Comparative connectivity correlates of dystonic and essential tremor deep brain stimulation.

The pathophysiology of dystonic tremor and essential tremor remains partially understood. In patients with medication-refractory dystonic tremor or essential tremor, deep brain stimulation (DBS) targeting the thalamus or posterior subthalamic area has evolved into a promising treatment option. However, the optimal DBS targets for these disorders remains unknown. This retrospective study explored the optimal targets for DBS in essential tremor and dystonic tremor using a combination of volumes of tissue activated estimation and functional and structural connectivity analyses. We included 20 patients with dystonic tremor who underwent unilateral thalamic DBS, along with a matched cohort of 20 patients with essential tremor DBS. Tremor severity was assessed preoperatively and approximately 6 months after DBS implantation using the Fahn-Tolosa-Marin Tremor Rating Scale. The tremor-suppressing effects of DBS were estimated using the percentage improvement in the unilateral tremor-rating scale score contralateral to the side of implantation. The optimal stimulation region, based on the cluster centre of gravity for peak contralateral motor score improvement, for essential tremor was located in the ventral intermediate nucleus region and for dystonic tremor in the ventralis oralis posterior nucleus region along the ventral intermediate nucleus/ventralis oralis posterior nucleus border (4 mm anterior and 3 mm superior to that for essential tremor). Both disorders showed similar functional connectivity patterns: a positive correlation between tremor improvement and involvement of the primary sensorimotor, secondary motor and associative prefrontal regions. Tremor improvement, however, was tightly correlated with the primary sensorimotor regions in essential tremor, whereas in dystonic tremor, the correlation was tighter with the premotor and prefrontal regions. The dentato-rubro-thalamic tract, comprising the decussating and non-decussating fibres, significantly correlated with tremor improvement in both dystonic and essential tremor. In contrast, the pallidothalamic tracts, which primarily project to the ventralis oralis posterior nucleus region, significantly correlated with tremor improvement only in dystonic tremor. Our findings support the hypothesis that the pathophysiology underpinning dystonic tremor involves both the cerebello-thalamo-cortical network and the basal ganglia-thalamo-cortical network. Further our data suggest that the pathophysiology of essential tremor is primarily attributable to the abnormalities within the cerebello-thalamo-cortical network. We conclude that the ventral intermediate nucleus/ventralis oralis posterior nucleus border and ventral intermediate nucleus region may be a reasonable DBS target for patients with medication-refractory dystonic tremor and essential tremor, respectively. Uncovering the pathophysiology of these disorders may in the future aid in further improving DBS outcomes.

Neural endophenotypes and predictors of laryngeal dystonia penetrance and manifestation.

Focal dystonias are the most common forms of isolated dystonia; however, the etiopathophysiological signatures of disorder penetrance and clinical manifestation remain unclear. Using an imaging genetics approach, we investigated functional and structural representations of neural endophenotypes underlying the penetrance and manifestation of laryngeal dystonia in families, including 21 probands and 21 unaffected relatives, compared to 32 unrelated healthy controls. We further used a supervised machine-learning algorithm to predict the risk for dystonia development in susceptible individuals based on neural features of identified endophenotypes. We found that abnormalities in prefrontal-parietal cortex, thalamus, and caudate nucleus were commonly shared between patients and their unaffected relatives, representing an intermediate endophenotype of laryngeal dystonia. Machine learning classified 95.2% of unaffected relatives as patients rather than healthy controls, substantiating that these neural alterations represent the endophenotypic marker of dystonia penetrance, independent of its symptomatology. Additional abnormalities in premotor-parietal-temporal cortical regions, caudate nucleus, and cerebellum were present only in patients but not their unaffected relatives, likely representing a secondary endophenotype of dystonia manifestation. Based on alterations in the parietal cortex and caudate nucleus, the machine learning categorized 28.6% of unaffected relative as patients, indicating their increased lifetime risk for developing clinical manifestation of dystonia. The identified endophenotypic neural markers may be implemented for screening of at-risk individuals for dystonia development, selection of families for genetic studies of novel variants based on their risk for disease penetrance, or stratification of patients who would respond differently to a particular treatment in clinical trials.

