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PubMed1999

Re-emergent tremor of Parkinson's disease.

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.

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PubMed1998

Time-frequency analysis of tremors.

Time-frequency analysis methods were applied to surface EMG records of patients with tremor. Variation in tremor frequency over time and between muscles was measured in subjects with Parkinson's disease (n = 20), essential tremor (n = 8) and psychogenic tremor (n = 7). The effect of externally paced voluntary contractions on tremor frequency was also characterized. Psychogenic tremor involved fewer limbs and fewer limb segments than Parkinson's disease rest tremor and essential tremor, and its frequency was less consistent. In all subject groups, muscles within a single extremity generally had identical instantaneous frequencies. Frequency dissociation, used here to describe a modal contemporaneous frequency difference of more than 0.1 Hz between two extremities, was demonstrated for symptomatic tremors in 17 subjects with Parkinson's disease, in four subjects with essential tremor and in none of the subjects with psychogenic tremor. Dissociation between tapping and tremor limbs was demonstrated in an additional two subjects with Parkinson's disease and in all four remaining essential tremor subjects but in none of the psychogenic tremor subjects. Tremor maintained a different frequency from the tapping limb in Parkinson's disease and essential tremor, and its frequency in many cases shifted by at least 0.3 Hz compared with the non-tapping condition. For example, arm and leg tremors at 5.2 and 3.8 Hz, respectively, shifted to a common frequency of 4.6 Hz in one Parkinson's disease patient while using the contralateral arm to perform a tapping movement in time with a metronome at 2 Hz. These observations suggest the existence of distinct oscillator systems projecting to each tremoring limb, which can be linked to a variable degree, and which can be modulated by voluntary activation of another limb. Psychogenic tremor was not maintained while tapping with the contralateral arm: tremor either dissipated or shifted to the metronome's frequency. The latter response was also seen in normal volunteers mimicking tremor, but not in Parkinson's disease or essential tremor. We suggest that maintenance of phasic contraction in psychogenic tremor is not due to intrinsic instability of the motor system and that muscle activation in involved limbs may instead be synchronized to a common oscillator. As in voluntary movements, only a single rhythm may be easily followed at a time. Coexistence of muscle groups phasically contracting at consistently different instantaneous frequencies is evidence against a psychogenic aetiology of tremor.

Activity Cycles↗
PubMed2001

Clinical correlates of action tremor in Parkinson disease.

BACKGROUND: Action tremor is often noted in patients with Parkinson disease (PD), yet the clinical correlates of this type of tremor have been the focus of few studies. It is not clear whether this action tremor is a manifestation of the underlying basal ganglia disease. OBJECTIVE: To determine whether the severity of action tremor in PD is associated with age, age at disease onset, disease duration, levodopa dose, severity of rest tremor, or other motor (ie, bradykinesia, rigidity) and nonmotor manifestations of PD. METHODS: Patients with PD (N = 197) were ascertained as part of a familial aggregation study. All patients underwent a neurological examination. Rest tremor was rated with the Unified Parkinson Disease Rating Scale; and action tremor, with the Washington Heights-Inwood Genetic Study of Essential Tremor Rating Scale. RESULTS: Action tremor was present in 184 (93.4%) of 197 patients. Four patients (2%) met criteria for definite essential tremor. The action tremor score was not associated with age, age at onset, or disease duration. The action tremor score was associated with the rest tremor score (r = 0.37; P<.001), and more strongly with the ipsilateral than contralateral rest tremor score. The association between the action tremor score and the rest tremor score was diminished but still significant (r = 0.21, P<.02) even when we excluded these 63 patients with re-emergent tremor. Neither the action nor the rest tremor score was associated with the bradykinesia or rigidity scores, Hoehn and Yahr scale score, or modified Mini-Mental State Examination score. CONCLUSIONS: Action tremor was associated with rest tremor in PD, suggesting that, at least in part, action tremor is a manifestation of the underlying basal ganglia disease. Neither tremor was associated with other motor and nonmotor manifestations of PD. This in turn suggests that tremor in PD may represent an underlying pathophysiological process different from these other manifestations.

Adult↗
PubMed1997

Hand tremor in patients with spasmodic torticollis.

The occurrence of hand tremors in patients with spasmodic torticollis (ST) was investigated in 55 patients by clinical and quantitative measurements. Ten patients had first-order or second-order relatives affected with postural tremor. Although 40% of the patients had a medical history and clinical findings for mild postural and action tremor of the hands, only four had moderate tremor amplitudes. One patient had a severe tremor, including resting tremor, and two had mild voice tremor. A positive correlation was found between hand and head tremor. Patients with hand tremor were younger at the onset of ST than were those without. The mean amplitudes of postural tremor were only slightly higher than for the controls and much smaller than those found in classic essential tremor. The tremor caused only mild disabilities. The tremor frequencies were indistinguishable from physiologic tremor. Further analysis of the tremor records showed evidence for physiologic tremor mechanisms only. We conclude that slightly enhanced postural hand tremors are common in ST but have a low amplitude and are only rarely clinically relevant for ST patients. Although the present data support the notion of an enhanced risk of postural tremor in families of patients affected with ST, none of the criteria allowed the separation of the hand tremor of ST from other postural/action tremors and especially from enhanced physiologic tremor. Thus, the present data do not support the classification of hand tremor in ST as either "dystonic" or essential tremor.

Adolescent↗
PubMed2001

A cross-over clinical and electromyographic assessment of treatment for parkinsonian tremor.

BACKGROUND: Whether dopaminergic and anticholinergic drugs exert influence on parkinsonian rest and postural tremor is a subject of debate. Different types of tremor may be influenced differently by the drugs. The aim of this study was to reevaluate the differential effects of levodopa and anticholinergic drugs on parkinsonian tremor in different limb positions and on different types of postural tremor. METHODS: Thirty-eight patients with parkinsonian resting tremor and postural tremor were included in this study. Patients were divided into two groups according to the electromyographic pattern of the postural tremor. We found fast synchronous postural tremor (>7 Hz) in 16 patients, and slow alternating postural tremor in 22 patients. The tremor was scored clinically in each limb position using the Webster Tremor Scale. Surface electromyographic recordings from the most involved limb in all positions were also performed. The patients were randomly assigned to levodopa (one 250/50-mg tablet), or to biperiden (one 3-mg tablet). Tremor was assessed by clinical and electromyographic examinations at base line 1h following ingestion of the drug. The subjective tremor improvement was also assessed. RESULTS: We found that levodopa had a good effect on the amplitude of the resting tremor, while the effect of biperiden was weaker. Both levodopa and biperiden has less effect on postural tremor. However, levodopa's effect was better than that of biperiden. Levodopa and biperiden had better effect on slow alternating postural tremor than on fast synchronous postural tremor. They had no effect on kinetic and intention tremors. CONCLUSIONS: Levodopa and anticholinergic drugs have differing effects on both resting and postural tremor Also, the different categories of postural tremor respond differently to treatment. The mechanisms underlying resting parkinsonian tremor may be different from those underlying postural, kinetic and intention tremor. Moreover, the mechanisms underlying different types of postural tremor may be different.

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