trisomy 21

Neuroimaging
assessment in Down syndrome: a pictorial review. Axial (a) and sagittal (b) T1/3D in a 5-year-old child with Down syndrome. Measurements of biparietal and occipitofrontal diameters are presented, showing increased cephalic index (129/147 × 100 = 88) (normal value ranges from 74 to 83), in relation to brachycephaly, a common feature of this condition. The cranial sutures remain patent
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Neuroimaging
assessment in Down syndrome: a pictorial review. Temporal bone CT (a) and MRI (axial T2/3D) (b) from a 2-year-old Down syndrome patient at the level of the lateral semi-circular canal, revealing left hypoplastic bone island (less than 3 mm in greatest diameter). Axial temporal bone CT (c) at the same level of a normal 2-year-old boy for comparison
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Preschooler
with Trisomy 21. Lateral radiographs of the cervical spine show a mildly enlarged atlanto dens interval in neutral position (left), that increases significantly on flexion (center) and reduces on extension (right).The diagnosis was atlanto axial instability in a patient with Trisomy 21.
pediatricimaging.org • CC-by-nc-sa 4.0
Neuroimaging
assessment in Down syndrome: a pictorial review. Three-dimensional reconstruction of a CT angiography of the supra-aortic trunks of a 49-year-old patient with Down syndrome depicting an aberrant right subclavian artery
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Neuroimaging
assessment in Down syndrome: a pictorial review. Cerebral angiography in a 46-year-old Down syndrome patient with moyamoya pattern. a Frontal view, right internal carotid artery injection, showing occlusion of the right anterior cerebral artery, with a network of collateral vessels (moyamoya vessels) in the supra-sellar cistern with reconstitution of the anterior cerebral artery arterial flow distally. b Lateral view, left internal carotid artery injection, showing severe narrowing of this artery, which ends on the cavernous segment, where the arterial flow diverges to a meningohypophyseal trunk with anastomosis with the ophthalmic artery and dural branches of the middle meningeal artery, forming a network of collateral capillaries, typical of moyamoya syndrome
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Neuroimaging
assessment in Down syndrome: a pictorial review. Three-dimensional reconstruction of MRI angiography (time-of-flight technique) of a 46-year-old Down syndrome patient, illustrating occlusion of the left internal carotid artery (ICA) and stenosis of the supraclinoid segment of the right ICA, as well as subocclusion of the right anterior cerebral artery (ACA). The left ACA and middle cerebral artery are not depicted. There are also multiple thin anomalous collateral vessels around the basal cisterns; these findings are compatible with moyamoya syndrome, which is known to have a high incidence in this population
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Neuroimaging
assessment in Down syndrome: a pictorial review. Axial FLAIR image in a 12-year-old girl with Down syndrome and moyamoya pattern depicting the classical ivy sign, corresponding to areas of absence of normal FLAIR suppression of CSF within cortical sulci. This sign probably represents slow flow in leptomeningeal collaterals. The exam was performed without general anesthesia
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Neuroimaging
assessment in Down syndrome: a pictorial review. Axial T2* (a) and T2/TSE (b) of a 46-year-old patient with Down syndrome, presenting signs of an old hemorrhagic stroke involving the left thalamic-capsular area. Note also the prominent flow voids from collateral vessels involving the basal cisterns and horizontal segments of the Sylvian fissures. These features suggest associated moyamoya syndrome, which was confirmed in angiographic studies (not shown)
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Neuroimaging
assessment in Down syndrome: a pictorial review. Plain radiograph of the pelvis in a 7-year-old Down syndrome girl, showing the typical “Mickey Mouse” pelvis
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Neuroimaging
assessment in Down syndrome: a pictorial review. Sagittal cervical CT of a 68-year-old Down syndrome patient, showing the presence of an os odontoideum with atlanto-axial and atlanto-odontoid luxation; there is severe stenosis of the craniocervical junction, with space conflict in the bulbo-medullary junction
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Neuroimaging
assessment in Down syndrome: a pictorial review. 3D Reconstruction of MR T1/3D in a 5-year-old child with Down syndrome, showing flat occiput with brachycephaly. Note also the small ear with an overfolded helix, which is a common feature of Down syndrome patients
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Neuroimaging
