Anti-NMDA receptor encephalitis overview

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# Overview
Anti-NMDA encephalitis is an autoimmune disorder where antibodies attack NMDA receptors in the brain. It presents with psychiatric symptoms, seizures, memory loss, and movement abnormalities. Treatment involves immunotherapy, such as corticosteroids and intravenous immunoglobulin, along with tumor removal if applicable. Symptom management includes antiepileptic drugs, sedatives, and supportive care. Early diagnosis and prompt treatment are crucial for better outcomes in managing this potentially severe and life-threatening condition.

# Historical Perspective
Anti-NMDA encephalitis, initially documented in a case report dating back to 1830, is an autoimmune condition marked by neuropsychiatric manifestations. In some instances, the presence of an ovarian teratoma is observed. The case of Susannah Cahalan played a significant role in raising public awareness regarding this disorder.

# Classification
Anti-NMDA encephalitis can be categorized into three distinct subtypes based on the timing of onset and duration of the illness.

# Pathophysiology
Anti-NMDA receptor encephalitis is an autoimmune disorder characterized by the presence of autoantibodies directed against the GluN1 subunit of the NMDA receptor. The presence of tumors, particularly ovarian teratomas in women and testicular teratomas or lung carcinomas in men, is frequently associated with the condition. Dysregulation of NMDA receptors contributes to the development of diverse neurological and psychiatric symptoms.

# Causes
In anti-NMDA receptor encephalitis, autoantibodies targeting the GluN1 subunit of the NMDA receptor are present. These antibodies lead to internalization of NMDA receptors, disrupting synaptic plasticity and causing a range of neurological and psychiatric symptoms.
Various causes of the antibodies include , infections, vaccinations and tumors

# Differentiating Anti-NMDA receptor encephalitis from other Diseases
In the differential diagnosis of anti-NMDA encephalitis, other autoimmune encephalitides with specific antibody associations should be considered, including those associated with antibodies against AMPA receptors, GABA-B receptors, LGI1, Caspr2, and MOG. Clinical and serological evaluations are crucial for accurate diagnosis and appropriate management.

# Epidemiology and Demographics
Encephalitis has an annual incidence of 2-3 per 100,000, with 40% being infectious, 40% of unknown cause, and 20% immune-mediated. Anti-NMDA receptor encephalitis and VGK Complex antibody-positive encephalitis are major immune-mediated categories. It is more common in women and younger patients.

# Risk Factors
Risk factors for anti-NMDA encephalitis include female predominance, higher incidence in young individuals, and increased likelihood of underlying teratoma in African-Americans and teratomas in Asians.

# Screening

# Natural History, Complications and Prognosis
Anti-NMDA encephalitis typically exhibits a characteristic trajectory, wherein initial neuropsychiatric manifestations advance to neurological symptoms.
The acute phase of the condition can be severe and protracted, extending over a period of weeks to months. 
Timely initiation of immunotherapy and surgical intervention for tumor removal have shown to enhance prognosis. Gradual amelioration of symptoms occurs, although the duration of recovery varies. Long-term neurological and psychiatric recuperation may necessitate several months to years, with the possibility of relapses. Mortality rates are associated with complications such as infections, cardiac arrest, and respiratory distress. Favorable prognostic indicators include early intervention, milder symptomatology, and resection of associated tumors.

# Diagnosis

## History and Symptoms
Anti-NMDA receptor encephalitis presents with neuropsychiatric manifestations, neurological symptoms, altered consciousness, and a subacute time frame. Early recognition is important for prompt intervention.

## Physical Examination
The physical examination findings in Anti-NMDA encephalitis are non-specific. Patients may exhibit symptoms of widespread encephalopathy, altered states of consciousness, orofacial dysostosis, dyskinesis, dystonia, and autonomic storming. Neurological examination may reveal signs of diffuse cerebral dysfunction, including reflex abnormalities and mild ataxia.

## Laboratory Findings
In Anti-NMDA encephalitis, cerebrospinal fluid (CSF) analysis often shows mildly elevated white blood cell count, modestly increased protein levels, and the presence of oligoclonal bands. CSF-specific tests like IgG index and oligoclonal band tests can provide diagnostic value.

## Electrocardiogram
There are no distinctive electrocardiogram (ECG) findings associated with Anti NMDA encephalitis.

## Chest X Ray
Chest X-ray imaging does not reveal any characteristic findings specifically associated with Anti-NMDA receptor encephalitis

## CT
CT imaging has limited diagnostic utility in anti-NMDA encephalitis, but it can help exclude other conditions, identify associated tumors, and detect complications. MRI is the preferred imaging modality for this condition.

## MRI
In approximately 50% of cases, brain magnetic resonance imaging (MRI) may appear normal in Anti-NMDA receptor encephalitis. Non-specific abnormalities, such as temporal lobe involvement, can be observed in the remaining cases. However, neuroimaging alone is not sufficient for diagnosis due to the lack of specific patterns of brain involvement.

## Echocardiography or Ultrasound

## Other Imaging Findings
FDG-PET scan plays a crucial role in the diagnosis, differential diagnosis, assessment of disease activity, treatment response, and prognostication of anti-NMDA encephalitis. It reveals characteristic metabolic changes in the brain, aids in distinguishing it from other conditions, monitors treatment efficacy, and identifies prognostic indicators.

## Other Diagnostic Studies

# Treatment

## Surgery
Surgery plays a crucial role in the treatment of anti-NMDA encephalitis when an associated tumor, typically an ovarian teratoma, is present. Tumor removal can improve prognosis, reduce relapse risk, and enhance response to immunotherapy. A multidisciplinary approach is essential for optimal patient management.

## Medical Therapy
The treatment of anti-NMDAR encephalitis involves immunotherapy, tumor diagnosis, and excision. Early immunotherapy has shown to improve outcomes. Treatment options include corticosteroids, plasmapheresis, immunoglobulins, and rituximab

## Primary Prevention
Primary prevention of anti-NMDA encephalitis focuses on general measures to promote overall health and immune function, including a healthy lifestyle, good hygiene practices, and routine vaccinations. No specific preventive measures exist.

## Secondary Prevention
Secondary prevention of anti-NMDA encephalitis involves strategies aimed at early detection, timely intervention, and management to prevent disease progression and complications. Since anti-NMDA encephalitis often presents with neuropsychiatric symptoms, prompt recognition and appropriate referral to specialized medical care are crucial.

## Cost-Effectiveness of Therapy

## Future or Investigational Therapies

# Case Studies

## Case #1