Autoimmune encephalitis | Acute disseminated encephalomyelitis

Autoimmune encephalitis (AE) occurs when healthy cells and tissues in the brain or spinal cord are attacked by the body’s immune system, leading to inflammation. AE is a collection of conditions and some types, such as ADEM, can be caused by an infection while other forms are associated with finding specific antibodies in the blood. In most cases, it remains unknown why these antibodies are produced, while in other cases it may be due to the presence of a tumor.

Acute disseminated encephalomyelitis (ADEM) causes brief but widespread inflammation and demyelination (white matter tissue damage) of the brain and spinal cord. Unfortunately, reviewing the existing medical literature on the topic can prove challenging, given that different terms have been used to describe and define the disorder. “Typically, ADEM is considered a monophasic disorder, which is a disorder that has a single occurrence of one phase in a particular individual.”  However, there is confusion over whether symptomatic recurrences are relapses of ADEM or if they are instead the presentation of other diseases with similar symptoms, such as multiple sclerosis.

Autoimmune rhombencephalitis is a rare form of autoimmune encephalitis that causes inflammation in the brainstem (also called the rhombencephalon). The immune system mistakenly attacks this region, leading to neurological symptoms that affect movement, speech, swallowing, and eye coordination. Autoimmune rhombencephalitis may be associated with specific autoantibodies, including anti-Ma2, anti-Hu, and anti-GAD, or it may develop as part of a paraneoplastic syndrome related to an underlying cancer.

Autoimmune encephalitis: Impaired memory and cognition, abnormal movements, seizures, and/or problems with balance, speech, or vision, psychosis, aggression, inappropriate sexual behaviors, panic attacks, compulsive behaviors, euphoria, or fear.

ADEM: Fever, headaches, irritability, fatigue, lethargy, malaise, unintended weight loss, nausea, and vomiting, vision loss in one or both eyes, muscle weakness even to the point of paralysis, difficulty coordinating voluntary muscle movements, confusion, stupor, delirium, and potentially coma.

Autoimmune rhombencephalitis: Dizziness, difficulty speaking (dysarthria), trouble swallowing (dysphagia), double vision (diplopia), loss of coordination (ataxia), facial paralysis, limb weakness, abnormal eye movements, confusion, and, in severe cases, respiratory failure or coma.

Autoimmune encephalitis: Multiple sclerosis, Hashimoto’s thyroiditis, and vasculitis.

ADEM: While ADEM does have a lot in common with multiple sclerosis (MS), there are some key differences:

• In most but not all cases, ADEM occurs only once, while patients with MS have further, repeated attacks of inflammation in their brains and spinal cords.
• Typical symptoms of ADEM such as fever, headache and confusion, vomiting, and seizures are not usually seen in people with MS, although they can be seen in pediatric MS onset especially in patients younger than 11 years.
• Sometimes the pattern of MRI abnormalities helps differentiate these two disorders.
• Most patients with MS are treated with ongoing medication to prevent attacks. Patients with ADEM generally do not require such medication because they do not experience flare-ups.
• ADEM occurs more frequently in males; MS occurs more frequently in females.
• ADEM is more common in children; MS is more common in adults.

Autoimmune rhombencephalitis: May occur alongside or be triggered by other autoimmune or immune-mediated diseases, including:

• Paraneoplastic syndromes, especially those linked to small cell lung cancer, testicular cancer, or other malignancies
• Neuromyelitis optica spectrum disorder
• Multiple sclerosis
• Anti-GAD antibody syndromes, such as stiff person syndrome
• Other forms of autoimmune encephalitis, such as anti-NMDA receptor encephalitis

Autoimmune encephalitis: Research has shown that herpes simplex encephalitis can trigger autoimmune encephalitis. Other risk factors include infectious causes, HIV diagnosis, and tumors.

ADEM: Environmental factors, including exposure to viral infections. Currently, it is not believed to be inherited, as the NIH has no reports of ADEM occurring in more than one family member.

Autoimmune rhombencephalitis: Rare and most commonly associated with paraneoplastic syndromes or other autoimmune conditions mentioned above. The presence of specific autoantibodies, such as anti-Ma2, anti-Hu, or anti-GAD, is a significant risk factor.

Additional encephalitis resources can be found at https://www.encephalitis411.org/

• Clinical and Autoimmune Profiles of Omani Patients with True Versus False Positive Autoimmune Encephalitis Antibodies Panels (2025)
• [Autoimmune encephalitis-An update] (2023)
• Autoimmune encephalitis: recent clinical and biological advances (2023)
• Acute disseminated encephalomyelitis (ADEM) following recent Oxford/AstraZeneca COVID-19 vaccination (2022)
• Autoimmune encephalitis associated with COVID-19: A systematic review (2022)
• Autoimmune Rhombencephalitis as a Presentation of Post-COVID-19 Syndrome: A Case Report (2025)
• Rhombencephalitis with longitudinal extensive transverse myelitis in lupus: an overlap syndrome? (2023)
• Rhombencephalitis in Pregnancy-A Challenging Case of Probable Listeria Infection (2022)