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Cerebellitis
KEY FACTS
Terminology
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Acute cerebellitis
Imaging
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Bilateral cerebellar hemispheric gray and white matter low attenuation (NECT), T2/FLAIR hyperintensity (MR); unilateral involvement less common
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Confluent regions of T2 prolongation, affecting gray and white matter
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± pial or subtle parenchymal enhancement
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DWI/ADC → affected regions typically show increased diffusivity
Top Differential Diagnoses
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Acute disseminated encephalomyelitis (ADEM)
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Infiltrating cerebellar neoplasm
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Cerebellar infarct
Pathology
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Reported in association with varicella, Epstein-Barr, enterovirus, rotavirus, human herpesvirus-7, mumps, measles, influenza, and mycoplasma pneumoniae
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In most cases, definite etiology remains unknown
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Moderate to severe cerebellar swelling → vascular compression, upward transtentorial herniation, tonsillar herniation, brainstem compression, obstructive hydrocephalus
Clinical Issues
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Truncal ataxia, dysmetria, and headache
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Symptoms of ↑ intracranial pressure: Irritability, occipital headache, and vomiting may overshadow manifestations of cerebellar dysfunction
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Most symptoms and signs resolve completely over weeks to months
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Surgery rarely necessary to decompress herniating cerebellum, ventricular drain for hydrocephalus
Axial NECT in a 4-year-old girl with proven influenza A infection shows cerebellar hemispheric edema (low attenuation)
involving both gray and white matter. The edema causes upward cerebellar herniation and effacement of the quadrigeminal plate cistern
. The resultant aqueductal compression causes hydrocephalus
.
involving both gray and white matter. The edema causes upward cerebellar herniation and effacement of the quadrigeminal plate cistern . The resultant aqueductal compression causes hydrocephalus .
Axial T2WI MR demonstrates cerebellar edema (T2 hyperintensity) involving both gray and white matter
. Note the compressed 4th ventricle
.
. Note the compressed 4th ventricle .
Axial FLAIR MR in a 12-year-old patient with acute onset of cerebellar ataxia demonstrates high signal in the left cerebellar hemisphere
. Note mild mass effect on the 4th ventricle.
. Note mild mass effect on the 4th ventricle.
Sagittal T1 C+ MR in the same patient shows patchy areas of pial enhancement
along the left cerebellar hemisphere. In acute cerebellitis, unilateral involvement is far less common than bilateral.
along the left cerebellar hemisphere. In acute cerebellitis, unilateral involvement is far less common than bilateral.
TERMINOLOGY
Synonyms
-
Acute cerebellitis
Definitions
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Parainfectious, postinfectious, or postvaccination cerebellar inflammation
IMAGING
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