Background. Assessment of short-interval intracortical inhibition (SICI) using paired-pulse transcranial magnetic stimulation (TMS) and the threshold tracking technique is a promising approach to develop biomarkers of motor cortex damage in amyotrophic lateral sclerosis (ALS). Both high sensitivity and specificity of this approach were shown previously; however, almost all studies in this field were conducted by one group of authors.

Aim. The replication of data showing impairment of SICI assessed by threshold tracking technique in patients with ALS.

Materials and methods. 18 patients with ALS and 13 healthy volunteers were included into the study. Functional state of the patients was assessed as well as disease duration, form, stage and progression rate. Following values were determined in all participants using TMS: 1) resting motor threshold (MT); 2) mean motor evoked potential (MEP) amplitude of 30 stimuli applied with an intensity of 120 % MT; 3) SICI assessed using an algorithm based on paralleled optimized threshold tracking with interstimulus interval (ISI) of 1.0 ms, 1.5 ms, 2.0 ms, 2.5 ms, 3.0 ms, 3.5 ms, 4.0 ms, 5.0 ms, 7.0 ms, as well as mean inhibition for values with ISI from 1.0 to 3.0 ms and from 1.0 to 7.0 ms.

Results. No significant differences between groups were observed for MT and MEP amplitude. Significant decrease of SICI with ISI 1.0 and 2.0 ms as well as mean SICI from 1.0 and 3.0 ms was observed in ALS. No significant correlations of MT, MEP amplitude or SICI with clinical values were found.

Conclusion. This replication study has shown the ability of paired-pulse TMS with threshold tracking technique to identify the impairment of intracortical inhibition in patients with ALS.

Background. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by loss of motor neurons. The cause of neurodegeneration is predominantly a homozygous deletion of the SMN1 gene, leading to a decrease in the synthesis of the SMN protein. The clinical picture of the disease is heterogeneous and varies depending on the age of onset and the ability to perform motor functions. Several genetic and molecular modifiers have been identified that are thought to influence the severity of SMA. One of the most proven factors is the number of copies of the SMN2 gene.

Aim. Description of quantitative and structural features of the SMN1 and SMN2 genes in patients with SMA 5q.

Materials and methods. The study included DNA samples from patients examined for the number of copies of the SMN1 and SMN2 genes at the Scientific and Methodological Center for Molecular Medicine, I.P. Pavlov First Saint Petersburg State Medical University, for the period from 2021 to 2022. Gene copy numbers were determined by multiplex ligation-dependent probe amplification using the SALSA MLPA P021 SMA kit (MRC Holland). We assessed an indirect parameter of aggressiveness (the age of the patient’s visit to the laboratory) to assess the severity of clinical manifestations of SMA. Statistical analysis was carried out using the statistical data processing program GraphPad Prism9.

Results. A statistically significant direct correlation was found when studying the relationship between the number of copies of the SMN2 gene and the age of molecular diagnosis (r = 0.3960, p <0.0001). An assessment of the significance of differences between individual groups of patients gave a statistically significant result: <0.0001 when comparing groups of patients with 2 and 3 copies; <0.0001 – with 2 and 4 copies; 0.0370 – with 3 and 4 copies. 9 % of patients had a hybrid SMN1/SMN2 structure. Therefore, the significance of differences between the age of molecular diagnosis of patients with homozygous deletion of SMN1 and the age of molecular diagnosis of patients with the hybrid SMN1/SMN2 gene between groups with the same number of copies of the SMN2 gene was assessed. A statistically significant result (p = 0.0070) was found between patients with SMN1 deletion + 2 copies of SMN2 and patients with the hybrid gene SMN1/SMN2 + 2 copies of SMN2.

Conclusion. The number of SMN2 gene copies correlates with the age of molecular diagnosis and indirectly predicts the age of SMA onset. The effect of the SMN1/SMN2 hybrid gene on the age of molecular diagnosis of SMA was comparable to the effect of the regular SMN2 gene.

Background. A clinical application of scales and questionnaires is essential for the objective evaluation of treatment response, disease course, quality of life and the disability level in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Neuropathy Impairment Score (NIS) has become widespread in epidemiological and clinical studies of various polyneuropathies, including CIDP. However, its application in Russia is limited by the absence of its validated version for Russian-speaking patients. Aim. To develop the Russian validated version of the NIS for its application in patients with CIDP. Materials and methods. The study involved 50 patients with CIDP (25 with multifocal variant of CIDP (Lewis–Sumner syndrome) and 25 with typical CIDP). The validation process included two stages: translation and linguocultural ratification of the scale according to the standard protocol and an assessment of its psychometric properties, such as reliability, validity and sensitivity. Results. The developed Russian version of the NIS demonstrated the high level of reliability, sensitivity and validity. Conclusion. The validated Russian version of the NIS can be recommended for application in research and clinical practice.

