History and Physical
A previously well 5-year-old boy presented with progressively worsening headache over 2 days, unsteadiness when walking, poor coordination, and slurred speech. On examination, he was drowsy with a Glasgow coma score of 13. Speech was slow and lacked rhythm, with a staccato tone. He was unable to walk unaided and veered from side to side. Even sitting on the bed was challenging with trunk unsteadiness. There was bilateral horizontal nystagmus, most notable on lateral gaze, although ocular movements were full. Reflexes were slightly brisk bilaterally, but plantars were downgoing. Fundoscopy revealed bilateral optic disc edema.
Diagnostic Workup
Brain MRI showed patchy cerebellar edema ( Fig. 49.1 ) with sparing of the cerebrum. MR angiography was normal.
Cerebellitis. Brain MRI, (A) coronal FLAIR and (B) axial T2 show patchy edema involving bilateral cerebellar hemispheres. FLAIR , Fluid-attenuated inversion recovery.
Lumbar puncture was not performed due to the concern for cerebellar tonsillar herniation.
Clinical Differential Diagnoses
Rapidly worsening intracranial pressure and new-onset cerebellar syndrome can be seen with posterior fossa tumor, hemorrhage, hydrocephalus, metabolic decompensation, infection, or inflammation.
Imaging Differential Diagnoses
Isolated involvement of the cerebellum is classically seen in postinfectious cerebellitis. Other inflammatory disorders, such as opsoclonus-myoclonus-ataxia syndrome (OMAS), cause less mass effect and involve additional deep gray and supratentorial structures. Demyelinating disorders show additional supratentorial, optic nerve, and/or cord involvement. Some metabolic disorders can selectively involve the cerebellum but show progressive signal abnormality and atrophy.
Final Diagnosis
Cerebellitis.
Discussion
Cerebellitis is an inflammatory condition that can occur during or after infection with various pathogens including Epstein-Barr virus, group A streptococcus, and Mycoplasma pneumoniae . Paraneoplastic causes are also possible, including lymphoma and lung cancer.
In adults with autoimmune cerebellitis, antibodies against metabotropic glutamate receptor 5, septin-5, Homer-3 antibodies, and GluR1 antibodies can be found. Recent reports have also found autoantibodies against metabolomic glutamate receptor 1. GluR1 antibodies appear to have the strongest association with cerebellar inflammation in adults, with edema and/or atrophy at imaging and bilateral or unilateral involvement ( Fig. 49.2 ). At present, there are few reports of antibody associations in children.
