Tomoyuki Noguchi, Presenter: Nothing to Disclose

Futoshi Mihara MD, PhD, Abstract Co-Author: Nothing to Disclose

Takashi Yoshiura MD, PhD, Abstract Co-Author: Nothing to Disclose

Osamu Togao, Abstract Co-Author: Nothing to Disclose

Koji Yamashita MD, Abstract Co-Author: Nothing to Disclose

Hiroshi Honda MD, Abstract Co-Author: Nothing to Disclose

Akira Uchino MD, PhD, Abstract Co-Author: Nothing to Disclose

Kanehiro Hasuo MD, Abstract Co-Author: Nothing to Disclose

Kazushige Atsumi, Abstract Co-Author: Nothing to Disclose

Takashi Matsuura MD, PhD, Abstract Co-Author: Nothing to Disclose

Toshiro Kuroiwa, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

Human herpesvirus-6 (HHV-6) associated encephalopathy is a cause of central nervous system problems in immunocompromised patients. The imaging characteristics are reportedly similar to herpes simplex virus (HSV) encephalitis in regard to the involvement of mesial temporal lobe. It is important to differentiate HHV-6 encephalopathy from HSV encephalitis because the former is insensitive but the latter is sensitive to acyclovir. We retrospectively reviewed CT and MR findings of HHV-6 encephalopathy in adults and compared with those of HSV encephalitis.

Between 2003 and 2005, we encountered 7 cases of HHV-6 encephalopathy (3 men and 4 women; age range, 36-55 years old) and 9 cases of HSV encephalitis (3 men and 6 women; age range, 24-79 years old) in 5 hospitals. The diagnosis was established by the detection of viral DNA in cerebrospinal fluid or peripheral blood by polymerase chain reaction or increase of antibodies against the virus in paired serum.

On CT within 2 days from onset, none of 4 patients (0%) with HHV-6 encephalopathy and 6 of 7 patients (86%) with HSV encephalitis showed the abnormal findings (p<0.05). On MR within 30 days, 6 of 7 patients (86%) with HHV-6 encephalopathy showed exclusive involvement of the mesial temporal lobe while all 9 patients (100%) with HSV encephalitis showed involvement of other regions as well as the mesial temporal lobe (p<0.01). On MR over 30 days, 5 of 5 patients (100%) with HHV-6encephalopathy but none of 6 patients (0%) with HSV encephalitis showed the resolution of the hyperintensity of the affected regions on T2-weighted images and FLAIR (p<0.01), and none of 5 patients (0%) with HHV-6encephalopathy but 5 of 6 patients (83%) with HSV encephalitis showed the cortical T1-shortening in the affected region (p<0.05).

We demonstrated the different findings on CT and MR between HHV-6 encephalopathy and HSV encephalitis, which may be useful for differential diagnosis of the two diseases.

CT and MR could differentiate HHV-6 encephalopathy from HSV encephalitis.

Noguchi, T, Mihara, F, Yoshiura, T, Togao, O, Yamashita, K, Honda, H, Uchino, A, Hasuo, K, Atsumi, K, Matsuura, T, Kuroiwa, T, et al, , CT and MR Findings of Human Herpesvirus-6 Associated Encephalopathy in Adults: Comparison with Herpes Simplex Virus Encephalitis.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4438161.html