PubMed Health⌕ Search

Biomedical subjects

M W Horstink

Publications and source records attributed to M W Horstink.

At least 19 recordsLinked to original sources
PubMed1999

Decreased striatal dopamine-receptor binding in sporadic ALS: glutamate hyperactivity?

The pathogenesis of ALS may be related to increased glutamatergic excitotoxicity. The striatum receives massive glutamatergic input. Animal studies suggest that glutamate decreases striatal D2-receptor synthesis. In drug-naive, sporadic ALS patients we demonstrated decreased striatal D2-receptor binding in vivo that could be partially reversed by the glutamatergic transmission blocker riluzole. Our findings support the glutamatergic excitotoxicity hypothesis in sporadic ALS.

Aged↗
PubMed1999

Motor cortex activation in Parkinson's disease: dissociation of electrocortical and peripheral measures of response generation.

This study investigated characteristics of motor cortex activation and response generation in Parkinson's disease with measures of electrocortical activity (lateralized readiness potential [LRP]), electromyographic activity (EMG), and isometric force in a noise-compatibility task. When presented with stimuli consisting of incompatible target and distractor elements asking for responses of opposite hands, patients were less able than control subjects to suppress activation of the motor cortex controlling the wrong response hand. This was manifested in the pattern of reaction times and in an incorrect lateralization of the LRP. Onset latency and rise time of the LRP did not differ between patients and control subjects, but EMG and response force developed more slowly in patients. Moreover, in patients but not in control subjects, the rate of development of EMG and response force decreased as reaction time increased. We hypothesize that this dissociation between electrocortical activity and peripheral measures in Parkinson's disease is the result of changes in motor cortex function that alter the relation between signal-related and movement-related neural activity in the motor cortex. In the LRP, this altered balance may obscure an abnormal development of movement-related neural activity.

Aged↗
PubMed1999

The Symptom Checklist-90 Revised questionnaire: no psychological profiles in complex regional pain syndrome-dystonia.

Complex regional pain syndrome (CRPS) is a syndrome usually localized in the extremities, mostly occurring after a preceding trauma or operation. Dystonia is present in a minority of CRPS patients, but, when present, leads to severe disability. Various pathological factors have been postulated to present in CRPS-dystonia, such as involvement of the sympathetic system, reorganization of the central nervous system, and psychological distress. In the present study, we investigated the involvement of psychological distress in CRPS-dystonia with the aid of the Symptom Checklist-90 Revised (SCL-90R) questionnaire. The SCL-90R is a multidimensional self-report inventory covering various dimensions of psychological distress. In a population of 1006 CRPS patients, we analyzed the SCL-90R scores of 27 patients with CRPS-dystonia (23 female and 4 male) and compared the scores to sample scores of a control female (n = 577) and a control rehabilitation population (n = 56). Insomnia scored significantly higher in the female CRPS-dystonia population, as compared to the control female population (P < 0.001), and in the total CRPS-dystonia population, as compared to the rehabilitation population (P < 0.01). Remarkable was the significantly higher score of somatization in the rehabilitation population, as compared to the CRPS-dystonia population (P = 0.006). For the other dimensions of psychological distress of the SCL-90R, the scores of the CRPS-dystonia and control populations were similar. With regard to the SCL-90R scores, we conclude that specific psychological profiles are not present in CRPS-dystonia.

Adolescent↗
PubMed1999

Donders' law in torticollis.

We investigated head movements of patients with spasmodic torticollis toward targets in various directions. These patients, whose severe dystonia was reflected in an abnormal resting head position, appeared to retain a Donders'-type strategy for the control of the rotational degrees of freedom of the head. As in normals, rotation vectors, representing head orientation, were confined to a curved surface, which specifies how head torsion depends on gaze direction. The orientation of the surface in body coordinates, which was very stereotyped in normals, was different for patients. The same Donders surface was found for head movements and for stationary head postures, indicating that the same neural mechanism governs its implementation in both tasks. To interpret our results, we propose a conceptual scheme incorporating the basal ganglia, which are thought to be involved in the etiology of torticollis, and an implementation stage for Donders' law.

