By Dr. Lee,Kang-Po, Dept. of Neurology, Tainan Sin-Lau Hospital
A 17-year-old girl, nicknamed Xiao-Ling, was once a lively and high-achieving student. Out of nowhere, she began to display unusual behavior. At first, she was frequently absent-minded and forgetful. Then, she became irritable, paranoid that her family was spying on her, and began lashing out—throwing objects and claiming to hear voices. Her family initially assumed she was stressed by school. But when she collapsed and began convulsing at home, they rushed her to the hospital.
Her condition rapidly worsened—she became disoriented, spoke incoherently, and even turned aggressive toward medical staff. After neurological consultation, doctors suspected Limbic Encephalitis (LE). MRI scans and cerebrospinal fluid analysis were performed, along with autoantibody testing, which confirmed a diagnosis of anti-NMDAR encephalitis. Following high-dose steroid and IVIG treatment, her condition gradually improved, and she was discharged three months later with ongoing follow-up care.
Limbic Encephalitis: Memory, Emotion, and Behavior in Crisis
The limbic system is a critical brain region responsible for memory, emotional regulation, and learning. It includes structures such as the hippocampus, amygdala, and cingulate gyrus. When this system is attacked, symptoms such as memory loss, psychosis-like behavior, and severe emotional disturbances can occur.
Limbic encephalitis is an autoimmune condition in which the immune system mistakenly attacks the brain, causing inflammation. It may be triggered by tumors (paraneoplastic) or immune dysfunction (non-paraneoplastic). Regardless of the cause, patients can suddenly lose normal function, becoming erratic or incapable of basic daily activities.
Why Test for Autoantibodies?
Because the symptoms often mimic psychiatric disorders, limbic encephalitis is frequently misdiagnosed as schizophrenia or bipolar disorder. Accurate diagnosis requires antibody testing through blood and cerebrospinal fluid samples.
Known associated antibodies include anti-NMDAR, anti-LGI1, anti-CASPR2, and anti-GABA_B receptor antibodies. Each corresponds to different disease mechanisms and treatment strategies. For example, anti-NMDAR encephalitis is more common in young women and may be linked to ovarian teratomas, while anti-LGI1 encephalitis is more often seen in middle-aged and elderly individuals and is associated with seizures and memory loss. Precise antibody testing not only confirms diagnosis but also helps determine whether tumor screening or long-term immunotherapy is needed to prevent recurrence.
Diagnosis and Treatment: A Race Against Time
Diagnosis requires comprehensive testing—including brain MRI, cerebrospinal fluid analysis, blood antibody panels, and tumor screening. Once confirmed, treatment must begin immediately to prevent neurological deterioration. First-line treatments include steroids, IVIG, and plasma exchange. In some cases, long-term immunosuppressive therapy is needed. If a tumor is present, surgical removal is crucial.
Due to the early symptoms’ similarity to psychiatric illness, many patients are misdiagnosed, leading to delayed treatment and irreversible damage. Therefore, sudden memory loss, personality changes, or unexplained seizures should be evaluated promptly by a neurologist with antibody testing to improve outcomes through early intervention.
李剛伯 醫師
新樓醫院神經內科