Evoked Potentials During Peripheral Stimulation Confirm Electrode Location in Thalamic Subnuclei in Children With Secondary Dystonia.

Deep brain stimulation is an elective surgical intervention that improves the function and quality of life in children with dystonia and other movement disorders. Both basal ganglia and thalamic nuclei have been found to be relevant targets for treatment of dystonia in children, including the ventral intermediate nucleus of the thalamus, in which stimulation can control dystonic spasms. Electrophysiological confirmation of correct electrode location within the ventralis intermediate nucleus is thus important for the success of the surgical outcome. The present work shows the evoked potentials response during contralateral median-nerve stimulation at the wrist at low frequency (9 Hz) provides physiological evidence of the electrode's localization within the thalamus. We show the correlation between evoked potentials and magnetic resonance imaging (MRI) and computed tomography (CT) in 14 children undergoing implantation of deep brain stimulation electrodes for secondary dystonia. High fidelity and reproducibility of our results provides a new approach to ensure the electrode localization in the thalamic subnuclei.

Dystonia-Ataxia with early handwriting deterioration in COQ8A mutation carriers: A case series and literature review.

Cerebellar ataxia is a hallmark of coenzyme Q10 (CoQ10) deficiency associated with COQ8A mutations. We present four patients, one with novel COQ8A pathogenic variants all with early, prominent handwriting impairment, dystonia and only mild ataxia. To better define the phenotypic spectrum and course of COQ8A disease, we review the clinical presentation and evolution in 47 reported cases. Individuals with COQ8A mutation display great clinical variability and unpredictable responses to CoQ10 supplementation. Onset is typically during infancy or childhood with ataxic features associated with developmental delay or regression. When disease onset is later in life, first symptoms can include: incoordination, epilepsy, tremor, and deterioration of writing. The natural history is characterized by a progression to a multisystem brain disease dominated by ataxia, with disease severity inversely correlated with age at onset. Six previously reported cases share with ours, a clinical phenotype characterized by slowly progressive or static writing difficulties, focal dystonia, and speech disorder, with only minimal ataxia. The combination of writing difficulty, dystonia and ataxia is a distinctive constellation that is reminiscent of a previously described clinical entity called Dystonia Ataxia Syndrome (DYTCA) and is an important clinical indicator of COQ8A mutations, even when ataxia is mild or absent.

Neuromodulation: Deep Brain Stimulation for Treatment of Dystonia.

Dystonia is a heterogeneous, hyperkinetic movement disorder with sustained or intermittent abnormal postures, hyperkinetic muscle contractions, or repetitive movements. Classification of dystonia involves 2 axes: axis I and axis II, defining relevant clinical features and etiology, respectively. Medical therapy varies based on subtype and includes intramuscular botulinum toxin injections and oral anticholinergic pharmaceuticals. Deep brain stimulation became widely incorporated in 1999 after several landmark studies and has been effectively used in targets of the thalamus, pallidum, and subthalamic nucleus. New insights into pathophysiology of dystonia and genetic analysis continue to guide surgical technique toward ever-effective treatment.

Deep Brain Stimulation of the Caudal Zona Incerta and Motor Thalamus for Postischemic Dystonic Tremor of the Left Upper Limb: Case Report and Review of the Literature.

