Risk factors of myelopathy at the atlantoaxial level in spondyloepiphyseal dysplasia congenita

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.

Mobility Assessment Using Multi-Positional MRI in Children with Cranio-Vertebral Junction Anomalies

OBJECTIVE

This study aimed to assess the relevance of using multi-positional MRI (mMRI) to identify cranio-vertebral junction (CVJ) instability in pediatric patients with CVJ anomalies while determining objective mMRI criteria to detect this condition.

MATERIAL AND METHODS

Data from children with CVJ anomalies who underwent a mMRI between 2017 and 2021 were retrospectively reviewed. Mobility assessment using mMRI involved: (1) morphometric analysis using hierarchical clustering on principal component analysis (HCPCA) to identify clusters of patients by considering their mobility similarities, assessed through delta (Δ) values of occipito-cervical parameters measured on mMRI; and (2) morphological analysis based on dynamic geometric CVJ models and analysis of displacement vectors between flexion and extension. Receiver operating characteristics (ROC) curves were generated for occipito-cervical parameters to establish instability cut-off values. (3) Additionally, an anatomical qualitative analysis of the CVJ was performed to identify morphological criteria of instability.

RESULTS

Forty-seven patients with CVJ anomalies were included (26 females, 21 males; mean age: 10.2 years [3-18]). HCPCA identified 2 clusters: cluster №1 (stable patients, n = 39) and cluster №2 (unstable patients, n = 8). ΔpB-C2 (pB-C2 line delta) at ≥2.5 mm (AUC 0.98) and ΔBAI (Basion-axis Interval delta) ≥ 3 mm (AUC 0.97) predicted instability with 88% sensibility and 95% specificity and 88% sensitivity and 85% specificity, respectively. Geometric CVJ shape analysis differentiated patients along a continuum, from a low to a high CVJ motion that was characterized by a subluxation of C1 in the anterior direction. Qualitative analysis found correlations between instability and C2 anomalies, including fusions with C3 (body p = 0.032; posterior arch p = 0.045; inferior articular facets p = 0.012; lateral mass p = 0.029).

CONCLUSIONS

We identified a cluster of pediatric patients with CVJ instability among a cohort of CVJ anomalies that were characterized by morphometric parameters with corresponding cut-off values that could serve as objective mMRI criteria. These findings warrant further validation through prospective case-control studies.

Management of Craniocervical Instability in Spondyloepiphyseal Dysplasia Congenita: Assessment of Literature and Presentation of Two Cases

Spondyloepiphyseal dysplasia congenita (SEDC) is a rare autosomal dominant skeletal dysplasia resulting in impairment of type II collagen function. Phenotypically, this results in various skeletal, ligamentous, ocular, and otologic abnormalities. Platyspondyly, scoliosis, ligamental laxity, and odontoid hypoplasia are common, resulting in myelopathy in a high number of patients due to atlantoaxial instability. Despite patients undergoing surgical fixation, complication rates such as nonunion have been reported to be high. Here within, we present two patients treated with occipitocervical fusion for atlantoaxial instability and early symptoms of progressive myelopathy. We additionally provide a detailed review of the literature to inform practitioners of the spinal manifestations and clinical considerations in SEDC.

Sleep-disordered breathing and its management in children with rare skeletal dysplasias

