Atlantoaxial instability and abnormalities of the odontoid in Down's syndrome

Repeat Pediatric Trisomy 21 Radiographic Exam: Does Atlantoaxial Instability Develop Over Time?

BACKGROUND

Atlantoaxial instability (AAI) is common in pediatric patients with Trisomy 21 and can lead to spinal cord injury during sports, trauma, or anesthetized neck manipulation. Children with Trisomy 21 therefore commonly undergo radiographic cervical spine screening, but recommendations on age and timing vary. The purpose of this study was to determine if instability develops over time.

METHODS

We performed a retrospective review for all pediatric Trisomy 21 patients receiving at least 2 cervical spine radiographic series between 2008 and 2020 at our institution. Atlantodens interval (ADI) and space available for the cord at C1 (SAC) were measured; bony abnormalities such as os odontoidium, and age and time between radiographs were noted. AAI was determined by ADI ≥6 mm or SAC ≤14 mm based on our groups' prior study. Those who developed instability were compared with those who did not.

RESULTS

A total of 437 cervical spine radiographic series from 192 patients were evaluated, with 160 included. Mean age at first radiograph was 7.4±4.4 years, average ADI was 3.1 mm (±1.2), and SAC was 18.1 mm (±2.6). The average time between first and last radiographs was 4.3 years (±1.8), with average final ADI 3.2 mm (±1.4) and SAC 18.9 mm (±2.9). Seven patients (4%) had instability: 4 were unstable on their initial studies and 3 (1.6%) on subsequent imaging. Os odontoideum was found in 5 (71%) unstable spines and 3 (2%) stable spines (P<0.0001); only 1 patient that became unstable on subsequent radiograph did not have an os. There was no specific age cut-off or surveillance time period after which one could be determined no longer at risk.

CONCLUSIONS

Trisomy 21 patients have a 4.4% overall rate of AAI in our series with a 1.6% rate of progression to instability over ∼4 years. Given this nearly 1 in 23 risk of instability, we recommend initial surveillance radiograph for all children over 3 years with Trisomy 21; repeat asymptomatic surveillance should continue in those with os odontoideum given their high instability risk.

LEVEL OF EVIDENCE

Level II-diagnostic study.

Endoscopic ear surgery in children with down syndrome

INTRODUCTION

Children with Down syndrome (DS) have a high incidence of chronic middle ear disease. Surgery to manage this disease is challenging due to the severity of illness and narrow ear canal dimensions. Endoscopic ear surgery is used to manage tympanic membrane and middle ear disease with the advantages of improved visualization and avoidance of post-auricular incisions. However, its application in children with DS has not been reported. We aim to compare the outcomes of endoscopic versus microscopic ear surgery in children with DS.

METHODS

All patients with DS who underwent tympanoplasty without mastoidectomy between 2012 and 2018 were identified, and their charts retrospectively reviewed. Rate of residual perforation, hearing, surgical time, and surgical details were recorded.

RESULTS

37 surgeries in 26 patients were identified that met inclusion criteria. Two subgroups were analyzed. The first included 14 cases that were done using traditional microscopic visualization (MV). The second included 17 cases that had substantial or exclusive use of endoscopic visualization (EES). Due to a learning curve, the number of cases done endoscopically increased over time. The average age in MV was 13.9 years vs 11.0 in EES. The MV cases included 2 with cholesteatoma vs 4 in EES. In cases with adequate follow up, residual perforations were found in 1/13 MV, and 4/17 EES. All of the residual perforation cases in EES used acellular porcine submucosa grafts. None of the cases in MV used this material. Average air bone gap reduction was seen in both groups; 4.2 dB in MV, 9.8 dB in EES. Average surgical time was similar between groups; 124 min in MV, 115 min in EES. All cases in MV required a post-auricular incision and approach to the middle ear. Only four cases in EES required this approach. Six cases in EES did not require any incision outside of the ear canal for either graft harvest or middle ear approach.

