Autoimmune epilepsy: clinical characteristics and response to immunotherapy.

OBJECTIVE To describe clinical characteristics and immunotherapy responses in patients with autoimmune epilepsy. DESIGN Observational, retrospective case series. SETTING Mayo Clinic Health System. PATIENTS Thirty-two patients with an exclusive (n=11) or predominant (n=21) seizure presentation in whom an autoimmune etiology was suspected (on the basis of neural autoantibody [91%], inflammatory cerebrospinal fluid [31%], or magnetic resonance imaging suggesting inflammation [63%]) were studied. All had partial seizures: 81% had failed treatment with 2 or more antiepileptic drugs and had daily seizures and 38% had seizure semiologies that were multifocal or changed with time. Head magnetic resonance imaging was normal in 15 (47%) at onset. Electroencephalogram abnormalities included interictal epileptiform discharges in 20; electrographic seizures in 15; and focal slowing in 13. Neural autoantibodies included voltage-gated potassium channel complex in 56% (leucine-rich, glioma-inactivated 1 specific, 14; contactin-associated proteinlike 2 specific, 1); glutamic acid decarboxylase 65 in 22%; collapsin response- mediator protein 5 in 6%; and Ma2, N-methyl-D-aspartate receptor, and ganglionic acetylcholine receptor in 1 patient each. INTERVENTION Immunotherapy with intravenous methylprednisolone; intravenous immune globulin; and combinations of intravenous methylprednisolone, intravenous immune globulin, plasmapheresis, or cyclophosphamide. MAIN OUTCOME MEASURE Seizure frequency. RESULTS After a median interval of 17 months (range, 3-72 months), 22 of 27 (81%) reported improvement postimmunotherapy; 18 were seizure free. The median time from seizure onset to initiating immunotherapy was 4 months for responders and 22 months for nonresponders (P<.05). All voltage-gated potassium channel complex antibody-positive patients reported initial or lasting benefit (P<.05). One voltage-gated potassium channel complex antibody-positive patient was seizure free after thyroid cancer resection; another responded to antiepileptic drug change alone. CONCLUSION When clinical and serological clues suggest an autoimmune basis for medically intractable epilepsy, early-initiated immunotherapy may improve seizure outcome.