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PubMed2001

Quantitative and qualitative outcome measures after thalamic deep brain stimulation to treat disabling tremors.

OBJECTIVE: We studied outcome measures after unilateral and bilateral thalamic stimulation to treat disabling tremor resulting from essential tremor and Parkinson's disease. The surgical technique, qualitative and quantitative tremor assessments, stimulation parameters, locations of active electrodes, complications, and side effects are described and analyzed. METHODS: Forty-one patients with essential tremor or Parkinson's disease underwent implantation of 56 thalamic stimulators. Preoperative qualitative and quantitative tremor measurements were compared with those obtained after unilateral and bilateral surgery, with activated and deactivated stimulators. Stimulation parameters and stimulation-related side effects were recorded, and outcome measures were statistically analyzed. RESULTS: Qualitative measurements demonstrated significant improvement of contralateral upper-limb (P < 0.001), lower-limb (P < 0.01), and midline (P < 0.001) tremors after unilateral surgery. Ipsilateral arm tremor also improved (P < 0.01). No differences were observed with the Purdue pegboard task. Quantitative accelerometer measurements were correlated with qualitative assessments and confirmed improvements in contralateral resting (P < 0.001) and postural (P < 0.01) tremors and ipsilateral postural tremor (P < 0.05). Activities of daily living improved after unilateral surgery (P < 0.001) and additionally after bilateral surgery (P < 0.05). Adjustments of the pulse generator were required more frequently for tremor control than for amelioration of side effects. Bilateral thalamic stimulation caused more dysarthria and dysequilibrium than did unilateral stimulation. Stimulation-related side effects were reversible for all patients. Stimulation parameters did not change significantly with time. A significantly lower voltage and greater pulse width were used for patients with bilateral implants. CONCLUSION: Unilateral thalamic stimulation and bilateral thalamic stimulation are safe and effective procedures that produce qualitative and quantitative improvements in resting, postural, and kinetic tremor. Thalamic stimulation-related side effects are mild and reversible.

Activities of Daily Living↗
PubMed1995

Essential tremor and its variants.

Essential tremor is the commonest of movement disorders. Although sometimes prefaced with the term 'benign', it often causes significant disability. Diagnosis is based on the clinical finding of a postural tremor, predominantly affecting the upper limbs, that is absent at rest and not associated with extrapyramidal or cerebellar signs. There are, as yet, no specific anatomical, physiological, biochemical or genetic markers for the condition. Postural limb tremors, clinically indistinguishable from essential tremor, may occur in patients who have, or will later develop, other neurological conditions; whether such patients have essential tremor is a matter of controversy that will only be resolved with a better understanding of the pathophysiology of essential tremor. Positron emission tomography in patients with essential tremor reveals increased cerebellar activity even at rest, a finding that is consistent with the cerebellum having an important role in the generation of tremor. Abnormal cerebellar function has also been invoked to account for the abnormal manner in which patients with essential tremor perform rapid voluntary wrist movements. Molecular genetic studies in hereditary essential tremor have been initiated, but with negative results so far. Several new drug treatments have been tried, but with limited success; the role of thalamic stimulation and botulinum toxin in the treatment of essential tremor remains to be judged.

Cerebellum↗
PubMed2001

Chronic mercury exposure examined with a computer-based tremor system.

Tremor is being increasingly evaluated by quantitative computer-based systems to differentiate its causes. In this study, a group of mercury-exposed workers were assessed to determine whether tremor characteristics differed by exposure level. Workers were classified into two groups: those with an average urine mercury concentration below the American Conference of Government Industrial Hygienist Biological Exposure Index of 35 micrograms/g creatinine, and those with an average urine mercury concentration above the Biological Exposure Index. Tremor characteristics (including intensity, harmonic index, center frequency, standard deviation of the center frequency, and tremor index) were measured and recorded with a computer-based tremor system. Sixteen of 17 workers who were potentially exposed to mercury participated in the study. Three workers had a mean urine mercury concentration of 27.0 micrograms/g-creatinine and were assigned to the low-exposure group, and 13 workers had a mean urine mercury concentration of 200.2 micrograms/g-creatinine and were assigned to the high-exposure group. There was a statistically significant difference in the tremor index (which compiles five individual tremor parameters into a single value) between the two groups (P = 0.04; Wilcoxon's rank sum test). Other tremor characteristics did not differ significantly between the groups. Tremor index may be more useful than measures of individual tremor parameters in differentiating normal from subclinical pathological tremors among groups of workers with chronic mercury exposure.