CONCLUSION

Endoscopic and microscopic ear surgery in children with DS have similar outcomes. There were no statistical differences in hearing results, surgical times, or residual tympanic membrane perforations, although the rate of perforations in the endoscopic group trended higher. Most endoscopic cases did not require conversion to a post-auricular approach. Endoscopic surgery allows some DS patients to avoid any incision outside of the ear canal.

Evaluation of spinal involvement in children with mucopolysaccharidosis VI: the role of MRI

OBJECTIVE

To evaluate spinal MRI features of mucopolysaccharidosis (MPS) VI and to assess the correlation with clinical findings.

METHODS

We retrospectively evaluated spinal MRI scans and clinical findings at the time of imaging in 14 patients (8 male, 6 female) with MPS VI. Craniometric measurements were performed and the images were assessed for bony anomalies, spinal stenosis and spinal cord compression. The degree of cervical cord compression was scored and correlated with neurological examination findings at the time of imaging. Vertebral alignment, structural changes in spinal ligaments and intervertebral discs were also assessed.

RESULTS

All patients had cervical stenosis due to bony stenosis and thickened retrodental tissue (median: 6.05 mm, range 3.3-8 mm). Retrodental tissue thickness was found to increase with age (p = 0.042). Compressive myelopathy was detected at upper cervical level in 11 (79%) and lower thoracic level in 2 patients (14%). Significant inverse correlation was found between cervical myelopathy scores and neurological strength scores. The most common bony changes were hypo/dysplastic odontoid; cervical platyspondyly with anterior inferior beaking; thoracic posterior end plate depressions and lumbar posterior scalloping. Kyphosis due to retrolisthesis of the beaked lumbar vertebrae and acute sacrococcygeal angulations were other remarkable findings.

CONCLUSION

MRI is an essential component in evaluation of spinal involvement in MPS VI, and scanning of the entire spine is recommended to rule out thoracic cord compression. Advances in knowledge: This study provides a detailed description of spinal MRI findings in MPS VI and underlines the role of MRI in management of cord compression.

Co-occurring medical conditions in adults with Down syndrome: A systematic review toward the development of health care guidelines

Adults with Down syndrome (DS) represent a unique population who are in need of clinical guidelines to address their medical care. The United States Preventive Service Task Force (USPSTF) has developed criteria for prioritizing conditions of public health importance with the potential for providing screening recommendations to improve clinical care. The quality of existing evidence needed to inform clinical guidelines has not been previously reviewed. Using the National Library of Medicine (NLM) database PubMed, we first identified 18 peer reviewed articles that addressed co-occurring medical conditions in adults with DS. Those conditions discussed in over half of the articles were prioritized for further review. Second, we performed detailed literature searches on these specific conditions. To inform the search strategy and review process a series of key questions were formulated a priori. The quality of available evidence was then graded and knowledge gaps were identified. The number of participating adults and the design of clinical studies varied by condition and were often inadequate for answering all of our key questions. We provide data on thyroid disease, cervical spine disease, hearing impairment, overweight-obesity, sleep apnea, congenital heart disease, and osteopenia-osteoporosis. Minimal evidence demonstrates massive gaps in our clinical knowledge that compromises clinical decision-making and management of these medically complex individuals. The development of evidence-based clinical guidance will require an expanded clinical knowledge-base in order to move forward.

Congenital defects of C1 arches and odontoid process in a child with Down's syndrome: A case presentation

We present the case of a 2-year-old child with Down's syndrome who presented to our unit with torticollis. Imaging studies revealed the rare occurrence of anterior and posterior C1 arch defects, absent odontoid process, and atlantoaxial subluxation. We managed her conservatively for 3 years without neurological deficits or worsening of atlantoaxial subluxation. We discuss the rare occurrences of anterior and posterior arch defects of the atlas, the radiological presentations of axis defects in patients, and the occurrence of atlantoaxial instability in patients with Down's syndrome. Management options with consideration to surgery in asymptomatic and symptomatic patients are also discussed.

