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Introduction: A wide range of pulse widths (PWs) has been used in globus pallidus internus (GPi) deep brain stimulation (DBS) for dystonia. However, no specific PW has demonstrated clinical superiority, and the paradigm may differ among DBS centers.

Objective: To investigate how different paradigms of PWs in GPi DBS for dystonia affect implantable pulse generator (IPG) longevities and energy consumption.

Methods: Thirty-nine patients with dystonia treated with bilateral GPi DBS at 2 Swedish DBS centers from 2005 to 2015 were included. Different PW paradigms were used at the 2 centers, 60–90 µs (short PWs) and 450 µs (long PW), respectively. The frequency of IPG replacements, pulse effective voltage (PEV), IPG model, pre-/postoperative imaging, and clinical outcome based on the clinical global impression (CGI) scale were collected from the medical charts and compared between the 2 groups.

Results: The average IPG longevity was extended for the short PWs (1,129 ± 50 days) compared to the long PW (925 ± 32 days; χ² = 12.31, p = 0.0005, log-rank test). IPG longevity correlated inversely with PEV (Pearson’s r = –0.667, p < 0.0001). IPG longevities did not differ between Kinetra® and Activa® PC in the short (p = 0.319) or long PW group (p = 0.858). Electrode distances to the central sensorimotor region of the GPi did not differ between the short or long PW groups (p = 0.595). Pre- and postoperative CGI did not differ between groups.

Conclusions: Short PWs were associated with decreased energy consumption and increased IPG longevity. These effects were not dependent on the IPG model or the anatomic location of the electrodes. PWs did not correlate with symptom severities or clinical outcomes. The results suggest that the use of short PWs might be more energy efficient and could therefore be preferred initially when programming patients with GPi DBS for dystonia.

Diffuse reflectance spectroscopy as a method for improving intracerebral guidance during functional neurosurgery has been investigated. An optical probe was developed for measurements during stereotactic and functional neurosurgery in man. The aim of the study was to investigate the spectral differences between white and grey matter and between white matter and functional targets. Diffuse reflectance spectroscopy measurements in ten patients were recorded at incremental steps towards and in three different functional targets (STN, GPi and Zi). The recorded spectra along the trajectory were sorted into white or grey matter, based on preoperative MRI images or the recorded spectral shape and intensity. The difference between tissue types was calculated as a quotient. Significant intensity differences between white and grey matter were found to be at least 14% (p < 0.05) and 20% (p < 0.0001) for MRI and spectral-sorted data respectively. The reflectance difference between white matter and the functional targets of GPi was higher than for STN and Zi. The results indicate that diffuse reflectance spectroscopy has a potential to be developed to a suitable complement to other intracerebral guidance methods.

BACKGROUND: Despite >30 years of clinical use, the literature is still sparse when it comes to comparisons between percutaneous balloon compression (PBC) and percutaneous retrogasserian glycerol rhizolysis (PRGR) as treatments for trigeminal neuralgia.

OBJECTIVE: To perform a retrospective cohort comparison between PBC and PRGR with regard to therapeutic effect, side effects, and complications.

METHODS: Medical records and follow-up data from 124 primary PRGRs performed from 1986 to 2000 and 82 primary PBCs performed from 2000 to 2013 were reviewed. All patients had undergone clinical sensory testing and assessment of sensory thresholds. Analyses were performed to compare duration of pain relief, frequency of sensory disturbances, and side effects.

RESULTS: Median duration of pain relief was 21 months after PRGR and 20 months after PBC. Both methods carried a high risk of hypesthesia/hypalgesia (P < .001) that was partly reversed with time. Decreased corneal sensibility was common after PRGR (P < .001) but not after PBC. Dysesthesia was more common after PRGR (23%) compared after PBC (4%; P < .001). Other side effects were noted but uncommon.

CONCLUSION: PBC and PRGR are both effective as primary surgical treatment of trigeminal neuralgia. Both carry a risk of postoperative hypesthesia, but in this series, the side effect profile favored PBC. Furthermore, PBC is technically less challenging, whereas PRGR requires fewer resources. Between these 2 techniques, we propose PBC as the primary surgical technique for percutaneous treatment of trigeminal neuralgia on the basis of its lower incidence of dysesthesia, corneal hypesthesia, and technical failures.

ABBREVIATIONS: MS, multiple sclerosisPBC, percutaneous balloon compressionPRGR, percutaneous retrogasserian glycerol rhizotomyTN, trigeminal neuralgiaThis is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work, provided it is properly cited. The work cannot be changed in any way or used commercially.

Essential tremor is effectively treated with deep brain stimulation (DBS), but the neural mechanisms underlying the treatment effect are poorly understood. Essential tremor is driven by a dysfunctional cerebello-thalamo-cerebral circuit resulting in pathological tremor oscillations. DBS is hypothesised to interfere with these oscillations at the stimulated target level, but it is unknown whether the stimulation modulates the activity of the cerebello-thalamo-cerebral circuit during different task states (with and without tremor) in awake essential tremor patients. To address this issue, we used functional MRI in 16 essential tremor patients chronically implanted with DBS in the caudal zona incerta. During scanning, the patients performed unilateral tremor-inducing postural holding and pointing tasks as well as rest, with contralateral stimulation turned On and Off.

