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Ralph Gregory

Publications and source records attributed to Ralph Gregory.

17 recordsLinked to original sources
PubMed2006

A dominant bursting electromyograph pattern in dystonic conditions predicts an early response to pallidal stimulation.

Although chronic pallidal deep brain stimulation (DBS) is effective in the treatment of medically intractable dystonia, there is no way of predicting the variations in clinical outcome, partly due to our limited understanding of the pathophysiological mechanisms underlying this condition. We recorded electromyographic (EMG) activity from the most severely affected muscle groups in seven dystonia patients before and after pallidal DBS. Patient EMG recordings could be classified into two groups: one consisting of patients who at rest demonstrated a dominant low frequency component of activity on power spectral analysis (ranging from 2 to 5 Hz), and one group in which this dominant pattern was absent. Early postoperative improvements (within 2-3 days) were observed in the former group, whereas the latter group benefited more gradually (over several months). Analysis of EMG activity may provide a sensitive means of identifying dystonic patients who are likely to be most responsive to functional neurosurgical intervention.

Action Potentials↗
PubMed2006

Use of surface electromyography to assess and select patients with idiopathic dystonia for bilateral pallidal stimulation.

OBJECT: The object of this study was to identify a preoperative physiological index by using surface electromyography (EMG) signals that would correlate with clinical outcome in dystonic patients following bilateral pallidal stimulation. METHODS: In 14 patients with spasmodic torticollis, generalized dystonia, and myoclonic dystonia, surface EMG signals were recorded from the most affected muscle groups. Although the dystonia affected different body segments, the EMG signals in all patients could be decomposed into bursting and sustained components. Subsequently, a ratio of the EMG amplitude was calculated between the two components and then correlated with clinical outcome. Patients who experienced rapid improvement following bilateral pallidal stimulation had a significantly higher EMG ratio compared with those who did not. Furthermore, a significant correlation was found between the EMG ratio and clinical improvement during the 12-month period following pallidal stimulation. CONCLUSIONS: The authors concluded that surface EMG studies could be used to predict the clinical outcome of and to select patients for pallidal stimulation for dystonia.

Adult↗
PubMed2005

Deep brain stimulation for generalised dystonia and spasmodic torticollis.

Dystonia appears distinct from the other tremulous disorders in that improvement following deep brain stimulation frequently appears in a delayed and progressive manner. The rate of this improvement and the point at which no further progress can be expected are presently unknown. The establishment of these parameters is important in the provision of accurate and relevant prognostic information to these patients, their carers, and their treating physicians. We studied 12 consecutive patients with generalised dystonia (n=6) and spasmodic torticollis (n=6) who underwent bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) and were followed up for a minimum of 2 years postoperatively. Standard rating scales were used to quantify their neurological improvement. Both groups experienced a statistically significant improvement in their rating scores at both one and two years following surgery. At 2 years follow-up, the spasmodic torticollis group exhibited a 59% improvement in their total Toronto Western Spasmodic Torticoilis Rating Scale (TWSTRS) rating score and the generalised dystonia group attained a 46% improvement in their overall Burke, Fahn and Marsden Dystonia Rating Scale (BFMDRS) evaluation. Ninety-five percent of the final improvement was attained by 6.4 months in the generalised dystonia group and by 6.6 months in those with spasmodic torticollis. There was no significant improvement after one year postoperatively. These findings add further support to GPi DBS as an effective treatment for generalised dystonia and spasmodic torticollis, and furnish important information as to the expected rate of improvement and the point at which no further gains can be reasonably anticipated.

Adolescent↗
PubMed2005

Effect of GPi DBS on functional imaging of the brain in dystonia.

Five patients with idiopathic dystonic conditions, treated successfully with deep brain stimulation (DBS) of the globus pallidus internus (GPi), were studied using single-photon emission tomography (SPET) in order to evaluate brain perfusion in the presence and absence of DBS. Comparison was made between the "on" and "off" DBS scans on an individual basis and also as part of a group analysis. Whilst the individual data suggested great regional variation in cerebral perfusion between individuals, the results of the group analysis revealed several topographically similar areas of the brain where relative hyperperfusion in the absence of DBS was common to all patients. Based on these results we postulate on possible mechanisms for this phenomenon.

Adult↗
PubMed2005

Thalamotomy versus thalamic stimulation for multiple sclerosis tremor.

Disabling intractable tremor occurs frequently in patients with multiple sclerosis (MS). There is currently no effective medical treatment available, and the results of surgical intervention have been variable. Thalamotomy has been the mainstay of neurosurgical therapy for intractable MS tremor, however the popularisation of deep brain stimulation (DBS) has led to the adoption of chronic thalamic stimulation in an attempt to ameliorate this condition. With the goal of examining the relative efficacy and adverse effects of these two surgical strategies, we studied twenty carefully selected patients with intractable MS tremor. Thalamotomy was performed in 10 patients, with chronic DBS administered to the remaining 10. Both thalamotomy and thalamic stimulation produced improvements in postural and intention tremor. The mean improvement in postural tremor at 16.2 months following surgery was 78%, compared with a 64% improvement after thalamic stimulation (14.6 month follow-up) (P > 0.05). Intention tremor improved by 72% in the group undergoing thalamotomy, a significantly larger gain than the 36% tremor reduction following DBS (P < 0.05). Early postoperative complications were common in both groups. Permanent complications related to surgery occurred in four patients overall. Following thalamotomy, long-term adverse effects were observed in three patients (30%), and comprised hemiparesis and seizures. Only one patient in the thalamic stimulation group experienced a permanent deficit (monoparesis). We conclude that thalamotomy is a more efficacious surgical treatment for intractable MS tremor, however the higher incidence of persistent neurological deficits in patients receiving lesional surgery may support the use of DBS as the preferred surgical strategy.

