Author contribution: Poydasheva AG, Bakulin IS, Suponeva NA designed and planned the study; Poydasheva AG analyzed the literature; Poydasheva AG, Sinitsyn DO collected and analyzed the obtained data, wrote the draft version of the manuscript; All authors participated in editing the manuscript.

Compliance with ethical standards: the study was approved by the local Ethics Committee of the Research Center of Neurology (Protocol № 9–4/16 dated October 5, 2016) and complied with the Declaration Helsinki; informed consent was obtained from all study participants.