From the Guidelines
Limbic encephalitis is a rare inflammatory condition characterized by rapidly progressive short-term memory deficits, psychiatric symptoms, and seizures, associated with a wide variety of autoantibodies, as described in the consensus statement of the international encephalitis consortium 1. This condition affects the limbic system of the brain, which controls emotions, behavior, and memory, and can be either autoimmune or paraneoplastic. Some key features of limbic encephalitis include:
- Rapidly progressive short-term memory deficits
- Psychiatric symptoms
- Seizures
- Association with autoantibodies, including onconeuronal antibodies and antibodies to neuronal cell surface/synaptic antigens, as noted in the study published in Clinical Infectious Diseases 1 Diagnosis of limbic encephalitis involves:
- Brain MRI
- Cerebrospinal fluid analysis
- EEG
- Blood tests to detect specific antibodies, with serum testing being sufficient in most cases, according to the study 1 Treatment depends on the cause, but generally includes immunotherapy, such as corticosteroids, intravenous immunoglobulin, or plasma exchange. Early diagnosis and treatment are crucial for better outcomes, as untreated limbic encephalitis can lead to permanent cognitive impairment, highlighting the importance of prompt intervention, as implied by the clinical characteristics described in the study 1.
From the Research
Definition and Classification of Limbic Encephalitis
- Limbic encephalitis (LE) is a clinical syndrome defined by subacutely evolving limbic signs and symptoms with structural and functional evidence of mediotemporal damage in the absence of a better explanation than an autoimmune (or paraneoplastic) cause 2.
- LE can be classified into different subtypes based on the presence of specific antibodies, which are distinct regarding underlying pathophysiologic processes, clinical and magnetic resonance imaging courses, cerebrospinal fluid signatures, treatment responsivity, and likelihood of a chronic course 2.
Clinical Presentation of Limbic Encephalitis
- Patients with LE usually present with rapidly progressive short-term memory deficits, psychiatric symptoms, and seizures 3, 4.
- Other symptoms may include disorientation, agitation, hallucinations, and sleep disturbance 4.
- The clinical manifestation of LE is primarily defined by the subacute onset of short-term memory loss, seizures, confusion, and psychiatric symptoms suggesting the involvement of the limbic system 5.
Diagnosis and Treatment of Limbic Encephalitis
- The diagnosis of LE involves excluding other causes of subacute encephalopathy, especially those resulting from infectious aetiologies 5.
- Investigations that may aid in the diagnosis of LE include analysis of cerebrospinal fluid, electroencephalography, magnetic resonance imaging, fluorodeoxyglucose positron emission tomography, and neuronal antibodies in the serum and CSF 4.
- Treatment options for LE largely depend on the aetiology of the disease and involve the removal of the primary neoplasm, as well as immunotherapy, which has been successful in a significant number of patients where LE is not associated with cancer 3, 5.
Pathophysiology and Impact of Limbic Encephalitis
- LE is characterized by adaptive autoimmune inflammation of the gray matter structures of the limbic system 6.
- Autoimmune inflammation of the hippocampus is likely to be responsible for declarative memory disturbance, while consequences of autoimmune inflammation of the amygdala are largely unknown 6.
- The amygdala is central for the generation of adequate homoeostatic behavioral responses to emotionally significant external stimuli, and adaptive cellular and humoral autoimmunity may target and modulate distinct inhibitory or excitatory neuronal networks within the amygdala, impacting processing of emotional stimuli and corresponding behavioral responses 6.