GAD65‐Ab encephalitis and subtle focal status epilepticus

Abstract

Aims . To delineate common epilepsy features associated with the presence of glutamic acid decarboxylase autoantibodies (GAD65‐Ab). Methods . Three consecutive cases of GAD65‐Ab encephalitis patients, followed in our neurological department, were investigated with regards to clinical semiology and EEG. Results . These patients presented new‐onset subtle ictal clinical features. Patients 1 and 2 described prolonged and transitory feelings of “ déjà vu ‐ déjà vécu ” and a “ dreamy state ”. Patient 3 was admitted for subsequent transient aphasia events followed by paroxysmal behavioural disturbances. Epileptic origin of the symptoms was confirmed using either a standard EEG (observation of temporal status epilepticus in one case) or a prolonged EEG (focal epileptiform activity during an asymptomatic period for two patients). All patients suffered from clinical focal status epilepticus. Patients 1 and 2 presented with temporo‐mesial seizures in agreement with the definition for limbic encephalitis, whereas Patient 3 presented with neocortical (lateral temporal and frontal lobe) seizures arguing for a non‐limbic encephalitis. A high level of GAD65‐Ab was found in cerebral spinal fluid, confirming a diagnosis of epilepsy associated with GAD65‐Ab encephalitis. Conclusion . Encephalitis seems to be a frequent neurological syndrome associated with GAD65‐Ab disorders. Epilepsy may be more frequent and severe than currently suggested, as ictal semiology may be subtle for these outpatients in whom standard EEG is commonly falsely reassuring. Subtle focal status epilepticus is a particular semiology of the GAD65‐Ab encephalitis spectrum.