Sleep-disordered breathing (SDB) is common in patients with skeletal dysplasias. The aim of our study was to analyze SDB and respiratory management in children with rare skeletal dysplasias. We performed a retrospective analysis of patients with spondyloepiphyseal dysplasia congenita (SEDC), metatropic dysplasia (MD), spondyloepimetaphyseal dysplasia (SEMD), acrodysostosis (ADO), geleophysic dysplasia (GD), acromicric dysplasia (AD), and spondylocostal dysplasia (SCD) between April 2014 and October 2020. Polygraphic data, clinical management, and patients' outcome were analyzed. Thirty-one patients were included (8 SEDC, 3 MD, 4 SEMD, 1 ADO, 4 GD, 3 AD, and 8 SCD). Sixteen patients had obstructive sleep apnea (OSA): 11 patients (2 with SEDC, 1 with SEMD, 1 with ADO, 1 with GD, 2 with AD, and 4 with SCD) had mild OSA, 2 (1 SEMD and 1 GD) had moderate OSA, and 3 (1 SEDC, 1 MD, 1 SEMD) had severe OSA. Adenotonsillectomy was performed in one patient with SCD and mild OSA, and at a later age in two other patients with ADO and AD. The two patients with moderate OSA were treated with noninvasive ventilation (NIV) because of nocturnal hypoxemia. The three patients with severe OSA were treated with adenotonsillectomy (1 SEDC), adeno-turbinectomy and continuous positive airway pressure (CPAP; 1 MD), and with NIV (1 SEMD) because of nocturnal hypoventilation. OSA and/or alveolar hypoventilation is common in patients with skeletal dysplasias, underlining the importance of systematic screening for SDB. CPAP and NIV are effective treatments for OSA and nocturnal hypoventilation/hypoxemia.

The Managment of cervical spine abnormalities in children with spondyloepiphyseal dysplasia congenita: Observational study

Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant disorder, characterized by disproportionate dwarfism with short spine, short neck associated with variable degrees of coxa vara. Cervical cord compression is the most hazardous skeletal deformity in patients with SEDC which requires special attention and management.Ten patients with the clinical and the radiographic phenotypes of spondyloepiphyseal dysplasia congenita have been recognized and the genotype was compatible with single base substitutions, deletions or duplication of part of the COL2A1 gene (6 patients out of ten have been sequenced). Cervical spine radiographs showed apparent atlantoaxial instability in correlation with odontoid hypoplasia or os-odontoideum.Instability of 8 mm or more and or the presence of symptoms of myelopathy were the main indications for surgery. Posterior cervical fusion from the occiput or C1-3, decompression of C1-2 and application of autorib transfer followed by halo vest immobilization have been applied accordingly.Orthopedic management of children with spondyloepiphyseal dysplasia congenita (SEDC) should begin with the cervical spine to avoid serious neurological deficits and or mortality.

Cleft Palate Repair in Spondyloepiphyseal Dysplasia Congenita: Minimizing the Risk of Cervical Cord Compression

Objective

Spondyloepiphyseal dysplasia congenita (SEDC) is a rare, inheritable condition that can include dwarfism, cleft palate, and C1–2 instability. When repairing a cleft palate in a patient with SEDC, there is a significant risk of cord compression at the C1–2 level because of neck hyperextension required for the operation. This reports presents a patient with SEDC who underwent surgery for a cleft palate, using a Ferno vacuum splint to immobilize the spine.

Intervention

The patient underwent general anesthesia. Good access was gained to the palate, and it was repaired without any complications. Particular attention was paid to maintaining the neck in a neutral position.

Conclusions

The described technique provides the patient with the safest possible situation during anesthesia for cleft palate repair.

Upper cervical spine fusion in children with skeletal dysplasia

BACKGROUND

Skeletal dysplasias have been associated with upper cervical instability. Many patients are initially asymptomatic, but the instability may progress to subluxation and dislocation and complications thereof, including death. Surgery is hampered by petite osseous structures and low bone formation rate.

AIM

To review the outcomes of surgical fusion of upper cervical instability in children with rare skeletal dysplasias.

MATERIAL AND METHODS

A retrospective study of eight children with five different rare skeletal dysplasias needing upper cervical instrumented stabilization. Cases were evaluated for clinical, radiologic, and quality-of-life outcomes, with median follow-up time of 5 years.

RESULTS

Six patients underwent posterior, segmental cervical spine instrumentation and fusion (three C1/C2 fusions, three occipitocervical fusions), one anterior cervical instrumented spinal fusion, and one anteroposterior fusion. Autogenous bone grafting was used in all patients, and seven were immobilized using a halo body jacket. Nonunion in occipitocervical fusions was common in these patients (3/8 patients). Rib autograft from occiput to cervical spine with recombinant human BMP-2 was used to salvage nonunions.

