Relative efficacy of alcohol and propranolol in action tremor

Cerebellar α6GABAA Receptors as a Therapeutic Target for Essential Tremor: Proof-of-Concept Study with Ethanol and Pyrazoloquinolinones

Ethanol has been shown to suppress essential tremor (ET) in patients at low-to-moderate doses, but its mechanism(s) of action remain unknown. One of the ET hypotheses attributes the ET tremorgenesis to the over-activated firing of inferior olivary neurons, causing synchronic rhythmic firings of cerebellar Purkinje cells. Purkinje cells, however, also receive excitatory inputs from granule cells where the α6 subunit-containing GABAA receptors (α6GABAARs) are abundantly expressed. Since ethanol is a positive allosteric modulator (PAM) of α6GABAARs, such action may mediate its anti-tremor effect. Employing the harmaline-induced ET model in male ICR mice, we evaluated the possible anti-tremor effects of ethanol and α6GABAAR-selective pyrazoloquinolinone PAMs. The burrowing activity, an indicator of well-being in rodents, was measured concurrently. Ethanol significantly and dose-dependently attenuated action tremor at non-sedative doses (0.4-2.4 g/kg, i.p.). Propranolol and α6GABAAR-selective pyrazoloquinolinones also significantly suppressed tremor activity. Neither ethanol nor propranolol, but only pyrazoloquinolinones, restored burrowing activity in harmaline-treated mice. Importantly, intra-cerebellar micro-injection of furosemide (an α6GABAAR antagonist) had a trend of blocking the effect of pyrazoloquinolinone Compound 6 or ethanol on harmaline-induced tremor. In addition, the anti-tremor effects of Compound 6 and ethanol were synergistic. These results suggest that low doses of ethanol and α6GABAAR-selective PAMs can attenuate action tremor, at least partially by modulating cerebellar α6GABAARs. Thus, α6GABAARs are potential therapeutic targets for ET, and α6GABAAR-selective PAMs may be a potential mono- or add-on therapy.

Mixed Motor Disorder: Essential Tremor Families With Heterogeneous Motor Phenomenology

Background and Objectives

Essential tremor (ET) is one of the most prevalent movement disorders. Because ET is so common, individuals with other neurologic disorders may also have ET. There is evidence, however, that the cooccurrence of ET with Parkinson disease (PD) and/or dystonia is not merely a chance cooccurrence. We have observed combinations of these 3 movement disorders within individuals and across individuals within families containing multiple individuals with ET. This observation has a number of implications. Our objective is to present 4 ET families in whom motor phenomenology was heterogeneous and discuss the implications of this finding.

Methods

ET cases and their relatives were enrolled in the Family Study of Essential Tremor (2015-present). Phenotyping was performed by a senior movement disorders neurologist based on neurologic examination.

Results

We present 4 families, including 14 affected individuals, among whom assigned diagnoses were ET, PD, ET + PD, and ET + dystonia. In those with ET and another movement disorder, the predominant and earliest phenotype was ET.

Discussion

There are assortments of these 3 involuntary motor disorders, ET, dystonia, and PD, both within individuals and in different individuals within ET families. This observation has mechanistic implications. Furthermore, we believe that the concept of the mixed motor disorder should enter into and inform the clinical dialogue. In assigning diagnoses, clinicians are swayed by family history information, and they should be prepared to observe a mix of different motor disorders to manifest within particular families.

Dopamine transporter (DAT) imaging in Parkinson's disease and related disorders

This review gives an insight into the beginnings of dopamine transporter (DAT) imaging in the early 1990s, focussing on single photon emission tomography (SPECT). The development of the method and its consolidation as a now widely used clinical tool is described. The role of DAT-SPECT in the diagnosis and differential diagnosis of PD, atypical parkinsonian syndromes and several other different neurological disorders is reviewed. Finally the clinical research using DAT-SPECT as a biomarker for the progression of PD, for the detection of a preclinical dopaminergic lesion and its correlation with neuropathological findings is outlined.

Treatment of essential tremor: current status

Essential tremor is the most common cause of tremor involving upper limbs, head and voice. The first line of treatment for limb tremor is pharmacotherapy with propranolol or primidone. However, these two drugs reduce the tremor severity by only half. In medication refractory and functionally disabling tremor, alternative forms of therapy need to be considered. Botulinum toxin injections are likely efficacious for limb, voice and head tremor but are associated with side effects. Surgical interventions include deep brain stimulation; magnetic resonance-guided focused ultrasound and thalamotomy for unilateral and deep brain stimulation for bilateral procedures. Recent consensus classification for essential tremor has included a new subgroup, ‘Essential tremor plus’, who have associated subtle neurological ‘soft signs’, such as dystonic posturing of limbs and may require a different treatment approach. In this review, we have addressed the current management of essential tremor with regard to different anatomical locations of tremor as well as different modalities of treatment.

