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Biomedical subjects

Peter G Bain

Publications and source records attributed to Peter G Bain.

At least 19 recordsLinked to original sources
PubMed2006

Identifying cardiorespiratory neurocircuitry involved in central command during exercise in humans.

For almost one hundred years, the exact role of human brain structures controlling the cardiorespiratory response to exercise ('central command') has been sought. Animal experiments and functional imaging studies have provided clues, but the underlying electrophysiological activity of proposed relevant neural sites in humans has never been measured. In this study, local field potentials were directly recorded in a number of 'deep' brain nuclei during an exercise task designed to dissociate the exercise from peripheral feedback mechanisms. Several patient groups had electrodes implanted sterotaxically for the treatment of movement disorder or chronic pain. Fast Fourier transform analysis was applied to the neurograms to identify the power of fundamental spectral frequencies. Anticipation of exercise resulted in increases in heart rate, blood pressure and ventilation. The greatest neural changes were found in the periaqueductal grey area (PAG) where anticipation of exercise was accompanied by an increase of 43% in the power of the 12-25 Hz frequency band (P = 0.007). Exercise increased the activity by 87% compared to rest (P = 0.006). Changes were also seen in the 60-90 Hz band when anticipation or exercise increased power by 32% (P = 0.006) and 109% (P < 0.001), respectively. In the subthalamic nucleus there was a reduction in the power of the beta frequency during both anticipation (7.6 +/- 0.68% P = 0.001) and exercise (17.3 +/- 0.96% P < 0.001), whereas an increase was seen with exercise only at higher frequencies (93 +/- 1.8% P = 0.007). No significant changes were seen in the globus pallidus during anticipation of exercise. We provide direct electrophysiological evidence highlighting the PAG as an important subcortical area in the neural circuitry of the cardiorespiratory response to exercise, since stimulation of this structure is known to alter blood pressure in awake humans.

Adult↗
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

Physiological and harmonic components in neural and muscular coherence in Parkinsonian tremor.

OBJECTIVE: To differentiate physiological from harmonic components in coherence analysis of the tremor-related neural and muscular signals by comparing power, cross-power and coherence spectra. METHODS: Influences of waveform, burst-width and additional noise on generating harmonic peaks in the power, cross-power and coherence spectra were studied using simulated signals. The local field potentials (LFPs) of the subthalamic nucleus (STN) and the EMGs of the contralateral forearm muscles in PD patients with rest tremor were analysed. RESULTS: (1) Waveform had significant effect on generating harmonics; (2) noise significantly decreased the coherence values in a frequency-dependent fashion; and (3) cross-spectrum showed high resistance to harmonics. Among six examples of paired LFP-EMG signals, significant coherence appeared at the tremor frequency only, both the tremor and double tremor frequencies and the double-tremor frequency only. CONCLUSIONS: In coherence analysis of neural and muscular signals, distortion in waveform generates significant harmonic peaks in the coherence spectra and the coherence values of both physiological and harmonic components are modulated by extra noise or non-tremor related activity. SIGNIFICANCE: The physiological or harmonic nature of a coherence peak at the double tremor frequency may be differentiated when the coherence spectra are compared with the power and in particular the cross-power spectra.

Electric Stimulation↗
PubMed2006

Different mechanisms may generate sustained hypertonic and rhythmic bursting muscle activity in idiopathic dystonia.

Despite that deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favored intervention for patients with medically intractable dystonia, the pathophysiological mechanisms of dystonia are largely unclear. In eight patients with primary dystonia who were treated with bilateral chronic pallidal stimulation, we correlated symptom-related electromyogram (EMG) activity of the most affected muscles with the local field potentials (LFPs) recorded from the globus pallidus electrodes. In 5 dystonic patients with mobile involuntary movements, rhythmic EMG bursts in the contralateral muscles were coherent with the oscillations in the pallidal LFPs at the burst frequency. In contrast, no significant coherence was seen between EMG and LFPs either for the sustained activity separated out from the compound EMGs in those 5 cases, or in the EMGs in 3 other cases without mobile involuntary movements and rhythmic EMG bursts. In comparison with the resting condition, in both active and passive movements, significant modulation in the GPi LFPs was seen in the range of 8-16 Hz. The finding of significant coherence between GPi oscillations and rhythmic EMG bursts but not sustained tonic EMG activity suggests that the synchronized pallidal activity may be directly related to the rhythmic involuntary movements. In contrast, the sustained hypertonic muscle activity may be represented by less synchronized activity in the pallidum. Thus, the pallidum may play different roles in generating different components of the dystonic symptom complex.