Adult↗
PubMed1980

Inhibition and synchronisation of tremor induced by a muscle twitch.

The effects of a muscle twitch on the tremor of the extensor indicis muscle and of the tibial anterior muscle have been recorded in 14 patients with essential tremor and in 10 patients with Parkinson's disease. The muscle twitch evoked by the electrical stimulation of the motor nerve inhibits the tremor and synchronises it. The mean duration of the inhibition is 92.1 +/- 6.8 ms for essential tremor and 183.0 +/- 16.8 ms for Parkinsonian tremor. This inhibitory phase lasts longer when the muscle twitch is induced during the second half of the Parkinsonian tremor cycle. The effects of voluntary contraction and of unloading suggest that inhibition and resetting of the tremor can be attributed to the autogenic mechanism induced by Ib fibres discharges. The presence of a rhythmic inhibition in the cycle of Parkinsonian tremor accounts for the longer duration of the inhibitory phase. In practice, these techniques aid the diagnosis of tremor in these two conditions, for example they assist the identification of low frequency essential tremor and of postural tremor in Parkinson's disease.

Aged↗
PubMed1983

The response of essential tremor to propranolol: evaluation of clinical variables governing its efficacy on prolonged administration.

The factors influencing the response of essential tremor to prolonged administration of propranolol (120 mg daily for two weeks followed by 240 mg daily for a further two weeks) were investigated in a double-blind, cross-over, placebo-controlled study in 16 patients. Hand tremor was assessed by means of accelerometers with off-line computer analysis. Propranolol was found to be superior to placebo only at the higher dosage regimen (240 mg daily). At this dosage, the median reduction in tremor amplitude (as compared to the control value) was by 45%. The response to the drug (expressed as percentage change in tremor amplitude) was correlated positively with the control amplitude (rs = 0.71, p < 0.01) and negatively (but more weakly) with the control peak frequency of tremor (rs = -0.53, p < 0.05). In the patients with hand tremor greater than 6 x 10(-3) cm hand displacement the tremor amplitude was reduced by 65%, as compared to only 17% in patients whose tremor amplitude was below this limit. No statistically significant relationship could be found between percentage change in tremor amplitude and duration of the disorder, age of the patients, degree of cardiac beta-blockade or serum propranolol levels. The results suggest that patients with small tremor amplitude should not be treated with propranolol unless their tremor becomes severely aggravated under conditions of excessive adrenergic discharge.

Adult↗
PubMed1980

Importance of microstereoencephalotomy for tremor alleviation.

Application of the microelectrode technique in human stereotactic surgery, which is especially important for tremor control, is now routine for the procedure in our surgical theater. Neurons responsible for tremor generation can very delicately and exactly be identified within the ventralis intermedius nucleus (Vim) of the thalamus, which automatically determines the location of the minimum required thermocoagulation lesion to abolish tremor. Neurons with rhythmic burst discharges, which are synchronus in phase to the peripheral tremor, are organized in delicate somatotopic fashion within the Vim. Electrical stimulation of the neuron area through this microelectrode usually inhibits tremor of the corresponding area and a small thermocoagulation lesion, usually 3 mm in diameter, permanently abolishes tremor. These three findings, i.e., existence of rhythmic bursts, effect of the stimulation and surgical lesion, are the same in parkinsonian tremor, postural tremor and intention tremor. Physiological interpretation of different types of tremor will be proposed. In the cases of idiopathic neck tremor, a single Vim neuron corresponded to four neck muscles, i.e., bilateral sternocleidomastoid muscle (SCM) and bilateral posterior neck muscles, and most markedly to the controlateral posterior neck muscle and the ipsilateral SCM. Instrumentation of microstereoencephalotomy is also explained.