Hand Tremor Questionnaire: A Useful Screening Tool for Differentiating Patients with Hand Tremor between Parkinson's Disease and Essential Tremor

Background and Purpose

Hand tremor is one of the most frequent symptoms in movement disorders, and differential diagnoses for hand tremor include Parkinson's disease (PD) and essential tremor (ET). However, accurately differentiating between PD and ET in clinical practice remains challenging in patients presenting with hand tremor. We investigated whether a questionnaire-based survey could be useful as a screening tool in patients with hand tremor.

Methods

A questionnaire related to hand tremor consisting of 12 items was prospectively applied to patients with PD or ET in three movement-disorder clinics. Each question was analyzed, and a query-based scoring system was evaluated for differentiating hand tremors between PD and ET.

Results

This study enrolled 24 patients with PD and 25 patients with ET. Nine of the 12 questions differed significantly between PD and ET: 1 about resting tremor, 4 questions about action tremor, and 4 about asymmetry. A receiver operating characteristics curve analysis revealed that the 9-item questionnaire showed a good discrimination ability, with a sensitivity of 88% and a specificity of 84%.

Conclusions

The developed Hand Tremor Questionnaire might be a good screening tool for hand tremors in patients with PD and ET.

Testing for alcohol sensitivity of tremor amplitude in a large cohort with essential tremor

BACKGROUND

Improvement of essential tremor (ET) amplitude after alcohol ingestion is usually based on patient reports but a quantitative test for large numbers of patients is lacking and the percentage of ET patients with a detectable alcohol effect is therefore unknown.

METHODS

A validated and published alcohol home test was used in 104 ET patients. The Archimedes spiral was drawn before alcohol ingestion and at 4 time points after alcohol consumption and rated on a 10-point rating scale according to Bain and Findley. A second identical test without alcohol ingestion was performed by the same patients and evaluated by the same two raters to analyze the total variability of the spiral ratings.

RESULTS

Alcohol reduces tremor in ET patients as a group and a rebound effect with an increase in tremor intensity was found the next morning. Sex, family history of ET, diagnosis (definite vs. probable) and medical history of alcohol responsiveness do not predict the alcohol response. The minimal detectable difference in the spiral score was 2 due to spontaneous tremor fluctuations and inter-rater differences. The test demonstrated alcohol sensitivity of the tremor in 46% of the patients. Responsivity to alcohol could only be seen in patients with spiral scores above 3.

CONCLUSIONS

Alcohol sensitivity is a feature of ET in at least 46% of the patients. We could not find predictors for alcohol sensitivity. The minimal detectable change is 2 scores and alcohol responsivity was only detected in patients with baseline Archimedes spiral rating of ≥3.

Saskatchewan movement disorders program

We review the Saskatchewan Movement Disorders Program, which started in 1968 and has had the dual goals of patient care and research. The clinics are structured to collect research-worthy data including videos, longitudinal follow-up, and autopsy studies of patients seen in the clinics. At every clinic visit, the patient is evaluated by one or both authors. A total of 25% to 30% of the deceased come to autopsy. Frozen half-brain and formalin-fixed remnants from autopsy are preserved in our laboratories. Patients not seen in our clinic are not included in research, which makes it different from brain banks. So far, 515 cases have come to autopsy. So far, there have been 17 collaborating scientific teams from Canada, the United States, Europe, and Japan. The collaborators are not charged for access to our resources. This program offers a unique opportunity to study multiple aspects of movement disorder patients seen in clinical practice.

Action tremor in Parkinson's disease: frequency and relationship to motor and non-motor signs

BACKGROUND AND PURPOSE

Action tremor may occur in patients with Parkinson's disease and cause misdiagnosis with other movement disorders such as essential tremor and dystonia. Data on the frequency of action tremor in Parkinson's disease and on the relationships with other motor and non-motor signs are limited.

METHODS

A cross-sectional study of 237 patients with Parkinson's disease staging 1-2 on the Hoehn-Yahr scale was conducted. Data on action tremor and other motor and non-motor signs were collected using the Unified Parkinson's Disease Rating Scale part III and the Non-Motor Symptoms Scale.

RESULTS

Action tremor was found in 46% of patients and was associated with both severity of rest tremor (adjusted odds ratio 3.0, P < 0.001) and severity of rigidity (adjusted odds ratio 1.5, P = 0.004). No association was found between action tremor and severity of bradykinesia (adjusted odds ratio 0.97, P = 0.4) or axial symptoms (adjusted odds ratio 0.9, P = 0.3). Moreover, patients who had action tremor reported a significant lower mean number of non-motor symptoms than those who had not (2.1 ± 1.3 vs. 2.4 ± 1.3; P = 0.04).

CONCLUSIONS

Action tremor is a relatively frequent motor sign in patients with Parkinson's disease staging 1-2 on the Hoehn-Yahr scale. Action tremor correlates with rest tremor and rigidity and may be associated with a lower burden of non-motor symptoms. These findings suggest a contribution of non-dopaminergic mechanisms to action tremor pathophysiology.

