Potentially Pathological Alpha-Pattern as a Variant of Vigilance EEG in Drug-Resistant Epilepsy

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As a result of pathomorphosis affecting the mechanisms of electrical activity generation interictal EEG may show reduced epileptiform changes whereas clinically apparent epileptic seizures may be present. In these cases patterns of dominant alpha activity are sometimes recorded on the scalp. In this study variations of alpha activity in patients with refractory epilepsy are classified. A group of 50 refractory epilepsy patients aged between 20 and 55 years who were submitted to Polenov Russian Scientific Research Institute of Neurosurgery in 2014-2017 was included in this study. They underwent scalp EEG as a part of their presurgical assessment. In 12 cases patterns of potentially pathological alpha activity were observed. Three variations of alpha-patterns were described: 1) alpha-rhythm with decreased regional diversity and a marked synchronization in temporal areas; 2) alpha-rhythm with reduced epileptiform complexes integrated into the spindles, 3) decelerated non-rhythmic alpha activity distorted by the higher frequency components. Distinguished varieties of potentially pathological alpha-activity according to their order here represent gradual functional decline of normal thalamo-cortical interaction. Considering clinical manifestation of drug-resistant epilepsy with frequent seizures in these patients, reported varieties of alpha activity can not be interpreted as Landolt’s syndrome (forced normalization of EEG). Invasive electrocorticographic monitoring demonstrated that bursts of sharpened polyphasic waves coinciding with alpha-rhythm on scalp EEG are consistent with epileptic discharges on the brain cortex surface. This allows to think of these components as correlates of epileptic activity. Therefore, on a number of occasions in patients with epilepsy a dissonance between clinical signs and electroencephalographic patterns recorded during restful wakefulness may be observed, when epileptiform components are absent or reduced to nonspecific complexes.

Aleksandr A. Chukhlovin

Author for correspondence.
Russian Polenov Research Neurosurgical Institute
Russian Federation, Saint Petersburg

MD, PhD, Laboratory of Neurophysiological Monitoring

Mikhail V. Aleksandrov

Russian Polenov Research Neurosurgical Institute
Russian Federation, Saint Petersburg

MD, PhD, Dr Med Sci, Professor, Deputy Director, Scientific Research Department of Clinical Neurophysiology and Epileptology

Sergey A. Lytaev

St Petersburg State Pediatric Medical University, Ministry of Healthcare of the Russian Federation
Russian Federation, Saint Petersburg

MD, PhD, Dr Med Sci, Professor, Head, Department of Human Physiology

Vugar R. Kasumov

Russian Polenov Research Neurosurgical Institute
Russian Federation, Saint Petersburg

MD, PhD, Dr Med Sci, Senior researcher, Department of reconstructive-regenerative and functional surgery of injuries and diseases of the central and peripheral nervous system

Marina E. Pavlovskaya

Russian Polenov Research Neurosurgical Institute
Russian Federation, Saint Petersburg

Doctor of functional diagnostics, Epileptological center

Nastasia B. Arkhipova

Federal Almazov North-West Medical Research Center
Russian Federation, Saint Petersburg

Postgraduate Student, Department of Neurosurgery

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Copyright (c) 2017 Chukhlovin A.A., Aleksandrov M.V., Lytaev S.A., Kasumov V.R., Pavlovskaya M.E., Arkhipova N.B.

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