Occult Autoimmune Background for Epilepsy-The Preliminary Study on Antibodies Against Neuronal Surface Antigens

Abstract

Objective: The objective of the study was to determine the incidence of antibodies against neuronal surface antigens (NSA-ab) in patients with different types of epilepsy, in comparison with the subjects diagnosed with immune-mediated disorders. Methods: Forty patients with drug-resistant epilepsy (DRE) of unknown origin, 16 with post-stroke epilepsy, and 23 with systemic autoimmune disorders (SAD) with CNS involvement were included. NSA-ab were sought in serum using indirect immunofluorescence method. Relationships were analyzed between presence of NSA-ab and clinical presentation. Results: NSA-ab was detected in the sera from five patients: anti-DPPX in one patient, anti-AMPAR1/R2 in two, anti-LGI1 in one and, in one case, both anti-CASPR2 and DPPX IgG. Out of these five patients, three represented the SAD subgroup and two the DRE subgroup. None of the patients with post-stroke epilepsy was positive for NSA-ab. Significance: Autoimmune etiology is worth considering in patients with drug-resistant epilepsy of unknown origin. The presence of NSA-ab in patients with systemic autoimmune disorders may be caused by unspecifically enhanced autoimmune reactivity. NSA-ab seem not to be related to epilepsy resulting from ischemic brain injury.

Keywords: autoimmune reactivity; connective tissue disorders; epilepsy; epileptogenesis; neuronal autoantibodies.

Figure 1

Detection of human antineuronal antibodies in the serum of patients using indirect immunofluorescence methods (IIFT Autoimmune Encephalitis Mosaic 6 test, EUROIMMUN, Poland). Slides were evaluated using fluorescence microscopy with excitation filter 450–490 nm, color separator 510 nm, blocking filter 515 nm, and optical magnification of × 400 (AMPAR 1/2, CASPR2, DPPX, GABARB1/B2, LGI1; ×200 (NMDAR). Positive staining: (a1, b1) anti-AMPAR1/R2 positive; (c5) anti-LGI1 positive; (d3), (e3) anti-DPPX positive; (e2) anti-CASPR2 positive. Negative reaction: (a2–a6, b2–b6, c1–c4, c6, d1–d2, d4–d6, e1, e4–e6).