While
encephalitis is rare in the United States, when it
does occur it is usually caused by the
herpes simplex virus.1
Symptoms typical of herpes simplex encephalitis (HSE) that are less
likely to occur in other types of encephalitis include speech problems, a
reduced sense of smell, and
partial seizures. Fever and headache occur as in other
types of encephalitis. HSE usually can be diagnosed through analysis of spinal
fluid obtained through a lumbar puncture (spinal tap).
In cases of
HSE, early treatment (before the person becomes unconscious) with an antiviral
medicine called acyclovir greatly increases the possibility of survival and
recovery.1
When HSE is not treated, it
has a death rate of 70% to 80%.2 Of people who survive
the disease, many have permanent neurological problems, including seizures,
memory loss, and
dementia.