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Biomedical subjects

E B Montgomery

Publications and source records attributed to E B Montgomery.

At least 19 recordsLinked to original sources
PubMed2003

A longitudinal study of neuropsychological change in individuals with Parkinson's disease.

OBJECTIVES: Neuropsychological changes in individuals with Parkinson's disease (PD) were studied longitudinally. METHODS: Sixty-nine idiopathic PD patients, with Mini-Mental State Examination (MMSE) scores falling within normal range, and 37 elderly control participants were given neuropsychological tests twice approximately two years apart. RESULTS: The PD group performed poorer than the control group on Semantic Fluency, Letter Fluency, Modified Wisconsin Card Sorting Task, and Block Design at test time 1. Two years later, the PD group showed significant decline in Semantic and Letter Fluency. A subset of 12 PD patients declined in mental status by second testing (>4 MMSE points). Cox proportional-hazards models were used to see if any baseline measures were associated with relative risk of decline in mental status. In the final model, Repetition performance and Age were significantly associated with cognitive decline. CONCLUSIONS: Consistent with previous studies, executive function tasks were those most susceptible to disease progression.

Aged↗
PubMed2001

Performance on the PD test battery by relatives of patients with progressive supranuclear palsy.

OBJECTIVE: To determine whether there is a greater prevalence of asymptomatic first-degree relatives (FDR) of patients with progressive supranuclear palsy (PSP) performing abnormally on the PD test battery (PD Battery) compared to sex- and age-matched normal control (NC) individuals. The PD Battery incorporates tests of motor function, olfaction, and mood. It has high specificity and sensitivity in distinguishing mildly affected PD patients from NC individuals in previous studies. METHODS: This test battery and regression analysis-derived scoring equations were applied to asymptomatic FDR. RESULTS: Twenty-three FDR and 23 NC individuals were tested. Of the FDR, 39% scored in the abnormal range, whereas none of the NC individuals achieved abnormal scores. This difference was significant. Further analysis demonstrated that the two groups differed significantly on a measure of simple reaction time. CONCLUSIONS: The proportion of FDR who demonstrated abnormal performance on the PD Battery was greater than NC individuals. Thus, the PD Battery may detect the asymptomatic carrier state or risk for PSP or a subclinical effect of a shared environmental exposure.

Adult↗
PubMed2001

Deep brain stimulation in epilepsy.

Since the pioneering studies of Cooper et al. to influence epilepsy by cerebellar stimulation, numerous attempts have been made to reduce seizure frequency by stimulation of deep brain structures. Evidence from experimental animal studies suggests the existence of a nigral control of the epilepsy system. It is hypothesized that the dorsal midbrain anticonvulsant zone in the superior colliculi is under inhibitory control of efferents from the substantia nigra pars reticulata. Inhibition of the subthalamic nucleus (STN) could release the inhibitory effect of the substantia nigra pars reticulata on the dorsal midbrain anticonvulsant zone and thus activate the latter, raising the seizure threshold. Modulation of the seizure threshold by stimulation of deep brain structures-in particular, of the STN-is a promising future treatment option for patients with pharmacologically intractable epilepsy. Experimental studies supporting the existence of the nigral control of epilepsy system and preliminary results of STN stimulation in animals and humans are reviewed, and alternative mechanisms of seizure suppression by STN stimulation are discussed.

Animals↗
PubMed2000

Early detection of probable idiopathic Parkinson's disease: II. A prospective application of a diagnostic test battery.

We developed a battery of tests, incorporating motor function, olfaction, and mood, that distinguishes between early mild, probable idiopathic Parkinson's disease (iPD), and normal control subjects. Here, we determined the PD Battery's ability to prospectively identify which patients with symptoms and signs suggestive of, but not yet diagnostic of, iPD who would subsequently be diagnosed as having iPD. Of 212 enrolled patients, 194 have been followed for at least 1 year. Among these 194, 59 were diagnosed with iPD, 40 as neurologically normal, and the remaining 106 with other neurologic conditions such as essential tremor. The test battery was 92% specific and 68% sensitive for iPD. The area under the Receiver Operating Characteristics curve was 0.88 for predicting which participants would subsequently be diagnosed as having iPD or as being neurologically normal.

Adult↗
PubMed2000

Motor initiation and execution in essential tremor and Parkinson's disease.