BACKGROUND: Dystonic tremor is defined as a tremor occurring in a body region affected by dystonia. The pathophysiologic mechanisms behind dystonic tremor supposedly involve anomalies affecting the pallidothalamic-receiving area (for the dystonic component) and the ventralis intermedius-cortical loop (for the tremor component). Interest in posterior subthalamic area stimulation for various types of involuntary abnormal movements has arisen owing to positive results in patients affected by tremor refractory to ventralis intermedius deep brain stimulation. CASE DESCRIPTION: A 23-year-old man, with a 15-year history of left upper limb dystonic tremor due to a stroke in the right thalamus, underwent deep brain stimulation with a single electrode passing through the right ventralis oralis anterior/ventralis oralis posterior nuclei and caudal zona incerta. Objective movement outcomes were assessed through the Unified Dystonia Rating Scale and Fahn-Tolosa-Marin Clinical Rating Scale for Tremor. The impact of tremor on activities of daily living was assessed with the ADL-T24 questionnaire, and quality of life was assessed with the Quality of Life Scale. All questionnaires were administered before deep brain stimulation and at 5-year follow-up. Unified Dystonia Rating Scale and Fahn-Tolosa-Marin Clinical Rating Scale for Tremor scores decreased from 14.5 to 4.5 and from 46 to 7, respectively. ADL-T24 score decreased from 19 to 3, whereas Quality of Life Scale score increased from 49 to 82. CONCLUSIONS: Stimulation of motor thalamus and caudal zona incerta could be a viable treatment for patients affected by tremor of various origins, including dystonic tremor, refractory to medical therapy.

Stereotactic Selective Thalamotomy for Focal Dystonia with Aid of Depth Microrecording.

OBJECTIVE: Long-term effectiveness of selective ventralis intermedius nucleus (VIM)-ventralis oralis nucleus (VO) thalamotomy with depth microrecording for the treatment of focal dystonia was evaluated. The optimal thalamic areas for controlling focal dystonia were studied based on the electrophysiologic and anatomic data. METHODS: Stereotactic selective VIM-VO thalamotomy with depth microrecording was carried out in 8 patients with focal arm and hand dystonia and in 1 patient with cervical dystonia. Electrophysiologic data on the lateral part of thalamic VIM were studied in patients with focal dystonia. A very small and narrow therapeutic lesion was formed in the shape of a square on the sagittal plane and of an I, rotated V, Y, or inverse Y on the axial plane in the VIM-VO, which covered the kinesthetic response area topographically related to focal dystonia. Patients with arm and hand dystonia were followed up for 4.7 ± 3.0 years and 1 patient with cervical dystonia was followed up for 18.2 years. RESULTS: Marked improvement of focal dystonia was shown by functional assessment using the Unified Dystonia Rating Scale. Transient dysarthria was recognized in 1 patient. The sequence of body localization of kinesthetic response in the VIM was clearly shown in patients with focal dystonia. Decreases in the amplitude and amplitude ratio of electromyography on the forearm muscles were markedly significant after VIM thalamotomy, but insignificant after VO thalamotomy immediately after VIM thalamotomy. CONCLUSIONS: Marked reduction of electromyographic tonic discharges of focal dystonia was shown after VIM lesioning. Selective VIM-VO thalamotomy showed good and long-term stable effects for focal dystonia.

Severity of Writer's Cramp is Related to Faulty Motor Preparation.

We characterized, in 37 writer's cramp (WC) patients and 14 healthy volunteers (HV), the buildup of motor representations contralateral ("intended") and ispsilateral ("unintended") to the movement to be produced and the excitability changes in left primary motor cortex during the early reaction time (RT) of a pre-cued reaching movement to pick up a pen with either hand to write. We also tested the excitability of interhemispheric pathways from right dorsal premotor and motor cortices to left motor cortex. During early RT (1) the motor cortex excitability of unintended muscle representations did not decrease in patients as in HV and (2) the connection from the contralateral dorsal premotor cortex to the "intended" motor representation did not function in patients. In HV, the efficiency of intracortical GABA-ergic circuits at rest predicted the degree of excitability changes in the intended motor representation in the early RT. This was not true in patients who had lower efficiency of GABA-ergic circuits. Interestingly, the more severe was the writing impairment, the higher was the level of excitability in the intended and unintended motor representations. It demonstrates, for the first time, that abnormal motor preparation influences the severity of the writing impairment in WC patients.

