Targeted neurotechnology restores walking in humans with spinal cord injury.

Spinal cord injury leads to severe locomotor deficits or even complete leg paralysis. Here we introduce targeted spinal cord stimulation neurotechnologies that enabled voluntary control of walking in individuals who had sustained a spinal cord injury more than four years ago and presented with permanent motor deficits or complete paralysis despite extensive rehabilitation. Using an implanted pulse generator with real-time triggering capabilities, we delivered trains of spatially selective stimulation to the lumbosacral spinal cord with timing that coincided with the intended movement. Within one week, this spatiotemporal stimulation had re-established adaptive control of paralysed muscles during overground walking. Locomotor performance improved during rehabilitation. After a few months, participants regained voluntary control over previously paralysed muscles without stimulation and could walk or cycle in ecological settings during spatiotemporal stimulation. These results establish a technological framework for improving neurological recovery and supporting the activities of daily living after spinal cord injury.

[Operative and perioperative aspects of deep brain stimulation]. / Aspects opératoires et péri-opératoires de la stimulation cérébrale profonde.

Deep brain stimulation (DBS) requires the surgical implantation of a system including brain electrodes and impulsion generator(s). The nuclei targeted by the stereotaxic implantation methodology have to be visualized at best by high resolution imaging. The surgical procedure for implanting the electrodes is performed if possible under local anaesthesia to make electro-physiological measurements and to test intra-operatively the effect of the stimulation, in order to optimize the position of the definitive electrode. In a second step, the impulsion generator(s) are implanted under general anaesthesia. DBS for movement disorders has a very good efficacy and a low albeit non-zero risk of serious complications. Complications related to the material are the most common.

Recording of ventral posterior lateral thalamus neuron response to contact heat evoked potential in patient with neurogenic pain.

Microrecording of single unit response to contact heat-evoked potential (CHEP) were performed in right ventral posterior lateral (VPL) thalamus during deep brain stimulation (DBS) surgery in a patient with chronic neurogenic pain. In our patient, neurons (n = 10) recorded in the ventral thalamus fired at a higher rate of 40 Hz compared to neurons recorded in Parkinsonian patients (24 Hz). Contact heat was applied by a fast heating and cooling probe of 5 cm2 area on the dermatome C6 territory of the left hand. One out of four thalamic cells located in the VPL responded repetitively 325 ms after the peak temperature was reached with a burst of action potential, suggesting A-delta fibre activation. This observation supports the use of CHEP for mapping nociceptive neurons location during DBS surgery for intractable pain.

Quality index for the quantification of the information recorded along standard microelectrode tracks to the subthalamic nucleus in parkinsonian patients.

OBJECTIVE: To quantify the usefulness of the neuronal activity recorded on a standard microelectrode track to the subthalamic nucleus (STN) for the determination of the transition between the thalamus and the STN. METHODS: The study is based on analysis of 689 extracelullar single units recorded on 70 tracks passing through the thalamus and the STN. Using four neuron parameters that were correlated with electrode depth, a quality index (QI) for each track was computed and compared with the subjective assessment by the electrophysiologist of the track quality. RESULTS: Subjectively, the transition between the thalamus and the STN was detected in 49 tracks (usual track) and not detected on 21 tracks (unusual tracks). Objectively, spike frequency, cell burst index (BI), signal relative root mean square (RMS) and spike relative amplitude were correlated with electrode depth and used to compute track QI. The average QI index of usual and unusual tracks was 0.25 +/- 0.9 and 0.85 +/- 0.15 (mean +/- confidence interval at P < 0.001), respectively. In 20 patients, QI correlates with post-operative measurement of electrode length in the STN. CONCLUSION: These results demonstrate that simple statistical analysis taking into account the variation of single-unit characteristics with electrode depth can discriminate between useful and useless tracks for the determination of the STN localisation.

Electrophysiological localization of the subthalamic nucleus in parkinsonian patients.

Deep brain stimulation of the subthalamic nucleus (STN) is becoming the procedure of choice to reduce symptoms of Parkinson's disease such as rigidity, akinesia and tremor. We present here a series of electrophysiological recordings performed in 34 patients along a standardized electrode trajectory. Neuronal activity along the trajectory consists of a first heterogeneous population of thalamic cells with a mean frequency of 24.8+/-1.4 Hz followed by a silent zone and a second population of STN neurones with a significantly higher spiking frequency (P<0.001) of 42.3+/-1.8 Hz. This study confirms previous findings and suggests that rapid measurement of neuronal spiking frequency and burst index is sufficient to determine precisely the vertical position of the STN.