Morphofunctional Basis of Stuttering and the Use of Transcranial Magnetic Stimulation as a Therapeutic Approach

This review presents data from contemporary studies of the neurobiological and physiological bases of stuttering. According to the International Classification of Diseases, 10th Revision, stuttering is characterized by repetitions or prolongations of sounds, syllables, or words, as well as by delays or pauses that disrupt the rhythm of speech. Stuttering affects social communication as well as family, educational, professional, and other areas of life. Behavioral modification of speech patterns (speech therapy) is mainly used in the treatment of stuttering. When considering the physiological bases of stuttering, abnormal cortical activation is observed (hyperactivation of speech and motor areas of the right hemisphere and the supplementary motor area), as well as dysfunction of the basal ganglia. These changes may be associated with altered activity and reduced gray matter volume in speech motor areas, white matter deficits (in the regions of the motor representation of the tongue and larynx), and abnormalities of conducting pathways (the frontal aslant tract, corticobulbar, and corticospinal pathways). The review also discusses methods of noninvasive neuromodulation, such as transcranial magnetic stimulation, used both to study the neurophysiology of stuttering and for therapy. During transcranial magnetic stimulation, a short magnetic field pulse passes through the scalp and induces an electrical current in the cerebral cortex. The delivered impulses can modulate neuronal activity, depolarize neurons, alter intracortical excitability, and activate distant corticosubcortical and spinal structures. Prospects for further development of transcranial magnetic stimulation protocols to optimize the correction of stuttering are presented.