BackgroundDéjà vu (DV, from French déjà vu — “already seen”) is an aberration of psychic activity associated with transitory erroneous perception of novel circumstances, objects, or people as already known.ObjectiveThis study aimed to record the EEG pattern of déjà vu.MethodsThe subjects participated in a survey concerning déjà vu characteristics and underwent ambulatory EEG monitoring (12–16 h).ResultsIn patients with epilepsy, DV episodes began with polyspike activity in the right temporal lobe region and, in some cases, ended with slow-wave theta–delta activity over the right hemisphere. There were no epileptic discharges in healthy respondents during DV.ConclusionTwo types of déjà vu are suggested to exist: “pathological-epileptic” déjà vu, characteristic of patients with epilepsy and equivalent to an epileptic seizure, and “nonpathological-nonepileptic” déjà vu, which is characteristic of healthy people and psychological phenomenon.

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The results of complex studies were used to formulate a concept of the development of neurological impairments in multiple sclerosis (MS). Acutely developing impairments to spike propagation, reaching the level of conduction blockade, due to the active pathological process with demyelinating and axonal damage to the CNS lead to the formation of neurological impairments in exacerbations of MS, while complete or partial reversion (regression) of these symptoms in the stage of remission results from compensatory changes in the nature of conduction, which were not, however, accompanied by recovery of electrophysiological measures. The development of stable neurological deficit in secondary-progressive MS is determined by impairments to spike conduction processes associated with significant levels of demyelination and atrophic changes in the CNS, with myelin loss and axon death. Finally, the severity of cognitive changes is determined by differences in the severities of both the focal demyelinating process and diffuse damage to brain substance in MS, including the neurodegenerative component. The main factor in transient increases in symptoms is the universal lability of electrophysiological parameters, including those developing on the background of ion and neurotransmitter imbalance.

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Introduction. Déjà vu (DV, from French "already seen") is an aberration of psychic activity associated with transitory erroneous perception of novel circumstances, objects, or people as already known. Aim. Investigation of clinical and diagnostic significance of derealization episodes in epilepsy. Materials and methods. The study involved 166 individuals (mean age 25.2 ± 9.2 yrs; 63.2% women). DV episodes were characterized and compared in groups of healthy volunteers (n = 139) and epilepsy patients (n = 27). The subjects participated in a survey concerning déjà vu characteristics and in a long-time ambulatory EEG monitoring (12-16 h). Results. In epilepsy patients, DV episodes were equally frequent in cryptogenic and symptomatic focal epilepsy, occurred in combination with nearly all types of seizures, and could occur both as an aura and as an individual seizure. The major clinical features distinguishing DV in healthy subjects from DV in epilepsy patients were the frequency and emotional perception of DV episodes, and preceding fear. A critical diagnostic marker is the dynamics of DV characteristics: an increase in frequency and duration, negative emotional background. In EEG, DV episodes in patients began with polyspike activity in the right temporal lobe and, in some cases, ended with slow-wave theta-delta activity in the right hemisphere. Conclusion.Our combined clinical and electrophysiological investigation identified two separate DV types: epileptic Déjà Vu characteristic of epilepsy patients and equivalent to an epileptic seizure, and non-epileptic Déjà Vu occurring in healthy individuals, which is basically a psychological phenomenon.