We show that DBS exerts both task-dependent as well as task-independent modulation of the sensorimotor cerebello-cerebral regions (p ​≤ ​0.05, FWE cluster-corrected for multiple comparisons). Task-dependent modulation (DBS ​× ​task interaction) resulted in two patterns of stimulation effects. Firstly, activity decreases (blood oxygen level-dependent signal) during tremor-inducing postural holding in the primary sensorimotor cortex and cerebellar lobule VIII, and activity increases in the supplementary motor area and cerebellar lobule V during rest (p ​≤ ​0.05, post hoc two-tailed t-test). These effects represent differences at the effector level and may reflect DBS-induced tremor reduction since the primary sensorimotor cortex, cerebellum and supplementary motor area exhibit less motor task-activity as compared to the resting condition during On stimulation. Secondly, task-independent modulation (main effect of DBS) was observed as activity increase in the lateral premotor cortex during all motor tasks, and also during rest (p ​≤ ​0.05, post hoc two-tailed t-test). This task-independent effect may mediate the therapeutic effects of DBS through the facilitation of the premotor control over the sensorimotor circuit, making it less susceptible to tremor entrainment.

Our findings support the notion that DBS in essential tremor is modulating the sensorimotor cerebello-cerebral circuit, distant to the stimulated target, and illustrate the complexity of stimulation mechanisms by demonstrating task-dependent as well as task-independent actions in cerebello-cerebral regions.

While the effectiveness of deep brain stimulation in alleviating essential tremor is well-established, the underlying mechanisms of the treatment are unclear. Essential tremor, as characterized by tremor during action, is proposed to be driven by a dysfunction in the cerebello-thalamo-cerebral circuit that is evident not only during motor actions but also during rest. Stimulation effects on resting-state functional connectivity were investigated by functional MRI in 16 essential tremor patients with fully implanted deep brain stimulation in the caudal zona incerta during On-and-Off therapeutic stimulation, in a counterbalanced design. Functional connectivity was calculated between different constellations of sensorimotor as well as non-sensorimotor regions (as derived from seed-based and data-driven approaches), and compared between On and Off stimulation. We found that deep brain stimulation did not modulate resting-state functional connectivity. The lack of modulation by deep brain stimulation during resting-state, in combination with previously demonstrated effects on the cerebello-thalamo-cerebral circuit during motor tasks, suggests an action-dependent modulation of the stimulation in essential tremor.

Background The last decade has witnessed a renaissance of functional stereotactic neurosurgery in the treatment of patients with movement disorders, especially advanced Parkinson’s disease (PD), essential tremor (ET) and dystonia. Ablative lesions such as thalamotomy and pallidotomy have been gradually replaced by the technique of chronic deep brain stimulation (DBS) applied to targets in the basal ganglia and thalamus, and assumed to be more lenient to the brain than stereotactic radiofrequency lesions. Since the aim of functional neurosurgery is to alleviate symptoms of these chronic, progressive, non-fatal diseases, and to improve life quality of the patients, it is imperative that the surgical procedures remain safe and do not result in complications mitigating any anticipated positive effect of the surgery on the symptoms of the disease.

Aim The aim of this thesis is to evaluate, compare and analyse the safety of various surgical procedures used to treat patients with movement disorders, and to document side effects and complications both peri operatively and in a long term follow-up. Further to compare the effects of pallidotomy and pallidal DBS, and to evaluate the longterm efficacy of Vim-DBS.

Method 256 consecutive surgical procedures, 129 DBS and 127 stereotactic lesions, were reviewed with respect to complications in 197 treated patients. In a series of 119 patients operated on with DBS during a 10 year period, the occurrence of hardware related complications (infection, breakage, erosion etc) was documented and analysed. Additionally, the interference of external magnetic field with the stimulation was documented. In one patient operated on with subthalamic nucleus DBS, a highly unusual and unexpected psychiatric side effect was carefully analysed. In 5 patients operated on with both methods (lesion and DBS) on each hemisphere, respectively, the effect and side effects of each method were compared. The long term effect and side effects of thalamic DBS was analysed in a series of patients with ET followed for 7 years.

Results There were no deaths and few severe neurological complications in this material. Unilateral ablative lesions in the pallidum were well tolerated by patients with advanced PD, while for tremor, thalamic DBS was much safer than thalamotomy, even if its effect on certain aspects of tremor could show some decrease of efficacy over time. Some of the side effects of lesioning are transient while most but not all side effects of DBS are reversible. Hardware-related complications were not uncommon especially in the early “learning curve” period, and the DBS technique, being a life-long therapy, will necessitate a life long follow up of patients. Provided safety protocols are followed and provided patient’s and carer’s education and awareness, external electromagnetic interference should not constitute a risk for patients with DBS. PD patients undergoing STN DBS should be carefully selected to avoid psychiatric or cognitive side effects, due to this brain target´s proximity to, and involvment in, non-motor associative and limbic circuitry.

Conclusions In terms of mortality and morbidity, modern stereotactic neurosurgery for movement disorders, both ablation and DBS, is a safe procedure even in advanced stages of disease. Symptoms of PD, ET and dystonia can be alleviated mainly with DBS and even unilaterally with pallidal lesions, at the expense of, in most cases, minor side-effects.

Ophthalmology was one of the most important specialties in Egyptian medicine, and more specialists are known in this field than in any other. This specialization seems, however, to have been of a purely noninvasive nature. Even though it has been claimed that cataract surgery was performed in pharaonic Egypt, careful analysis of the sources does not support the claim. No example of cataract surgery or of any other invasive ophthalmologic procedure can be found in the original sources.