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.
