Autoimmune Encephalitis: Neurological Manifestations and Management

Introduction

Autoimmune encephalitis (AE) is a group of severe brain inflammatory diseases caused by the immune system's misdirected attack on healthy brain cells, leading to various neurologic and psychiatric symptoms. The diagnosis can be challenging, and a broad approach to testing for infectious diseases and autoantibodies is necessary. Treatment involves escalating immune therapies based on the specific autoimmune cause and the patient's condition. This article will explore the various neurological manifestations and the management of autoimmune encephalitis in detail.

What Are the Neurological Manifestations of Autoimmune Encephalitis?

The neurological manifestations of autoimmune encephalitis include:

1. Altered Level of Consciousness and Confusion: Patients may experience changes in their awareness and mental clarity.

2. Disturbed Sleep: Sleep disturbances can be common, leading to insomnia or changes in sleep patterns.

3. Movement Disorders: Over one-third of patients may exhibit abnormal movements, such as ataxia (lack of muscle coordination), chorea (involuntary, jerky movements), dystonia (sustained muscle contractions causing twisting movements), myoclonus (quick, involuntary muscle jerks), or tremor (rhythmic shaking).

4. Seizures: Seizures are the most common feature in AE and can be focal or generalized, often multifocal.

5. Cognitive Impairment: Most AE patients experience some degree of cognitive impairment, which is considered a cardinal symptom. It can manifest as memory deficits, developmental regression, language loss, or speech impairments.

In addition to these neurological manifestations, pediatric AE may also present with behavioral changes and psychiatric symptoms, such as:

1. Repetitive or stereotypical behaviors.

2. Irritability, hyperactivity, hypersexuality, insomnia, and anger outbursts.

3. Psychiatric symptoms include mood swings, mild personality changes, and, in some cases, fulminant psychosis.

4. In contrast to primary psychiatric problems, new-onset psychosis in children under the age of 13 is seen as a warning sign for an underlying medical condition.

Furthermore, the clinical presentations of children with AE may be more varied than those of adults and may involve multifocal neuropsychiatric symptoms rather than isolated syndromes. Moreover, pediatric AE is less associated with tumors compared to adult cases. Due to the variability and overlap of symptoms with more common conditions, AE may not be initially considered, leading to delays in diagnosis and the need for multiple visits with different healthcare providers before initiating the appropriate work-up and treatment.

What Is the Management of Autoimmune Encephalitis?

The management of autoimmune encephalitis involves a step-wise approach with various treatment options:

• First-Line Therapy: When AE is suspected, initial treatment is often given empirically before specific antibody test results are available. First-line therapy includes intravenous, high-dose corticosteroids and intravenous immunoglobulins (IVIG) or plasmapheresis. The choice between IVIG and plasmapheresis is often based on personal preference and experience since data on the optimum choice is lacking. Prompt and aggressive treatment of patients with AE, with escalation if necessary, generally leads to better outcomes and fewer relapses.

• Second-Line Therapy: If first-line therapy fails to reverse the symptoms, second-line treatments are typically initiated. Rituximab is a monoclonal anti-CD20 antibody and is often used as a second-line therapy. It effectively depletes CD20/CD19 B cells (which secrete antibodies) from the blood and is administered weekly for four weeks. In children, Rituximab may be used as a single drug due to its safety and efficacy against diseases caused by IgG4 antibody reactions. Cyclophosphamide is another option for second-line therapy, but it has potential toxicities, including a risk of infertility, especially with repeated doses.

• Treatment Based on Antibody Type: The specific type of synaptic or cell-surface antibody detected in the patient guides the treatment approach. For example, Rituximab is considered more effective against neurological diseases where autoantibodies are of the IgG4 subtype, supporting its use in LGI1 (leucine-rich glioma inactivated 1) and CASPR 2 (contactin-associated protein 2) encephalitis.

• Timing of Second-Line Treatment: Second-line therapies may be initiated within two weeks if the patient remains significantly impaired after first-line therapy. In certain cases, early escalation to second-line therapy is practiced, especially in critically ill patients.

• Empirical Treatment: Treatment for suspected AE may be initiated even before specific antibody test results are available. This may include the use of steroids or IVIG.

How Is Relapse of Autoimmune EncephalitisTreated?

Treatment of relapsing encephalitis in the context of autoimmune encephalitis is primarily focused on managing relapses that occur after the initial attack. Here are the key points about the treatment of relapse in autoimmune encephalitis.

• Relapse Patterns: In autoimmune encephalitis, relapse follows a similar clinical course to the initial attack. For instance, in anti-NMDAR encephalitis, relapses are often milder than the initial attack and may present with symptoms such as confusion, worsening memory, personality changes, hallucinations, or new seizures.

• Risk of Relapse: The risk of relapse in anti-NMDAR encephalitis is approximately 12 % over two years, with the highest risk observed in untreated patients, intermediate risk in patients who had only received first-line therapy, and lowest risk in patients treated with second-line therapies.

• Second-Line Therapies: Relapsed patients are usually treated with second-line therapies, especially rituximab. Rituximab is a monoclonal antibody targeting CD20 and is used to deplete CD19+/CD20+ B-cells, which secrete antibodies. It is administered weekly for a period of four weeks.

• Duration of Treatment: It is currently unknown how long relapsed patients should get second-line treatments, particularly Rituximab. Depending on the characteristics of each patient and their reaction to therapy, the length of treatment may be decided differently.

• Other Autoimmune Encephalitis Types: It is less certain whether other varieties of autoimmune encephalitis, such as those connected to LGI1 and Caspr2 antibodies, are at risk of relapsing. These cases' relapse management techniques might resemble those employed for anti-NMDAR encephalitis.

• Evaluation for Post-Infectious Complications: A patient with HSV encephalitis may occasionally develop anti-NMDAR encephalitis as a post-infectious consequence. Hence it is important to evaluate for this condition. When a patient worsens after an initial incident of infectious encephalitis, careful assessment is necessary to differentiate between infectious and autoimmune causes.

Conclusion

In conclusion, autoimmune encephalitis is characterized by the development of autoantibodies against neurons, which leads to neurologic symptoms in the central nervous system. Relapses may occur more frequently or less frequently depending on the condition, and the severity frequently requires lengthy intensive care. In some circumstances, receiving early and efficient therapy can help lower the risk of relapse. Therefore, clinical diagnosis and quick treatment start are given precedence over waiting for the results of autoantibody tests.