Diagnosis | Herpes simplex encephalitis

Diagnosis

The rapid detection of the genetic material of the herpes virus in the cerebrospinal fluid (liquor) (DNA detection by PCR) is the most important form of diagnosis. A small amount of cerebrospinal fluid must be obtained for this purpose. To extract it, a hollow needle is inserted between the 3rd and 4th or the 4th and 5th lumbar vertebrae into the subarachnoid space (space of the nerve fluid) below the spinal cord (lumbar puncture).

It then drips through this needle into sterile tubes. Its appearance alone can provide information about the type of disease and possible pathogens. This procedure is known medically as liquor diagnostics.

Antibodies against HSV 1 are only produced from day 7 onwards and can be detected in the blood and spinal fluid. However, a therapy must be started much earlier. In the cerebrospinal fluid, there is still an increase in the number of cells to several hundred per microliter (mainly lymphocytes (white blood cells)) and an increase in the protein content to 1.0 to 1.5 g/l.With the help of magnetic resonance imaging (MRI), the early diagnosis of herpes encephalitis is possible.

It is therefore the method of choice for early diagnosis, which allows an early start of therapy. The MRI image of herpes encephalitis usually shows a typical pattern of infection. The viruses spread mainly into the areas of the temporal lobe (temporal lobe) and the limbic system (processing of emotions).

There the brain tissue becomes swollen (edema). It is no longer possible to differentiate between the cerebral cortex and the cerebral marrow. Due to the storage of water during the brain swelling, the inflammation areas appear hyperintensive (white) in T2-weighted frequencies of the MRI.

Therapy

In case of justified suspicion, therapy with Aciclovir must be initiated immediately. Aciclovir is a nucleoside analogue, i.e. it is incorporated into the DNA by the viruses instead of their own genetic material and thus leads to the termination of virus DNA synthesis (replication). Aciclovir is for example also used in ointments for the treatment of cold sores.

Herpes simplex encephalitis is treated intravenously (IV) and in high doses with 10 mg acyclovir per kg body weight, usually 750 mg, three times a day for at least 14 days. Other drugs used to treat the virus (virustatics) are Famciclovir and Valaciclovir. For brain edema, which always develops around inflammatory processes as swelling, glycerol 10% or mannitol 20% is given (osmotherapy). Epileptic seizures are treated with Phenytoin (trade names in Germany: Epanutin ®, Phenhydan ® and Zentropil ®). Phenytoin is an anticonvulsant (anti-convulsant) and is effective against epilepsy emanating from a specific focus (focal seizures, focus = focus), as is the case with HSV encephalitis.