Aged↗
PubMed1994

Writing tremor after discrete cortical infarction.

BACKGROUND: Hand tremor is a rare manifestation of stroke, and writing tremor has not been reported to be produced by stroke. We describe a patient who developed a unilateral hand tremor mimicking primary writing tremor after discrete cerebral cortical infarction. CASE DESCRIPTION: A 67-year-old man developed mild right hemiparesis. Brain magnetic resonance imaging showed a discrete cortical infarct in the left frontal area. After recovery of motor power, the patient showed significant right hand tremor exclusively during writing or similar motor activities including tooth brushing or shaving. The tremor was temporarily alleviated by clonazepam but persisted until 7 months of follow-up. Medical history suggested that the patient had mild essential tremor, but he did not experience tremor on writing before the onset of stroke. CONCLUSIONS: This observation suggests that unilateral hand tremor mimicking primary writing tremor may be produced by cortical infarction. It remains unclear whether the patient's previous essential tremor played an additional role in the development of this symptom.

Aged↗
PubMed2003

Vagus nerve stimulation for essential tremor: a pilot efficacy and safety trial.

OBJECTIVE: To assess the safety and efficacy of vagus nerve stimulation (VNS) for essential tremor (ET). METHODS: This was a pilot open-treatment trial at three centers, with masked videotape tremor assessments. Inclusion required a severity score of 3 or 4 on the Tremor Rating Scale (TRS) in one or both hands. At baseline, tremor was assessed with TRS and Unified Tremor Rating Assessment (UTRA), accelerometry, and a videotape protocol. The VNS device was implanted with leads placed around the left cervical vagus nerve. Stimulation was adjusted over 4 weeks before the repeat tremor assessments. Two raters masked to the study visit scored the videotapes. RESULTS: Nine subjects participated, with a mean age of 65 years and a mean age at onset of tremor of 24. Investigators rated hand tremor as mildly improved (TRS 2.3 +/- 0.7 during VNS vs 3.0 +/- 0.4 during baseline, p = 0.06). Accelerometry-measured total power improved 50.2 +/- 31.8% (p < 0.01). Videotape tremor scores were highly correlated between the masked raters and revealed no changes in tremor scores with treatment. VNS was well tolerated, with the most common adverse events being stimulation related. CONCLUSIONS: VNS was judged by investigators to mildly improve upper extremity tremor. This finding was not confirmed in videotape scoring by masked raters. VNS is not likely to have a clinically meaningful effect on ET.

Adolescent↗
PubMed1985

Tremor in chronic alcoholism.

We examined 100 alcoholics who had had no alcohol for more than 21 days, 100 controls, and 50 patients with essential tremor. Three percent of the controls and 47% of the alcoholics had a postural tremor. Alcoholic tremor was never severe, and functional disability occurred in only 17% of patients. There was no relation to age or duration of drinking, and only 1% of the alcoholics had a family history of tremor compared with 46% in essential tremor. Tremor frequency was significantly greater in the alcoholics than in essential tremor. Propranolol therapy decreased tremor more in the alcoholics than in essential tremor. The tremor of chronic alcoholism differs from essential tremor.

Adult↗
PubMed1997

Clozapine in Parkinson's disease tremor. Effects of acute and chronic administration.

