Affiliations: Department of Neurology, Children's National Medical
Center, The George Washington University, Washington, DC, USA | Molecular Infectious Disease Laboratory, Genetics IVF
Institute, Fairfax, VA, USA
Note: [] Correspondence: Dr. John R. Crawford, Department of
Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla
CA 92093-0662, USA. Tel.: +1 858 534 9434; Fax: +1 858 534 8980; E-mail:
jrcrawford@ucsd.edu
Abstract: Human herpesvirus-6 (HHV-6) has been associated with central nervous
system encephalitis in immunocompetent children. To determine acute and chronic
changes on magnetic resonance imaging (MRI) of a series of consecutive
pediatric immunocompetent patients diagnosed with HHV-6 associated
encephalitis. A retrospective review of acute and chronic MRI findings of
immunocompetent children diagnosed with HHV-6 associated encephalitis from
2001–2008 was performed. Diagnosis was established by real time polymerase
chain reaction using HHV-6 U77 helicase gene-specific primers on cerebrospinal
fluid during the acute phase of illness, excluding other known causes of
encephalitis. Seven patients (four girls, ages 9 months–7 years) were
diagnosed with HHV-6 associated encephalitis from 2001–2008. MRI abnormalities
were present in six of seven patients. Three had bithalamic signal
abnormalities on T2 weighted sequences that mimicked metabolic or demyelinating
disease. All patients with MRI abnormalities had diffuse signal changes in the
brainstem (n=5) and/or cerebellum (n=4).
One patient with diffuse abnormalities in cortical grey and white matter,
hippocampus, and cerebellum showed complete resolution of MRI findings after
1~month. Five patients had extensive necrosis of the acutely affected regions
on follow up MRI 3 to 16~months post diagnosis. HHV-6 associated encephalitis
can occur in immunocompetent children with a myriad of acute and chronic
necrotizing changes on MRI. MRI abnormalities were seen predominantly in the
thalami, brainstem, and cerebellum; and may be reflective of anatomical viral
tropism. HHV-6 should be considered in the differential diagnosis of
unexplained MRI changes in patients with encephalitis.
Keywords: Human herpesvirus-6, encephalitis, child, HHV-6
