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Clinical Neuroscience

JULY 30, 2016

Four cases of GABAB receptor encephalitis

SZŐTS Mónika, MORTEN Blaabjerg, KONDZIELLA Daniel, DIÓSZEGHY Péter, BAJZIK Gábor, BERKI Tímea, KÁLMÁN Endre, NAGY Ferenc, ILLÉS Zsolt

GABAB receptor (gamma-aminobutyric acid type B receptors - GABABR) encephalitis is a rare manifestation of autoimmune encephalitides. We report four cases - including the first two Hungarian patients - with some peculiar features. One patient developed subacute disorientation and almost complete loss of short-term memory, but no epilepsy. Without immunotherapy, his memory spontaneously improved up to mild cognitive impairment in six weeks. GABABR antibodies persisted in his serum, and 18 months later, FDG-PET detected abnormal mediastinal lymph nodes and small cell lung cancer (SCLC). Another patient had persistently decreased sodium content in the peripheral blood. In those three patients who died, CSF was abnormal, but CSF was not pathological in the patient, who spontaneously improved. Brain MRI indicated signal intensity changes in the medial temporal areas in three cases. SCLC was found in three patients. Only the patient, who spontaneously improved, survived for more than 24 months. In summary, our cases show that (i) GABABR encephalitis may develop without epilepsy; (ii) the severe short-term memory loss can spontaneously improve; (iii) persistent hyponatremia can be present in the blood; (iv) the patient with benign course without epilepsy and CSF abnormality survived; (v) spontaneously remitting encephalitis can precede SCLC by 1.5 year, which emphasizes that repeated search for cancer is of paramount importance even in cases with spontaneous improvement.

Clinical Neuroscience

JULY 20, 2011

[Recent changes in the paradigm of limbic encephalitis]

ILLÉS Zsolt

[In the recent years, novel antibodies associated with limbic encephalitis have been described, which target such extracellular receptors or proteins that have been already indicated in the pathogenesis of hereditary or degenerative diseases. In a number of cases, where pathogenic role of antibodies generated against the voltage-gated potassium channel (VGKC) had been presumed, antibodies against a trans-synaptic scaffolding protein, LGI1 were indicated. Antibody response against NMDA-receptors has been suggested as a major cause of limbic encephalitis especially in young females, resulting in a typical clinical syndrome sometimes triggered by an ovarian teratoma. Antibodies against other receptors essential in synaptic transmission and plasticity (AMPA and GABAB receptors) have been also indicated, partially elicited by paraneoplastic processes. Such antibodies against surface proteins result in severe but potentially treatable diseases due to reversible internalization of the antigens crosslinked by the bivalent antibodies. In contrast, the rare classical onconeural antibodies reacting with intracellular targets (anti-Hu, anti-Ta/Ma2, anti- CV2/CRMP5) may elicit additional symptoms beside limbic encephalitis and the prognosis of such syndromes is poor.]