Historical developments in children's deep brain stimulation.

BACKGROUND: Heterogeneous by the underlying pathobiology and clinical presentation, childhood onset dystonia is most frequently progressive, with related disability and limitations in functions of daily living. Consequently, there is an obvious need for efficient symptomatic therapies. METHODS AND RESULTS: Following lesional surgery to basal ganglia (BG) and thalamus, deep brain stimulation (DBS) is a more conservative and adjustable intervention to and validated for internal segment of the globus pallidus (GPi), highly efficient in treating isolated "primary" dystonia and associated symptoms such as subcortical myoclonus. The role of DBS in acquired, neurometabolic and degenerative disorders with dystonia deserves further exploration to confirm as an efficient and lasting therapy. However, the pathobiological background with distribution of the sequellae over the central nervous system and related clinical features, will limit DBS efficacy in these conditions. Cumulative arguments propose DBS in severe life threatening dystonic conditions called status dystonicus as first line therapy, irrespective of the underlying cause. There are no currently available validated selection criteria for DBS in pediatric dystonia. Concurrent targets such as subthalamic nucleus (STN) and several motor nuclei of the thalamus are under exploration and only little information is available in children. DBS programming in paediatric population was adopted from experience in adults. The choice of neuromodulatory DBS parameters could influence not only the initial therapeutic outcome of dystonic symptoms but also its maintenance over time and potentially the occurrence of DBS related side effects. CONCLUSION: DBS allows efficient symptomatic treatment of severe dystonia in children and advances pathophysiological knowledge about local and distributed abnormal neural activity over the motor cortical-subcortical networks in dystonia and other movement disorders.

Mild cerebello-thalamo-cortical impairment in patients with normal dopaminergic scans (SWEDD).

INTRODUCTION: Patients with Scans-Without-Evidence-of-Dopaminergic-Deficit (SWEDD) often present asymmetric rest tremor not responsive to levodopa. Although a dystonic origin of this tremor has been proposed, the underlying pathophysiology of such condition is still unclear. An abnormal activity in the Cerebello-Thalamo-Cortical circuit is involved in the pathogenesis of tremor and other movement disorders. Here we used different paradigms of cerebellar transcranial magnetic stimulation to evaluate the Cerebello-Thalamo-Cortical functioning in patients with normal scans. METHODS: Cerebello-Thalamo-Cortical circuit was investigated in 12 patients with normal scans, 8 patients with Parkinson's Disease (PD), 8 patients with adult-onset isolated dystonia and 9 healthy controls. We studied the effects of a single cerebellar magnetic pulse over the excitability of the contralateral primary motor cortex tested with Motor-Evoked-Potentials (Cerebellar-Inhibition) both at rest and during arm extension. Furthermore, we also tested the effects of cerebellar continuous-Theta-Burst-Stimulation on Motor-Evoked-Potentials amplitude. RESULTS: patients with normal scans compared to controls show a deficient Cerebellar-Inhibition at rest but not in arm extension; in both conditions they differ from PD but not from dystonic patients. Cerebellar Continuous-Theta-Burst-Stimulation induced the expected long-lasting cortical inhibition of Motor-Evoked-Potentials amplitude in patients with normal scans differently from PD and dystonic patients. CONCLUSIONS: patients with normal scans show a mild impairment in Cerebello-Thalamo-Cortical circuit that emerges only at rest. Such neurophysiological phenotype differs from the one observed in PD and dystonic patients, suggesting a distinct involvement of this pathway in the pathophysiology of these disorders.

A prospective, randomized, blinded assessment of multitarget thalamic and pallidal deep brain stimulation in a case of hemidystonia.

