Abstrakt

High cervical spinal cord stimulation: Effects on consciousness for minimally conscious patients

Albert J Fenoy, Catarina Couras, Laura Barros, Georgios Matis, Serdar Baki Albayrak, Aslihan Cevik, Turker Karanci, Ibrahim Halil Ural, Arzu Dinc Yavas, David Darrow, Igor A. Lavrov, Amit, Kumar Tomar,Therana Aliyeva, Leyla Shahbazova, Pritam Majumdar*

Background: The concept of Minimally Conscious condition or State (MCS) was proposed in the year 2002 and it is characterized by inconsistent but clearly discernible behavioural evidence of consciousness, which can be distinguished from coma and vegetative state by the presence of specific behavioural features not found in either of these conditions. Literary evidence exists for the usage of Deep Brain Stimulation (DBS) and High Cervical Spinal Cord Stimulation (HC-SCS) to restore consciousness for vegetative state and minimally conscious state patients.

Objective: The aim of this study is to determine: 1) Specific stimulation related neurophysiological responses in patients, such as Cerebral Blood Flow level (rCBF), auditory brain stem responses, somatosensory evoked potential responses, pain responses (related P-250 scaling), and electroencephalography responses. 2) Neuromuscular activity in upper extremities during stimulation by providing Electromyography (EMG) biofeedback data. 3) HC-SCS efficacy in spasticity level for brain injury patients using Modified Ashworth Scaling (MAS). 4) Post-stimulation therapy efficacy measure in combination with Bispectral Index Scoring (BIS). 5) Patient selection criteria for optimal therapy resulting in high cervical stimulation.

Materials and methods: Six patients with minimally consciousness condition were selected for this study. Eight electrode cylindrical leads were implanted at the C2-C6 level in six MCS patients followed by stimulation with 30 minute cycles (30 minutes ‘ON’ and 30 minutes ‘OFF’) for one year. Several sets of electrode configurations, with variable amplitude, pulse width and frequency, were applied. For each combination, Cerebral Blood Flow (CBF), Electromyography (EMG) signals, Bispectral Index Scoring (BIS), auditory brainstem responses with Electroencephalography (EEG) as well as Modified Ashworth Scaling (MAS) for spasticity were measured and recorded.

Results: One week post-high cervical stimulation, an increment of CBF was observed in all six patients that correlated with an improvement of responses in the upper extremities. In all patients, the mean CBF without stimulation was 37.67+1.91 ml/100 g/min, while at the 2 nd week post-stimulation, the mean CBF was 49.31+2.25 ml/100 g/min. The increment in post stimulation within 2 nd week CBF level in these patients was observed to be approximately 12% (p<0.05, paired t-test). There was a continuous improvement in the consciousness level as evident by the measured BIS value throughout the year and even after stimulation was stopped completely (post 52nd week).

Conclusions: HC-SCS therapy shows significant improvements in patients with MCS. Improvements were observed after terminating the stimulation after 12 months in 5 out of 6 patients. Such results are highly dependent on proper lead placement and optimal programming of the SCS device.