scoliosis was observed in eight patients. Hip dysplasia was present in all patients and showed no tendency of improvement. In all but one patient, knee valgus remained more than two standard deviations above normal.Dysostosis remains a major problem after haematopoietic stem cell transplantation in Hurler patients. Moreover, except for dens hypoplasia, it appears to be progressive and therefore surgical interventions may be necessary in the majority of these patients.

Anesthetic care and perioperative complications of children with Morquio syndrome

OBJECTIVES

Our objective was to make recommendations based on our experience and findings from this study regarding the anesthetic care of children with Morquio syndrome (MS). We emphasize information not readily available in the Anesthesiology literature.

AIM

To describe the unique nature of difficulties, especially the relationship of the head and neck to airway patency. In addition, we aim to examine 83 intubations performed in 28 patients and report on observed preferences.

BACKGROUND

Much of the available literature in Anesthesiology consists of case reports of single or small groups of cases, many describing a nonhomogenous population inclusive of many mucopolysaccharidoses.

METHODS/MATERIALS

We retrospectively studied 28 children with MS who underwent 108 surgical procedures at our pediatric hospital, which provides multidisciplinary, comprehensive care to children with skeletal dysplasia.

RESULTS

Cervical fusion was performed in 22 of 28 patients in our study. Eight children after cervical fusion became difficult to intubate for subsequent surgical procedures. In addition, we found airway abnormalities including tortuous appearance of the trachea and bronchi, evident on chest radiograph, as a result of the abnormalities in the hyaline cartilage and deposits of glycosaminoglycans.

CONCLUSION

Morquio syndrome results in abnormalities of not only upper airway but also of large airways. Information from 83 intubations of 108 anesthetics (in 28 patients) shows a preference for Glidescope when intubating children with MS. Displacing the tongue anteriorly prior to intubation by manual retraction using a ring forceps or a piece of gauze helps to access the larynx in children with MS.

Spinal cord infarction remote from maximal compression in a patient with Morquio syndrome

Morquio syndrome, or mucopolysaccharidosis type IV, is a rare enzyme deficiency disorder and results in skeletal dysplasia. Odontoid dysplasia is common among affected patients, resulting in atlantoaxial instability and spinal cord compression. Surgical treatments include decompression and prophylactic fusion, during which intraoperative neuromonitoring is important to alert the surgical team to changes in cord function so that they can prevent or mitigate spinal cord injury. This report describes a 16-year-old girl with Morquio syndrome who developed paraplegia due to thoracic spinal cord infarction during foramen magnum and atlantal decompression. This tragic event demonstrates the following: 1) that patients with Morquio syndrome are at risk for ischemic spinal cord injury at levels remote from areas of maximal anatomical compression while under anesthesia in the prone position, possibly due to impaired cardiac output; 2) the significance of absent motor evoked potential responses in the lower limbs with preserved upper-limb responses in an ambulatory patient; 3) the importance of establishing intraoperative neuromonitoring baseline assessments prior to turning patients to the prone position following induction of anesthesia; and 4) the importance of monitoring cardiac output during prone positioning in patients with chest wall deformity.

Review of cervical spine anomalies in genetic syndromes

STUDY DESIGN

Focused review of the literature.

OBJECTIVE

Assist spine specialists in diagnosis and treatment of cervical spine anomalies found in selected genetic syndromes.

SUMMARY OF BACKGROUND DATA

Cervical spine instability and/or stenosis are potentially debilitating problems in many genetic syndromes. These problems can be overlooked among the other systemic issues more familiar to clinicians and radiologists evaluating these syndromes. It is imperative that spine specialists understand the relevant issues associated with these particular syndromes.

METHODS

The literature was reviewed for cervical spine issues in 10 specific syndromes. The information is presented in the following order: First, the identification and treatment of midcervical kyphosis in Larsen syndrome and diastrophic dysplasia (DD). Next, the upper cervical abnormalities seen in Down syndrome, 22q11.2 Deletion syndrome, pseudoachondroplasia, Morquio syndrome, Goldenhar syndrome, spondyloepiphyseal dysplasia congenita, and Kniest dysplasia. Finally, the chin-on-chest deformity of fibrodysplasia ossificans progressiva.

RESULTS

Midcervical kyphosis in patients with Larsen syndrome and DD needs to be evaluated and imaged often to track deformity progression. Upper cervical spine instability in Down syndrome is most commonly caused by ligamentous laxity at C1 to C2 and occiput-C1 levels. Nearly 100% of patients with 22q11.2 deletion syndrome have cervical spine abnormalities, but few are symptomatic. Patients with pseudoachondroplasia and Morquio syndrome have C1 to C2 instability related to odontoid dysplasia (hypoplasia and os odontoideum). Morquio patients also have soft tissue glycosaminoglycan deposits, which cause stenosis and lead to myelopathy. Severely affected patients with spondyloepiphyseal dysplasia congenita are at high risk of myelopathy because of atlantoaxial instability in addition to underlying stenosis. Kniest syndrome is associated with atlantoaxial instability. Cervical spine anomalies in Goldenhar syndrome are varied and can be severe. Fibrodysplasia ossificans progressiva features severe, deforming heterotopic ossification that can become life-threatening.

CONCLUSION

It is important to be vigilant in the diagnosis and treatment of cervical spine anomalies in patients with genetic syndromes.

Neurosurgical management of congenital malformations and inherited disease of the spine

Congenital malformations encompass a diverse group of disorders present at birth as result of genetic abnormalities, infection, errors of morphogenesis, or abnormalities in the intrauterine environment. Congenital disorders affecting the brain and spinal cord are often diagnosed before delivery with the use of prenatal ultrasonography and maternal serum screening. Over the past several decades there have been major advances in the understanding and management of these conditions. This article focuses on the most common spinal congenital malformations.