Ultrasound-guided spinal stereotactic system for intraspinal implants.

OBJECTIVE The overall goal of this study was to develop an image-guided spinal stereotactic setup for intraoperative intraspinal microstimulation (ISMS). System requirements were as follows: 1) ability to place implants in various segments of the spinal cord, targeting the gray matter with a < 0.5-mm error; 2) modularity; and 3) compatibility with standard surgical tools. METHODS A spine-mounted stereotactic system was developed, optimized, and tested in pigs. The system consists of a platform supporting a micromanipulator with 6 degrees of freedom. It is modular and flexible in design and can be applied to various regions of the spine. An intraoperative ultrasound imaging technique was also developed and assessed for guidance of electrode alignment prior to and after electrode insertion into the spinal cord. Performance of the ultrasound-guided stereotactic system was assessed both in pigs (1 live and 6 fresh cadaveric pigs) and on the bench using four gelatin-based surrogate spinal cords. Pig experiments were conducted to evaluate the performance of ultrasound imaging in aligning the electrode trajectory using three techniques and under two conditions. Benchtop experiments were performed to assess the performance of ultrasound-guided targeting more directly. These experiments were used to quantify the accuracy of electrode alignment as well as assess the accuracy of the implantation depth and the error in spatial targeting within the gray matter of the spinal cord. As proof of concept, an intraoperative ISMS experiment was also conducted in an additional live pig using the stereotactic system, and the resulting movements and electromyographic responses were recorded. RESULTS The stereotactic system was quick to set up (< 10 minutes) and provided sufficient stability and range of motion to reach the ISMS targets reliably in the pigs. Transverse ultrasound images with the probe angled at 25°-45° provided acceptable contrast between the gray and white matter of the spinal cord. In pigs, the largest electrode alignment error using ultrasound guidance, relative to the minor axis of the spinal cord, was ≤ 3.57° (upper bound of the 95% confidence interval). The targeting error with ultrasound guidance in bench testing for targets 4 mm deep into the surrogate spinal cords was 0.2 ± 0.02 mm (mean ± standard deviation). CONCLUSIONS The authors developed and evaluated an ultrasound-guided spinal stereotactic system for precise insertion of intraspinal implants. The system is compatible with existing spinal instrumentation. Intraoperative ultrasound imaging of the spinal cord aids in alignment of the implants before insertion and provides feedback during and after implantation. The ability of ultrasound imaging to distinguish between spinal cord gray and white matter also improves confidence in the localization of targets within the gray matter. This system would be suitable for accurate guidance of intraspinal electrodes and drug or cell injections.

Using electroacupuncture at acupoints to predict the efficacy of hippocampal high-frequency electrical stimulation in pharmacoresistant temporal lobe epilepsy patients.

Hippocampal high-frequency electrical stimulation (HFS) shows long-term efficiency in some pharmacoresistant temporal lobe epilepsy patients. However, the success of the procedure varies from patient to patient and neither neurologists nor neurosurgeons are currently unable to pre-operatively predict which patients will respond to the stimulation. Just like electrical stimulation of the hippocampus in the brain, electroacupuncture (EA) at acupoints involves electrical stimulation and is also efficient in treating epilepsy. However, the stimulation targets are acupoints, which are located outside of the brain, and we presume that electrical stimulation of both targets can activate therapeutic neuronal networks, which explains why both stimulations are effective in treating epilepsy. Despite the involvement of different activated positions, the neurotransmitters, including both excitatory and inhibitory amino acids, generated from the stimulation are similar. It has been shown that both hippocampal HFS and EA at acupoints are related to the metabolism of amino acids and thus, we propose the hypothesis that EA at acupoints can predict the curative effect of hippocampal HFS: if EA at acupoints is effective, HFS of hippocampus will also be effective.

Deep brain stimulation for early-stage Parkinson's disease: an illustrative case.

OBJECTIVES: Subthalamic nucleus (STN) deep brain stimulation (DBS) is an effective intervention in advanced Parkinson's disease (PD), but its efficacy and safety in early PD are unknown. We are conducting a randomized pilot trial investigating DBS in early PD. This report describes one participant who received bilateral STN-DBS. MATERIALS AND METHODS: Thirty subjects have been randomized to either optimal drug therapy (ODT) or DBS + ODT. Microelectrode recordings from the STN and substantia nigra are collected at implantation. The Unified Parkinson's Disease Rating Scale Motor Subscale (UPDRS-III) is administered in the ON and OFF states semi-annually and neuropsychological function and quality of life are assessed annually. We describe a 54-year-old man with a two-year history of PD who was randomized to DBS + ODT and followed for two years. RESULTS: The subject showed a lower STN to substantia nigra ratio of neuronal activity than advanced PD patients, and higher firing rate than non-PD patients. The subject's total UPDRS and UPDRS-III scores improved during the two-year follow-up, while his OFF UPDRS-III score and levodopa equivalent daily dose increased. Quality of life, verbal fluency, and verbal learning improved. He did not experience any serious adverse events. CONCLUSIONS: This report details the first successful application of bilateral STN-DBS for early-stage PD during a clinical trial.

Subthalamic nucleus neuronal firing rate increases with Parkinson's disease progression.

Parkinson's disease is a neurodegenerative disorder characterized by progressive loss of dopaminergic cells in the central nervous system, in particular the substantia nigra, resulting in an unrelenting loss of motor and nonmotor function. Animal models of Parkinson's disease reveal hyperactive neurons in the subthalamic nucleus that have increased firing rates and bursting activity compared with controls. Although subthalamic nucleus activity has been characterized in patients with advanced-stage Parkinson's disease, it has not been described in patients with early-stage Parkinson's disease. Here we present the results of subthalamic nucleus neuronal recordings from patients with early-stage Parkinson's disease (Hoehn and Yahr stage II) enrolled in an ongoing clinical trial compared with recordings from age- and sex-matched patients with advanced Parkinson's disease. Subthalamic nucleus neurons had a significantly lower firing rate in early versus advanced Parkinson's disease (28.7 vs 36.3 Hz; P<.01). The overall activity of the subthalamic nucleus was also significantly lower in early versus late Parkinson's disease, as measured by background neuronal noise (12.4 vs 14.0 mV; P<.05). No significant difference was identified between groups in the bursting or variability of neuronal firing in the subthalamic nucleus, as measured by a burst index or the interspike interval coefficient of variability. The results suggest that neuronal firing in the subthalamic nucleus increases with Parkinson's disease progression.