Aged↗
PubMed1998

Genetic and environmental risk factors in Parkinson's disease.

Parkinson's disease (PD) is a multifactorial disorder, caused by a combination of age, genetics and environmental factors. Nigral cells are susceptible to multiple causes of derangement of normal cell function, all of which may contribute to the same Parkinson phenotype. Autosomal dominant alpha-synuclein-gene PD represents one of the pure genetic forms, whereas cases of sporadic PD probably depend more on age and environmental factors, MPTP-Parkinsonism being the purest example of an environmentally caused Parkinson phenotype. This review suggests that pesticides-herbicides, smoking and head trauma probably represent the most eligible candidates for environmental factors involved in provoking PD or influencing its natural course.

Aging↗
PubMed1998

Reliance on external cues for movement initiation in Parkinson's disease. Evidence from movement-related potentials.

The aim of this study was to investigate the neurophysiological mechanisms underlying Parkinson's disease patients' increased reliance on external cues for the initiation of movement. Lateralized movement-related cortical potentials were recorded in a noise-compatibility task with seven patients and seven age-matched control subjects. In this two-choice task, visual stimuli containing incompatible target and distractor elements, which simultaneously instructed for responses from both hands, initially caused activation of the motor cortex controlling the wrong response hand. The incorrect response activation was of higher amplitude in patients than in control subjects, causing a longer response delay relative to response times when target and distractors instructed the same hand. In addition, hand-specific motor cortex activation started earlier in patients than in control subjects. These results indicate that visual stimuli exerted an earlier and stronger influence on movement initiation in patients than in control subjects. We hypothesize that information from sensory stimuli relevant for the generation of a response can have rapid access to motor structures in Parkinson's disease patients, thereby facilitating the initiation of movement. The findings may reflect a compensatory mechanism, but could also be related to excitability changes in the motor cortex intrinsic to the pathophysiology of Parkinson's disease.

Aged↗
PubMed1998

EEG findings in patients with vascular parkinsonism.

OBJECTIVES: To investigate whether the conventional and quantitative EEGs of patients with vascular parkinsonism (VP) differ from those of idiopathic Parkinson's disease (PD) patients. MATERIAL AND METHODS: The EEGs of 13 patients with vascular parkinsonism and 14 patients with idiopathic Parkinson's disease were scored on a simple scale regarding aspects of conventional EEG variables. Alpha band power asymmetry and EEG slowing (increased delta and theta power) were calculated by the neurometrics method of quantitative EEG data evaluation. RESULTS: Analysis of both conventional and quantitative EEG data shows that VP patients had significantly less EEG slowing than PD patients. CONCLUSION: This study shows that the EEG in a group of patients with vascular parkinsonism differ from a patient group with idiopathic Parkinson's disease. Our results indicate that VP patients are not PD patients with subcortical vascular lesions, because then they would have had at least as much EEG slowing as PD patients.

Aged↗
PubMed1998

Cognitive deficits following stroke in the basal ganglia.

OBJECTIVE: To examine the effect of a stroke in the basal ganglia on cognitive functioning. DESIGN: As part of a larger prospective study on the neuropsychological and psychosocial consequences of stroke, 12 patients with a stroke confined to the basal ganglia were examined. SETTING: The patients were assessed in one of the three participating hospitals. SUBJECTS: The results of 12 patients with a stroke in the basal ganglia (mean age 55 years), were compared to 24 controls (mean age 54.3 years). MAIN OUTCOME MEASURES: Different aspects of memory, attention and concentration, visuospatial and visuoconstructive functions, language and arithmetic were assessed using neuropsychological tests. RESULTS: The data show a significant abnormality in cognitive functioning on all cognitive domains. CONCLUSIONS: The results stress the notion that subcortical damage may lead to substantial neuropsychological disorders and have clear implications for neurological rehabilitation.

