Cervical spinal cord stimulation for minimally conscious state treatment
High-cervical spinal cord stimulation can alter cortical activity and cerebral metabolism. These effects are potentially beneficial for disorders of consciousness. A better understanding of the effects of clinical application of stimulation is needed. Piedade et al. aimed to evaluate the existing literature to determine the state of available knowledge. They performed a literature review of clinical studies assessing cervical spinal cord epidural stimulation for disorders of consciousness. Only peer-reviewed articles reporting preoperative and postoperative clinical status were included.
Nineteen studies were included. A total of 532 cases were reported, and 255 patients were considered responsive (47.9%). Considering only studies published after the definition of minimally conscious state (MCS) as an entity, 402 individuals in unresponsive wakefulness syndrome (UWS) and 113 in MCS were reported. Responsiveness to SCS was reported in 170 UWS patients (42.3%) and in 78 MCS cases (69.0%), although the criteria for responsiveness and outcome measures varied among publications.
Cervical spinal cord stimulation yielded encouraging results in patients with disorders of consciousness and seems to be more effective in minimally conscious state. More extensive investigation is needed to understand its potential role in clinical practice 1).
The aim of a study was to measure the effects of SCS on the EEG of patients in a minimally conscious state (MCS), which would allow them to explore the possible workings underpinning of the approach. Resting state EEG was recorded before and immediately after SCS, using various frequencies (5Hz, 20Hz, 50Hz, 70Hz and 100Hz), for 11 patients in MCS. Relative power, coherence, S-estimator and bicoherence were calculated to assess the EEG changes. Five frequency bands (delta, theta, alpha, beta and gamma) and three regions (frontal, central and posterior) were divided in the calculation. The main findings of this study were that: (1) significantly altered relative power and synchronisation was found in delta and gamma bands after one SCS stimulation using 5Hz, 70Hz or 100Hz; (2) bicoherence showed that coupling within delta was significantly decreased after stimulation using 70Hz, while reduction of coupling between delta and gamma was found when using 5Hz and 100Hz. However, SCS of 20Hz, 50Hz and sham stimulation did not induce changes in any frequency band at any region. This study showed EEG evidence that SCS can modulate the brain function of MCS patients, speculatively by activating the formation-thalamus-cortex network 2).