Adult↗
PubMed2006

Pregnancy in dystonic women with in situ deep brain stimulators.

In the past few years, an increasing number of dystonic patients, of both sexes, have undergone insertion of deep brain stimulators (DBS) with consistent improvement of their symptoms and enhancement of their quality of life. We describe 3 women with dystonia who, after insertion of bilateral globus pallidus internus stimulators, succeeded in conceiving and completing pregnancies, 2 of them having married. These histories illustrate the significant positive impact that DBS can have on women's social relationships. Based on this experience, we also provide an overview of some of the issues that might arise in pregnancy and during delivery in dystonic women with an in situ deep brain stimulator.

Adult↗
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 can regulate arterial blood pressure in awake humans.

The periaqueductal grey matter is known to play a role in cardiovascular control in animals. Cardiovascular responses to electrical stimulation of the periventricular/periaqueductal grey matter were measured in 15 awake human study participants following implantation of deep brain stimulating electrodes for treatment of chronic pain. We found that stimulation of the ventral periventricular/periaqueductal grey matter caused a mean reduction in systolic blood pressure of 14.2+/-3.6 mmHg in seven patients and stimulation of the dorsal periventricular/periaqueductal grey matter caused a mean increase of 16.7+/-5.9 mmHg in six patients. A comparison between ventral and dorsal electrodes demonstrated significant differences (P<0.05). These changes were accompanied by analogous changes in diastolic blood pressure, pulse pressure, maximum dP/dt but not in the time interval between each R wave on the electrocardiogram.

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

Deep brain stimulation for movement disorders and pain.

Deep brain stimulation (DBS) is an expanding field within neurosurgery. With many neurosurgeons performing relatively small numbers of these procedures, detailed descriptions of the technical aspects and nuances of DBS may be worthwhile. We describe our technique for DBS, based on over 300 procedures. This methodology continues to evolve and is refined according to our own experience, our observations of others, technological innovations, and information derived from the neurosurgical literature. The indications for DBS in our service are outlined, the anatomical targets described, and the anaesthetic and surgical aspects detailed.

Deep Brain Stimulation↗
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↗
PubMed2005

Intraoperative monitoring of motor symptoms using surface electromyography during stereotactic surgery for movement disorders.

The authors present practical evidence for the usefulness of intraoperative monitoring with surface electromyograms (sEMGs) from the affected muscles to assist electrode implantation and lesioning in patients with movement disorders. In 22 consecutive patients with various movement disorders, sEMGs were monitored in selected muscles during stereotactic surgery that involved either lesioning or electrode implantation. The electromyograms related to major motor symptoms such as tremor, rigidity, myoclonus, dystonia, and chorea were monitored and characterized on-line by both amplitude and frequency. Major motor symptoms were revealed by sEMGs recorded from the affected muscles. Tremor manifested as highly rhythmic bursts with a narrow frequency band; dyskinesias and chorea appeared as irregularly repeated bursts within a broad frequency range of 1 to 5 Hz; and rigidity and dystonia appeared as sustained high-frequency activity and co-contraction between antagonist muscles. The results suggest that intraoperative monitoring of sEMGs could help to functionally refine and confirm target localization. Surface EMGs could be used (1) as reference signals of the motor symptoms so that other signals, such as the oscillatory local field potentials simultaneously recorded via the implanted electrodes, could be correlated with the sEMGs and used to fine-tune or confirm the target localization; (2) to quantify the effects of acute electrical stimulation on the motor symptoms; and (3) to sensitively detect unwanted capsular responses induced by direct stimulation of the internal capsule. The authors conclude that intraoperative monitoring of sEMGs of the affected muscles of patients with movement disorders during stereotactic surgery provides sensitive and quantitative information that can contribute to improved electrode or lesion placement.

Electric Stimulation↗
PubMed2004

Quantifying drug-induced dyskinesias in the arms using digitised spiral-drawing tasks.

