Herpes simplex encephalitis

Most individuals with HSE show a decrease in their level of consciousness and an altered mental state presenting as confusion, and changes in personality. Increased numbers of white blood cells can be found in patient's cerebrospinal fluid, without the presence of pathogenic bacteria and fungi. Patients typically have a fever Definite diagnosis requires testing of the cerebrospinal fluid (CSF) by a lumbar puncture (spinal tap) for presence of the virus. The testing takes several days to perform, and patients with suspected Herpes encephalitis should be treated with acyclovir immediately while waiting for test results. Atypical stroke-like presentation of HSV encephalitis has been described as well, and the clinicians should be aware that HSV encephalitis can mimic a stroke. Associated conditions Herpesviral encephalitis can serve as a trigger of anti-NMDA receptor encephalitis. About 30% of HSE patients develop this secondary immunologic reaction, which is associated with impaired neurocognitive recovery. == Epidemiology ==

The annual incidence of herpesviral encephalitis is from 2 to 4 cases per 1 million population. ==Pathophysiology==

HSE is thought to be caused by the transmission of virus from a peripheral site on the face following HSV-1 reactivation, along a nerve axon, to the brain. which may explain its predilection for the temporal lobes of the brain, as the olfactory nerve sends branches there. In horses, a single-nucleotide polymorphism is sufficient to allow the virus to cause neurological disease; but no similar mechanism has been found in humans. ==Diagnosis==

Brain CT scan (with/without contrast). Complete prior to lumbar puncture to exclude significantly increased ICP, obstructive hydrocephalus, mass effect Brain MRI—Increased T2 signal intensity in frontotemporal region → viral (HSV) encephalitis ==Treatment==

Herpesviral encephalitis can be treated with high-dose intravenous acyclovir, which should be infused 10 mg/kg (adult) over 1 hour to avoid kidney failure. Without treatment, HSE results in rapid death in approximately 70% of cases; survivors suffer severe neurological damage. While the herpes virus can be spread, encephalitis itself is not infectious. Other viruses can cause similar symptoms of encephalitis, though usually milder (Herpesvirus 6, varicella zoster virus, Epstein-Barr, cytomegalovirus, coxsackievirus, etc.). == References ==