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  • Deep brain stimulation in the management of neuropathic pain and multiple sclerosis tremor.

    7 February 2018

    Deep brain stimulation (DBS) of the central gray matter was an important component of the surgical management of chronic, drug-refractory, central neuropathic pain until only a decade ago. However, in the recent past, this technique has been increasingly neglected and has been largely replaced by motor cortex stimulation (MCS). The results of MCS, however, are far from uniform, and the best reports quote a range of 50% to 75% success in providing satisfactory pain relief. In recent years, there has been considerable success in treating various movement disorders, particularly in Parkinson's disease (PD) and dystonia, by chronic high-frequency DBS of nuclear structures in the basal ganglia. This technique has also been shown to be relatively effective in some selected cases of tremulous conditions like essential tremor and posttraumatic tremor. However, when the same techniques have been applied to patients with multiple sclerosis tremor (MST), the results have been mixed. As a result, DBS for MST has often been perceived as an unreliable and inconsistent therapeutic intervention. The authors present their experience with the application of DBS in these two relatively unpopular areas for neuromodulation in the current practice of functional stereotactic neurosurgery. The results demonstrate that with careful patient selection, DBS can offer significant functional benefit in both of these difficult clinical conditions.

  • Thalamic field potentials in chronic central pain treated by periventricular gray stimulation -- a series of eight cases.

    28 January 2018

    Chronic deep brain stimulation (DBS) of the periventricular gray (PVG) has been used for the treatment of chronic central pain for decades. In recent years motor cortex stimulation (MCS) has largely supplanted DBS in the surgical management of intractable neuropathic pain of central origin. However, MCS provides satisfactory pain relief in about 50-75% of cases, a range comparable to that reported for DBS (none of the reports are in placebo-controlled studies and hence the further need for caution in evaluating and comparing these results). Our experience also suggests that there is still a role for DBS in the control of central pain. Here we present a series of eight consecutive cases of intractable chronic pain of central origin treated with PVG DBS with an average follow-up of 9 months. In each case, two electrodes were implanted in the PVG and the ventroposterolateral thalamic nucleus, respectively, under guidance of corneal topography/magnetic resonance imaging image fusion. The PVG was stimulated in the frequency range of 2-100 Hz in alert patients while pain was assessed using the McGill-Melzack visual analogue scale. In addition, local field potentials (FPs) were recorded from the sensory thalamus during PVG stimulation. Maximum pain relief was obtained with 5-35 Hz stimulation while 50-100 Hz made the pain worse. This suggests that pain suppression was frequency dependent. Interestingly, we detected low frequency thalamic FPs at 0.2-0.4 Hz closely associated with the pain. During 5-35 Hz PVG stimulation the amplitude of this potential was significantly reduced and this was associated with marked pain relief. At the higher frequencies (50-100 Hz), however, there was no reduction in the FPs and no pain suppression. We have found an interesting and consistent correlation between thalamic electrical activity and chronic pain. This low frequency potential may provide an objective index for quantifying chronic pain, and may hold further clues to the mechanism of action of PVG stimulation. It may be possible to use the presence of these slow FPs and the effect of trial PVG DBS on both the clinical status and the FPs to predict the probable success of future pain control in individual patients.

  • Electrophysiological confirmation of the zona incerta as a target for surgical treatment of disabling involuntary arm movements in multiple sclerosis: use of local field potentials.

    19 March 2018

    Lesioning or chronic deep brain stimulation (DBS) of the nucleus ventralis intermedius results in abolition of tremor in the contralateral limbs in Parkinson's disease (PD) and also in essential tremor. Recently, chronic DBS of the subthalamic nucleus has also proved to be very effective in reducing contralateral limb tremor in PD. These targets have been less effective in controlling the complex limb tremor often seen in multiple sclerosis (MS). Consequently, other targets have been sought in cases of MS with tremor. We describe a patient with MS with disabling proximal and distal involuntary arm movements in whom we were able to obtain sustained control of contralateral arm tremor and achieve functional improvement of the affected arm by chronic DBS of the region of the zona incerta. We also highlight the important role played by local field potentials recorded from the brain, with simultaneous recording of corresponding EMGs, in target localisation.

  • Quality of life outcomes following surgical treatment of Parkinson's disease.

