Re-emergent tremor of Parkinson's disease.
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OBJECTIVE: To characterise postural tremors in patients with Parkinson's disease. Rest tremor is a well recognised cardinal symptom of Parkinson's disease, but postural tremors associated with the disease may cause more disability than the more typical rest tremor. Postural tremor of Parkinson's disease has been attributed to enhanced physiological tremor, clonus, or coexistent essential tremor. It is postulated that one type of postural tremor in Parkinson's disease represents a rest tremor that re-emerges after a variable delay while maintaining posture, hence "re-emergent tremor". METHODS: Accelerometry, peak frequency, peak frequency amplitude, root mean square (RMS) amplitude, and latency were determined in 18 patients (mean age: 63.2 (SD 9.8) years) with Parkinson's disease who had clinically evident postural tremor, 20 (mean age: 66.9 (SD 5. 8) years) with typical essential tremor, and seven (mean age: 68.7 (SD 15.3) years) with the combination of pre-existing essential tremor and subsequent Parkinson's disease (essential tremor/Parkinson's disease). Latency, the time interval starting with the assumption of an outstretched posture and ending with the onset of postural tremor, was measured by marking the start time by a pulse produced from interrupting a beam to a photocell when the arm reached a horizontal position. RESULTS: The latency for the re-emergent tremor (9.37 (SD 10.66) s), present in 12 of 18 patients with Parkinson's disease, was significantly (p<0.0005) longer than the latency for postural tremor of essential tremor (1.29 s in one patient, absent in 19 others); five of seven essential tremor/Parkinson's disease patients had an observed latency (6.57 (SD 8.23 s) which was also significantly (p<0.005) longer than that for essential tremor. There was no difference in the mean tremor frequency ( approximately 5.5 Hz) between the re-emergent tremor and the more typical Parkinson's disease rest tremor. The amplitudes were generally higher for the postural tremor associated with Parkinson's disease compared with those of essential tremor. CONCLUSION: These studies suggest that the re-emergent tremor of Parkinson's disease can be differentiated from the postural tremor of essential tremor and that it may share pathophysiological mechanisms with the more typical rest tremor. (+info)
Reorganization in the cutaneous core of the human thalamic principal somatic sensory nucleus (Ventral caudal) in patients with dystonia.
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A wide range of observations suggest that sensory inputs play a significant role in dystonia. For example, the map of the hand representation in the primary sensory cortex (area 3b) is altered in monkeys with dystonia-like movements resulting from overtraining in a gripping task. We investigated whether similar reorganization occurs in the somatic sensory thalamus of patients with dystonia (dystonia patients). We studied recordings of neuronal activity and microstimulation-evoked responses from the cutaneous core of the human principal somatic sensory nucleus (ventral caudal, Vc) of 11 dystonia patients who underwent stereotactic thalamotomy. Fifteen patients with essential tremor who underwent similar procedures were used as controls. The cutaneous core of Vc was defined as the part of the cellular thalamic region where the majority of cells had receptive fields (RFs) to innocuous cutaneous stimuli. The proportion of RFs including multiple parts of the body was greater in dystonia patients (29%) than in patients with essential tremor (11%). Similarly, the percentage of projected fields (PFs) including multiple body parts was higher in dystonia patients (71%) than in patients with essential tremor (41%). A match at a thalamic site was said to occur if the RF and PF at that site included a body part in common. Such matches were significantly less prevalent in dystonia patients (33%) than in patients with essential tremor (58%). The average length of the trajectory where the PF included a consistent, cutaneous RF was significantly longer in patients with dystonia than in control patients with essential tremor. The findings of sensory reorganization in Vc thalamus are congruent with those reported in the somatic sensory cortex of monkeys with dystonia-like movements resulting from overtraining in a gripping task. (+info)
A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor.