OBJECTIVE: Dystonia is increasingly being interpreted as a multi-nodal "network" disorder. We aimed to investigate multitarget DBS (pallidal and thalamic) versus each target alone in a prospective, randomized, blinded trial in a case of hemidystonia secondary to putaminal stroke. METHODS: DBS leads were implanted in the GPi and Vim/Vop and each stimulation combination (GPi, Vim/Vop, and both) was tested for three months in a single patient. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Short-Form 36 (SF-36) were completed at the end of each trial period. RESULTS: Multitarget (GPi+Vim/Vop) stimulation was clinically the most effective treatment and resulted in the most improvement in function and quality of life. The patient's hemidystonia improved by 25% as measured by the BFMDRS during the multitarget stimulation trial period and at the 6-month follow-up. The patient's quality of life improved by 86% and 59% during the multitarget stimulation trial period and at the 6 month follow-up respectively. CONCLUSION: Multitarget thalamic and pallidal DBS proved to be the most effective therapy for this patient with secondary hemidystonia due to a putaminal stroke. A single-lead approach may not be sufficient in neuromodulating a highly disorganized motor network seen in hemidystonia. Multitarget DBS should be further explored in post-stroke dystonia and may offer improved outcome in other forms of secondary dystonia with limited response to GPi DBS.

A multifactorial conceptual model of peripheral neuromusculoskeletal predisposing factors in task-specific focal hand dystonia in musicians: etiologic and therapeutic implications.

A model is presented showing how peripheral factors may cause a process of movement adaptation that leads to task-specific focal hand dystonia in musicians (FHDM). To acquire a playing technique, the hand must find effective and physiologically sustainable movements within a complex set of functional demands and anatomic, ergonomic, and physiological constraints. In doing so, individually discriminating constraints may become effective, such as limited anatomic independence of finger muscles/tendons, limited joint ranges of motion, or (subclinical) neuromusculoskeletal defects. These factors may, depending on the instrument-specific playing requirements, compromise or exclude functional playing movements. The controller (i.e., the brain) then needs to develop alternative motions to execute the task, which is called compensation. We hypothesize that, if this compensation process does not converge to physiologically sustainable muscle activation patterns that satisfy all constraints, compensation could increase indefinitely under the pressure of practice. Dystonic symptoms would become manifest when overcompensation occurs, resulting in motor patterns that fail in proper task execution. The model presented in this paper only concerns the compensatory processes preceding such overcompensations and does not aim to explain the nature of the dystonic motions themselves. While the model considers normal learning processes in the development of compensations, neurological predispositions could facilitate developing overcompensations or further abnormal motor programs. The model predicts that if peripheral factors are involved, FHDM symptoms would be preceded by long-term gradual changes in playing movements, which could be validated by prospective studies. Furthermore, the model implies that treatment success might be enhanced by addressing the conflict between peripheral factors and playing tasks before decompensating/retraining the affected movements.

Functional recovery from chronic writer's cramp by brain-computer interface rehabilitation: a case report.

BACKGROUND: Dystonia is often currently treated with botulinum toxin injections to spastic muscles, or deep brain stimulation to the basal ganglia. In addition to these pharmacological or neurosurgical measures, a new noninvasive treatment concept, functional modulation using a brain-computer interface, was tested for feasibility. We recorded electroencephalograms (EEGs) over the bilateral sensorimotor cortex from a patient suffering from chronic writer's cramp. The patient was asked to suppress an exaggerated beta frequency component in the EEG during hand extension. RESULTS: The patient completed biweekly one-hour training for 5 months without any adverse effects. Significant decrease of the beta frequency component during handwriting was confirmed, and was associated with clear functional improvement. CONCLUSION: The current pilot study suggests that a brain-computer Interface can give explicit feedback of ongoing cortical excitability to patients with dystonia and allow them to suppress exaggerated neural activity, resulting in functional recovery.

Multiple changes of functional connectivity between sensorimotor areas in focal hand dystonia.