assessment in Down syndrome: a pictorial review. Coronal (a), sagittal (b), and axial (c) T1/3D reconstructions of a 58-year-old Down syndrome patient presenting with new-onset myoclonic seizures and showing imaging findings similar to Alzheimer disease, with diffuse atrophy predominantly involving the temporal mesial (a, c) (grade 4 in the visual rating scale) and parietal structures with ex-vacuo widening of adjacent CSF spaces (b). The clinical and radiological picture allowed the diagnosis of late-onset myoclonic epilepsy in Down syndrome (LOMEDS)
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Neuroimaging
assessment in Down syndrome: a pictorial review. Coronal T1/3D reconstructions of a 48-year-old Down syndrome patient with dementia. a Grade 2 anterior cingulate gyrus atrophy (MRI visual rating scale). b Grade 2 orbito-frontal cortex volume loss. c Grade 2 anterior temporal cortex atrophy. d Grade 3 fronto-insular loss of volume. e Grade 4 medial temporal atrophy, including the amygdala and hippocampus. f Grade 3 posterior parieto-occipital cortex atrophy
insightsimaging.springeropen.com • CC-by-4.0
Neuroimaging
assessment in Down syndrome: a pictorial review. a Sagittal T2/TSE of a 12-year-old Down syndrome patient showing a small and flattened shape of the occipital condyle as well as the C1 superior articular facet, with some degree of anterior luxation of C1. b Sagittal T2/TSE of a normal 12-year-old boy for comparison; there is normal curved shape of articular facets
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Neuroimaging
assessment in Down syndrome: a pictorial review. Axial (a) and sagittal (b) T1/3D of a 12-year-old girl with Down syndrome, showing small brainstem structures with enlargement of the IV ventricle. In particular, there is a reduced cranio-caudal diameter of the pons. Also, the agenesis of the splenium of corpus callosum, a finding that has been occasionally described in Down syndrome
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Neuroimaging
assessment in Down syndrome: a pictorial review. Temporal bone CT (a) and MRI (axial T2/3D) (b) from a 2-year-old patient with Down syndrome at the level of the internal auditory canal, showing complete absence of the right bone island and consequent aplasia of the lateral semi-circular canal. Note also the dysplastic vestibule as a result of the absence of the lateral semi-circular canal
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Neuroimaging
assessment in Down syndrome: a pictorial review. Axial reconstruction of a temporal bone CT, at the level of the ossicular chain, of a 36-year-old Down syndrome patient demonstrating hypopneumatization of the mastoid and signs of left middle chronic otitis, with an erosion of the ossicular chain, namely the stapes
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Neuroimaging
assessment in Down syndrome: a pictorial review. Coronal (a) and axial (b) reconstruction of a temporal bone CT of a 2-year-old boy with Down syndrome, at the level of the mesotympanum, depicting a right stenotic external auditory canal (less than 4 mm in diameter as defined by Cole and Jahrsdoerfer, 2009). Axial reconstruction (c) of a temporal bone CT of a normal 2-year-old boy for comparison. Measurement is done in the bony component of the external auditory canal at the most stenotic point
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Neuroimaging
assessment in Down syndrome: a pictorial review. Sagittal T1/SE of a 38-year-old Down syndrome patient with platybasia (skull base angle > 143°). As shown in the figure, this angle is measured using a line joining the nasion with the center of the pituitary fossa and a line joining the anterior border of the foramen magnum and the center of the pituitary fossa
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Neuroimaging
assessment in Down syndrome: a pictorial review. Coronal (a, b) and axial (c) reconstruction of paranasal sinus CT of a 21-year-old Down syndrome patient, depicting absent frontal sinuses and hypoplasia of the maxillary and sphenoid sinuses
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School ager
with Trisomy 21. Lateral radiograph of the cervical spine in flexion (left) shows a normal atlanto dens interval and normal relationship of the occipital condyles to the lateral masses of C1 while on extension (right) there is posterior translation of the occipital condyles in relation to the lateral masses of C1.The diagnosis was atlanto occipital instability in a patient with Trisomy 21.
pediatricimaging.org • CC-by-nc-sa 4.0
Newborn with
Trisomy 21 who has large residuals after feeding. AP (above) and lateral (below) images from an UGI exam show a dilated stomach and first part of the duodenum. On a delayed image obtained 15 minutes later, no contrast was seen to have passed out of the duodenum into the remainder of the bowel.The diagnosis was duodenal atresia in a patient with Trisomy 21.
pediatricimaging.org • CC-by-nc-sa 4.0
Neuroimaging
assessment in Down syndrome: a pictorial review. Axial CT of a 46-year-old Down syndrome patient with basal ganglia calcifications, mainly involving the globus pallidus
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Radiopaedia • CC-by-nc-sa 3.0 • de