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BACKGROUND: Deep-brain stimulation through an electrode implanted in the thalamus was developed as an alternative to thalamotomy for the treatment of drug-resistant tremor. Stimulation is thought to be as effective as thalamotomy but to have fewer complications. We examined the effects of these two procedures on the functional abilities of patients with drug-resistant tremor due to Parkinson's disease, essential tremor, or multiple sclerosis. METHODS: Sixty-eight patients (45 with Parkinson's disease, 13 with essential tremor, and 10 with multiple sclerosis) were randomly assigned to undergo thalamotomy or thalamic stimulation. The primary outcome measure was the change in functional abilities six months after surgery, as measured by the Frenchay Activities Index. Scores for this index can range from 0 to 60, with higher scores indicating better function. Secondary outcome measures were the severity of tremor, the number of adverse effects, and patients' assessment of the outcome. RESULTS: Functional status improved more in the thalamic-stimulation group than in the thalamotomy group, as indicated by increases in the score for the Frenchay Activities Index (from 31.4 to 36.3 and from 32.0 to 32.5, respectively; difference between groups, 4.4 points; 95 percent confidence interval, 2.0 to 6.9). After adjustment for base-line characteristics, multivariate analysis also showed that the thalamic-stimulation group had greater improvement (difference between groups, 5.1 points; 95 percent confidence interval, 2.3 to 7.9). Tremor was suppressed completely or almost completely in 27 of 34 patients in the thalamotomy group and in 30 of 33 patients in the thalamic-stimulation group. One patient in the thalamic-stimulation group died perioperatively after an intracerebral hemorrhage. With the exception of this incident, thalamic stimulation was associated with significantly fewer adverse effects than thalamotomy. Functional status was reported as improved by 8 patients in the thalamotomy group, as compared with 18 patients in the thalamic-stimulation group (P=0.01). CONCLUSIONS: Thalamic stimulation and thalamotomy are equally effective for the suppression of drug-resistant tremor, but thalamic stimulation has fewer adverse effects and results in a greater improvement in function. (+info)
Effect of low and high frequency thalamic stimulation on sleep in patients with Parkinson's disease and essential tremor.
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Continuous high frequency stimulation of the ventral intermediate nucleus of the thalamus (Vim), delivered through surgically implanted quadripolar electrodes, alleviates tremor in Parkinson's disease (PD) and essential tremor (ET). The Vim is adjacent to the thalamic reticular nuclei, where sleep spindles originate according to animal models. In order to determine whether Vim stimulation affects sleep spindles, six patients (4 PD, 2 ET), aged 60-69 years, were recorded on a control night and a stimulation night (130 Hz, 2-3 V; right stimulation in five patients and bilateral stimulation in one patient). Stimulation did not modify sleep quality or architecture. Sleep spindles were present and symmetrical in five out of six patients under stimulation. However, in one patient with a sustained 'thalamotomy-like effect' that abolished tremor, spindles were asymmetrical even without stimulation. In each patient, spindle density was similar on both nights (mean+/- SEM: 2.25+/-0. 61 spindles per min of stage 2 sleep vs. 1.84+/-0.31). In an attempt to promote sleep two different patterns of stimulation were applied in the region of ventrooralis posterior and reticularis nuclei in five patients in the awake state. Continuous low frequency stimulation (5 Hz, 0.1 V), and repeated trains of 15 Hz for 1 s every 15 s mimicking the pattern of physiological spindles, each failed to induce sleep or cortical synchronization. We conclude that Vim stimulation, unlike thalamotomy, selectively reduces tremor without altering sleep or sleep spindles. Our results also suggest that low frequency stimulation applied in the region of the reticular nuclei does not induce sleep. (+info)
Essential tremor and cerebellar dysfunction clinical and kinematic analysis of intention tremor.
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The cerebellum is assumed to play a major role in the pathophysiology of essential tremor (ET). As intention tremor is considered one of the classical features of cerebellar disease, we have assessed a large group of patients with ET for the semiology of the tremor and have performed objective quantitative analysis of a grasping movement in patients with ET, cerebellar disease and a normal control group. We found 25% of the patients to have a moderate or severe kinetic tremor with clear-cut features of a classical intention tremor. Another 33% of the patients had a mild intentional component of their kinetic tremor. Patients with intention tremor (ET(IT)) did not differ from those with predominant postural tremor (ET(PT)) with respect to alcohol sensitivity of the tremor and the frequency of a family history. ET(IT) patients were older and more often showed head and trunk involvement. The onset of this intention tremor has been assessed retrospectively. It was found to begin at a randomly distributed time interval after the onset of the postural tremor, but older patients had a shorter time to development of intention tremor. Quantitative accelerometry of postural tremor showed similar tremor frequencies in both patient groups, but ET(IT) patients had a slightly larger tremor amplitude. Quantitative analysis of a grasping movement using an infrared-camera system was performed in two subgroups of the patients with ET(PT) and ET(IT) and control groups with cerebellar disease or normal subjects. The intention tremor could be quantified objectively as an increased amplitude of curvature during the deceleration and target phase of the movement. The amplitude measurements of intention tremor were clearly abnormal and of comparable magnitude for ET(PT) and cerebellar disease. Additionally, the patients with ET(IT) had a significantly slowed grasping movement during the deceleration and target period. Hypermetria was significantly increased for the patients with ET(IT) and cerebellar disease. We conclude that intention tremor is a feature of ET. ET(IT) patients have abnormalities of their upper limb function compatible with cerebellar disease. This suggests that patients with more advanced ET show abnormalities of cerebellar functions. (+info)
Clinical-molecular study of a family with essential tremor, late onset seizures and periodic paralysis.
