The diagnosis of AE is complicated because symptoms can be different in different people and because finding inflammation in the brain often requires multiple tests. Sometimes, invasive tests, such as a spinal tap or brain biopsy, are needed to confirm a diagnosis of AE or to make sure that the symptoms are not caused by another diagnosis. Also, it can take several weeks to get the results of tests for antibodies to cells in the brain or spinal cord (or anti-neuronal antibodies) that are part of the criteria to make the diagnosis of “definite AE”.
Because of the time it takes to get the results of all tests and also because early treatment for AE helps people get better faster, many experts recommend starting treatment in children or adults who may have AE, or who meet the criteria for “possible AE”. If test results in a person who was thought to have “possible AE” do not fit with this diagnosis, then they should continue being tested for other conditions that may cause similar symptoms. It is important not to confuse “possible AE” with an actual diagnosis of AE.
Experts have developed criteria for “possible AE”, “definite antibody-positive AE” and “probable antibody-negative AE” in adults and children.