Limbic encephalitis is a disorder characterized primarily by inflammation of the limbic system, which is a group of structures located at the base of the brain. The issue can occur for one of two main reasons. The first is infection, because certain viruses tend to target this portion of the brain. The other is the result of an autoimmune response, where the body's own immune system attacks it. This category can be further broken down into two types: paraneoplastic limbic encephalitis, or PLE, and non-paraneoplastic limbic encephalitis, or NPLE.
An infection in the brain that attacks the limbic system can lead to limbic encephalitis. Though there are several viruses that might be to blame, the most common is the herpes simplex virus. The condition is sometimes known as herpes simplex encephalitis for this reason.
Paraneoplastic limbic encephalitis, or PLE, typically occurs in patients with certain types of cancer. The antibodies produced by the body to fight the cancer may incorrectly attack the structures of the limbic system, leading to inflammation. The most common type of cancer that leads to this situation is small cell carcinoma of the lungs, but it may also occur with cancers of the stomach, breasts, testes, or thymus gland.
In cases of non-paraneoplastic limbic encephalitis, the limbic structures in the brain are also attacked by antibodies, but they are not generated as an immune response to cancer in the body. Typically, these antibodies target and destroy proteins called potassium channels, which reduce control over how electrical signals travel through the brain. Another name for this issue is voltage-gated potassium channel antibody-associated encephalitis.
Regardless of the underlying cause, patients suffering from limbic encephalitis typically experience similar symptoms. Memory loss is common, as the limbic system is critical to the formation of memories. Some patients may become confused or disoriented, or may even show signs of delirium. In some cases, the disorder may trigger seizures. Brain scans done with an MRI often show changes in the brain signals associated with the limbic structures.
Treatment of limbic encephalitis depends on the cause of the disease. Viral infections may be treated with anti-viral medications to help clear the infection. In cases where an autoimmune response is to blame, immunosuppressive drugs can often be helpful. For those with PLE, treatment of the cancer causing the antibodies often plays a role as well.