[Necrotizing herpes simplex encephalitis as the cause of a progressive dementia syndrome]

A 65-year-old woman was twice hospitalized because of disorientation and insomnia with depression. In the course of antidepressive treatment the symptoms regressed each time so that the diagnosis was made of pseudo-dementia during depression. About a year after the first admission the symptoms recurred, despite continued antidepressive treatment. Clinical criteria now suggested Alzheimer-type dementia as the diagnosis.

The symptoms of dementia increased markedly and generalized seizures requiring anticonvulsive drugs occurred after 4 months. Although IgG antibodies against Herpes simplex virus (HSV) were demonstrated in cerebrospinal fluid (CSF), no antiviral treatment was instituted because HSV encephalitis appeared unlikely at this stage. But the patient's mental and physical state further deteriorated in subsequent months. During an attack of pneumonia the patients became somnolent and went into status epilepticus. Repeat virological examination of CSF now revealed IgG and IgM antibodies against HSV, confirming encephalitis. Her condition markedly improved over 12 days on aciclovir, 750 mg 3 times daily intravenously. 6 weeks later the pneumonia recurred, as did the encephalitis, with apnoeic phases and massive left heart failure. The patient died a few days later. Immunohistochemical tests of brain tissue were positive for HSV type II.

This case report demonstrates that an investigation on dementia must include a complete liquor analysis. If HSV encephalitis is suspected, an antiviral therapy must be administered immediately. Even in adults who seem to have normal immunity HSV type II can cause HSV encephalitis.