The signs and symptoms of most antibody mediated neurologic diseases start suddenly and progress rapidly over several weeks or months.  Specific signs and symptoms vary between disease.  In the classic presentation, frequently but not always, there is a distinct phase or period of time where the illness is developing.  This is called the prodromal stage.  In Autoimmune Encephalitis, the prodromal symptoms, if they occur with the patient, are flu like symptoms which include headache, fever, nausea, vomiting, diarrhea, or upper respiratory tract symptoms. 

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Frequently the dominant feature that is seen in children following this first phase is seizure activity.  While in adults, psychiatric symptoms are the dominant feature.  Common behavioral and personality changes seen early on include psychosis, aggression, inappropriate sexual behaviors, panic attacks, compulsive behaviors, euphoria or fear.

 

Psychiatric Symptoms may fluctuate rapidly coming on and receding in severity and length of time.  Cognitive impairments or abnormalities such as thinking, memory loss, especially the ability to retain new information may be impaired, seizures, problems with concentration and reasoning are severe enough that they interfere with daily functioning. 

 

There is progressive decrease of level of consciousness which can progress to coma.  All these signs and symptoms are often occurring within the first few days to several weeks of the disease appearing.