BACKGROUND: Task-specific focal hand dystonia impairs the control of arm muscles during fine motor skills such as writing (writer's cramp (WC)). Functional imaging found abnormal task-related activation of sensorimotor areas in this disorder, but little is known on their functional connectivity (FC). METHODS: Resting-state fMRI and regions of interest (ROI)-voxel cross-correlation analyses were used for systematically analysing the FC between multiple ROIs within the cerebello-basal ganglia-thalamocortical network in 15 patients with right-sided WC and 15 healthy volunteers. RESULTS: Patients with WC showed a lower positive FC of several seed ROIs (left lateral premotor cortex, left thalamus, left/right pallidum) to the symptomatic left primary sensorimotor cortex compared with controls. The FC of the left primary motor cortex to prefrontal areas, pre- supplementary motor area and right somatosensory cortex was reduced and correlated with disease severity. Several cerebellar seed ROIs (right dentate nucleus, right crus I and bilateral crus II) revealed a stronger negative FC to primary and secondary sensorimotor areas. CONCLUSIONS: An increase of negative cerebello-cortical FC at rest is in line with the hypothesis of a pathogenetic role of the cerebellum in dystonia. The deficit of positive subcortico-cortical FC indicates more generalised changes within the basal ganglia-thalamocortical motor loops beyond primary sensorimotor areas in WC. As patients with WC are asymptomatic during rest, these functional network changes could reflect an underlying abnormality or compensatory neuroplastic changes of network architecture in this disorder.

Shorter pulse generator longevity and more frequent stimulator adjustments with pallidal DBS for dystonia versus other movement disorders.

BACKGROUND: Deep brain stimulation has become a routine therapy for movement disorders, but it is relatively invasive and costly. Although stimulation intensity relates to battery longevity, less is known about how diagnosis and stimulation target contribute to this clinical outcome. Here we evaluate battery longevity in movement disorders patients who were treated at a tertiary referral center. OBJECTIVE: To compare single channel pulse generator longevity in patients with movement disorders. METHODS: With Institutional Review Board approval, we evaluated 470 consecutive Soletra implants for routine care. Battery longevity was estimated with Kaplan-Meier analyses, and group comparisons were performed with the log rank mean test. The frequency of clinic encounters for ongoing care was evaluated across diagnoses with analysis of variance (ANOVA). RESULTS: The mean pulse generator longevity was 44.9 ± 1.4 months. Pallidal DBS for dystonia was associated with shorter battery longevity than subthalamic and thalamic DBS for Parkinson's disease and essential tremor (28.1 ± 2.1 versus 47.1 ± 1.8 and 47.8 ± 2.6 months, respectively, mean ± standard error, P < 0.001), and dystonia patients required more frequent clinic visits for routine care (F = 6.0, P = 0.003). Pallidal DBS for Parkinson's disease and thalamic DBS for cerebellar outflow tremor were associated with shorter battery longevity, as well (35.3 ± 4.6 and 26.4 ± 4.3 months, respectively). CONCLUSIONS: Pallidal DBS for dystonia was associated with shorter battery longevity and more frequent stimulator adjustments versus DBS for Parkinson's disease and essential tremor. Characteristics of the stimulation target and disease pathophysiology both likely contribute to battery longevity in patients with movement disorders.

Temporal expectation in focal hand dystonia.