Atlanto-Axial Instability in People with Down's Syndrome and its Impact on the Ability to Perform Sports Activities - A Review

Atlanto-axial instability (AAI) is a developmental anomaly often occurring in persons with Down’s syndrome (DS). According to various reports, AAI affects from 6.8 to 27% of the population with DS. The aim of this review was to illustrate the issue of AAI with regard to the progressively changing state of scientific knowledge. The extended distance between the rear surface of the frontal arcus of the C1 cervical vertebra and the anterior surface of C2 cervical vertebra dens (anterior atlanto-odontoid distance, AAOD) indicates the occurrence of AAI and is detectable through X-ray examination. Hypoplasia of the C2 dens, also detectable through X-ray examination, is another suggested risk factor for AAI. According to current data, the methodology of taking measurements is inconsistent, which leads to errors in interpretation. As research focusing on AAI was progressing, new data emerged from other studies on persons with DS, suggesting that neurological symptoms in persons with DS that indicated the occurrence of spinal cord compression were an important factor in medical imaging detection of AAI. One of the main arguments supporting this thesis is that in isolated cases spinal cord (SC) damage was noted during screening examinations conducted on a large population of subjects. Moreover, cases in which the neurological symptoms indicate spinal cord compression existed long before the occurrence of the actual damage also remain of significant importance. Therefore, it is necessary to promote neurological studies on persons with DS to enable early diagnosis of spinal cord compression and, at the same time, reduce the use of medical imaging in cases of neurological symptoms.

Skeletal and hematological anomalies in HYAL2-deficient mice: a second type of mucopolysaccharidosis IX?

The metabolism of hyaluronan (HA) relies on HA synthases and hyaluronidases, among which hyaluronidase-1 (HYAL1) and -2 (HYAL2) have been proposed as key actors. Congenital HYAL1 deficiency leads to mucopolysaccharidosis IX (MPS IX), a rare lysosomal storage disorder characterized by joint abnormalities. Knowledge of HYAL2 is limited. This protein displays weak in vitro hyaluronidase activity and acts as a receptor for oncogenic ovine retroviruses. We have generated HYAL2-deficient mice through a conditional Cre-lox system. Hyal2(-/-) mice are viable and fertile. They exhibit localized congenital defects in frontonasal and vertebral bone formation and suffer from mild thrombocytopenia and chronic, possibly intravascular, hemolysis. In addition, Hyal2(-/-) mice display 10-fold increases in plasma levels of HA and 2-fold increases in plasma hyaluronidase activity. Globally, there is no HA accumulation in tissues, including bones, but liver sinusoidal cells seem overloaded with undigested HA. Taken together, these elements demonstrate for the first time that murine HYAL2 has a physiological activity in vivo that is relevant for craniovertebral bone formation, maintenance of plasma HA concentrations, and erythrocyte and platelet homeostasis. In addition, the viability of HYAL2-deficient mice raises the possibility that a similar defect, defining a new MPS disorder, exists in humans.

Spontaneous rotatory atlantoaxial dislocation without neurological compromise in a child with Down syndrome: a case report

Spontaneous atlantoaxial dislocation is a rare recognised complication of Down syndrome. In the majority of cases, dislocation takes place in an anteroposterior direction and is often associated with abnormalities of odontoid development or ossification. Rotatory atlantoaxial dislocation is extremely rare in Down syndrome and this is to our knowledge the first reported case in which modern imaging methods have been described; surface shaded reformats derived from a multislice CT scan were of fundamental importance in making the diagnosis.

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.