The effects of the acute administration of clozapine on parkinsonian mixed tremor (i.e., resting and postural tremors) were evaluated to establish clozapine's predictive value for long-term response and to determine if there is a difference in the pharmacologic responses of the two tremors. We also investigated the correlation between reduction of tremor and induction of sedation after acute and chronic administration of clozapine. Clozapine (12.5 mg) or placebo were administered po in a double-blind manner to 17 PD patients with mixed L-dopa-resistant tremors. Two patients did not reach 50% improvement and were considered nonresponders. The remaining 15 patients reported moderate to marked reduction of tremor. Responsive patients in the acute test moved on to a long-term, open clozapine add-on study receiving an average daily dose +/- SD of 45 +/- 9.6 mg for a period of 15.5 +/- 8.3 months. A significant reduction of both resting (p < 0.05) and postural (p < 0.05) tremors was observed under clozapine from the first week of treatment through the entire period of the study. There was no statistically significantly difference between the degree of improvement for resting and postural tremors after either single or chronic clozapine administration. Sedation was the only side effect reported after clozapine; however, the time courses of sedation and tremor reduction did not coincide in the acute or in the chronic experimental paradigm, where it decreased considerably in a few weeks in all patients. During long-term clozapine treatment, neither systemic side effects nor worsening of motor disability scores were noted. Thus we wish to propose an acute test or a therapeutic attempt, or both, with clozapine before defining a case of mixed parkinsonian tremor as resistant tremor and therefore resorting to a neurosurgical approach.

Aged↗
PubMed1994

Weak electromagnetic fields attenuate tremor in multiple sclerosis.

It has been estimated that about 75% of patients diagnosed with multiple sclerosis (MS) have tremor which can be exceedingly disabling. The most common tremor observed in patients with MS is a cerebellar intention tremor ('kinetic tremor') although postural tremor ('static tremor') is also common and often extremely incapacitating. Currently there is no effective medical treatment for the tremor of MS which, in some severe cases, may be abolished by stereotactic thalamotomy. It was reported recently that extracranial application of brief AC pulsed electromagnetic fields (EMFs) in the picotesla (pT) range produced improvement in motor and cognitive functions in patients with MS. The present communication concerns three MS patients with a chronic progressive course of the disease (mean age: 39.3 +/- 8.3 years; mean duration of illness: 11.3 +/- 3.2 years) in whom brief external applications of pulsed EMFs of 7.5 pT intensity reduced intention and postural tremors resulting in significant functional improvement. The report suggests that these extremely low intensity EMFs are beneficial also in the treatment of tremors in MS and that this treatment may serve as an alternative method to stereotactic thalamotomy in the management of tremor in MS. The mechanisms by which EMFs attenuate the tremors of MS are complex and are thought to involve augmentation of GABA and serotonin (5-HT) neurotransmission in the cerebellum and its outflow tracts.

Adult↗
PubMed2004

Stimulation of the subthalamic region for essential tremor.

OBJECT: The goal of this study was to determine the safety and efficacy of bilateral subthalamic region stimulation in the treatment of essential tremor (ET). METHODS: Following induction of general anesthesia, four patients with disabling tremor that had proved to be refractory to pharmacotherapy underwent magnetic resonance imaging-guided deep brain stimulation (DBS) of the bilateral subthalamic region. Tremor was assessed by applying the Fahn-Tolosa-Marń Tremor Rating Scale at baseline and again at the 12-month follow-up examination. Following surgery the total tremor score improved by 80.1% (from a baseline mean score of 63 +/- 15.1 to a score of 11.8 +/- 3.9 at 12 months postoperatively). There was a significant improvement (p < 0.0001) in the mean tremor score of the upper limb (postural and action component) from a baseline score of 3 +/- 0.9 to a score of 0.5 +/- 0.5 at 12 months postoperatively. In two patients with Score 4 head tremor complete arrest of the tremor was observed at 12 months. Motor function scores of the upper limb for drawing spirals, pouring water, and drawing lines improved significantly (p < 0.05) by 66.7, 76.9, and 58.3%, respectively. Handwriting improved by 68%, but this gain was not significant. The mean activities of daily living score at baseline was 20 +/- 3.2; there was an 88.8% improvement in this score to 2.3 +/- 1.5 at the 12-month evaluation. The voltage required for effective tremor control was low (mean 1.8 +/- 0.2 V) and, along with the other parameters of DBS (frequency and pulse width), did not change significantly over the 12-month period. Tolerance to the action component of tremor was not seen. There was no procedural or stimulation-related complication. CONCLUSIONS: Bilateral subthalamic region stimulation is effective in arresting tremor and head titubation, as well as functional disability in ET. Complications like dysarthria and disequilibrium were not seen. These patients required low voltages of stimulation and did not develop a tolerance to the treatment.