Patients with writer's cramp present sensory and representational abnormalities relevant to motor control, such as impairment in the temporal discrimination between tactile stimuli and in pure motor imagery tasks, like the mental rotation of corporeal and inanimate objects. However, only limited information is available on the ability of patients with dystonia to process the time-dependent features (e.g. speed) of movement in real time. The processing of time-dependent features of movement has a crucial role in predicting whether the outcome of a complex motor sequence, such as handwriting or playing a musical passage, will be consistent with its ultimate goal, or results instead in an execution error. In this study, we sought to evaluate the implicit ability to perceive the temporal outcome of different movements in a group of patients with writer's cramp. Fourteen patients affected by writer's cramp in the right hand and 17 age- and gender-matched healthy subjects were recruited for the study. Subjects were asked to perform a temporal expectation task by predicting the end of visually perceived human body motion (handwriting, i.e. the action performed by the human body segment specifically affected by writer's cramp) or inanimate object motion (a moving circle reaching a spatial target). Videos representing movements were shown in full before experimental trials; the actual tasks consisted of watching the same videos, but interrupted after a variable interval ('pre-dark') from its onset by a dark interval of variable duration. During the 'dark' interval, subjects were asked to indicate when the movement represented in the video reached its end by clicking on the space bar of the keyboard. We also included a visual working memory task. Performance on the timing task was analysed measuring the absolute value of timing error, the coefficient of variability and the percentage of anticipation responses. Patients with writer's cramp exhibited greater absolute timing error compared with control subjects in the human body motion task (whereas no difference was observed in the inanimate object motion task). No effect of group was documented on the visual working memory tasks. Absolute timing error on the human body motion task did not significantly correlate with symptom severity, disease duration or writing speed. Our findings suggest an alteration of the writing movement representation at a central level and are consistent with the view that dystonia is not a purely motor disorder, but it also involves non-motor (sensory, cognitive) aspects related to movement processing and planning.

Cathodal transcranial direct current stimulation in children with dystonia: a pilot open-label trial.

Studies suggest that dystonia is associated with increased motor cortex excitability. Cathodal transcranial direct current stimulation can temporarily reduce motor cortex excitability. To test whether stimulation of the motor cortex can reduce dystonic symptoms in children, we measured tracking performance and muscle overflow using an electromyogram tracking task before and after stimulation. Of 10 participants, 3 showed a significant reduction in overflow, and a fourth showed a significant reduction in tracking error. Overflow decreased more when the hand contralateral to the cathode performed the task than when the hand ipsilateral to the cathode performed the task. Averaged over all participants, the results did not reach statistical significance. These results suggest that cathodal stimulation may allow a subset of children to control muscles or reduce involuntary overflow activity. Further testing is needed to confirm these results in a blinded trial and identify the subset of children who are likely to respond.

Cerebral palsy: the whys and hows.

The descriptive term of cerebral palsy encompasses the largest group of childhood movement disorders. Severity and pattern of clinical involvement varies widely dependent on the area of the central nervous system compromised. A multidisciplinary team approach is vital for all the aspects of management to improve function and minimise disability. From a medical viewpoint, there are two pronged approaches. First a focus on developmental and clinical comorbidities such as communication, behaviour, epilepsy, feeding problems, gastro-oesophageal reflux and infections; and second on specifics of muscle tone, motor control and posture. With regards to the latter, there is an increasing number of available treatments including oral antispasticity and antidystonic medications, injectable botulinum toxin, multilevel orthopaedic and neurosurgical options and a variety of complementary and alternative therapies.

Improved dexterity after chronic electrical stimulation of the motor cortex for central pain: a special relevance for thalamic syndrome.

OBJECTIVES: To demonstrate that motor cortex stimulation (MCS) could improve motor function in patients with neuropathic pain. METHODS: In this prospective clinical study of 38 patients referred for MCS as treatment for their neuropathic pain, we collected any declaration of improvement in motor performance that could be attributed to MCS. RESULTS: Ten patients (26%) declared a benefit in their motor function. Eight presented objective evidence of recovered dexterity for rapid alternating movements. A minor proportion had improvement in dystonic posture (n = 2), but none had detectable increased motor strength or tonus changes. Overall, 73% of the patients with limb ataxia declared a benefit after MCS. In 6 out of 10 patients (60%), the anatomic lesion responsible for pain was restricted to the lateral aspect of the thalamus. All of them had either clinical or electrophysiological evidence of lemniscal dysfunction (proprioceptive ataxia). No correlation was found between the scores of pain relief and the modification of motor status. The correlation between thalamic lesions and benefits in motor performance was significant (Fisher's exact test, two-tailed, p = 0.0017). CONCLUSIONS: Up to 26% of patients estimated that MCS improved their motor outcome through recovered dexterity and in cases of lateral thalamic lesions.