Down syndrome (or trisomy 21) is the most common trisomy and also the commonest chromosomal disorder. It is a major cause of intellectual disability, and also has numerous multisystem manifestations.

Epidemiology

The approximate worldwide incidence is approximately 1 in 800live births . The individual risk is strongly dependent on maternal risk, and therefore incidence varies with regional and temporal variation in maternal age distribution and the implementation of antenatal screening.

Risk factors
  • increased incidence with increasing maternal age
  • translocation Down syndrome gene carriers
  • previous pregnancy with Down syndrome

Clinical presentation

Diagnosis is often made antenatally and this must occur in conjunction with genetic counseling, which should begin prior to the testing.

In the postnatal period, characteristic phenotypical features point to the diagnosis:

  • depressed nasal bridge
  • epicanthal folds
  • abundant neck skin
  • macroglossia
  • simian crease (single palmar crease)
  • hypotonia

Intellectual disability becomes evident in early childhood as the failure to reach developmental milestones in an expected timeframe.

Pathology

In ~95% of cases, the chromosomal abnormality is trisomy of chromosome 21 due to meiotic non-disjunction (i.e. failure of a chromosome pair to separate during meiosis, so that both go to one daughter cell, and none to the other). Thus, the individual’s chromosome count is 47, rather than 46. Maternal non-disjunction accounts for ~95% of such cases.

An alternative chromosomal abnormality that results in the syndrome involves Robertsonian translocation of paternal chromosomal material, such that the overall number of chromosomes remains the same. This happens in ~3% of cases . Very rarely (~2%) some individuals have mosaic trisomy 21.

Clinicopathological spectrum
Neurological manifestations

Cognitive disability and epilepsy are the most common neurological manifestations . Structurally evident abnormalities include:

Cardiovascular

Congenital heart disease affects ~40%. In particular, defects affecting the endocardial cushion are common:

Respiratory
Gastrointestinal
Musculoskeletal
Endocrine
Others
  • significantly increased incidence of leukemia (although the individual may be protected against other solid organ tumors)

Radiographic features

The manifestations of Down syndrome are protean and can affect multiple systems. Some of these are better discussed under individual features in the wide clinicopathological spectrum of the condition (listed above).

Antenatal features

These are discussed in detail in a separate article.

Treatment and prognosis

Survival can be variable with the mean survival often considered at ~20 years-. Respiratory infections stay considerably predominant cause of death. Moreover, other causes of early mortality, include congenital heart defects and dementia

History and etymology

Down syndrome was named after John Langdon Haydon Down (1828-1896), an English physician .

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Down-Syndrom:
Atriumseptumdefekt
 
Wikipedia • CC BY-SA 4.0
Analatresie
 
Wikipedia • CC BY-SA 3.0
Lungenhypoplasie
 
www.eurorad.org • CC by-nc-sa-4.0
Duodenalatresie
 
Wikipedia • CC BY-SA 3.0
Morbus
Hirschsprung
pediatricimaging.org • CC-by-nc-sa 4.0
Moyamoya-Erkrankung
 
Wikipedia • CC BY-SA 3.0
atlantoaxiale
Subluxation
pediatricimaging.org • CC-by-nc-sa 4.0