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We report the clinical features of, and the molecular study performed on, a Spanish family with essential tremor (ET), late onset epilepsy and autosomal dominant hypokalemic periodic paralysis (hypoPP). The presence of hypoPP in this kindred suggested an ion channel as a candidate gene for ET. Our study identified an Arg528His CACNL1A3 mutation in patients with hypoPP, and excluded this mutation as the cause of tremor or epilepsy in this kindred. (+info)
Arm tremor in cervical dystonia differs from essential tremor and can be classified by onset age and spread of symptoms.
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The pathophysiology of arm tremor in patients with cervical dystonia (CD) and its relationship to other types of tremor is unclear. In the present study, we have compared the tremor in these patients with that seen in patients with essential tremor (ET) using two neurophysiological techniques: the triphasic EMG pattern accompanying ballistic wrist flexion movements; and reciprocal inhibition between forearm muscles. During ballistic wrist flexion movements, the latency of the second agonist EMG burst was later in ET than CD patients. This suggests that the mechanism of the arm tremor in CD may differ from that in ET. There was no group difference between reciprocal inhibition in patients with ET or CD. However, there was much more variability in the data from patients with CD. Because of this, we subdivided the CD patients into two groups, group A with normal levels of presynaptic inhibition and group B with reduced or absent presynaptic inhibition. A posteriori, it turned out that the patients in these two subgroups had similar clinical symptoms, but different clinical histories. The arm tremor of patients in group A started simultaneously with torticollis (mean onset age of arm tremor 40 years +/- 20.7 SD, interval between onset of arm tremor and torticollis 0 +/- 2.9 years) whereas it began much earlier (mean onset age 14 years +/- 6 SD) and preceded onset of torticollis by a longer interval (21.6 +/- 17.5 years) in patients of group B. Patients in group A also had less co-contraction in their ballistic wrist movements between the first agonist and the antagonist burst than those patients in group B. We conclude that arm tremor in patients with CD may have a mechanism different from that seen in patients with ET. Moreover, the data imply that there are two subgroups of CD patients with arm tremor, one with a late and simultaneous onset of arm tremor and torticollis (group A), and another with an early onset of arm tremor and later development of torticollis (group B). These groups do not correspond to the currently proposed clinical subdivision of 'dystonic tremor' and 'tremor associated with dystonia'. (+info)
The gait disorder of advanced essential tremor.
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Gait disturbances of patients with essential tremor (ET) have been described anecdotally, but have never been investigated quantitatively. Recent studies provided evidence for a cerebellar-like hand tremor in some patients with ET. Therefore, we designed a study to assess cerebellar-like abnormalities of leg function. Twenty-five patients with ET, eight patients with cerebellar diseases (CD) and 21 age-matched healthy subjects were studied for their normal and tandem gait using a three-dimensional gait analysis system. During normal walking, CD and ET patients showed only slight abnormalities. However, ET patients exhibited abnormalities in tandem gait with an increased number of mis-steps and a broad-based, ataxic and dysmetric gait which was indistinguishable from the findings in CD. When ET patients were separated into groups of those with or without intention tremor of the hands, the gait disorder was found to be much more pronounced in the intention tremor group. Patients with this gait disorder were more severely disturbed in their activities of daily living, and suffer from an advanced stage of ET. The present results quantitatively describe a gait disturbance in advanced ET which affects tandem gait, but leaves normal gait almost unaffected. This is strong evidence for a cerebellar-like disturbance in ET. (+info)