Postinfectious epilepsy: clinical and diagnostical features

Background. According to some authors, neuroinfection agents play a role in the development of several neurological disorders, including epilepsy. For many years, it was believed that acute infectious diseases, such as tick-borne encephalitis virus and meningococcus played a leading role in the emerging epileptic process of postinfectious etiology. Regarding a role for chronically persistent infections, it has not been fully explored.Objective: to identify clinical, diagnostic, and morphological features of locally induced postinfectious epilepsy, both at disease onset upon emergence of the first epileptic seizures during acute infectious process and during their recurrence in a chronically persistent infection.Material and methods. The study included observations of 1500 patients with locally induced epilepsy admitted and treated from 2007 to 2017 in various medical inpatient and outpatient institutions. Post-infection locally induced epilepsy with clear causality link between previous neuroinfection and onset of epileptic seizure was found in 127 patients (Group 1). During initial visits, infectious agents in a cohort of patients with recurrent epileptic seizures manifested as chronic persistent infection were suspected in more than 1/3 of the 1373 subjects who sought medical aid comprising 550 people (Group 2). In addition to the clinical evaluation of patients, instrumental studies were performed, including routine electroencephalography (EEG), sleep video-EEG monitoring, magnetic resonance imaging (MRI), and some patients underwent pathomorphological examination using electron microscopy and histological techniques.Results. Gross and marked diffuse disturbances in brain bioelectrical activity were most often detected (58% and 31%, respectively) during video-EEG monitoring in Group 1, whereas moderate alterations were recorded less frequently (11% of observations). In Group 2, the majority of diffuse disturbances in brain bioelectrical activity were of moderate level (79%) followed by mild and irritative changes recorded less frequently (in 21% of cases). MRI data showed that disorders of the amygdala-hippocampal system were observed in 41 (32%) and 211 (38%) patients in Groups 1 and 2, respectively. Histological and electron microscopic data revealed a number of morphological disorders in patients with locally induced postinfectious epilepsy common with earlier described mitochondrial encephalomyopathies (mitochondrial megaconia and pleioconia) as well as a set of specific manifestations typical to such pathology.Conclusion. The conducted clinical, neurophysiological, neuroimaging, and pathomorphological studies of postinfectious epilepsy revealed specific features underlying its development at different stages, from its onset in acute infectious process to chronization in persistent infection. It was found that a comprehensive analysis of the presence and impact of infectious agents in patients with epileptic seizures is important for course and prognosis of postinfectious epilepsy, which is relevant for timely diagnosis and development of specific pharmacotherapy.