Neuroimaging assessment in Down syndrome: a pictorial review

Abstract

Down syndrome (DS), or trisomy 21, is the leading genetic cause of intellectual incapacity worldwide, with a reported incidence of about 1 in 1,000 to 1 in 1,100 live births. Besides the several commonly known physical features characteristic of this syndrome present at birth, DS may additionally affect every organ system. In addition, despite the large number of published papers concerning this syndrome, there is scarce literature focusing specifically in the typical neuroimaging features associated with this condition. The aim of this paper is to review and systematize the distinctive characteristics and abnormalities of the central nervous system, head and neck, and spine present in DS patients that should actively be searched for and evaluated by radiologists and/or neuroradiologists.

Keywords: Brain abnormalities; Down syndrome; Head and neck malformations; Spine malformations; Vascular abnormalities.

Fig. 1

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

Fig. 2

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

Fig. 3

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

Fig. 4

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

Fig. 5

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

Fig. 6

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

Fig. 7

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

Fig. 8

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

Fig. 9

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

Fig. 10

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

Fig. 11

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)

Fig. 12

Axial CT of a 46-year-old Down syndrome patient with basal ganglia calcifications, mainly involving the globus pallidus

Fig. 13

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

Fig. 14

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

Fig. 15

Plain radiograph of the pelvis in a 7-year-old Down syndrome girl, showing the typical “Mickey Mouse” pelvis

Fig. 16

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)

Fig. 17

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

Fig. 18

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

Fig. 19

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

Fig. 20

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