CONCLUSIONS

Surgical fixation in the pediatric cervical spine is hampered by fragile posterior structures. A postoperative immobilization by halo vest for 4 months is customary. Selective anterior corpectomy and plate fixation is not recommended in pediatric patients with skeletal dysplasias.

LEVEL OF EVIDENCE

Level 4, Case Series.

Defining hyoplasia of the atlas: a cadaveric study

STUDY DESIGN

Cadaveric study.

OBJECTIVE

To define congenital hypoplasia of the atlas.

SUMMARY OF BACKGROUND DATA

Little has been written about hypoplasia of the atlas and it is usually described in the setting of other skeletal dysplasias or syndromes.

METHODS

A total of 543 cervical spine specimens were randomly selected from the Hamann-Todd collection. Sagittal and coronal diameters of the atlas, axis, and C3 (when available), and the dens diameter were measured using digital calipers. Correction for modern size and radiographical magnification was performed. Hypoplasia of the atlas was defined as the lowest 2.5% of measurements. The correlation between inner sagittal diameters at C1 and C3 was calculated.

RESULTS

The mean C1 inner sagittal diameter was 30.8 ± 2.4 mm (range, 23.5-38.1 mm). We defined C1 hypoplasia as an inner sagittal diameter value representing the smallest 2.5% of subjects. Because the mean was 30.8 mm, hypoplasia was defined as a diameter of ≤26.1 mm or less. Correcting for size and magnification of radiographs, hypoplasia is defined as an inner sagittal diameter of the atlas of 28.9 mm. Approximately 10% of cases had a dens that occupied more than 40% of the spinal canal at C1, thus not following Steel's Rule of Thirds. There was only a moderate correlation between the spinal canal diameter at C1 and at C3 (r = 0.483, N = 345; P < 0.001).

CONCLUSION

With an inner sagittal diameter of 26 mm or less, one may describe the atlas as hypoplastic. Ten percent of the specimens had an odontoid process that occupied more than 40% of the spinal canal at C1. There was little correlation between the inner sagittal diameter at C1 and the diameter at C3.

LEVEL OF EVIDENCE

N/A.

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.

Isolated cervical spinal canal stenosis at C-1 in the pediatric population and in Williams syndrome

OBJECT

Isolated cervical canal stenosis at the level of the atlas (C-1) is a rare cause of cervical myelopathy in the pediatric population. It has been associated with several genetic disorders including spondyloepiphysial dysplasia congenita, Down syndrome, and Klippel-Feil syndrome. The purpose of this study is to highlight the authors' experience with 4 additional pediatric cases, review the literature, and report a new association of this disease with Williams syndrome.

METHODS

The medical records and radiological imaging studies of 4 patients treated at Texas Children's Hospital for symptomatic hypoplasia of the atlas were retrospectively reviewed. Pertinent patient demographic data, clinical presentation, imaging findings, and outcomes after surgery were recorded. A thorough literature review was performed, allowing the authors to compare and contrast their 4 cases to surgical cases already published in the literature.

RESULTS

There were 11 boys and 1 girl in the aggregate series. The average age of the patients was 7 years (range 13 months-14 years), and the duration of symptoms prior to presentation was 6 months (range 0-36 months). The mean sagittal diameter of the spinal canal at the level of the atlas measured from the posterior aspect of the dens to the anterior aspect of the arch of C-1 was 11.9 mm (range 8.3-16 mm) in the aggregate series. In 2 new pediatric patients with hypoplasia of the atlas the disease was associated with Williams syndrome, which has not been previously described. Patients in the aggregate series were followed for an average of 18 months (range 3-50 months). Laminectomy of C-1 provided neurological improvement in all patients who presented.

CONCLUSIONS

Isolated cervical spinal canal stenosis at the level of the atlas is a rare cause of cervical myelopathy. The authors hope that this report will prompt clinicians to consider it when searching for the origin of signs and symptoms of cervical myelopathy, especially in children.

