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  • Comparison of contralateral pallidotomy vs. pallidal stimulation after prior unilateral pallidotomy for Parkinson's disease.

    3 July 2018

    OBJECTIVES: Pallidal stimulation and pallidotomy are known to improve the symptoms of Parkinson's disease (PD). However, it is not known which modality produces greater benefit in patients who have already undergone unilateral pallidotomy. It is also suggested that the original pallidal surgery provides a greater benefit than subsequent pallidal surgery. The aim of this study was to analyze which modality produced greater PD symptom improvement in patients with a prior pallidotomy and whether the chronological order of the pallidal surgery influenced the size of the improvement. METHODS: Five patients who had undergone a prior unilateral pallidotomy for PD were studied. Because of ongoing Parkinsonian symptoms, all patients subsequently underwent contralateral pallidal surgery, either a further pallidotomy or pallidal stimulation. All surgeries were performed by a single functional neurosurgeon and the patients prospectively assessed and scored at routine follow-ups. Paired-sample t-tests were used to detect differences in outcomes after first and second surgeries. RESULTS: Two patients underwent pallidal stimulation and three underwent a second pallidotomy. Mean follow-up was 13.5 months and 12.3 months, respectively. Greater percentage improvements in the majority of scores were found after pallidal stimulation compared with a second pallidotomy, namely Unified Parkinson's Disease Rating Scale (UPDRS) II off (25.22% vs. -3.27%), UPDRS III off (36.15% vs. 5.21%), rigidity (58.34% vs. 11.54%), tremor (5.56% vs. -30.48%), bradykinesia (48.55% vs. -2.23%), gait composite (16.52% vs. -51.79%), dyskinesia duration (83.33% vs. 66.67%), dyskinesia disability (100% vs. 66.67%), speech (10% vs. -50%), and the proportion of the day spent in the "off" state (50% vs. 25%). Comparing outcomes after the first surgery to those after the second surgery, statistical differences were found in dyskinesia duration improvement and ipsilateral dyskinesia improvement after the second surgery (p < 0.004 and p = 0.021, respectively). CONCLUSIONS: Pallidal stimulation produced greater symptom improvement than a second pallidotomy and subsequent surgery did not produce inferior results to the original pallidal surgery.

  • Controlling the lungs via the brain: a novel neurosurgical method to improve lung function in humans.

    3 July 2018

    BACKGROUND: Deep brain stimulation (DBS) of subcortical brain areas such as the periaqueductal grey and subthalamic nucleus has been shown to alter cardiovascular autonomic performance. The supramedullary circuitry controlling respiratory airways is not well defined and has not been tested in humans. OBJECTIVE: To use direct electric stimulation via DBS macroelectrodes to test whether airway resistance could be manipulated by these areas in awake humans. METHODS: Thirty-seven patients with in-dwelling deep brain electrodes for movement disorders or chronic pain underwent spirometry according to the European Respiratory Society guidelines. Testing was performed randomly 3 times on stimulation and 3 times off stimulation; patients were blinded to the test. Thoracic diameter changes were measured by a circumferential pressure-sensitive thoracic band. Ten periaqueductal grey and 10 subthalamic nucleus patients were tested. To control for confounding pain and movement disorder relief, the sensory thalamus in 7 patients and globus pallidus interna in 10 patients, respectively, were also tested. RESULTS: Peak expiratory flow rate (PEFR) increased significantly with periaqueductal grey and subthalamic nucleus stimulation by up to 14% (P = .02 and .005, respectively, paired-samples Student t tests). Stimulation of control nuclei produced no significant PEFR change. Similarly, changes in thoracic diameter reflecting skeletal activity rather than airway caliber did not correlate with the improvement in PEFR. Forced expiratory volume in 1 second was unchanged by stimulation. CONCLUSION: DBS can improve PEFR in chronic pain and movement disorder patients. This finding provides insights into the neural modulation of respiratory performance and may explain some of the subjective benefits of DBS.

  • Contrasting connectivity of the ventralis intermedius and ventralis oralis posterior nuclei of the motor thalamus demonstrated by probabilistic tractography.

