Abstract The pathophysiology of dystonia has been best studied in patients with focal hand dystonia. A loss of inhibitory function has been demonstrated at spinal, brainstem and cortical levels. Many ...cortical circuits seem to be involved. One consequence of the loss of inhibition is a failure of surround inhibition, and this appears to directly lead to overflow and unwanted muscle spasms. There are mild sensory abnormalities and deficits in sensorimotor integration; these also might be explained by a loss of inhibition. Increasing inhibition may be therapeutic. A possible hypothesis is that there is a genetic loss of inhibitory interneurons in dystonia and that this deficit is a substrate on which other factors can act to produce dystonia. This article is part of a Special Issue entitled “Advances in dystonia”.
Abstract Functional or psychogenic movement disorders are common and disabling, and sometime difficult to diagnose. The history and physical exam can give positive features that will support the ...diagnosis, which should not be based solely on exclusion. Some clues in the history are sudden onset, intermittent time course, variability of manifestation over time, childhood trauma, history of other somatic symptom and secondary gain. Anxiety and depression are common, but not necessarily more than the general population. On examination, distraction and suggestibility may be present. There are specific signs that should be looked for with different types of movements. For example, with tremor, change in frequency over time and entrainment are common features. With myoclonus, the movements might be complex in type with long latencies to stimulus induced jerks. Gait disorders show good balance despite claims to the contrary. Functional dystonia still remains a challenging diagnosis in many circumstances, although fixed dystonia is one sign more likely to be functional.
Abstract Tourette Syndrome is a disorder characterized by tics. It typically begins in childhood and often improves in adult life. Tics are best described as voluntary movements made automatically so ...that volition is not ordinarily appreciated. There is frequently an urge, sometimes in the form of a specific sensory feeling (sensory tic), that precedes the tic. Patients say that they make the tic in order to reduce the urge, although shortly after the tic, the urge recurs. The sensory feeling may arise due to defective sensory habituation. Since tics relieve the urge, this can be considered rewarding, and repetition of this behavior may perpetuate the tic as a habit. Tourette Syndrome affects boys more than girls and is associated with attention deficit hyperactivity disorder and obsessive compulsive disorder. Although Tourette Syndrome often appears to be autosomal recessive in inheritance, it has been difficult to find any abnormal genes. There is a loss of inhibition in these patients and recent studies show abnormalities in brain GABA. Certainly there is also an abnormality in dopamine function and dopamine blocking agents are effective therapy. In severe drug-refractory patients, deep brain stimulation can be effective.
Parkinson's disease is a chronic progressive neurodegenerative disorder characterized by resting tremor, slowness of movements, rigidity, gait disturbance and postural instability. Most ...investigations on Parkinson's disease focused on the basal ganglia, whereas the cerebellum has often been overlooked. However, increasing evidence suggests that the cerebellum may have certain roles in the pathophysiology of Parkinson's disease. Anatomical studies identified reciprocal connections between the basal ganglia and cerebellum. There are Parkinson's disease-related pathological changes in the cerebellum. Functional or morphological modulations in the cerebellum were detected related to akinesia/rigidity, tremor, gait disturbance, dyskinesia and some non-motor symptoms. It is likely that the major roles of the cerebellum in Parkinson's disease include pathological and compensatory effects. Pathological changes in the cerebellum might be induced by dopaminergic degeneration, abnormal drives from the basal ganglia and dopaminergic treatment, and may account for some clinical symptoms in Parkinson's disease. The compensatory effect may help maintain better motor and non-motor functions. The cerebellum is also a potential target for some parkinsonian symptoms. Our knowledge about the roles of the cerebellum in Parkinson's disease remains limited, and further attention to the cerebellum is warranted.
Abstract This review deals with the physiology of the initiation of a voluntary movement and the appreciation of whether it is voluntary or not. I argue that free will is not a driving force for ...movement, but a conscious awareness concerning the nature of the movement. Movement initiation and the perception of willing the movement can be separately manipulated. Movement is generated subconsciously, and the conscious sense of volition comes later, but the exact time of this event is difficult to assess because of the potentially illusory nature of introspection. Neurological disorders of volition are also reviewed. The evidence suggests that movement is initiated in the frontal lobe, particularly the mesial areas, and the sense of volition arises as the result of a corollary discharge likely involving multiple areas with reciprocal connections including those in the parietal lobe and insular cortex.
Abstract Bradykinesia is the most important feature contributing to motor difficulties in Parkinson’s disease (PD). However, the pathophysiology underlying bradykinesia is not fully understood. One ...important aspect is that PD patients have difficulty in performing learned motor skills automatically, but this problem has been generally overlooked. Here we review motor automaticity associated motor deficits in PD, such as reduced arm swing, decreased stride length, freezing of gait, micrographia and reduced facial expression. Recent neuroimaging studies have revealed some neural mechanisms underlying impaired motor automaticity in PD, including less efficient neural coding of movement, failure to shift automated motor skills to the sensorimotor striatum, instability of the automatic mode within the striatum, and use of attentional control and/or compensatory efforts to execute movements usually performed automatically in healthy people. PD patients lose previously acquired automatic skills due to their impaired sensorimotor striatum, and have difficulty in acquiring new automatic skills or restoring lost motor skills. More investigations on the pathophysiology of motor automaticity, the effect of L-dopa or surgical treatments on automaticity, and the potential role of using measures of automaticity in early diagnosis of PD would be valuable.
Evolving concepts on bradykinesia Bologna, Matteo; Paparella, Giulia; Fasano, Alfonso ...
Brain,
03/2020, Letnik:
143, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Bradykinesia is one of the cardinal motor symptoms of Parkinson's disease and other parkinsonisms. The various clinical aspects related to bradykinesia and the pathophysiological mechanisms ...underlying bradykinesia are, however, still unclear. In this article, we review clinical and experimental studies on bradykinesia performed in patients with Parkinson's disease and atypical parkinsonism. We also review studies on animal experiments dealing with pathophysiological aspects of the parkinsonian state. In Parkinson's disease, bradykinesia is characterized by slowness, the reduced amplitude of movement, and sequence effect. These features are also present in atypical parkinsonisms, but the sequence effect is not common. Levodopa therapy improves bradykinesia, but treatment variably affects the bradykinesia features and does not significantly modify the sequence effect. Findings from animal and patients demonstrate the role of the basal ganglia and other interconnected structures, such as the primary motor cortex and cerebellum, as well as the contribution of abnormal sensorimotor processing. Bradykinesia should be interpreted as arising from network dysfunction. A better understanding of bradykinesia pathophysiology will serve as the new starting point for clinical and experimental purposes.
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