Introduction
Limbic encephalitis causes inflammation of the limbic system and other brain parts. The brain is one of the most complex organs in the human body. It controls emotions, memory, motor skill, vision, and every other process that helps the body regulate. The main parts of the brain involve the cerebrum, cerebellum, and brainstem. The limbic system is situated in the cerebrum part of the brain below the temporal lobes. Its function is to help in processing memory and emotions. The limbic system is one of the essential parts of the brain as it helps in the body’s response to stress and is connected to the endocrine (it uses hormones to control the body’s metabolism and reproduction) and autonomic nervous system (it controls functions such as digestion and breathing).
What Is Limbic Encephalitis?
Limbic encephalitis is a group of autoimmune conditions that occur due to the inflammation of the limbic system and other brain parts. Depending on whether the tumors are due to antibodies, limbic encephalitis is divided into two types:
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Paraneoplastic Limbic Encephalitis - It affects the medial temporal lobe caused due to specific cancer or tumor. The antibodies are against the antigens and have a poor response to immunotherapy (a treatment in which an individual's immune system is modified to control autoimmune disorders).
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Non-neoplastic Limbic Encephalitis - It is not caused by any cancer or tumor; instead, infection and viruses such as herpes virus can cause this condition. The antibodies are against the extracellular antigens and have reversible neuronal dysfunction.
What Causes Limbic Encephalitis?
The causes of limbic encephalitis include:
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Herpes Simplex Virus (HSV) - It is one of the viruses associated with non-neoplastic encephalitis that can cause fog in the brain. Herpes simplex virus spreads from person to person by close contact or sharing food and water from the same utensils. It can also spread as a sexually transmitted infection. Herpes is more common in females. Other herpes viruses, such as the Epstein-Barr virus, cause mononucleosis.
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Immune System Reacting Against Limbic System - Immune system protects the body from any invading virus. The brain and immune system are linked through the signals activated by the immune system. The brain reacts to it and regulates immune responses. When cancer or tumor forms in the body, the immune system activates, which in reverse attacks the limbic system in the brain. When the immune system attacks the brain, it causes inflammation.
What Are the Symptoms of Limbic Encephalitis?
The symptoms of limbic encephalitis are reflected in the dysfunction of the limbic system of the brain, including:
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Short-term memory loss.
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Depression.
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Seizures.
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Confusion.
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Difficulty while sleeping.
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Altered personality.
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Hallucinations.
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Focal neurological deficits such as cerebral dysfunction.
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Brain fog.
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Fever.
How Is Limbic Encephalitis Diagnosed?
Autoimmune limbic encephalitis is diagnosed through the evaluation of symptoms, medical history, and specialized tests, which include:
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Magnetic Resonance Imaging - MRI helps detect infections such as herpes simplex encephalitis. A healthcare professional will ask the patient to lie down on the bed of the machine. Once the patient is settled, the expert will operate the machine in a different chamber. The machine will take several scans, which take around half an hour to complete. The sound of the machine will be very loud and high-pitched. The expert will be able to communicate with the patient with an intercom connected to the chambers. A headphone can be placed to listen to music to calm the patient.
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CT (Computed Tomography) Scan - A healthcare expert will conduct this test with or without giving the intravenous (IV) dye for better visualization. CT scan helps check muscles and the left temporal lobe. The patient is asked to lie down on the bed of the machine. The scanner’s x-ray will move around the body, and a buzzing sound will come. The pictures are taken and transferred to a computer. Once the images are scanned, it will help the doctor in giving a proper diagnosis.
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Electroencephalogram (EEG) - EEG is a test to measure the brain's electrical activity. It helps diagnose conditions such as sleep disorders, inflammation in the brain, and brain tumors. A technician will mark points with a pen or marker on the head, and these marks might be scrubbed with a cream to improve the recording. A disc or electrode is attached to the scalp, connected with wires that amplify the computer screen's brain waves. This test requires the patient to sleep, and the doctor may give a tablet. The test completes in 20 to 40 minutes. The body motions may be recorded in a video while taking the EEG test, as it helps diagnose and treat the condition better.
How Is Limbic Encephalitis Managed?
The treatment options for limbic encephalitis include:
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One of the treatment options is by giving intravenous immunoglobulin therapy. It helps in recovering the level of antibodies. It is given through an intravenous (IV) infusion, which may take some hours to complete, and the frequency varies depending on the patient’s condition. It usually is given 2 g/kg (gram per kilogram) for two to five days.
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Plasmapheresis is somewhat similar to dialysis. It removes plasma from the blood with antibodies. Before plasma exchange, a blood test and vitals are checked. Next, a tube (cannula) is inserted in the arm’s vein, and blood is taken and then circulated through a cell separator. The spinning separates the blood and plasma. Once the blood is separated, it is mixed with plasma substitute and transferred back into the body through a vein.
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In some cases, Corticosteroids and Rituximab are given to treat autoimmune diseases.
Conclusion:
A limbic encephalitis is a group of conditions due to the inflammation of various parts of the brain, mainly the limbic system, which is situated in the cerebrum. It is a rare condition that can occur due to viruses such as herpes or specific cancer or tumors. In addition, the immune system reacts due to cancers which can affect the brain's functions. Any visible symptoms should be informed to the doctor, and additional tests like MRI will help diagnose the condition.
