Practice Based Learning: Acute cerebellitis v. acute post-infectious cerebellar ataxia (APCA) – when to image?






Presented by Min Jie Lee, MD (PGY-1)

Acute post-infectious cerebellar ataxia (APCA):

  • Postinfectious (mostly viral) cerebellitis that is a pure pan-cerebellar syndrome w/o other signs of CNS infection.
  • In young children, most common preceding infection is varicella.
  • Often w/ normal MRI scan
  • Diagnosis of exclusion
  • Self-limited, often recovery within 2 weeks

Acute cerebellitis: 

  • May occur after a systemic illness or be the direct result of infection in the cerebellum.
  • Signs & symptoms beyond pure cerebellar syndrome –may include altered sensorium and manifestations of raised intracranial pressure
  • Often with abnormal MRI

Differential diagnosis:

  • Drug ingestion
  • Posterior fossa tumor
  • Meningitis / encephalitis
  • Brainstem encephalitis
  • Acute demyelinating encephalomyelitis (ADEM)
  • Neuroblastoma (opsoclonus-myoclonus syndrome)
  • Guillan-Barre syndrome
  • Trauma: contusion or hemorrhage, vertebrobasilar dissection
  • Hydrocephalus


  • If acute onset of ataxia (pure cerebellar syndrome) and recent viral illness, high likelihood of APCA → no imaging indicated
  • If cerebellar symptoms AND headache, fever, nuchal rigidity, altered mental status, nausea, LOC, or seizures → CT/MRI to rule out AC or other concerning diagnoses
  • Prognosis is good for both
  • Several case reports on steroids used to treat moderate-severe acute cerebellitis.


Connolly AM, et al. Course and outcome of acute cerebellar ataxia. Ann Neurol. 1994 Jun;35(6):673-9.

De Bruecker Y, et al. MRI findings in acute cerebellitis. Eur Radiol. 2004 Aug; 14(8):1478-83.

Gieron-Korthals MA, et al. Acute childhood ataxia: 10-year experience. J Child Neurol. 1994 Oct;9(4):381-4.

Montenegro MA, Santos SL, Li LM, Cendes F. Neuroimaging of acute cerebellitis.
J Neuroimaging. 2002 Jan;12(1):72-4.

Pruitt AA. Infections of the cerebellum. Neurol Clin. 2014 Nov;32(4):1117-31.

Sawaishi Y, Takada G. Acute cerebellitis. Cerebellum. 2002 Jul;1(3):223-8.

Sivaswamy L. Approach to acute ataxia in childhood: diagnosis and evaluation. Pediatr Ann. 2014 Apr;43(4):153-9.

Yiş U, et al. Acute cerebellitis with cerebellar swelling successfully treated with standard dexamethasone treatment. Cerebellum. 2008; 7(3):430-2.

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