Background. Mirror neurons (MN) are integral to linking the perception of actions with their execution, activating during both action observation and execution. While extensive research has elucidated their functional roles, the temporal dynamics of MN responses in humans remain insufficiently understood.

Aim. To investigate the temporal profile of MN activity during hand movement observation using transcranial magnetic stimulation at at different time intervals (0, 320, 640, 1000, 1320, 1640 ms from the beginning of the demonstrated movement, time ranges from 1000 to 1640 ms correspond to the time interval after the end of the movement).

Materials and methods. Twenty right-handed participants underwent neuronavigated transcranial magnetic stimulation targeting the left primary motor cortex during the observation of hand movements. Motor evoked potentials were recorded from the first dorsal interosseous and abductor digiti minimi muscles at various time points relative to movement onset.

Results. A three-way interaction between movement type, muscle, and time was observed. Muscle-specific responses and intermuscular differences became prominent at 640 ms, extending into post-movement periods (1000, 1320, 1640 ms). Notably, excitatory responses were seen in muscles corresponding to the observed action, while unrelated muscles exhibited inhibitory patterns, intensifying over time.

Conclusion. These findings reveal a complex excitatory-inhibitory interplay in the MN system, resembling motor surround inhibition. The extended temporal activity of MN suggests their role in processing action completion and potential outcomes. This study provides novel insights into MN dynamics and underscores the relevance of these mechanisms for motor rehabilitation strategies. Further research is required to explore MN activity at extended time points.

The year 2024 marks the 180th anniversary of the birth of the great artist Ilya Efimovich Repin, the brightest representative of the realist direction of academic art. The artist’s life was overshadowed by a disease that deprived him of the ability to work with his right hand. I.E. Repin, with an irresistible will to create, re-trained to paint with his left hand. Repin’s disease was not diagnosed both during his life and after his death. This article contains information about Ilya Repin’s disease and differential diagnosis with pathology, which can be followed by motor disorders of the hand and atrophy of the hand muscles. The conducted analysis, supported by literature and lifetime photographs, postmortem cast of the artist’s right hand indicate that the cause of Repin’s disease was a progressive ulnar neuropathy. The given historical information about the diseases of peripheral nerves indicates that this diagnosis could not have been established during the artist’s lifetime.

Spinal muscular atrophy 5q (SMA) is one of the most common inherited neuromuscular diseases in children with an autosomal recessive type of inheritance. Homozygous deletion of exons 7 or 7–8 of the SMN1 gene encoding the motor neuron survival protein is responsible for 95 % of cases. SMA is characterized by a steadily progressive course with the development of paresis, muscle atrophy, loss of previously acquired motor skills, respiratory failure and skeletal deformities. The introduction of pathogenetic therapy in recent years has significantly changed the trajectory of SMA – patients survive, restore previously lost motor skills and acquire new ones. The clinical classification, which includes 5 types of SMA, is currently not a reliable reflection of the functional state of the child in dynamics. In 2005, a functional classification was recommended based on the patient’s current status: non-sitters (lying), sitters, and walkers. The article provides a summary of historical concepts regarding functional classification in SMA patients, as well as the criteria used in clinical trials and observations. We proposed criteria for categorizing SMA patients into a specific functional class by analyzing the available literature and making recommendations on using the classification in real clinical practice.

According to research, transcranial magnetic stimulation has potential as a non-invasive prognostic method to quantify neurophysiological changes of brain after traumatic brain injury (TBI). The pathophysiological basis of changes in transcranial magnetic stimulation parameters in TBI includes impaired regulation of neurotransmitter release, changes in receptor expression, damage to interneurons and microcytoarchitectonics, which provokes a disturbance in the functional balance between cortical excitation and inhibition. The vulnerability of inhibitory mechanisms of interneurons due to decreased levels of GABAB receptor-mediated cortical inhibition was found to be a peculiarity of the pediatric population with the consequences of TBI. The purpose of this publication was to analyze the most informative parameters of diagnostic transcranial magnetic stimulation in the pediatric population with the consequences of TBI based on the available literature.