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Amnesia following herpes simplex encephalitis: diffusion-tensor imaging uncovers reduced integrity of

Håkon Grydeland1, Kristine B Walhovd, Lars T Westlye

  • 1Center for the Study of Human Cognition, Department of Psychology, University of Oslo, PO Box 1094, Blindern, 0317 Oslo, Norway. hakon.grydeland@psykologi.uio.no

Radiology
|October 12, 2010
PubMed
Abstract

Insights

Herpes simplex encephalitis (HSE) survivors show subtle white matter (WM) damage in unaffected brain areas, detectable with diffusion tensor imaging. This microstructural damage likely contributes to memory deficits in patients with HSE.

Area of Science:

  • Neuroimaging
  • Neurology
  • Radiology

Background:

  • Herpes simplex encephalitis (HSE) can cause significant brain damage, often affecting the medial temporal lobe (MTL).
  • Patients with HSE frequently experience persistent verbal and visuospatial memory deficits.
  • The integrity of white matter (WM) in brain regions not grossly affected by HSE is not well understood.

Purpose of the Study:

  • To investigate white matter (WM) and gray matter tissue integrity in the hemisphere contralateral to visible lesions in patients recovered from herpes simplex encephalitis (HSE).
  • To correlate microstructural integrity with memory deficits in HSE patients.

Main Methods:

  • Diffusion tensor imaging (DTI) was used to assess microstructural WM integrity via fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD).
  • Automated segmentation provided estimates of subcortical volumes and cortical thickness.
  • Five HSE patients and 51 age-matched controls underwent magnetic resonance (MR) imaging.

Main Results:

  • HSE patients exhibited reduced FA and increased MD and RD in WM tracts contralateral to the lesions.
  • Affected WM tracts included those connecting the MTLs to other brain regions.
  • No significant differences in subcortical volume or cortical thickness were found between HSE patients and controls.

Conclusions:

  • Patients with HSE demonstrate reduced microstructural integrity in apparently normal-appearing WM contralateral to gross lesions.
  • These subtle WM abnormalities, detectable by DTI, are likely contributors to the memory impairments observed in HSE patients.

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