Activities of Daily Living↗
PubMedDate not supplied

Joint amplitude and frequency analysis of tremor activity.

Clinical tremor analysis mostly is used for the measurement of tremor frequency. The analysis is based on short segments of EMG recordings and on clinical ratings of tremor intensity. Accelerometry appears to have some practical advantages. The present study was concerned with the development of a methodology for assessing tremor activity using the three parameters, frequency (Hz), amplitude (g), and occurrence of tremor (in per cent of time). These parameters were derived from joint amplitude frequency analysis of the calibrated accelerometer raw signal and from appropriate decision rules. This methodology was used in connection with 27 patients with Parkinson's disease, to investigate the aforesaid parameters of tremor activity. Postural tremor had a higher occurrence time (right-hand only) and higher frequency (left-hand only) than resting tremor, however, the average amplitudes did not differ. The correlations between right-hand and left-hand measures were higher during postural tremor test. Frequency was not correlated to amplitude or occurrence time, however, moderate correlations did exist between amplitude and occurrence time. In addition to the assessment of tremor activity, multi-channel accelerometry may be used for the detection of posture and motion. Further applications of this methodology, for example, in 24 hr ambulatory monitoring of tremor, are discussed.

Acceleration↗
PubMed2000

Relationships between quantitative measures and neurologist's clinical rating of tremor and standing steadiness in two epidemiological studies.

OBJECTIVE: The purpose of the present investigation was to 1) compare a neurologist's physical examination (NPx) rating of severity of postural tremor to several summary measures derived from quantitative measurements of tremor and 2) compare a NPx rating of standing steadiness and related clinical findings to quantitative sway speed measurements. METHODS: Comparisons were performed on data obtained from two epidemiological field studies: 1) retired heavy industrial workers (n= 198, approximately half previously exposed to elemental mercury), and 2) small town residents (n=234, approximately 40% with environmental exposure to arsenic). A commercially available tremor measurement instrument was used in both studies. To obtain standing steadiness measures, a head position monitoring device was used in the mercury study, and a force platform was used in the arsenic study. The NPx included assessment of postural tremor, as well as evaluation of vibration perception and proprioception of the great toe, Achilles tendon reflex activity, Romberg test status, and tandem gait. One neurologist performed all the NPx in both studies and results were graded as normal, equivocal, or abnormal. The square root of the proportion of variance accounted for by a linear trend term in ANOVA models was used as an estimate of association between quantitative tests and clinical examination grade. An estimate of agreement, kappa, was also calculated after both NPx and quantitative test results were dichotomized. RESULTS: Most tremor summary measures varied monotonically with NPx tremor severity grade. Moderately good associations were observed between the tremor acceleration measure and NPx postural tremor grade (correlations up to approximately 0.5). Sway speed with eyes open and with eyes closed increased monotonically with NPx grade for most of the clinical signs. The NPx signs showing the strongest relationships with sway speed were Romberg test performance, tandem gait, and proprioception and vibration sensation of the great toe (correlations up to approximately 0.5). CONCLUSIONS: Quantitative tremor measurements were related to a neurologist's grading of postural tremor. Sway speed was associated with several NPx findings related to standing stability. Quantitative measurements of tremor and standing stability may provide more precise and objective measures of neurological function than NPx by a neurologist and are likely to be more consistent across times and examiners.

Adult↗
PubMed2002

Clinical and electromyographic examinations of patients with midbrain and cerebellar tremor.

The aim of this study was to re-evaluate the controversial clinical and electromyographic findings of cerebellar and midbrain tremors. Neurological examination and surface electromyographic tremor recordings were performed on 46 patients (24 with midbrain and 22 with cerebellar tremor). Our results revealed that the midbrain tremor has involved the hand, sometimes the ipsilateral leg and regions outside the limbs. Usually it was combined rest, postural, kinetic and intention tremor, the amplitude of each next tremor progressively increased. The tremor had high amplitude, low frequency and typical long burst duration. The cerebellar tremor was quite different, as it was predominantly postural and kinetic and involved the upper limbs. The tremor had synchronous electromyographic pattern, high frequency, low amplitude and short burst duration. In conclusion although the cerebellar and midbrain tremors are caused by involvement of very close anatomical regions and sometimes one type of tremor may become into another, they have quite different clinical and electromyographic presentations.