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.

A case report of a patient with cleft palate carrying the risk of tetraplegia

Spondyloepiphyseal dysplasia congenita (SEDC) is an inherited disorder of bone growth that results in short-trunk dwarfism, skeletal abnormalities, disorders in vision and hearing, atlanto-axial instability, and cleft palate. This important anomaly of the cervical vertebrae carries the risk of tetraplegia during cleft palate operations. In this case report, we discuss a case of spondyloepiphyseal dysplasia congenita, the perioperative and postoperative measures, and the risk of tetraplegia.

Cervical myelopathy accompanied with hypoplasia of the posterior arch of the atlas: case report

STUDY DESIGN

Case reports of 2 patients having cervical myelopathy accompanied with idiopathic hypoplasia of the posterior arch of the atlas.

OBJECTIVE

A standard for the sagittal inside diameter (SID) of the vertebral foramen of the atlas was determined for use in the diagnosis of hypoplasia. From the point of view of short SID, the etiologies of myelopathy in patients with this disease were analyzed.

SUMMARY OF BACKGROUND DATA

There is no established definition of hypoplasia of the atlantal vertebral foramen. The mechanism underlying the occurrence of this myelopathy in adulthood is unknown.

METHODS

Lateral x-ray views of the cervical vertebrae of 150 Japanese men and 150 Japanese women were investigated, and the standard values of the SID were obtained. The features of myelopathy associated with this disease were analyzed in 2 cases managed at our facility and in the literature.

RESULTS

The mean standard value was 34.4 mm in women and 37.1 mm in men, showing a significant sex difference (P<0.0001). When a case with a value -2 SD below the standard was regarded as having hypoplasia, case 1 (female) showed 25 mm, that is, -3.9 SD, and case 2 (male) showed 30 mm, that is, -2.7 SD. The space available for the spinal cord of the atlas was 8.0 mm in case 1 and 9.5 mm in case 2. Both patients showed atlantoaxial subluxation on images, but atlantodental interval on flexion in cases 1 and 2 was 3.8 and 4.5 mm, respectively, showing the degree to be mild.

CONCLUSIONS

In the presence of congenital hypoplasia of the posterior arch of the atlas, the spinal cord is highly susceptible to injury because congenital spinal canal stenosis is present. Therefore, the presence of even a mild mechanical compressive lesion leads to myelopathy. Acquired mild atlantoaxial subluxation was associated with this hypoplasia, and the association was considered to be the mechanism underlying the occurrence of myelopathy in adulthood.

Specific entities affecting the craniocervical region: syndromes affecting the craniocervical junction

INTRODUCTION

The craniocervical junction is a vital component in understanding the function of the human central nervous system. It is the threshold for major pathways affecting both brain and spinal cord function, and these structures are intricately housed in a network of bone, ligaments, and soft tissues. Abnormal development of any of these components may lead to altered structure, and therefore, altered function in the central nervous system.

MATERIALS AND METHODS

We herein describe a set of genetic syndromes that commonly affect the craniovertebral junction and offer clinical examples from more than 6,000 patients who have been treated for these disorders.

DISCUSSION

The syndromes described include Chiari type I malformation, Conradi syndrome, Goldenhar syndrome, Klippel-Feil syndrome, Larsen syndrome, Morquio syndrome, Pierre-Robin syndrome, spondyloepiphyseal dysplasia congenital and Weaver syndrome. The genetic mechanisms responsible for these disorders may offer unique insight into the developmental pathways and patterning in the musculoskeletal and cranial systems and may, ultimately, guide future diagnosis and treatment.

Spinal disorders associated with skeletal dysplasias and syndromes

Skeletal dysplasias are a heterogeneous group of disorders in which there is abnormal cartilage and bone formation, growth, and remodeling. There are more than 200 described skeletal dysplasias. Skeletal dysplasias can affect the spine in various ways, with attendant neurosurgical implications for diagnosis and treatment. Craniocervical junction abnormalities, atlantoaxial subluxation, and kyphoscoliotic deformity are among the common spinal problems that are found in certain skeletal dysplasias.

