Dysfunction of dopaminergic pathways in dystonia.
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Animals↗
Biomedical subjects
Jonathan W Mink
Publications and source records attributed to Jonathan W Mink.
Progressive myoclonus in a child with a deep cerebellar mass.
Myoclonus is often associated with pathology of the cerebellum. However, the site of neurons responsible for the generation of myoclonus in cerebellar disease is not known. The authors report a young child with myoclonus associated with a ganglioglioma in the region of the deep cerebellar white matter and cerebellar nuclei. They hypothesize that abnormal paroxysmal discharge of neurons in the cerebellar nuclei can generate myoclonus.
Cerebellar Ataxia↗
The Basal Ganglia and involuntary movements: impaired inhibition of competing motor patterns.
The basal ganglia are organized to facilitate voluntary movements and to inhibit competing movements that might interfere with the desired movement. Dysfunction of these circuits can lead to movement disorders that are characterized by impaired voluntary movement, the presence of involuntary movements, or both. Current models of basal ganglia function and dysfunction have played an important role in advancing knowledge about the pathophysiology of movement disorders, but they have not contained elements sufficiently specific to allow for understanding the fundamental differences among different involuntary movements, including chorea, dystonia, and tics. A new model is presented here, building on existing models and data to encompass hypotheses of the fundamental pathophysiologic mechanisms underlying chorea, dystonia, and tics.
Basal Ganglia↗
Different effects of unilateral versus bilateral subthalamic nucleus stimulation on walking and reaching in Parkinson's disease.
The purpose of this study was to determine the effects of unilateral versus bilateral subthalamic nucleus (STN) stimulation on quantitative measures of walking and reaching in Parkinson's disease (PD). We used kinematic measures and the Unified Parkinson's Disease Rating Scale (UPDRS) motor subscale (subscale III) to evaluate the movement of 6 people with PD who had bilateral STN stimulators implanted for at least 6 months and withheld their anti-parkinson medication for at least 8 hours. Subjects were studied with both stimulators off, one on, and both on. Kinematic data were collected as subjects walked, reached to a target, and were rated using the UPDRS motor subscale. STN stimulation improved walking speed and stride length, with the greatest benefit from bilateral stimulation. Reaching speed was improved by unilateral STN stimulation alone, with no additive effect of bilateral stimulation. UPDRS motor subscale ratings paralleled the kinematic findings. STN stimulation did not restore PD subjects' movements to the level of age-matched controls. Overall, these results provide further evidence that the basal ganglia pathways involved in control of walking and reaching may be distinct. We speculate that basal ganglia may influence walking through bilateral pedunculopontine projections and reaching through ipsilateral thalamocortical projections. Our findings also suggest that maximal improvement of walking requires bilateral rather than unilateral STN stimulation.
Adult↗
Effects of pallidotomy and levodopa on walking and reaching movements in Parkinson's disease.
We examined the effects of levodopa and unilateral pallidotomy on quantitative measures of walking and reaching in Parkinson's disease (PD). We also compared quantitative measures of movement with standard clinical rating scales. We used kinematic measures and the Unified Parkinson's Disease Rating Scale (UPDRS) motor subscale (subscale III) to evaluate the movement of 10 people with PD. Subjects were tested after withholding PD medications for at least 8 hours and again 30 to 45 minutes after taking the first morning dose of levodopa. They were studied in this manner before unilateral pallidotomy and then 3.5 to 10 months after surgery. The UPDRS motor subscale was performed in each state. Kinematic data were collected as subjects reached to a target and walked. The UPDRS motor subscale ratings were similar to those reported in the literature: pallidotomy improved the overall motor score and the contralateral bradykinesia + rigidity score, but not the gait + posture score. In contrast, kinematic measures demonstrated that levodopa and pallidotomy had different effects on walking and reaching speed. Both treatments improved walking speed, and the effect was additive. Levodopa improved reaching speed before pallidotomy but did not improve it as much after pallidotomy. Additionally, pallidotomy had inconsistent effects on reaching; some subjects were faster and others were slower. The subjects who initially reached more slowly improved after pallidotomy; the subjects who initially reached more normally (faster) worsened after pallidotomy. On the basis of our results, we speculate that basal ganglia output pathways that control walking and reaching may be distinct, such that bilateral projections to the pedunculopontine area influence walking, whereas ipsilateral thalamocortical projections influence reaching.
Aged↗
Classification and definition of disorders causing hypertonia in childhood.
OBJECTIVE: This report describes the consensus outcome of an interdisciplinary workshop that was held at the National Institutes of Health in April 2001. The purpose of the workshop and this article are to define the terms "spasticity," "dystonia," and "rigidity" as they are used to describe clinical features of hypertonia in children. The definitions presented here are designed to allow differentiation of clinical features even when more than 1 is present simultaneously. METHODS: A consensus agreement was obtained on the best current definitions and their application in clinical situations. RESULTS: "Spasticity" is defined as hypertonia in which 1 or both of the following signs are present: 1) resistance to externally imposed movement increases with increasing speed of stretch and varies with the direction of joint movement, and/or 2) resistance to externally imposed movement rises rapidly above a threshold speed or joint angle. "Dystonia" is defined as a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. "Rigidity" is defined as hypertonia in which all of the following are true: 1) the resistance to externally imposed joint movement is present at very low speeds of movement, does not depend on imposed speed, and does not exhibit a speed or angle threshold; 2) simultaneous co-contraction of agonists and antagonists may occur, and this is reflected in an immediate resistance to a reversal of the direction of movement about a joint; 3) the limb does not tend to return toward a particular fixed posture or extreme joint angle; and 4) voluntary activity in distant muscle groups does not lead to involuntary movements about the rigid joints, although rigidity may worsen. CONCLUSION: We have provided a set of definitions for the purpose of identifying different components of childhood hypertonia. We encourage the development of clinical rating scales that are based on these definitions, and we encourage research to relate the degree of hypertonia to the degree of functional ability, change over time, and societal participation in children with motor disorders.
Child↗
Volumetric MRI in autism: can high-tech craniometry provide neurobiological insights?
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Autistic Disorder↗
Clinical features and comorbidity of mood fluctuations in Parkinson's disease.
Parkinson's disease (PD) patients commonly develop fluctuations in their motor responses to levodopa within several years of initiation of treatment; some also develop nonmotor fluctuations. The authors performed a case-control study comparing the frequency of comorbid symptoms in 70 PD patients who experienced clinically apparent mood changes during their motor "on" or "off" states with two control groups with no mood fluctuations. Mood fluctuators had significantly younger age at onset and longer disease duration and were significantly more likely to have dementia, psychosis, clinical depression, and motor complications. This association remained after removing effects of age and disease duration.
Adult↗