Functional imaging and electrophysiological data from patients with primary dystonia reveal widespread abnormalities in brain areas associated with higher motor functions but to date there has been ...little investigation of the functional consequences of these abnormalities. The aim of this study was to use a battery of tests of praxis, based on those tests used in routine clinical examination, to uncover evidence of higher motor dysfunction in patients with primary cervical dystonia.
Praxis was assessed in 13 patients with primary cervical dystonia without hand involvement and in 29 age and sex matched controls. A semiquantitative praxis assessment was used which combined timed tests of meaningful and meaningless movements with copying of transitive and intratransitive hand movements and pantomime of tool use. Control tasks consisted of evaluation of motor speed, strength and a number of additional cognitive tasks.
Patients made significantly more errors in copying meaningless gestures and were slow in the performance of meaningless sequences of hand movements. Copying meaningful gestures and performance of meaningful sequences of hand movements were normal.
This study has identified a discrete deficit in praxis in dystonia patients and suggests additional functional consequences from the widespread pathophysiological abnormalities seen in primary dystonia.
Bradykinesia represents one of the cardinal and most incapacitating features of Parkinson’s disease (PD). In this context, investigating the cerebral control mechanisms for limb movements and ...defining the associated functional neuroanatomy is important for understanding the impaired motor activity in PD. So far, most studies have focused on motor control of upper limb movements in PD. Ankle movement functional MRI (fMRI) paradigms have been used to non-invasively investigate supraspinal control mechanisms relevant for lower limb movements in healthy subjects, patients with Multiple sclerosis, and stroke. Using such an active and passive paradigm in 20 PD patients off medication (mean age 66.8 ± 7.2 years) and 20 healthy controls (HC; mean age 62.3 ± 6.9 years), we here wished to probe for possible activation differences between PD and HC and define functional correlates of lower limb function in PD. Active ankle movement versus rest was associated with a robust activation pattern in expected somatotopy involving key motor areas both in PD and HC. However, contrasting activation patterns in patients versus controls revealed excess activation in the patients in frontal regions comprising pre-supplementary motor areas (pre-SMA) and SMA proper. The extent of SMA activation did not correlate with behavioural parameters related to gait or motor function, and no differences were seen with the passive paradigm. This finding might be indicative of higher demand and increased effort in PD patients to ensure adequate motor function despite existing deficits. The missing correlation with behavioural variables and lack of differences with the passive paradigm suggests that this excess activation is not exclusively compensatory and also not hard-wired.
Holmes' tremor is characterized by a combination of rest, postural, and kinetic tremor that is presumably caused by interruption of cerebello-thalamo-cortical and nigrostriatal pathways. Medical ...treatment remains unsatisfactory.
A 16-year-old girl presented with Holmes' tremor caused by a transient midbrain abnormality on magnetic resonance imaging (MRI). To explore the discrepancy between persistent tremor and resolved MRI changes, we performed dopamine transporter single-photon emission computed tomography (DaT-SPECT) with a 123I-ioflupane that revealed nearly absent DaT binding in the right striatum. Levodopa dramatically improved the tremor.
This is only the second report of a transient midbrain MRI abnormality disrupting nigrostriatal pathways. The case highlights the sometimes limited sensitivity of morphologic imaging for identifying the functional consequences of tissue damage and confirms that DaT imaging may serve as a predictor for levodopa responsiveness in Holmes' tremor.
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