Encefalitis límbica: clínica, patogenia y problemas diagnósticos / Limbic encephalitis: clinic, pathogenesis and diagnostic problems

La encefalitis límbica es una enfermedad infrecuente y potencialmente grave, que puede o no ser paraneoplásica y se caracteriza por déficit de la memoria reciente, alteraciones psiquiátricas y convulsiones. De origen autoinmunitario, está asociada a anticuerpos séricos e intratecales contra antígenos neuronales intracelulares y de superficie, con especial afectación de zonas límbicas. En este artículo se revisan aspectos históricos y epidemiológicos, patogenia, síndromes más frecuentes y mejor delimitados, histopatología y estudios complementarios. Se repasan también las dificultades del diagnóstico diferencial y la necesidad de descartar siempre un tumor subyacente. La detección de autoanticuerpos neuronales es importante para el diagnóstico, la planificación terapéutica y el pronóstico. La inmunoterapia y, si corresponde, el tratamiento de la neoplasia son cruciales para lograr una recuperación neurológica sustancial. La encefalitis límbica es una entidad probablemente subdiagnosticada, con un pronóstico más favorable si se trata de forma temprana. El actual conocimiento de su patogenia puede además aportar claridad para la mejor comprensión de otros síndromes neurológicos y psiquiátricos que puedan compartir mecanismos autoinmunitarios, como algunos trastornos psicóticos y epilepsias farmacorresistentes. (AU)

Limbic encephalitis is a rare and potentially serious disease, which may or may not be paraneoplastic and is characterized by recent memory deficits, psychiatric disturbances and seizures. Of autoimmune origin, it is associated with serum and intrathecal antibodies against intracellular and surface neuronal antigens, with special involvement of limbic areas. This article reviews historical and epidemiological aspects, pathogenesis, more frequent and better defined syndromes, histopathology and complementary studies. The difficulties of differential diagnosis and the need to always rule out an underlying tumor are also reviewed. Detection of neuronal autoantibodies is important for diagnosis, therapeutic planning and prognosis. Immunotherapy and, if appropriate, neoplasm treatment, are crucial to achieve substantial neurological recovery. Limbic encephalitis is probably an underdiagnosed entity, with a more favorable prognosis if treated early. The current knowledge of its pathogenesis may also provide clarity for a better understanding of other neurological and psychiatric syndromes that may share autoimmune mechanisms, such as some psychotic disorders and drug-resistant epilepsies. (AU)

Occupation-Associated Fatal Limbic Encephalitis Caused by Variegated Squirrel Bornavirus 1, Germany, 2013.

Limbic encephalitis is commonly regarded as an autoimmune-mediated disease. However, after the recent detection of zoonotic variegated squirrel bornavirus 1 in a Prevost's squirrel (Callosciurus prevostii) in a zoo in northern Germany, we retrospectively investigated a fatal case in an autoantibody-seronegative animal caretaker who had worked at that zoo. The virus had been discovered in 2015 as the cause of a cluster of cases of fatal encephalitis among breeders of variegated squirrels (Sciurus variegatoides) in eastern Germany. Molecular assays and immunohistochemistry detected a limbic distribution of the virus in brain tissue of the animal caretaker. Phylogenetic analyses demonstrated a spillover infection from the Prevost's squirrel. Antibodies against bornaviruses were detected in the patient's cerebrospinal fluid by immunofluorescence and newly developed ELISAs and immunoblot. The putative antigenic epitope was identified on the viral nucleoprotein. Other zoo workers were not infected; however, avoidance of direct contact with exotic squirrels and screening of squirrels are recommended.

[Limbic encephalitis--history,symptoms,and the latest classification].

The concept of limbic encephalitis has changed over time. Since the introduction of "limbic encephalitis" (LE) in 1968, LE was thought to almost always be associated with carcinoma; this belief led to the coining of the term "paraneoplastic limbic encephalitis" (PLE). In the 1990s, antineuronal antibodies, including anti-Hu and anti-Ta/Ma2, were detected; this supported the hypothesis of an autoimmune mechanism for PLE. The prognosis of patients with PLE was, however, poor. Since 2001, there have been reports of patients with LE exhibiting antibodies to the voltage-gated potassium channel; this observation is intriguing because in such cases the encephalitis was usually independent of carcinoma, and its clinical course was often reversible. Since the 1990s, cases of non-herpetic acute limbic encephalitis have been reported in Japan. In some of these cases, an autoantibody to GluRepsilon2 (NR2B) has been detected; GluRepsilon2 is a subunit of the N-methyl-D-aspartate (NMDA) glutamate receptor found in the limbic forebrain. A postulated pathophysiologic role of this antibody led to the concept of autoantibody-mediated acute reversible LE (AMED-ARLE). In 2007, some patients with ovarian teratoma developed encephalitis and exhibited antibodies to the NMDA receptor; this antibody is thought to recognize NR1/NR2 heteromers. Later, anti-NMDA receptor antibodies were also detected in some Japanese patients who had been previously diagnosed with juvenile acute non-herpetic encephalitis. Currently, limbic encephalitis is categorized into 3 groups: limbic encephalitis caused by virus infection, autoantibody-mediated limbic encephalitis (AMLE), and limbic encephalitis with autoimmune disease. In AMLE, antibodies to cytoplasmic antigens cause classical PLE (type I). In contrast, antibodies to cell membrane antigens often cause reversible limbic encephalitis in patients with (PLE type II) or without tumors (AMED-ARLE).