Clinical Testing of Invasive Spinal Cord Stimulation and Evaluation of Its Physiological Effects Using the Electroencephalography

Under X-ray guidance and with neurophysiological supervision, the electrode is implanted. The stimulator is surgically placed in a pocket formed in the iliac crest area on the left side, where it is secured. The generator is connected to an electrode array positioned on the dorsal epidural surface of the spinal cord at the appropriate level (sacral-lumbar/cervical region), as confirmed by intraoperative fluoroscopy.

During the selection of the optimal stimulation program for spasticity suppression, spinal cord stimulation (SCS) is performed at various sites on the electrode array. Stimulation is initiated at a specific site with a frequency of 60 Hz, and the intensity is gradually increased until the spasticity is alleviated (i.e., the limb can flex and extend without restriction). If there is no effect, the stimulation frequency is increased by 5 Hz, and the intensity is again adjusted from 0 to comfortable values. Stimulation is sequentially applied at different sites, and those sites where muscle spasticity is most effectively suppressed are selected.

Over the course of two weeks, the configuration of the electrodes and the intensity of the stimulation are adjusted to ensure optimal voluntary muscle control. A systematic approach is used to determine the most suitable settings. First, the anodes and cathodes on the electrode array are identified. The desired frequency range is 20-40 Hz. The pulse width is determined empirically. The adjustment begins at 20 Hz, with the stimulation intensity gradually increased. If unpleasant sensations (such as muscle spasms or pain) occur, the intensity is reduced to comfortable values. If there is no effect, the stimulation frequency is increased by 5 Hz, and the intensity is adjusted again from 0 to comfortable levels. Stimulation is sequentially applied at different sites, with the sites that provide the most effective voluntary muscle control being selected.

The procedure utilizes the method of electroencephalography (EEG). Throughout the procedure, EEG signals are recorded. Initially, the participant is recorded in a resting state before the implantation of the stimulator for 20 minutes (5 minutes with eyes open, followed by 5 minutes with eyes closed). After the surgery, the participant is recorded in the same manner before the first activation of the stimulator. After selecting the programs, the participant is recorded without stimulation (eyes open, then closed), followed by recordings with the spinal cord stimulator (SCS) activated (eyes open, then closed). The stimulation is then turned off again, and recording is conducted with eyes open and closed. Before discharge, the participant is recorded in a resting state for 20 minutes with the stimulation program active.

The procedure utilizes the method of electroencephalography (EEG). Throughout the procedure, EEG signals are recorded. During the experiment, with the stimulator turned off, the participant views a fixation cross on a computer screen. Then, they hear an auditory signal and see a sign indicating a specific movement (complete flexion and extension of the left arm, complete flexion and extension of the right arm, complete flexion and extension of the left leg, complete flexion and extension of the right leg). The participant imagines the movements according to the auditory and visual signals on the screen. Subsequently, the participant performs the same movements in the same order. The motor control stimulation program is then activated, and the entire sequence is repeated (first imagining the movement, then performing the imagined movements). The timing of the command presentations is recorded with marker placements.