Basal Ganglia↗
PubMed1998

[Cognitive deficits in Parkinson's disease].

In neuropsychological studies of Parkinson's disease, cognitive deficits are frequently reported, but the nature of these deficits is not clear. As far as cognitive deficits are manifest in parkinsonian patients at an early stage of the disease, many studies tend to describe them as fitting a frontal syndrome. As a consequence of dysfunction of the striatum, the (pre)frontal cortex receives deficient input from the striatum, which might explain the similarity of the cognitive deficits of parkinsonian patients with those of patients with frontal dysfunction. The present studies provide evidence that the cognitive deficits of parkinsonian patients display a certain similarity with those of patients with frontal dysfunction at the level of the ultimate performance, but that the underlying processes have a distinct character. Parkinsonian patients exhibit a decrease in self-generated problem-solving. This deficit is manifest at a level of cognitive function, which goes beyond task or domain. Among all disease variables, only severity of the disease and especially rigidity proved to be related consistently to this decrease in self-generated problem-solving.

Adult↗
PubMed1997

Symptoms and duration of the prodromal phase in Parkinson's disease.

To investigate the duration of a prodromal phase before the onset of the classic symptoms of idiopathic Parkinson's disease, the authors conducted a retrospective case-control study of 60 patients with Parkinson's disease and 58 age- and sex-matched control subjects, covering the decade preceding the onset of classic Parkinson's disease. The symptoms were derived from files of the patients' general practitioners. Compared with control subjects, patients pre-Parkinson's disease had more central nervous system, psychologic, musculoskeletal, and cardiovascular (i.e., autonomic) symptoms. Patients pre-Parkinson's disease also made more visits to general practitioners and medical specialists. The results indicate that the onset of classic parkinsonism is frequently preceded by a prodromal phase lasting from 4-6 years.

Adult↗
PubMed1997

Q10 therapy in patients with idiopathic Parkinson's disease.

A 3-month open-label trial was performed to evaluate the efficacy of 200 mg Q10 daily in 10 patients with Parkinson's disease. Motor performance was assessed with UPDRS and motor tests. There was no significant effect on the clinical ratings.

Aged↗
PubMed1996

Movement-related potential measures of different modes of movement selection in Parkinson's disease.

Movement-related potentials were recorded preceding self-paced voluntary movements in patients with Parkinson's disease and in healthy subjects of the same age group. We compared the Readiness Potential preceding joystick movements in a fixed direction and preceding joystick movements in freely selected directions. In normal subjects the Readiness Potential amplitude was higher preceding freely selected movements than preceding movements in a fixed direction. The Readiness Potential in Parkinson patients failed to be modified by the different modes of movement selection. The modulation of the Readiness Potential by different ways of preparing for movement might be due to the supplementary motor area (SMA) being more strongly engaged by tasks requiring internal control of movements than by tasks that are externally structured. The results suggest that this task-dependent variation of SMA activity is reduced in Parkinson's disease. A failing capacity to adapt SMA activity to different task demands has previously been suggested by evidence from positron emission tomography studies using similar tasks.

Adult↗
PubMed1996

[Functional MRI: imaging of motor cortex function].

OBJECTIVE: To image the motor cortex with functional MRI (fMRI), and locate the activated area with the proportional grid of Talairach. DESIGN: Descriptive. SETTING: St. Radboud Academic Hospital Nijmegen. METHODS: In ten volunteers functional images of the motor cortex were made during execution of a motor task (finger movements). From the functional images the positions of activated areas were calculated using the 3D Talairach grid system. RESULTS: fMRI of the motor cortex was possible using a 1.5 T MRI scanner. Task activation of the motor cortex gave a signal increase in Brodmann's area 4, the precentral gyrus. CONCLUSION: Imaging of the active motor cortex with fMRI is feasible. The use of the 3D Talairach proportional grid system for the calculation of the position of an activated area in the motor cortex is possible with adequate accuracy.

Adult↗