Drowsiness and Ataxia after Gastroenteritis with Norovirus

Case Report: A 3 ½ year old, otherwise healthy girl presented at the emergency department with gastroenteritis and deteriorating lethargy. On the way to the hospital she lost consciousness and remained drowsy afterwards. When she arrived at the hospital she was somnolent, with global aphasia and ataxia. Her laboratory exam showed signs of a mild dehydration. In the patient’s stool norovirus was detected. Analysis of cerebrospinal fluid revealed an elevated cell count with 140 leukocytes/µl and mild protein elevation. The patient’s cerebral magnetic resonance imaging (MRI) showed a circumscribed diffusion restriction in the splenium of the corpus callosum and symmetrically in both cerebellar peduncles with apparent diffusion coefficient correlate, without contrast enhancement. The electroencephalography (EEG) displayed signs of generalized cerebral dysfunction. Assuming a seizure we started an anticonvulsive therapy with levetiracetam. The girl received aciclovir until an herpes simplex encephalitis was excluded and an empirical therapy with corticosteroids for several days. For two weeks she was given nasogastric feeding. We also administered clonidin to control agitation. When repeating cereral MRI, EEG and the lumbar punction after one week, all pathological changes were reduced. Clinically, our patient recovered gradually over several weeks. First she regained the ability to sit. Then she started to eat and drink and finally to speak. Gait ataxia was the symptom that persisted for the longest period of time.

Diagnosis: Based on the MRI images with transient diffusion restriction in the splenium of corpus callosum in combination with the clinical presentation of an altered consciousness and ataxia we diagnosed a mild encephalopathy with reversible splenial lesion (MERS).

Discussion: MERS is a parainfectious, inflammatory disease of the central nervous system (CNS). Besides the typical diffusion restriction in the corpus callosum, additional sites of white matter lesion have been described such as the cerebellar peduncles in our patient. The pathogenesis is largely unkown. No autoantibodies or intrathecal immunglobulin synthesis was found in MERS patients. Both lesion morphology and localization on MRI images differ from other inflammatory CNS diseases. MERS cases following infection with cytomegalovirus, rotavirus, influenza virus and mycoplasma pneumoniae have been described. To our knowledge, we present for the first time a case with MERS after gastroenteritis caused by norovirus. The disease occurs more frequently in children and most cases have been reported in Asia. As in our patient, prognosis is usually good.

No conflict of interest has been declared by the author(s).