Limbic encephalitis: types, symptoms, causes and treatment

Limbic encephalitis is a rare medical condition in which various parts of the brain's limbic system are inflated. The cause behind it may be a tumor or some autoimmune condition, resulting in psychiatric problems in the patient.

This disease has been of considerable interest in recent years because, although there are many neurological diseases that can present psychiatric symptoms, This is the one that goes unnoticed the most and its real diagnosis ends up being a bit late, sometimes misdiagnosing the patient with schizophrenia.

Next we are going to take a more in-depth look at limbic encephalitis, its types, most common symptoms, diagnosis and current treatments.

• Related article: "Limbic System: The Emotional Part of the Brain"

What is limbic encephalitis?

Like all encephalitis, limbic encephalitis is a disease characterized by inflammation of the brain, in this case the parts that make up the limbic system. This disease is usually caused by autoimmunity problems, that is, the body enters a strange state in which the body produces antibodies against itself, in other words, it attacks itself causing varied symptoms, especially areas such as the hypothalamus and the hippocampus.

Most cases of limbic encephalitis are caused by oncologic disease, some type of cancer that affects the brain in one way or another causing a wide repertoire of symptoms psychiatric. However, it is true that there are some cases in which there is no tumor present, the probable cause of limbic encephalitis being some autoimmune disorder or infection.

The disease was first described by J. b. Brierley et al. in 1960 evaluating three cases of this medical condition. In 1968 the link between limbic encephalitis and cancer would be discovered, although today there is evidence that it is not always caused by oncological diseases. In fact, the existence of different subtypes of limbic encephalitis is known thanks to the detection of various antibodies involved, including anti-Hu, anti-Ma2 and anti-NMDAR.

Classification of its types

Depending on whether or not there is a tumor behind its appearance we talk about two types of limbic encephalitis: paraneoplastic and non-paraneoplastic. Paraneoplastic limbic encephalitis is one that is caused by some type of cancer or tumor and that can be treated by removing and eliminating tumor cells, while non-paraneoplastic limbic encephalitis is not due to cancer and is usually caused by some type of infection, autoimmune disorder, or other non-cancer medical condition. identified.

The most common types of cancer behind paraneoplastic limbic encephalitis are cancer of the small cell lung, testicular tumors, ovarian teratoma, Hodgkin lymphoma, and breast cancer mother. Likewise, within limbic encephalitis we can talk about another classification depending on whether the Antibodies that appear in this autoimmune disease attack intracellular antigens or attack those of surface:

Antibodies to intracellular antigens

The best known is encephalitis associated with anti-Hu antibodies., associated with small cell lung cancer and which is typical of smokers in their 50s or 60s. Also found in this group is anti-Ma-associated encephalitis, testicular tumors in young people, or lung or breast cancer in older adults.

Surface antigen antibodies

Within this group is the encephalitis of antibodies against potassium channels, It is not usually paraneoplastic, although in 20% it is associated with oncological diseases, especially small cell lung cancer or a thymoma. There is also encephalitis mediated by anti-AMPA antibodies, more common in women over 60 years of age, with lung, breast or thymoma cancer.

Another very interesting type of encephalitis for psychiatry is limbic encephalitis due to antibodies against NMDA receptors or anti-NMDAR encephalitis. This is among those mediated by antibodies against surface antigens and despite the fact that it has been taking place for a relatively short time. identified, the conclusion is being reached that it could be the most frequent, in addition to the fact that it has a better prognosis than the rest of encephalitis paraneoplastic.

• You may be interested in: "Encephalitis: causes, symptoms, treatment and prognosis"

symptomatology

The symptoms of limbic encephalitis, both paraneoplastic and non-paraneoplastic, can appear in a matter of days or weeks. It is considered that the presence of short-term memory deficits is the hallmark of the disease, but it happens that on many occasions this sign goes very unnoticed or is directly ignored because There are many other symptoms also typical of the pathology that attract more attention in the psychiatric clinic:

• Headache
• Irritability
• Sleeping problems
• personality changes
• delusions
• auditory and visual hallucinations
• Paranoia
• soliloquies
• psychomotor agitation
• seizures
• catatonia
• Orolingual dyskinesias
• anomias
• Psychosis
• affective disorders
• Anxiety
• Obsessive-compulsive symptoms
• Loss of consciousness
• Eat
• Death

It may also happen that the patient's short-term memory is not evaluated because he arrives sedated at the consultation, probably after having suffered seizures, psychosis or general agitation. Since it is not possible to administer a memory test to someone who is under the effects of a sedative, this test is often omitted or left for later.

Diagnosis

As we said, despite the fact that its distinctive sign is memory problems, this disease it is extremely difficult to diagnose, especially its non-paraneoplastic modality. Since the rest of the symptoms attract more attention and are of a psychiatric nature, it may be thought that what is happening to the patient is that they have a mental disorder rather than a disease. neurological, which means that the correct diagnosis takes time to arrive and, meanwhile, the patient is admitted to a psychiatric hospital thinking that he has schizophrenia or another disorder psychotic.

In order to detect limbic encephalitis, it is necessary to have tests that analyze what types of antibodies are in the cerebrospinal fluid and if the immune system is attacking the organism. Unfortunately, this type of test is not usually done as a routine procedure and is not yet available. Tests for some of the auto-antibodies implicated in the disease are not commercially available.

It also happens that many patients with limbic encephalitis are initially diagnosed with herpes virus encephalitis Since both the limbic and the viral symptoms share symptoms and since antibody tests are not available, it is often assumed that it is caused by herpes simplex.

Treatment

In the case of paraneoplastic limbic encephalitis, treatment generally consists of immunotherapy and removal of the tumor., whenever possible. In this type of encephalitis, recovery will only occur when the tumor has been removed.

Regarding the pharmacological route and also applied to other encephalitis we have intravenous immunoglobulin, plasmapheresis, corticosteroids, cyclophosphamide and rituximab.

Bibliographic references:

• Rodríguez Millán, Julia, Garnica de Cos, Eva, & Malo Ocejo, Pablo. (2014). Psychosis seems, encephalitis is: case of onset with psychiatric symptoms in limbic encephalitis. Journal of the Spanish Association of Neuropsychiatry, 34(122), 375-382. https://dx.doi.org/10.4321/S0211-57352014000200009
• Dalmau J, Tüzün E, Wu H-Y, Masjuan J, Rossi JE, Voloschin A, et al (2007). Paraneoplastic anti-NMDA receptor encephalitis associated with ovarian teratoma. Ann Neurol. 61: 25-36.
• DeAngelis LM, Posner JB (2009). Paraneoplastic syndromes. In: DeAngelis LM, Posner JB, Neurological complications of cancer, 2nd ed, (577-617). New York: Oxford University Press.
• Graus F, Keime-Guibert F, Reñe R, Benyahia B, Ribalta T, Ascaso C, et al (2001). Anti-Hu-associated paraneoplastic encephalomyelitis: analysis of 200 patients. Brain. 124: 1138-1148.
• Graus F, Saiz A, Dalmau J (2010). Antibodies and neuronal autoimmune disorders of the CNS. J Neurol. 257: 509-517.
• Gultekin SH, Rosenfeld MR, Voltz R, Eichen J, Posner JB, Dalmau J (2000). Paraneoplastic limbic encephalitis: neurological symptoms, immunological findings and tumor association in 50 patients. Brain. 123: 1481-1494.