According to the National Institute for Neurological Disorders and Stroke, herpes simplex virus (HSV) causes approximately 10 percent of encephalitis cases in the U.S. With herpes encephalitis, the virus infects the brain tissues causing an intense inflammatory response by the immune system. HSV encephalitis is a rapidly progressive illness. Left untreated, most people die within 14 days of the onset of the illness. Early recognition of symptoms and prompt treatment significantly reduce the risk of death and permanent disability from this rare but serious infection.
Headache
The overwhelming majority of people with HSV encephalitis complain of headache, which is usually severe and unrelenting. A stiff neck due to inflammation of the brain covering (the meninges) may accompany the headache.
Fever
Fever is common with herpes encephalitis. However, people with a compromised immune system and infants may not exhibit fever.
Flu-Like Symptoms
Herpes encephalitis may begin with flu-like symptoms such as muscle aches and fatigue. In those with severe disease, these symptoms quickly give way to more serious brain-related symptoms.
Decreased Level of Consciousness
People with HSV encephalitis often exhibit a decreased level of consciousness, which ranges from drowsiness to stupor to coma depending on the severity of the infection.
Personality Changes and Behavioral Disturbances
A range of personality and behavioral changes can occur with herpes encephalitis. Irritability is almost universal. Short temperedness, aggression, inflexibility, anxiety and unprovoked hostility are common symptoms. Disinterest in normal activities and current circumstances and social withdrawal may occur. Diminished impulse control can lead to out-of-character and socially inappropriate behavior.
Cognitive Disturbances
Complex thought processes are characteristically impaired with herpes encephalitis. Sufferers are often confused and disoriented. They exhibit poor judgment and decreased capacity for problem solving. Memory loss and forgetfulness are common.
Problems with Speech, Hearing and Vision
Herpes encephalitis commonly affects speech. In extreme cases, people may lose their ability to speak. Vision is also commonly affected; double vision, blind spots and light sensitivity are typical symptoms. Hearing loss may also occur.
Localized Numbness and Weakness
Numbness or weakness may occur in a localized area such as one arm or one leg. As the HSV brain infection progresses, the affected area may expand. Without aggressive treatment, weakness advances to localized paralysis.
Focal Seizures
Abnormal electrical activity that occurs in only one area of the brain causes a focal seizure. The symptoms reflect the affected area of the brain and are limited to a specific region of the body. There is no loss of consciousness. This is in contrast to a generalized seizure, which involves the entire brain, causes a whole-body reaction, and is accompanied by loss of consciousness. Focal seizure activity is common with herpes encephalitis and can manifest in a variety of ways. A group of muscles in the arm, leg or face may rhythmically jerk. Seizure activity located in the brain area that controls the sense of smell may cause a sensory hallucination--tasting or smell something that is not present. Intense visual flashbacks to past events occur with focal seizures in the visual areas of the brain.
