With pictures and texts: an article to grasp the brainstem syndrome caused by developmental abnormalities

As the so-called "brain stem is small, nuclei are complete", brainstem injury can present a variety of clinical symptoms and signs
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Brainstem dysplasia is a rare disorder characterized by the absence or abnormal development of brainstem structures
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They can be difficult to diagnose on MRI
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Learn about syndromes caused by missing or dysplastic brainstem structures today
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Möbius Syndrome ➤ Etiology: A rare congenital disorder characterized by the absence or loss of the abducens and facial nuclei.
underdevelopment
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The brainstem is hypoplastic, with a flattened floor of the fourth ventricle due to the absence of the facial colliculus (Fig.
1)
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 ➤Clinical manifestations: unilateral or bilateral paralysis, expressionless face, inability to close mouth or eyes
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Figure 1 Möbius Syndrome, Axial (a, b) and sagittal (c) t2-weighted images showing loss of abducens and facial nerves at the level of Merkel's cavity
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 Axonal Guidance Disorders ➤ Etiology: Abnormal white matter fiber tracts are present, often unable to cross the midline or ectopic fiber tracts are present
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It is easier to identify in diffusion tensor imaging (DTI) and tractography
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(Figure 2) ➤Clinical manifestations: horizontal gaze palsy and progressive scoliosis, Joubert syndrome, and pontine tegmental dysplasia
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Figure 2 Horizontal gaze palsy and scoliosis
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(a) DTI shows absence of chiasm in the upper cerebellum and absence of chiasm of somatosensory and corticospinal tracts
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(be) Axial T2-weighted (b, d), axial inversion-recovery (c), and sagittal T1-weighted (e) images show a reduced pons with facial colliculus and medulla oblongata with midline cleft missing
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(f) Radiograph showing lumbar scoliosis
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 Multiple system atrophy (MSA) ➤ Etiology: Multiple system atrophy (MSA) is a sporadic neurodegenerative disease, and in MSA-C type, the cerebellar symptoms are dominated by olivopontocerebellar atrophy
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MRI showed T2 hyperintensity in the pontocerebellar tract, resulting in a "hot cross bun" sign in the pons and excessive atrophy of the cerebellum and brainstem (Figure 3)
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➤Clinical manifestations: Characterized by varying degrees of cerebellar ataxia, autonomic dysfunction, Parkinson's disease, and corticospinal dysfunction
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Figure 3 MSA-C.
(a) Sagittal T1-weighted image showing cerebellar atrophy
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(b) Axial T2-weighted image shows cruciform hyperintensity in the pons (hot cross sign), representing selective degeneration of the pontocerebellar tract
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 Wernicke Encephalopathy ➤Causes: Caused by thiamine (vitamin B1) deficiency, usually seen in cases of alcoholism
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MRI showed symmetrically enhanced areas of T2/FLAIR signal intensity, including the mammillary body, dorsomedial thalamus, tectum, periaqueductal areas, and peri-third ventricle (Figure 4)
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 ➤Clinical manifestations: altered consciousness, ataxia, and ocular dysfunction
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Figure 4 Axial FLAIR image showing signal enhancement in the dorsomedial area of ​​the thalamus (a), the mammillary body and the periaqueductal area of ​​the midbrain (b), and the tectum (c), typical of Wernicke's encephalopathy
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 Osmotic Demyelination Syndrome ➤ Etiology: This is an acute demyelination caused by altered osmosis, usually following rapid correction of hyponatremia
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 ➤ Imaging features: MRI showed symmetrical abnormal signal intensity in the pons, basal ganglia, midbrain, and subcortical white matter, low signal on T1-weighted images, and high signal on T2-weighted/FLAIR images
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Diffusion restriction is usually the earliest symptom, presenting in the lower pons within 24 hours of the onset of quadriplegia
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Enhancement with gadolinium contrast is usually absent
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 Progressive Supranuclear Palsy ➤Clinical manifestations: This neurodegenerative disease usually appears after age 60 and progresses to death within 10-20 years
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It is characterized by Parkinsonism, supranuclear vertical gaze palsy, cognitive and language decline, instability and falls
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➤ Imaging features: midbrain atrophy, resulting in loss of brainstem convexity, and hummingbird sign in the sagittal plane
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Decreased posterior midbrain interlobar diameter at the level of the superior colliculus may give a "Mickey Mouse" appearance (Mickey Mouse sign) in the axial plane
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T2 lesions can be seen in the pontine tegmentum, midbrain tectum, and inferior olivary nucleus
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Compiled from: Sciacca S, Lynch J, Davagnanam I, Barker R.
Midbrain, Pons, and Medulla: Anatomy and Syndromes.
Radiographics.
2019 Jul-Aug;39(4):1110-1125.
doi: 10.
1148/rg .
2019180126.
PMID: 31283463.