    3 July 2018

    BACKGROUND: Targeting of the motor thalamus for the treatment of tremor has traditionally been achieved by a combination of anatomical atlases and neuroimaging, intraoperative clinical assessment, and physiological recordings. OBJECTIVE: To evaluate whether thalamic nuclei targeted in tremor surgery could be identified by virtue of their differing connections with noninvasive neuroimaging, thereby providing an extra factor to aid successful targeting. METHODS: Diffusion tensor tractography was performed in 17 healthy control subjects using diffusion data acquired at 1.5-T magnetic resonance imaging (60 directions, b value = 1000 s/mm, 2 × 2 × 2-mm³ voxels). The ventralis intermedius (Vim) and ventralis oralis posterior (Vop) nuclei were identified by a stereotactic neurosurgeon, and these sites were used as seeds for probabilistic tractography. The expected cortical connections of these nuclei, namely the primary motor cortex (M1) and contralateral cerebellum for the Vim and M1, the supplementary motor area, and dorsolateral prefrontal cortex for the Vop, were determined a priori from the literature. RESULTS: Tractogram signal intensity was highest in the dorsolateral prefrontal cortex and supplementary motor area after Vop seeding (P < .001, Wilcoxon signed-rank tests). High intensity was seen in M1 after seeding of both nuclei but was greater with Vim seeding (P < .001). Contralateral cerebellar signal was highest with Vim seeding (P < .001). CONCLUSION: Probabilistic tractography can depict differences in connectivity between intimate nuclei within the motor thalamus. These connections are consistent with published anatomical studies; therefore, tractography may provide an important adjunct in future targeting in tremor surgery.

  • Alpha oscillations in the pedunculopontine nucleus correlate with gait performance in parkinsonism.

    3 July 2018

    The pedunculopontine nucleus, a component of the reticular formation, is topographically organized in animal models and implicated in locomotor control. In Parkinson's disease, pedunculopontine nucleus stimulation is an emerging treatment for gait freezing. Local field potentials recorded from pedunculopontine nucleus electrodes in such patients have demonstrated oscillations in the alpha and beta frequency bands, reactive to self-paced movement. Whether these oscillations are topographically organized or relevant to locomotion is unknown. Here, we recorded local field potentials from the pedunculopontine nucleus in parkinsonian patients during rest and unconstrained walking. Relative gait speed was assessed with trunk accelerometry. Peaks of alpha power were present at rest and during gait, when they correlated with gait speed. Gait freezing was associated with attenuation of alpha activity. Beta peaks were less consistently observed across rest and gait, and did not correlate with gait speed. Alpha power was maximal in the caudal pedunculopontine nucleus region and beta power was maximal rostrally. These results indicate a topographic distribution of neuronal activity in the pedunculopontine nucleus region and concur with animal data suggesting that the caudal subregion has particular relevance to gait. Alpha synchronization, proposed to suppress 'task irrelevant' distraction, has previously been demonstrated to correlate with performance of cognitive tasks. Here, we demonstrate a correlation between alpha oscillations and improved gait performance. The results raise the possibility that stimulation of caudal and rostral pedunculopontine nucleus regions may differ in their clinical effects.

  • Mapping the central neurocircuitry that integrates the cardiovascular response to exercise in humans.

    3 July 2018

    There are abundant animal data attempting to identify the neural circuitry involved in cardiovascular control. Translating this research into humans has been made possible using functional neurosurgery during which deep brain stimulating electrodes are implanted into various brain nuclei for the treatment of chronic pain and movement disorders. This not only allows stimulation of the human brain, but also presents the opportunity to record neural activity from various brain regions. This symposium review highlights key experiments from the past decade that have endeavoured to identify the neurocircuitry responsible for integrating the cardiovascular response to exercise in humans. Two areas of particular interest are highlighted: the periaqueductal grey and the subthalamic nucleus. Our studies have shown that the periaqueductal grey (particularly the dorsal column) is a key part of the neurocircuitry involved in mediating autonomic changes adapted to ongoing behaviours. Emerging evidence also suggests that the subthalamic nucleus is not only involved in the control of movement, but also in the mediation of cardiovascular responses. Although these sites are unlikely to be the 'command' areas themselves, we have demonstrated that the two nuclei have the properties of being key integrating sites between the feedback signals from exercising muscle and the feedforward signals from higher cortical centres.

  • Refractory epilepsy and deep brain stimulation.