Clinical differentiation of essential tremor (ET) from idiopathic Parkinson's disease (iPD) is based on the lack of akinesia and bradykinesia. Nevertheless, early tremor-predominant iPD often is difficult to distinguish from ET. Motor initiation and execution in ET, iPD, and normal control (NC) subjects were investigated. Individuals with iPD, ET and NC performed a reaction-time wrist flexion and extension task. Motor performances were similar between ET and iPD and both were different than normal control subjects. Both the patients with iPD and ET had longer reaction times and slower movement velocities than NC subjects. This may help to explain some of the difficulties in distinguishing patients with these two diseases. The similarities of motor performance suggest that while ET and iPD may be separate disease entities, they may share similar pathogenic motor mechanisms from the perspective of an integrated motor system that drives the motor cortex.

Adult↗
PubMed2000

Mechanisms of deep brain stimulation and future technical developments.

Possible mechanisms underlying the therapeutic effect of deep brain stimulation (DBS) are reviewed, particularly the notion that DBS is inhibitory. Computer simulations are described that model the effect of different frequencies and regularity of neuronal activity (target neuron), either spontaneous or stimulated, on information transfer between two other neurons. Most simulations resulted in a loss of information. These were the least with high frequency and regular activity or stimulation of the target neuron with regularity having the least deleterious effect on information transfer. The simulations suggest that irregular activity in neurons converging with other neurons can result in a loss of information transfer. This may explain why increased irregularity in globus pallidus activity associated with Parkinson's disease, dystonia and hemiballismus may result in symptoms. Further, the therapeutic effect of DBS may be due to driving neurons at higher and perhaps more importantly, regular frequencies. There were simulations in which information transfer was augmented suggesting the presence of stochastic resonance. This most often occurred with low frequency activity in the target neuron. It is hypothesized that low frequency activity, either spontaneous or stimulated, could account for involuntary movements, including tremor. Future directions and challenges to DBS are also discussed.

Animals↗
PubMed2000

Early detection of probable idiopathic Parkinson's disease: I. Development of a diagnostic test battery.

We developed a test battery as an inexpensive and objective aid for the early diagnosis of idiopathic Parkinson's disease (iPD) and its differential diagnoses. The test battery incorporates tests of motor function, olfaction, and mood. In the motor task, a wrist flexion-and-extension task to different targets, movement velocities were recorded. Olfaction was tested with the University of Pennsylvania Smell Identification Test. Mood was assessed with the Beck Depression Inventory. An initial regression model was developed from the results of 19 normal control subjects and 18 patients with early, mild, probable iPD. Prospective application to an independent validation set of 122 normal control subjects and 103 patients resulted in an 88% specificity rate and 69% sensitivity rate, with an area under the Receiver Operator Characteristic curve of 0.87.

Adult↗
PubMed1999

Chronic thalamic stimulation for the tremor of multiple sclerosis.

The authors studied chronic high-frequency stimulation of the ventral intermediate nucleus of the thalamus (Vim) for controlling upper extremity tremor in patients with MS using MRI, CT, and microelectrode recordings and stimulation to locate optimal target sites. Fifteen patients underwent surgery. All patients had reduced tremor but developed tolerance requiring repeated programming of the stimulator. Benefit at optimal stimulator settings was maintained. Two patients experienced complications: intracerebral hematoma and MS exacerbation. Chronic high-frequency stimulation of Vim provides tremor reduction if patients have access to frequent stimulator adjustments. This surgery is relatively safe.

Adult↗
PubMed1999

Abnormal performance on the PD test battery by asymptomatic first-degree relatives.

OBJECTIVE: To determine whether a sensitive and specific battery of tests (PD Battery) could identify a subset of asymptomatic first-degree relatives (FDRs) of PD patients who were significantly more impaired than age-matched normal control (NC) subjects. The PD Battery incorporates tests of motor function, olfaction, and mood. In previous studies, it has shown high specificity and sensitivity in distinguishing mildly affected PD patients from NC subjects. METHODS: The PD Battery and regression analysis-derived scoring equations were applied to asymptomatic FDRs. RESULTS: Eighty FDRs and 100 NC subjects were tested. Of the FDRs, 22.5% scored in the abnormal range, and 9% of NC subjects had abnormal scores. This difference was statistically significant. Further analysis demonstrated that FDRs with abnormal scores on the PD Battery differed on all three components of the test battery from FDRs who had normal scores. Among the sons and daughters whose scores were abnormal, there was a much higher prevalence of the affected parent being the father. CONCLUSIONS: The proportion of FDRs who demonstrated abnormal performance on the PD Battery was greater than that of NC subjects. Thus, the PD Battery may detect the asymptomatic carrier state or risk for PD. Sons and daughters whose scores were in the abnormal range were more likely to have fathers with PD.

