Limbic Encephalitis - A group of encephalitidis that have got more significance recently due to treatment options available.
Limbic encehalitis - the term imples encephalitis affecting the limbic system, casually used it includes even infective causes that can affect the Limbic connections profoundly causing amnesia, psychiatric manifestations, cognitive decline and seizures.
Now a days Limbic encephlitis is used to describe syndromes occuring secondary to a non-neoplastic autoimmune cause or paraneoplastic cause.
Non neoplastic autoimmune causes include mainly two antibody syndromes - Anti Voltage gated K+ channel syndrome and Anti NMDA-Receptor. VGKC- Occurs in Elderly. Starts as confusion, usually cause focal seizures, unilateral face and limb jerking, memory loss, cognitive decline and behavioral changes (something resembling adult onset- Mesial temporal sclerosis). Anti-NMDA R can predate an ovarian malignancy in a female usually young, and starts as psychotic syndrome. Usually they are treated for non organic psychosis. Soon they develop memory impairment, cognitive decline, seizures and they may slip into coma.
Anti VGKC is rarely associated with neoplasm. 30 to 50% of NMDA-R encephalitis presents with occult neoplasms, mostly of the ovary, benign>malignant. Diagnosed by serological tests, these respond very well to IVIg and plasma pheresis/ exchange. Usually followed up with a course of immune supression steroids +_ other steroid sparing agents. Diagnosed early in course of disease, these can prevent permanent cognitive decline and seizure disorder.
Paraneoplastic limbic encephalitis have similar presentation and occurs withmalignancies, in 6o%, precede them. Various antibodies like Hu, Ma, Amphyphsin etc exist. Importance of these antibodies is that they can be detected and the primary can be searched for before it becomes symptomatic at the site. Paraneoplastic limbic encephalitis usually presents with irritability, depression, insomnia or hypersomnia, seizures, hallucinations, and short-term memory loss that may progress to frank dementia.
Rule out HSV and MRI can reveal signal abnormalities in Medial temporal lobes. The use of corticosteroids, IVIg, or plasma exchange has limited value if the tumor is not treated.
pls refer Hematol Oncol Clin North Am. 2006 December ; 20(6): 1319–1335. for more details.