Adult↗
PubMed2004

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

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.

Adolescent↗
PubMed2003

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

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.

Adolescent↗
PubMed2003

Executive cognitive deficits in primary dystonia.

Primary dystonia is a disorder of movement for which no consistent pathophysiology has been identified; in the absence of evidence to the contrary, it is assumed to be cognitively benign. We have studied a clinically heterogeneous group of 14 patients with primary dystonia on a battery of neuropsychological tests. Despite well-preserved speed of information processing, language, spatial, memory and general intellectual skills relative to normal controls, we have identified a constellation of attentional-executive cognitive deficits on the Cambridge Neuropsychological Test Automated Battery (CANTAB). Specifically, patients demonstrated significant difficulties negotiating the extra-dimensional set-shifting phase of the IED task. The implications of these findings for the pathophysiology of primary dystonia are discussed. This is, to the best of our knowledge, the first report of a significant cognitive deficit in patients with primary dystonia.

Adult↗
PubMed2002

Camptocormia treated with bilateral pallidal stimulation: case report.

The authors report the neurological, neurophysiological, and neuropsychological effects of using chronic bilateral pallidal high-frequency deep brain stimulation (DBS) in a case of disabling camptocormia. Deep brain stimulation electrodes were implanted stereotactically to target the globus pallidus internus (GPi) bilaterally. Local field potentials (FPs) were recorded using the DBS electrodes and concurrent abdominal flexor electromyography (EMG) potentials during camptocormic episodes. Videotaped assessments of the movement disorder and neuropsychological evaluation before implantation and at 6 months after initiation of pallidal stimulation were recorded. There was significant functional improvement following chronic pallidal stimulation, and some improvement was noted in neuropsychological scores. The GPi FPs showed temporal correlation with EMG-recorded rectus abdominis potentials. There were no treatment-related adverse effects. The authors have found that chronic pallidal stimulation was safe and offered functional benefit in this severely disabling condition. The physiological studies may help further the understanding of the pathophysiology of this rare entity.

Abdominal Muscles↗
PubMed2002

Hardware-related problems of deep brain stimulation.

Deep brain stimulation for the alleviation of movement disorders and pain is now an established therapy. However, very little has been published on the topic of hardware failure in the treatment of such conditions irrespective of clinical outcome. Such device-related problems lead to significant patient morbidity and increased cost of therapy in the form of prolonged antibiotics, in-patient hospitalization, repeat surgery, and device replacement. We report a prospective review of our experience at the Radcliffe Infirmary Oxford from the period of April 1998 to March 2001. Overall there is a 20% rate of hardware-related problems in this series, which falls between the 7% and 65% rates reported by other groups. The majority of these failures occurred early on in the series, and numbers declined with experience. Some of the problems may be idiosyncratic to the methodology of individual groups.

Adolescent↗
PubMed2002

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

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.

Adult↗
PubMed2002

Global attentional-executive sequelae following surgical lesions to globus pallidus interna.

It has been demonstrated that selective unilateral surgical ablation of posteroventral globus pallidus interna relieves the movement disorders associated with advanced Parkinson's disease, without necessarily incurring the executive cognitive sequelae that have been observed following gross pathological lesions to this brain region. This finding is consistent with established theory that underlying neuronal circuitry is functionally segregated into parallel cortico-striatal-pallidal-thalamo-cortical 'loops'. We have studied a series of 12 patients with advanced Parkinson's disease at baseline, and then following bilateral pallidotomy, with a battery of neuropsychological tests including the Cambridge Neuro psychological Test Automated Battery. We identified a selective and universal loss of individual patients' ability to shift attention to novel dimensions in a test of abstract rule-learning following surgery, which was not reliably associated with any other change in cognition, personality, mood or medication. This finding is rare in its specificity and has implications for theoretical models of the functional architecture and pathophysiology of the globus pallidus, and the clinical practice of pallidotomy.

Adult↗
PubMed2002

Camptocormia treated with bilateral pallidal stimulation.

The authors report the neurological, neurophysiological, and neuropsychological effects of using long-term bilateral pallidal high-frequency deep brain stimulation (DBS) in a case of disabling camptocormia. Deep brain stimulation electrodes were implanted stereotactically to target the globus pallidus internus (GPi) bilaterally. Local field potentials (FPs) were recorded using the DBS electrodes and concurrent abdominal flexor electromyography (EMG) potentials during camptocormic episodes. Videotaped assessments of the movement disorder and neuropsychological evaluations of the patient before implantation and 6 months after initiation of pallidal stimulation were recorded. There was significant functional improvement following long-term pallidal stimulation, and some improvement was noted in neuropsychological scores. A temporal correlation between the GPi FPs and EMG-recorded rectus abdominis potentials was evident. There were no treatment-related adverse effects. The authors have found that long-term pallidal stimulation was safe and offered functional benefit to a patient with this severely disabling condition. The physiological studies may help further the understanding of the pathophysiology of this rare entity.

Adult↗