Adult↗
PubMed1999

Deep brain stimulation reduces symptoms of Parkinson disease.

Surgical ablation or continuous electrical stimulation of specific areas deep in the brain may help patients with Parkinson disease or other movement disorders for whom medications have failed or who experience dose-limiting side effects from medications.

Electric Stimulation Therapy↗
PubMed1997

Comparing the difficulty of letter, semantic, and name fluency tasks for normal elderly and patients with Parkinson's disease.

Research on the effect of Parkinson's disease (PD) on verbal fluency has produced conflicting results. In this study, 88 PD patients with no dementia, 11 PD patients with questionable mental status, 15 PD patients with dementia, and 46 elders free from mental disorder were administered a variety of semantic, letter, and name fluency tasks. The results revealed that, contrary to popular assumption, semantic fluency was not always superior to letter fluency. Rather, verbal fluency was influenced by the nature of the individual categories. Interestingly, the relative difficulty of many categories was fairly stable across groups. The results also indicated that the individual fluency tasks were differentially sensitive to the mental status of the PD patients. Overall, the findings suggest that closer attention to the nature of the tested categories may help clarify the inconsistent effects of PD on verbal fluency.

Aged↗
PubMed1997

Issues in the early diagnosis of Parkinson's disease.

The clinical diagnosis of Parkinson's disease (PD) is most difficult early in the disease when the signs and symptoms are most subtle. The differential diagnosis of PD includes a number of movement disorders with similar symptomatology (e.g., essential tremor, multiple system atrophy, vascular parkinsonism). In most published studies of PD, the disease is diagnosed simply by the presence of two of the three cardinal motor signs-tremor, rigidity, and bradykinesia-or by the presence of three of the four motor signs: tremor, rigidity, bradykinesia, and postural instability. However, there is an obvious need for better diagnostic criteria. Until discrete biologic markers are developed, the use of exclusion criteria may improve the accuracy of the presumptive diagnosis of PD.

Diagnosis, Differential↗
PubMed1996

Change in cognitive function in idiopathic Parkinson disease.

OBJECTIVE: To study the effects of Parkinson disease (PD) on cognitive function by determining the frequency and amount of change in Mini-Mental State Examination (MMSE) performance. DESIGN: During a 4-year period, 77 patients with idiopathic PD and 43 normal elders were administered a neuropsychological test battery twice at 2 years apart. RESULTS: A 4-point score difference on the MMSE was the amount that was statistically calculated to be a significant difference at the .05 probability level. Using this metric, 17 (22%) patients with PD had a change in their MMSE performance during a 2-year period. Fifteen individuals performed poorer, and 2 individuals improved. Using the same metric, no normal subjects changed in their MMSE performance. The groups of patients with PD who had a change and did not have a change in their MMSE performance were not characterized by significant differences in their years of education, duration of illness, age at onset, age at test time 1, estimated premorbid intelligence, Hamilton Psychiatric Rating Scale for Depression score at test time I, or Unified Parkinson's Disease Rating Scale score. The singular difference was the higher frequency of change that was found in subjects who were taking dopamine agonists at the second test time. CONCLUSION: A change in cognitive function in patients with PD, as measured by a change of 4 points or more in their MMSE performance, was observed in only 22% of a sample of 77 patients with idiopathic PD during a 2-year period.

Aged↗
PubMed1995

Heavy metals and the etiology of Parkinson's disease and other movement disorders.

Heavy metals, such as iron and manganese, are involved in neurologic disease. Most often these diseases are associated with abnormal environmental exposures or abnormal accumulations of heavy metals in the body. There is increasing recognition that heavy metals normally present in the body also may play a role in disease pathogenesis through free radical formation. When a part of the brain known as the basal ganglia is affected, movements become disordered. Parkinson's disease is one of the most common movement disorders and is related to destruction of neurons in the substantia nigra pars compacta (SNpc) of the basal ganglia. The combination of high concentration of iron and the neurotransmitter, dopamine, may contribute to the selective vulnerability of the SNpc. Dopamine can auto-oxidize to produce free radicals particularly in the presence of iron and other heavy metals.

Animals↗