A Systematic Review of Sodium Disorders in HHV-6 Encephalitis

Human herpesvirus 6 (HHV-6) encephalitis has a high mortality rate. Among those who survive, ~80% develop some type of permanent neurologic disorder. Early diagnosis and treatment may help prevent long-term sequelae. There have been several case reports as well as retrospective and prospective studies associating HHV-6 encephalitis with some form of sodium imbalance, either hyponatremia or hypernatremia; however, the exact frequency post-HCT is unknown, with reports ranging from 30% to 100%. We performed a systematic review of the literature and found 34 cases of HHV-6 encephalitis reported in conjunction with sodium imbalance that documented the timing of that imbalance relative to the onset of encephalitis. Sodium imbalance occurred before or at the onset of HHV-6 encephalitis in all but 2 cases (94%). This finding supports previous suggestions that sodium imbalance can be considered an early indicator of the potential development or presence of HHV-6 encephalitis in at-risk patient populations.