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  • Neurophysiologic intervention in deep brain stimulation treatment for movement disorders: a practical framework.

    12 December 2017

    Clinical neurophysiology has always played an important interventional role throughout the perioperative stages in functional neurosurgery. On the one hand, some neurophysiologic procedures have become an integrated part of neurosurgery. On the other hand, in deep brain stimulation, although the surgical electrode implantation is an essential step, the therapeutic effects are actually produced by electrically modulating the physiologic activity of the brain. We review the topic of neurophysiologic intervention in the deep brain stimulation for movement disorders by presenting the evidence derived from our own experiences based on an integrated group located at two hospitals in London and Oxford, UK, and mainly covering tremor caused by multiple sclerosis, Parkinson's disease and dystonia.

  • Somatotopic organization of the human periventricular gray matter.

    12 December 2017

    The periventricular gray (PVG) matter is an established anatomical target for chronic deep brain stimulation (DBS) in the treatment of certain intractable pain syndromes. Data relating to the representation of pain and other somatosensory modalities within the PVG in humans are negligible. We examined the character and location of somatosensory responses elicited by electrical stimulation along the length of the PVG in a patient who underwent unilateral DBS for intractable nociceptive head pain. Consistent responses were obtained and indicated the presence of a somatotopic representation in this region. The contralateral lower limb was represented cranially, followed by the upper limb and trunk, with the face area located caudally, near the level of the superior colliculi. Bilateral representation was only observed in the forehead and scalp.

  • Increased risk of lead fracture and migration in dystonia compared with other movement disorders following deep brain stimulation.

    8 December 2017

    Deep brain stimulation (DBS) therapy is a continually expanding field in the functional neurosurgical treatment of movement disorders. However, the occurrence of adverse events related to implanted hardware cannot be overlooked. We report on a specific feature noted in our experience of DBS-related complications. From 1998 until present we have found an overall rate of 5.3% of DBS electrode lead dysfunction (out of 133 patients) in our series (slipped leads 2.3%, lead fracture 3.8%). Interestingly, all of these failures occurred in dystonia patients (18.4% of all dystonia patients and 9.2% of all electrodes). We postulate on mechanisms that may explain why these complications predominate in this group of patients.

  • Globus pallidus internus deep brain stimulation for dystonic conditions: a prospective audit.

    8 December 2017

    In the current era of functional surgery for movement disorders, deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favoured target in the treatment of patients with dystonia. The results of 25 consecutive patients with medically intractable dystonia (12 with generalised dystonia, 7 with spasmodic torticollis, and 6 with other types of dystonia) treated with GPi stimulation are reported. Although comparisons were limited by differences in their respective neurological rating scales, chronic DBS benefited all groups, resulting in clear and progressive improvements in their condition. This study clearly demonstrates that DBS of the GPi provides amelioration of intractable dystonia.

  • The pallidotomy debate.

    8 December 2017

    It has been suggested that image-guidance and macro-stimulation alone are not sufficiently accurate to result in safe and effective lesion localization in pallidotomy for Parkinson's disease when compared with micro-electrode recording. This review analyses the data in the series published to date, and compares the safety and efficacy of the two techniques, finding no evidence to support this claim. In addition, evidence regarding the necessary accuracy of lesion placement is reviewed.

  • Neuropsychological, neurological and functional outcome following pallidotomy for Parkinson's disease. A consecutive series of eight simultaneous bilateral and twelve unilateral procedures.