Cervical spine abnormalities associated with Down syndrome

Atlantoaxial instability (AAI) affects 10-20% of individuals with Down syndrome (DS). The condition is mostly asymptomatic and diagnosed on radiography by an enlarged anterior atlanto-odontoid distance. Symptomatic AAI, which affects 1-2% of individuals with DS, manifests with spinal cord compression. Cervical spondylosis, which is common in DS, also has the potential for cord damage but it has received less attention because paediatric populations were mostly studied. Forty-four Kuwaiti subjects with DS, whose ages were > or = 15 years, were evaluated clinically and radiographically. Lateral neck radiographs were taken in the neutral and flexion positions. Asymptomatic AAI was diagnosed in eight subjects (18%) and congenital anomalies of C1-2 were found in five (12%). Five patients had AAI in flexion only while three patients had it in both views. Three patients with AAI had odontoid anomalies contributing to the condition. When assessing AAI, the posterior atlanto-odontoid distance has to be considered because it indicates the space available for the cord. Cervical spondylosis was noted in 16 (36%) subjects. Degenerative changes increased with age, occurred earlier than in the normal population, and affected mostly the lower cervical levels. Half the patients with AAI had cervical spondylosis, a comorbidity that puts the cord at increased risk.

Treatment of Down syndrome-associated craniovertebral junction abnormalities

OBJECT

Operative intervention for craniovertebral junction (CVJ) instability in patients with Down syndrome has become controversial, with reports of a low incidence of associated neurological dysfunction and high surgical morbidity rates. The authors analyzed their experience in light of these poor results and attempted to evaluate differences in management.

METHODS

Medical and radiographic records of 36 consecutive patients with Down syndrome and CVJ abnormalities were reviewed. The most common clinical complaints included neck pain (15 patients) and torticollis (12 patients). Cervicomedullary compression was associated with ataxia and progressive weakness. Hyperreflexia was documented in a majority of patients (24 cases), and 13 patients suffered from varying degrees of quadriparesis. Upper respiratory tract infection precipitated the presentation in five patients. Four patients suffered acute neurological insults after a minor fall and two after receiving a general anesthetic agent. Atlantoaxial instability was the most common radiographically observed abnormality (23 patients), with a rotary component present in 14 patients. Occipitoatlantal instability was also frequently observed (16 patients) and was coexistent with atlantoaxial dislocation in 15 patients. Twenty individuals had bone anomalies, the most frequent of which was os odontoideum (12 patients) followed by atlantal arch hypoplasia and bifid anterior or posterior arches (eight patients). Twenty-seven patients underwent surgical procedures without subsequent neurological deterioration, and a 96% fusion rate was observed. In five of 11 patients basilar invagination was irreducible and required transoral decompression. Overall, 24 patients enjoyed good or excellent outcomes.

CONCLUSIONS

The results of this series highlight the clinicopathological characteristics of CVJ instability in patients with Down syndrome and suggest that satisfactory outcomes can be achieved with low surgical morbidity rates.

Diagnosis of Os odontoideum using kinematic magnetic resonance imaging. A case report

STUDY DESIGN

A case of os odontoideum diagnosed using kinematic magnetic resonance imaging is presented.

OBJECTIVES

To evaluate the kinematic magnetic resonance imaging findings of os odontoideum and the possible use these findings might have to guide treatment.

BACKGROUND

Kinematic magnetic resonance imaging is a new imaging modality that is able to produce realtime images of a structure through a range of motion. This makes it well suited for investigating dynamic processes such as cervical instability.

METHODS

A single subject with known os odontoideum was examined using a Sigma SPR Kinematic Magnetic Resonance Imager (General Electric, Florence, SC).

RESULTS

Kinematic magnetic resonance imaging demonstrated cervical spinal cord impingement and cervical instability throughout flexion and extension, but not during lateral bending or rotation.

CONCLUSIONS

Kinematic magnetic resonance imaging can evaluate the cervical spine in an axially loaded position throughout its range of motion. This modality may be a useful method for diagnosing and classifying abnormalities of the spine.