Surgical treatment for atlantoaxial subluxation with myelopathy in spondyloepiphyseal dysplasia congenita

STUDY DESIGN

A retrospective review of 21 patients with spondyloepiphyseal dysplasia congenita (SEDC), including 7 operated patients for atlantoaxial subluxation.

OBJECTIVES

To clarify the morphological findings of atlantoaxial subluxation in SEDC patients and to evaluate the operative procedures based on these image findings.

SUMMARY AND BACKGROUND DATA

The presence of atlanto axial sublucation with hypoplasia of the odontoid and/or lax ligaments leads to myelopathy in patients with spondyloepiphyseal dysplasia congenita.

METHODS

We retropectively reviewed the physical and morphological findings on atlantoaxial images and the clinical findings of myelopathy in 21 patients with SEDC.

RESULTS

Myelopathy was found in 9 individuals with severe SEDC who presented with marked short stature and severe coxa vara; of these, 6 had gait disturbances. On the images of the 9 patients with myelopathy, the average sagittal canal diameter (SCD) at the level of the atlas was only 9.2 mm (range, 7-12 mm) with progressive atlantoaxial subluxation. The average atlantodental interval (ADI) was 3.5 mm (range, 2-6 mm) in the presence of a sagittal atlas diameter (SAD) of less than 27.1 mm (range, 22-36 mm). Surgery was performed for 6 of the patients with myelopathy. Since their SADs were small, and the average SCD, at 9.9 mm (8-14 mm), was narrow even at the position of extension (the position of reduction for atlantoaxial subluxation), C1 laminectomy was needed for all these patients, and occipital-cervical posterior fusion was performed. Stability was satisfactory in all cases and the operative outcome for myelopathy was excellent for 1 case, fine for 4, and fair for 2.

CONCLUSION

A small SAD may limit the effectiveness of reducing atlantoaxial subluxation. Persistent narrowing of the SCD may require concomitant C1 laminectomy and occipital-cervical fusion.

Double heterozygosity in bone growth disorders: four new observations and review

Because matings between individuals of small stature is common, information regarding double heterozygosity for dominantly inherited bone growth disorders is of considerable importance. We summarize seven occurrences of four combinations of double heterozygosity (achondroplasia/spondyloepiphyseal dysplasia congenita, achondroplasia/pseudoachondroplasia, achondroplasia/osteogenesis imperfecta type I, achondroplasia/hypochondroplasia (non-FGFR3)), and review additional reports from the literature. Each of the eight different examples of double heterozygosity for bone growth disorders now reported results in distinct phenotypic features, differing severity, and disparate expectations. We document the natural history of each. The genetic processes underlying these disorders also are examined to assess whether knowledge of molecular mechanisms can be used to predict clinical severity.

A case report of spondyloepiphyseal dysplasia congenita

Spondyloepiphyseal dysplasia congenita (SED) is a rare form of skeletal systemic disease, characterized by congenital dwarfism with a short trunk and epiphysial dysplasia in the long bones and vertebral bodies. Patients also frequently suffer from atlanto-axial instability due to os odontoideum. Compression of the spinal cord caused by atlanto-axial instability is a common, serious complication in SED patients, and causes severe spinal cord symptoms or occasionally sudden death. We present an SED patient who underwent a posterior fusion of the occiput to the cervical spine for severe spinal cord symptoms due to atlanto-axial instability.

Dolichoodontoid. A rare cranio-cervical anomaly--MRI findings

The case of a 40-year-old woman with a dolichoodontoid, a rare congenital anomaly of the cranio-cervical region, is presented. Due to summation image and overlying bony structures, plain radiographs in two planes were inconclusive. MRI revealed the hyperplasia of the odontoid process, allowed a grading of the subtype of this disorder and demonstrated its relationship to the neural structures within the foramen magnum and the upper cervical spine. Additional inflammatory disease, suspected in this patient with long standing rheumatoid arthritis could be excluded by MRI.