Adult↗
PubMed2006

[Social phobia in essential tremor].

OBJECTIVES: This study is aimed to determine the frequency of social phobia among a group of subjects with essential tremor, to compare subject groups with and without social phobia with regard to the level of social phobia and disability, and to study the effect of the severity of social phobia on disability in essential tremor. METHOD: 45 subjects, diagnosed with essential tremor were included in the study, and their severity of tremor and essential tremor-related functional impairment were determined. Subjects were evaluated in 2 groups; those with a social phobia diagnosis and those without, as determined with the SCID-I interview. Additionally, the Liebowitz Social Anxiety Scale (LSAS) and the Sheehan Disability Scale (SDS) were administered to both groups and the findings were statistically compared. RESULTS: Social phobia was observed in 19 subjects (42.2%) with essential tremor. While no difference was found between the groups in terms of tremor severity scores, the mean score of tremor-related functional disability in the social phobia group was found to be higher. Among subjects with social phobia, the mean fear and avoidance scores on LSAS were higher, whereas social lives and leisure activities of the same group were observed to have been affected more, according to SDS scores. Social avoidance and tremor severity were predictive for the difference on SDS. A significant and positive correlation between fear and avoidance, and disability in the group with social phobia was established. CONCLUSION: It was concluded that essential tremor patients diagnosed with social phobia demonstrated higher social anxiety and disability compared to those without social phobia, and that social avoidance contributed to disability. Identifying social phobia in essential tremor patients and diagnosing these patients with social phobia, contrary to DSM's restrictive approach, would be appropriate and beneficial in terms of providing sufficient treatment.

Adult↗
PubMed1985

Essential vocal tremor: clinical characteristics and response to therapy.

We evaluated four patients with an initial and predominant voice tremor. All were referred for evaluation for suspected parkinsonism, though vocal tremor was the only symptom. These three women and one man ranged in age from 37 to 59 years. Neurologic evaluation and laryngeal examination were unremarkable. No signs of parkinsonism were present. All patients had a family history of tremor, though in only one family was vocal tremor the sole manifestation. Tremor was suppressed by alcohol ingestion in all patients and with whisper in two. Duration of tremor before evaluation ranged from eight months to six years. Visual representation of tremor was obtained in three, with frequencies ranging from 4 to 10 cps. Three patients responded to treatment with propranolol (Inderal), and one did well with voice training. Follow-up was six months to ten years. Although previous cases of essential vocal tremor with concurrent tremor elsewhere have been noted, only six cases of isolated voice tremor had been reported and response to therapy was not mentioned. Essential tremor may also be isolated to the head, chin, and hands.

Adult↗
PubMed1995

[Most frequent causes for hand tremor in clinical practice].

The author summarises the various origins of hand tremor. Physiologic tremor can be demonstrated in any individual. This tremor is normally recordable at a stable frequency of 8-10 Hz, though this can be influenced by age, the amplitude can vary substantially. Physiological tremor is believed to have its origin in the mechanical properties of the extremities, and the firing properties of motoneurones. Essential tremor is an inherited autosomally dominant phenomenon, and is characterised by action and postural tremor. It is progressive with age. The use of low doses of theophylline in the treatment of essential tremor is emphasised, in view of the low incidence of side effects. A hypothesis is also presented to account for essential tremor in terms of an imbalance in the activity of excitatory and inhibitory amino acid system. Parkinsonian tremor may begin as postural or resting tremor on one side, and it is reduced by active movement of the affected extremity. The prognosis of Parkinson's disease presenting with tremor is better when presenting with hypokinesia. The increasing use of non-specific drugs in the treatment of Parkinsonism, and the use of thalamic high frequency stimulation are indicated.

Aged↗