Autoimmune and immune-mediated diseases of the central nervous system are relatively rare, but potentially severe and disabling complications of the novel coronavirus infection (COVID-19). Despite the lack of exact prevalence of this group among other complications of COVID-19, its study lately receives increasing attention. Big variety of mechanisms could be involved into pathogenesis of autoimmune and immune-mediated disorders of the central nervous system, including the aberrant immune response to direct viral invasion, neuroinflammation and activation of T- and B-lymphocytes, formation of autoantibodies as a result of cross-reactivity or due to molecular mimicry, etc. This review discusses recent data on the pathogenetic mechanisms as well as clinical features of the most common complications of COVID-19: myelitis, MOG-associated diseases, spectrum of neuromyelitis optica disorders. Multiple potential biomarkers detected in post-COVID-19 patients and their diagnostic and clinical value are discussed. Given the increased number of patients having COVID-19, the study of such diseases, their connection with infection, and possible mechanisms seems to be an extremely relevant area of modern neuroimmunology.

Stanford neuromodulation therapy (SNT) is the state-of-the-art magnetic stimulation protocol that has been developed for management of treatment-resistant depression (TRD). The study was aimed to assess the possibility of SNT implementation in clinical practice and to define the protocol safety and efficacy in patients with TRD being an episode of the recurrent depressive disorder or bipolar disorder at the independent center. The study involved six patients (among them three women aged 21–66) with TRD associated with recurrent depression and type 1 or 2 bipolar disorder. The patients received intermittent theta-burst stimulation in accordance with the SNT protocol for five days: applying 10 triple blocks of stimulation daily at intervals of 1 hr between the blocks to the selected stimulation site showing maximum negative functional connectivity with subgenual cingulate cortex within the left dorsolateral prefrontal cortex. The Montgomery–Asberg Depression Rating Scale (MADRS) was used for clinical assessment of the effects, the follow-up period was three months. The improvement of depressive symptoms to the levels characteristic of remission immediately after the SNT completion was observed in five patients (MADRS score ≤10). After three months, two patients still had remission, the condition of three patients met the criteria of mild depressive episode, and one female patient withdrew from the study due to logistical difficulties. No serious adverse events were reported. The findings confirm safety and potentially high efficacy of SNT, including in patients with type 1 and 2 bipolar disorders.

Background. Spasticity is a disabling syndrome frequently observed in progressive multiple sclerosis. One of the promising approaches to the treatment of spasticity is the use of therapeutic intermittent theta‑burst transcranial magnetic stimulation. In the last time new metaplasticity‑based protocols are being developed in order to increase the effectiveness of this technique. These protocols consist of several stimulation sessions in a day with an interval between sessions. However, there is no experience of use of such protocols in spasticity so far.Aim. To assess the safety and tolerability as well as provide first evidence of anti‑spastic effects of an original meta-plasticity‑based intermittent theta‑burst stimulation protocol in patients with progressive multiple sclerosis and spasticity.Materials and methods. In total, 5 patients with progressive multiple sclerosis and spasticity (2 females and 3 males, 28–53 y. o., disease duration – 11–18 years, EDSS – 6.5–8.5 points) were included into the study. 3 sessions of stimulation separated by an interval of 1 hour were applied daily, where a single session consisted of 3 protocols of theta‑burst stimulation with standard duration. Stimulation target was the area of cortical representation of the leg muscles, stimulation was applied consequently to both sides during 5 days (15 sessions in total). Before and after the treatment course anti‑spastic effect (modified Ashworth scale) as well as spasticity‑related pain, fatigue and clinical global impression were assessed.Results. No serious adverse events were observed during the study. Mild adverse events (sleepiness, pain at the stimulation site) developed in some cases, which did not affect patients’ willing to continue participation in the study. After the stimulation course decrease in spasticity in the legs was registered in 4 of 5 patients (to 12–39 % from the basic level). Decrease of fatigue (4 / 5) and pain severity (3 / 5) was also observed.Conclusion. According to the first experience, the proposed original metaplasticity‑based transcranial magnetic stimulation protocol is safe, well‑tolerable and potentially effective in patients with progressive multiple sclerosis. Therefore the further investigation of the protocol in a randomized controlled study seems justified.

The study of the metaplasticity-based transcranial magnetic stimulation (TMS) protocols is an extensively studied approach to increase the effectiveness of stimulation. However, the effects of protocols with different intervals between the TMS blocks on cognitive functions are poorly understood. The study was aimed to assess the effects of two theta-burst transcranial stimulation (iTBS) protocols with short and long intervals between blocks on the working memory (WM) performance in healthy volunteers. A total of 16 participants were underwent a single TMS session of each protocol, which were applied in random order (iTBS 0–15 — two iTBS blocks over the left dorsolateral prefrontal cortex (DLPFC) iTBS with an interval of 15 min between blocks followed by stimulation of the vertex area in 60 min after the first block; iTBS 0–60 — iTBS block over the left DLPFC iTBS, block of the vertex stimulation after 15 min, and the second block of iTBS over the left DLPFC iTBS 60 min after the first one; iTBS 0 — one block of iTBS over the left DLPFC iTBS and two blocks of the vertex stimulation; control protocol — three blocks of the vertex stimulation with similar intervals). WM was assessed using the n-back test before the first block and after the second and the third stimulation blocks. No significant effects of protocols on WM or differences between protocols in alterations of test results and the responder rates to TMS between protocols were observed. The trend toward statistical signficance was reported for the protocol with short interval (iTBS 0–15). Furthermore, low reproducibility of individual iTBS effect was reported. The study of protocols with short intervals between blocks involving larger cohort of volunteers and taking into account the other factors potentially influencing the effect of the protocol (number of blocks and duration of a single block) seems to be promising.

Studying rhythmic neural synchronization (cross-frequency coupling in various ranges) is an emerging topic in present-day neurophysiology. One of the best-studied cross-frequency couplings is theta-gamma phase-amplitude coupling that contributes to the cognitive function and may vary in patients with several conditions associated with cognitive impairment. Changes in theta-gamma coupling can be registered in a wide range of diseases associated with cognitive decline. The review covers the physiological basics of theta-gamma coupling, its registration and calculation, correlation with cognitive test results in healthy volunteers, and changes in patients. We have discussed the results of the preliminary studies of frequency-dependent non-invasive brain stimulation based on theta-gamma coupling.