    18 December 2017

    We assessed the impact of surgical treatment of Parkinson's disease on quality of life using generic quality of life instruments and utility scores. The Medical Outcomes Study short form health survey SF-36 and Parkinson's Disease Questionnaire PDQ-39 were used before and 3-6 months after surgery to assess quality of life, and the results were converted into utility valuations. Ninety-seven patients were studied; 33 underwent unilateral thalamotomy, 33 unilateral pallidotomy, 20 bilateral pallidotomy, six subthalamic nucleus (STN) lesions, four mixed lesions, and in one case bilateral STN stimulation. All dimensions of the SF-36 except role mental and mental health showed statistically significant improvement following surgery. The PDQ-39 recorded significant improvements in the mobility, stigma, and bodily discomfort dimensions. The rating scale and time trade-off scales showed statistically significant gains in utility of 8% and 3%, respectively. Gains were particularly marked in the bilateral pallidotomy group. Differences in patient characteristics and selection made direct comparisons between procedures unreliable. Quality of life in patients with advanced Parkinson's disease is amenable to measurement; such measurement provides tentative evidence of significant gains in quality of life following some neurosurgical procedures.

  • Surgical complications of functional neurosurgery treating movement disorders: results with anatomical localisation.

    8 December 2017

    Thalamic and pallidal lesions can alleviate movement disorders, but to achieve this safely and efficaciously requires accurate target localization. We report the surgical complications encountered using an anatomical localization technique to create 121 thalamic and pallidal lesions in 79 consecutive patients over a 3 year period. There was no perioperative mortality, although there was one late death indirectly related to surgery. The risk of haemorrhage was 3.3% per lesion made. Anatomical localization offers a relatively safe way of identifying targets for functional neurosurgery, with complication rates which compare favourably with the published literature. Copyright 1999 Harcourt Publishers Ltd.

  • Distal versus proximal arm tremor in multiple sclerosis assessed by visually guided tracking tasks.

    28 January 2018

    OBJECTIVES: To compare action tremor (AT) during manual tracking in normal subjects and patients with multiple sclerosis with tremor (MS-tremor group) and without tremor (MS-no tremor group), and to differentiate tremor occurring predominantly around the distal joint from that involving the proximal joints of the arm. METHODS: Subjects performed both a visually guided ramp tracking task using wrist flexion/extension and a whole arm circle tracking task using shoulder movement. Action tremor at the wrist or shoulder was computed as the SD of the tracking velocity. The ratio of wrist:arm tremor was then calculated to differentiate distal from proximal tremor in the tested arm. Frequency spectra of the records were also examined. RESULTS: During wrist tracking, AT in patients with multiple sclerosis contained a major frequency component at 4-5 Hz; the frequency was slightly lower during whole arm tracking. The ratio of wrist:arm tremor was significantly higher in the MS-tremor group. Of 12 tested arms, eight had tremor significantly weighted towards the distal joint, only one towards the proximal joint, and three had a ratio inside the control range. CONCLUSIONS: AT in the arms of patients with multiple sclerosis can be effectively differentiated into proximal or distal using these two different tracking tasks. Despite the variability of the effects of multiple sclerosis, most of the AT was distal rather than proximal in this group of patients. Possibly conduction block along the corticocerebellocortical pathways caused this distal tremor.

  • Use of the Radionics Image Fusiontrade mark and Stereoplantrade mark programs for target localization in functional neurosurgery.

    15 February 2018

    We describe the use of Radionics Image Fusiontrade mark and Stereoplantrade mark in defining the target for thalamotomy and pallidotomy in functional surgery for parkinsonism and tremor. Using this to fuse and spatially correct magnetic resonance imaging (MRI) to computed tomography (CT) images our calculated targets were a mean of 0.6 +/- 1.5 mm from the end target determined physiologically by stimulation. This is significantly better than the values of 2.6 +/- 1.6 mm for thalamic targets and 7.1 +/- 3.7 mm for pallidal targets using CT alone. As a consequence, determination of the target and the lesion making are routinely performed in one pass of the electrode allowing for faster, more accurate and, we believe, safer functional procedures.

  • Extracting burst and tonic components from surface electromyograms in dystonia using adaptive wavelet shrinkage.

    19 March 2018

    The compound surface electromyograms (EMGs) recorded from patients with dystonia commonly contains superimposed bursting and tonic activity representing various motor symptoms. It is desirable to differentially extract them from the compound EMGs so that different symptoms can be more specifically investigated and different mechanisms revealed. A non-linear denoising approach based on wavelet transformation was investigated by applying soft thresholding to the wavelet coefficients. Thresholds were determined according to three different principles and two models. Different techniques for wavelet shrinkage were investigated for separating burst and tonic activity in the compound EMGs. The combination of Stein's unbiased risk estimate principle with a non-white noise model proved optimal for separating burst and tonic activity. These turned out to be exponentially related; and the temporal relationships between antagonist muscle contractions could now be seen clearly. We conclude that adaptive soft-thresholding wavelet shrinkage provides effective separation of burst and tonic activity in the compound EMG in dystonia. This separation should improve our understanding of the pathophysiology of dystonia.