Value of cervical spine radiographs as a screening tool

A review of the reports of 848 cervical spine radiographs was done to assess the yield of useful and critical information in a group of patients without trauma. In 470 of these patients the clinical record also was reviewed; 54.2% of the radiographs were read as having degenerative change, 35% were read as normal, and 8.5% were read as being consistent with muscle spasm. The remaining 2.3% included diagnoses of anatomic or congenital variants, soft tissue calcification, or old compression fractures. There were no serious diagnoses such as acute fracture, dislocation, or neoplasm that, had they not been identified, would have put the patient in jeopardy. Thus, for most outpatients with nontraumatic symptoms of a nonspecific or nonlocalizing nature, the use of cervical spine radiographs as a screening tool is not justified.

Screening of children with Down syndrome for atlantoaxial (C1-2) instability: another contentious health question

Screening for atlantoaxial (C1-2) instability in children with Down syndrome before their participation in sport is called into serious question. Despite the lack of clear supporting data to justify screening, it has been widely recommended and enforced by some sporting organisations for several decades. Experience in New South Wales during the past 25 years strongly suggests that routine screening should be discontinued, and the existing literature supports this move.

Craniovertebral junction anomalies in inherited disorders: part of the syndrome or caused by the disorder?

Patterns of skeletal abnormality at the craniovertebral junction in the normal population and in syndromes such as Down, Morquio etc, are compared and the recent embryological data and comparative anatomy reviewed. The authors' view based on their own clinical and radiological experience is that the os odontoideum is the product of excessive movement at the time of ossification of the cartilaginous dens and is exactly analogous to the unfused Type II odontoid fracture. True hypoplasia of the odontoid peg is part of a wider segmentation defect associated with Klippel Feil, occipitalised atlas and/or basilar invagination; it is hardly ever associated with instability.

Atlantoaxial instability in Down's syndrome: a five year follow up study

In 1986 all 90 children aged 4-19 years with Down's syndrome attending school in the area served by the Southern Derbyshire Health Authority underwent radiography to identify atlantoaxial instability (AAI). This study details repeat observations five years later. Full results were available on 67 (74%), information on health status was available on the remaining 19 (21%); four (4%) were untraced. There was an overall significant reduction in the atlanto-axial gap over five years. No one developed AAI on repeat testing who had not had it earlier. One child who had previously had normal neck radiography developed acute symptomatic AAI after ear, nose, and throat surgery. Radiographs were done on three occasions on the same day in 49 individuals, ensuring full flexion of the upper neck. There were no significant differences between the radiographs, even in five subjects with AAI. Management of AAI in Down's syndrome is discussed in the light of these findings. Radiography can reliably detect children with chronic AAI who may be at risk of gradually developing symptoms; this may justify a screening programme. This must be distinguished from those who develop symptoms after acute trauma or anaesthesia, for which specific precautions are needed, and previous screening radiographs are unhelpful.

Down's syndrome and anaesthesia

Down's syndrome is a common congenital abnormality associated with characteristic morphological features, impaired intellectual development and disorders of many organ systems with a broad spectrum of severity. Many of these, including defects in cosmetic appearance, are amenable to surgical correction. The risks of anaesthesia are increased in these children. In this article the anaesthetic implications of the syndrome are reviewed and the principles of perioperative management discussed.

Radiological assessment of the atlantoaxial distance in Down's syndrome

People with Down's syndrome are pre-disposed to atlantoaxial instability. As part of a study to determine whether those with Down's syndrome should be screened for atlantoaxial instability before they participate in sport, a series of 279 children, aged 6 to 17 years was investigated radiologically. Lateral radiographs of the cervical spine were taken in neutral position and in flexion. The magnification factor was assessed by means of a marker attached to the nape of the neck. After correction for magnification 15% of the patients were found to have an atlantoaxial distance greater than 4 mm on the flexion film, especially boys under 11 years of age. However, sex and age together explained at most 9% of the variation in atlantoaxial distance. The maximum distance found was 6.5 mm. The disagreement between the means of first and second measurements by the same (test-retest) and by another (inter-) observer was more for those taken in the neutral position than in flexion. On a group level the results for reliability were satisfactory.

