[Temporal lobe seizures of immune and structural etiology]

The objective of the study is to conduct a comparative analysis of the clinical and electroencephalographic characteristics of seizures in patients with autoimmune encephalitis and temporal lobe epilepsy of structural etiology.

A retrospective cross-sectional study included 50 patients diagnosed with «possible» and «confirmed» autoimmune encephalitis and 59 patients with a structural etiology of temporal lobe epilepsy. In all patients, the sex and age characteristics, the number and variety of seizures, the history of bilateral tonic-clonic seizures (BTCS), and the findings of continued video-EEG monitoring and MRI were analyzed.

Among patients with seizures due to an immune condition, more females were affected than males. Patients in the autoimmune encephalitis group were slightly older than patients with structural temporal lobe epilepsy. Fifty-one (86.4%) patients with structural temporal lobe epilepsy had a history of more than one type of seizure, while 33 (66%) patients with autoimmune encephalitis had a combination of various paroxysmal conditions (p=0.013). Patients with GAD65-autoimmune encephalitis and structural epilepsy had a similar seizure pattern with transition to BTCS, whereas other types of autoimmune encephalitis were characterized by BTCS at the disease onset. Video EEG monitoring showed a higher frequency of seizures in patients with autoimmune encephalitis (p=0.007). Bilateral abnormalities on the EEG, a high index of epileptiform activity, the onset of the disease with BTCS, and a combination of different types of seizures in one patient do not distinguish patients with autoimmune encephalitis from patients with structural temporal lobe epilepsy.

Epilepsy of immune etiology is characterized by a high frequency of seizures and a later onset. Autoimmune encephalitis with anti-GAD65 antibodies can simulate structural temporal lobe epilepsy, and therefore, it is necessary to be alert to this condition. The high variability in the symptomatology of seizures in patients with structural temporal lobe epilepsy can be explained by the formation of an extensive epileptogenic network.