    12 December 2017

    Intellectual, psychological and functional outcomes were evaluated in a consecutive series of 20 Parkinsonian patients who had unilateral (UPVP) or simultaneous bilateral posteroventral pallidotomy (BPVP) using Image Fusion and Stereoplan (Radionics Inc., Boston, Mass., USA) with stimulation for lesion localization. Comprehensive baseline and 3-month postoperative neuropsychological and neurological assessment protocols were administered together with questionnaire measures of functional disability, quality of life and psychological symptomatology. Changes in patients' clinical presentation and scores on psychometric tests, questionnaires and observational rating scales were then examined. We observed no new neuropsychiatric sequelae directly related to pallidotomy. Cognitive sequelae were restricted to selective reductions in categorical verbal fluency following UPVP (P < 0.001) and BPVP (P < 0.01) and a reduction in phonemic verbal fluency following BPVP (P < 0.01); these changes were not reported subjectively. A fall in diadochokinetic rates (P < 0.01) and some subjective reports of a worsening in pre-existing dysarthria, hypophonia and hypersalivation/drooling following BPVP also suggested changes in speech motor apparatus; however, these changes did not have significant functional consequences. There was one case of more generalized cognitive impairment following BPVP. We also observed significant symptomatic improvement on neurological rating scales; following UPVP, Total Unified Parkinson's Disease Rating Scale (UPDRS) scores improved by 27% (P < 0.01) and following BPVP the improvement was 53% (P < 0.05). Patients' perceptions of reduced postoperative functional disability and improvements in 'quality of life' also achieved statistical significance on a number of both physical and psychosocial questionnaire subscales.

  • Involvement of the subthalamic nucleus in engagement with behaviourally relevant stimuli.

    12 December 2017

    In this study we investigate how the basal ganglia (BG) may process the behavioural relevance of environmental cues by recording local field potentials (LFPs) in the subthalamic nucleus of patients with Parkinson's disease who had undergone implantation of electrodes for deep brain stimulation. Fourteen patients were recorded as they performed a paradigm dissociating warning cue presentation from programming related to execution of specific tasks. Target and non-target warning cues of differing behavioural relevance were contrasted, and we evaluated if warning cue-evoked activities varied according to whether the eventual task to be performed was motor or cognitive and whether patients were receiving or withdrawn from dopaminergic therapy. Warning cues evoked a complex temporal sequence of activities with three epochs over the 760 ms following the onset of the warning cue. In contrast to the initial evoked LFP, evoked activities over two later periods were significantly influenced by behavioural relevance and by treatment state. The early activity was likely related to the initial orientating of attention induced by a novel target, while the delayed responses in our paradigm may reflect processing related to the non-motor resource implications of cues. The results suggest that the BG are intimately involved in the evaluation of changes in the environment and of their behavioural significance. The latter process is partly modulated by dopamine. Weakness in this function might contribute to the behavioural impairment that can follow BG lesions and surgery.

  • Cortical and subcortical connections within the pedunculopontine nucleus of the primate Macaca mulatta determined using probabilistic diffusion tractography.

    12 December 2017

    The anatomical connections of the pedunculopontine nucleus (PPN), a brainstem structure associated with locomotion, have been determined recently in healthy humans using probabilistic diffusion tractography (PDT). In order to compare these with histologically demonstrated connections of the PPN in monkeys, and thus to support the use of PDT in humans, we have carried out PDT in a fixed rhesus monkey (Macaca mulatta) brain. Probabilistic diffusion tractography was carried out in a fixed post-mortem rhesus monkey brain using diffusion data acquired at 3T MRI (60 directions x 5 averages, b=3000 s/mm(2), matrix size=104 x 132 x 96, 720 x 720 x 720 microm voxels). We identified the major connections of the PPN from single seed voxels that could be confidently located within the nucleus on the diffusion images. The organisation of these connections within a 3 x 3 x 3 voxel ( approximately 10 mm(3)) region surrounding the initial seed voxel was then examined. PDT confirmed that the rhesus monkey PPN connections with the basal ganglia and motor cortical areas matched those previously demonstrated using conventional anatomical tracing techniques. Furthermore, although the organisation of subcortical connections within the PPN has not been extensively demonstrated in animals, we show here in a rhesus monkey that there are clearly separated connections of the PPN with the thalamus, substantia nigra, and subthalamic nucleus. Thus, in addition to increasing confidence in the accuracy of PDT for tracing PPN connections and determining the organisation of these connections within the PPN in vivo, our observations suggest that diffusion tractography will be a useful new technique to rapidly identify connections in animal brains pre-mortem and post-mortem.