Health problems and health checks in school-aged children with Down syndrome

A survey by parent questionnaire and interview was carried out to determine the frequency of health problems in 204 children with Down syndrome. Seventy-two children (35.3%) had a congenital heart defect. Refraction had been performed on 196 and 68 (34.6%) of these had a refractive error. A diagnosis of 'glue ear' had been made in 112 (54.9%) and in 12 (11%) of these permanent hearing loss was present. Significant ill-health over the previous 12 months consisted of cardiac failure (two children), more than three upper respiratory tract infections (24 children), bronchitis (eight children), pneumonia (two children) and asthma (seven children). A neck X-ray had been performed in 172 (84.3%) and had demonstrated the presence of atlanto-axial instability in 12 (7%) of these. One hundred and thirty-two (64.7%) of the children had been tested for hypothyroidism in the previous 18 months and this had been found in four (3%) of these children. The implications of these and other findings are discussed in relation to parental counselling and planning of routine health checks.

Inhaled frusemide against cold air induced bronchoconstriction in asthmatic children

Inhaled frusemide prevents bronchoconstriction in asthmatic adults induced by various triggers. To determine if frusemide provides similar protection in children, whether this is age dependent and equally effective for central and peripheral airways, we performed a double blind, placebo controlled, randomised, crossover study on the effect of inhaled frusemide on lung function changes induced by cold air challenge in 21 asthmatic children. In addition, we measured diuresis before and after inhalation. Bronchodilatation after frusemide was not observed. However, deterioration in lung function after frusemide, compared with placebo, was significantly diminished: forced expiratory volume in one second (FEV1) was -5.7% v -11.5%, peak expiratory flow (PEF) -7.7% v -23.3%, maximum expiratory flow at 50% of vital capacity (MEF50VC) -16.0% v -35.2%, and at 60% of total lung capacity (MEF60TLC) -32.4% v -61.6%, and specific airways conduction -42.0% v -57.7%, respectively. This effect was not age dependent. Diuresis was significantly increased from a mean (SEM) of 198 (34) ml/3 hours before inhaled frusemide to 379 (62) ml/3 hours after nebulisation. We conclude that inhaled frusemide prevents cold air induced bronchoconstriction in asthmatic children and that increased diuresis can be expected with a dose as low as 28 mg of frusemide given by nebuliser.

Clinical predictors and radiological reliability in atlantoaxial subluxation in Down's syndrome

Clinical signs and symptoms that might predict atlantoaxial subluxation were studied prospectively in 135 of 180 children with Down's syndrome aged 6-14 years who form the Hester Adrian Research Centre cohort. Lateral radiographs of the cervical spine were taken in flexed, extended, and neutral positions, and the percentage of abnormalities in each view was 14, 10, and 10%, respectively. Gait was the only significant clinical predictor. The relative risk of having an abnormal neck radiograph with an abnormal gait was 2.91 (95% confidence interval (CI) 1 to 8). The sensitivity was 50% and the specificity 81%. Nineteen children had repeat radiographs to assess the reliability of radiological diagnosis. Six had abnormalities; five of 19 (26%) had an abnormality on the first radiograph, and four of 19 (21%) had an abnormality on a second radiograph, but only three (15%) had an abnormality on both occasions in any view (95% CI 0 to 25). We conclude that radiographs of the cervical spine are unreliable at identifying atlantoaxial subluxation in children with Down's syndrome, and we failed to identify any reliable clinical predictor.

Acquired cervical spine impairment in young adults with cerebral palsy

Three patients with spastic cerebral palsy and no associated movement disorder--each of whom presented with loss of functional skills and delay in the definitive diagnosis of cervical myelopathy--are reported, in order to increase awareness of the possibility of cervical spine pathology in these adults. The possibility of myelopathy should be investigated when considering the etiology of functional deterioration. A functional neurological examination for all multiply disabled individuals is proposed as a reference for future comparison.