In this study, we quantify the severity of drug-induced dyskinesias in the arms of Parkinson's disease (PD) patients using digitised spiral-drawing tasks. Two spiral drawings, namely a circular and a square spiral, are designed to, respectively, represent the continuous and discrete arm motions, and the size of the spiral is decided so that both the distal and proximal arm joints are involved. Fifteen PD patients, average disease duration 14.4+/-7.4 years, were assessed 30 min after a levodopa challenge whilst performing circular and square spiral-drawing tasks. The velocity of drawing movements was computed and the amplitude of the involuntary dyskinetic movements was measured as the standard deviation of the drawing velocity (SD-DV). The mean amplitude of dyskinetic movements was compared between arms and tasks and was correlated with clinical measures including the Bain dyskinesia scale and the total unified Parkinson's disease rating scale (UPDRS) score. The results showed that there was no statistically significant difference in the amplitude of dyskinesias either between the arms or between the continuous (circular) and discrete (square) spiral drawings in this group of PD patients, but interestingly the interaction between arm and drawing pattern was significant. Significant correlations were found between the magnitude of dyskinesia measured from the spiral-drawing tasks and both the 'on' or 'off' UPDRS and also the Bain dyskinesia scale. We conclude that the drawing tasks may be used to provide an objective method of quantifying the severity of drug-induced dyskinesias in the arm in PD patients.

Adolescent↗
PubMed2003

Double-blind, single-dose, cross-over study of the effects of pramipexole, pergolide, and placebo on rest tremor and UPDRS part III in Parkinson's disease.

Tremor is one of the cardinal signs of Parkinson's disease (PD) but its response to antiparkinsonian medication is variable. It has been postulated that pramipexole may have a stronger antiparkinsonian tremor effect than pergolide, another direct acting dopamine agonist medication, possibly because the former has preferential affinity for the dopamine D3 receptor. The purpose of this pilot study was to compare the effects of a single oral dose of either pramipexole (Pr) or pergolide (Pe) or placebo (Pl) on parkinsonian tremor and the motor (part III) subsection of the UPDRS. Ten patients (6 men, 4 women), mean age 65.3 years, mean duration from diagnosis of 2.6 years, with tremor dominant PD were recruited. On three separate occasions a single dose of pramipexole (salt) 500 microg, pergolide 500 microg or placebo were administered in random order to each patient, who were pretreated with domperidone and had their antiparkinsonian medication withheld from midnight before study. After each medication patients were assessed at baseline and then every 30 min for 4 hr using a 0 to 10 tremor rating scale and the UPDRS (part III) in a double-blind protocol. Adverse effects were systematically recorded. The results demonstrate that 500 microg of either pramipexole or pergolide reduced PD rest tremor scores to a similar degree, which at peak effect was significantly greater than placebo (respectively Pe v Pl: P < 0.006, Pr v Pl: P < 0.033). The two active drugs also had weaker beneficial effects on the UPDRS part III. Pergolide, however, was significantly more likely than pramipexole to cause nausea (P = 0.005) or vomiting (P = 0.014).

Aged↗
PubMed2003

Direct economic impact of Parkinson's disease: a research survey in the United Kingdom.

The direct costs of care were evaluated prospectively in a sample of people with Parkinson's disease (PD) in the United Kingdom in 1998. The subjects were drawn from a random sample of general practitioner practices within a representative sample of 36 Regional Health Authorities and the equivalent. A total of 444 resource use questionnaires with usable data were returned (response rate, 59%). The total mean annual cost of care per patient for all patients by age was 5,993 pounds (9,554 euro, n = 432). Hoehn and Yahr stage significantly (P < 0.001) influenced expenditure by stage as follows: 0 and I, 2,971 pounds (4,736 euro, n = 110); II, pound 3,065 (4,886 euro, n = 89); III, 6,183 pounds (9,857 euro, n = 120); IV, 10,134 pounds (euro;16,155, n = 87); V, 18,358 pounds (29,265 euro, n = 17). National Health Service costs accounted for approximately 38% and social services for 34% of the direct costs of care. Drug expenditure accounted for 24% of overall costs in the <65 years age group and 10% in patients aged >85 years. A move from home to residential care was associated with an approximately 500% cost increase. In conclusion, PD imposes significant direct costs on public services and on individuals. These costs should be taken into account when allocating public funds.

Aged↗