    3 July 2018

    Up to one-third of all patients with epilepsy have epilepsy refractory to medical therapy. Surgical options include temporal lobectomy, focal neocortical resection, stereotactic lesioning and neurostimulation. Neurostimulatory options comprise vagal nerve stimulation, trigeminal nerve stimulation and deep brain stimulation (DBS). DBS enables structures in the brain to be stimulated electrically by an implanted pacemaker after a minimally invasive neurosurgical procedure and has become the therapy of choice for Parkinson's disease refractory to or complicated by drug therapy. Here we review DBS for epilepsy, a powerful emerging treatment in the surgical armamentarium for drug refractory epilepsy, with a focus on extratemporal epilepsy.

  • Sustained reduction of hypertension by deep brain stimulation.

    3 July 2018

    Deep brain stimulators were implanted in the left periaqueductal gray matter (PAG) and sensory thalamus for right sided neuropathic facial pain refractory to other treatments in a man aged 58 years. PAG stimulation 8 months later acutely reduced systolic blood pressure by 25 mm Hg during revision surgery. One year post procedure, ambulatory blood pressure monitoring demonstrated significant and sustained reduction in blood pressure with PAG stimulation. Mean systolic blood pressure decreased by 12.6mm Hg and diastolic by 11.0mm Hg, alongside reductions in variability of heart rate and pulse pressure. This neurosurgical treatment may prove beneficial for medically refractory hypertension.

  • Deep brain stimulation for the alleviation of post-stroke neuropathic pain.

    3 July 2018

    Our aim was to asses the efficacy of deep brain stimulation in post-stroke neuropathic pain. Since 2000, 15 patients with post-stroke intractable neuropathic pain were treated with deep brain stimulation of the periventricular gray area (PVG), sensory thalamus (Ventroposterolateral nucleus-VPL) or both. Pain was assessed using both a visual analogue scale and the McGill's pain questionnaire. VAS scores show a mean improvement of 48.8% (SD 8.6%). However, there is a wide variation between patients. This study demonstrates that it is an effective treatment in 70% of such patients.

  • STN vs. Pallidal Stimulation in Parkinson Disease: Improvement With Experience and Better Patient Selection.

    3 July 2018

    Objectives.  This is a prospective study to determine the outcomes of subthalamic nucleus (STN) vs. globus pallidus internus (GPi) deep brain stimulation (DBS) at our institution. Materials and Methods.  We studied a total of 39 patients - 29 with STN and 10 with GPi DBS over a period of up to 6 years. Mean ages in the two groups were similar (59 and 60 years, respectively) and disease duration prior to implantation was similar (9.6 and 11.7 years, respectively). Unified Parkinson Disease Rating Scale (UPDRS) was recorded preoperatively and at follow-up (at least at 6-month intervals). Medications also were recorded, and each patient's levodopa equivalent units (LEU) were calculated. Results were analyzed using a paired Student's t-test. Results.  LEU reduced significantly (p < 0.05) in the STN group (5.7 to 3.7) but not the GPi group. Both targets significantly improved part 3 and part 4 scores of the UPDRS but GPi DBS did not improve part 2 scores (activities of daily living). STN DBS had much better outcome on the motor "off" scores of the UPDRS, whereas GPi only improved tremor. A comparison of the "earliest 10" and "most recent 10" STN patients showed a significant improvement in outcome in the most recent cases. Conclusions.  In our group, STN was more effective for alleviating the symptoms of Parkinson disease, even in older patients with significant dyskinesias. Better patient selection and greater experience have led to more improvement in the more recent patients.

  • Successful treatment of testicular pain with peripheral nerve stimulation of the cutaneous branch of the ilioinguinal and genital branch of the genitofemoral nerves.

    3 July 2018

    OBJECTIVES: To assess the effect of peripheral nerve stimulation on neuropathic testicular pain. MATERIAL AND METHODS: A 30-year-old man with a four-year history of chronic testicular pain following scrotal hydrocele surgery had two percutaneous leads implanted in his groin and low-frequency stimulation of the cutaneous branch of the ilioinguinal and genital branch of the genitofemoral nerves. RESULT: At seven-month follow-up, the pain intensity had declined from 9/10 to 2/10 on the numeric rating scale. CONCLUSION: We report the successful implantation of an ilioinguinal and genitofemoral nerve stimulator for sustained suppression of intractable neuropathic testicular pain.