title: Transient splenial lesion of the corpus callosum in clinically mild influenza-associated encephalitis/encephalopathy.
abstract: BACKGROUND
  Reversible lesions in the splenium of the corpus callosum (SCC), caused by various agents such as influenza, rotavirus, Escherichia coli, mumps, and adenovirus, were previously defined in a handful of cases. We present 5 cases with transient diffusion restriction of the SCC associated with influenza A virus infection.
  
  
  METHODS
  Five patients with influenza-associated encephalitis/encephalopathy and sudden-onset neurologic symptoms following a prodromal flulike episode were examined by MR and diffusion-weighted imaging (DWI).
  
  
  RESULTS
  Three patients, who had drowsiness and new-onset convulsions, recovered spontaneously without any medication. In the other 2 seizure-free patients, 1 had trigeminal neuralgia and headache and the other had facial numbness and left upper monoparesis. All patients had round well-defined ovoid hyperintense splenial lesions (14.94 +/- 1.87 mm) on DWI with a significantly low apparent diffusion coefficient (ADC) of 0.41 +/- 0.05 x 10(-3) mm(2)/s compared with 0.84 +/- 0.01 x 10(-3) mm(2)/s of normal-appearing white matter. In the patient with a motor deficit, additional lesions were found in the cerebral deep white matter. The high signal intensity of the splenial and deep white matter lesions on DWI completely disappeared on follow-up studies, and ADC values also improved, returning to those of normal-appearing white matter on days 8-11. Clinically, all patients completely recovered on days 4-9.
  
  
  CONCLUSIONS
  A transient lesion of the SCC is a significant but nonspecific finding. It is probably due to edematous and/or inflammatory changes of the SCC. It may be the only detectable change in patients with good prognosis, indicating a clinically mild form of encephalitis/encephalopathy.
authors.affiliation: Department of Radiology, Gulhane Military Medical Academy, Ankara, Turkey. nbulak@gata.edu.tr
authors.forename: N
authors.initials: N
authors.lastname: Bulakbasi
authors.forename: M
authors.initials: M
authors.lastname: Kocaoglu
authors.forename: C
authors.initials: C
authors.lastname: Tayfun
authors.forename: T
authors.initials: T
authors.lastname: Ucoz
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001921:Brain / Q000473:pathology*; D002648:Child; D003337:Corpus Callosum / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D018792:Encephalitis, Viral / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis*; D029521:Alphainfluenzavirus; D008297:Male; D009460:Neurologic Examination; D012075:Remission, Spontaneous; D013223:Statistics as Topic