Medical treatment of essential tremor

Essential tremor (ET) is the most common pathological tremor characterized by upper limb action-postural tremor (PT)/kinetic tremor (KT). There are no specific neuropathological or biochemical abnormalities in ET. The disability is consequent to amplitude of KT, which may remain mild without handicap or may become disabling. The most effective drugs for sustained tremor control are propranolol and primidone. Symptomatic drug treatment must be individualized depending on the circumstances that provoke the tremor-related disability. Broad guidelines for treatment are discussed in this review. Patients may be treated intermittently only on stressful occasions with propranolol, clonazepam, or primidone monotherapy, or an alcoholic drink. Those with persistently disabling tremor need continued treatment.

What is essential tremor?

Classic essential tremor is a clinical syndrome of action tremor in the upper limbs (at least 95 % of patients) and less commonly the head, face/jaw, voice, tongue, trunk, and lower limbs, in the absence of other neurologic signs. However, the longstanding notion that essential tremor is a monosymptomatic tremor disorder is being challenged by a growing literature describing associated disturbances of tandem walking, personality, mood, hearing, and cognition. There is also epidemiologic, pathologic, and genetic evidence that essential tremor is pathophysiologically heterogeneous. Misdiagnosis of essential tremor is common because clinicians frequently overlook other neurologic signs and because action tremor in the hands is caused by many conditions, including dystonia, Parkinson disease, and drug-induced tremor. Thus, essential tremor is nothing more than a syndrome of idiopathic tremulousness, and the challenge for researchers and clinicians is to find specific etiologies of this syndrome.

Essential tremor is not a neurodegenerative disease

The pathophysiology of essential tremor (ET) remains unknown. Standard neuropathological studies have reported no consistent changes but a detailed study found neurodegeneration in all ET cases - 24% demonstrated lower brainstem Lewy body (LB) inclusions and 76% experienced a loss of cerebellar Purkinje cells (PCs) and its sequelae. We review the evidence on neurodegeneration in ET. The prevalence of LB inclusions in ET brains is similar to that in the asymptomatic general population. These incidental LB disease cases have evidence for reduced striatal tyrosine hydroxylase levels, as found in Parkinson's disease, but there is no evidence for reduced tyrosine hydroxylase levels in ET patients. Reduced mean PC counts in ET cases compared with the controls reported by some studies could not be replicated by others. Most ET cases have the same number of PCs as controls of a comparable age. Neither the lower brainstem LB inclusions nor the cerebellar PC loss represent the neurodegenerative basis of ET. Further studies are needed to determine the pathophysiology of ET.

The effects of a novel histamine-3 receptor inverse agonist on essential tremor in comparison to stable levels of alcohol

Essential tremor (ET) is a common movement disorder. Animal studies show that histaminergic modulation may affect the pathological processes involved in the generation of ET. Histamine-3 receptor inverse agonists (H3RIA) have demonstrated attenuating effects on ET in the harmaline rat model. In this double-blind, three-way cross-over, single-dose, double-dummy study the effects of 25 mg of a novel H3RIA (MK-0249) and a stable alcohol level (0.6 g L(-1)) were compared with placebo, in 18 patients with ET. Tremor was evaluated using laboratory tremorography, portable tremorography and a clinical rating scale. The Leeds Sleep Evaluation Questionnaire (LSEQ) and a choice reaction time (CRT) test were performed to evaluate potential effects on sleep and attention, respectively. A steady state of alcohol significantly diminished tremor as assessed by laboratory tremorography, portable tremorography and clinical ratings compared with placebo. A high single MK-0249 dose was not effective in reducing tremor, but caused significant effects on the LSEQ and the CRT test. These results suggest that treatment with a single dose of MK-0249 does not improve tremor in alcohol-responsive patients with ET, whereas stable levels of alcohol as a positive control reproduced the commonly reported tremor-diminishing effects of alcohol.

The effects of TPA023, a GABAAα2,3 subtype-selective partial agonist, on essential tremor in comparison to alcohol

Essential tremor (ET) is a relatively frequent neurological disorder that responds in some patients to gamma-aminobutyric acid A (GABA(A)) agonists such as the benzodiazepines. Partial subtype-selective GABA(A) agonists may have an improved side effect profile compared to non-selective GABA(A) agonists. However, it is unknown which GABA(A) subtypes are involved in the therapeutic effects of benzodiazepines in ET. The effects of 2 mg TPA023, a GABA(A) α2,3 subtype-selective partial agonist, on ET were compared to the effects of a stable alcohol level (0.6 g/L) and placebo in nine patients with ET. Tremor evaluation included laboratory accelerometry and a performance-based scale. Additional measurements were performed to evaluate other effects on the central nervous system (CNS). Alcohol significantly diminished tremor symptoms in the postural and kinetic condition, as assessed by laboratory accelerometry, but the performance-based rating scale was unaffected. Tremor was also reduced after TPA023 treatment in the kinetic condition, albeit not significantly. Additionally, TPA023 decreased saccadic peak velocity, while alcohol decreased subjective feelings of alertness. This study showed that alcohol reduced maximum tremor power, as assessed by laboratory accelerometry, unlike TPA023, which decreased tremor symptoms to some extent but not significantly. This study showed that treatment with an α2,3 subunit-selective GABA(A) partial agonist was less effective than a stable level of alcohol in reducing ET symptoms. These results provide no support for a therapeutic role of TPA023 in the suppression of ET symptoms.

Management of essential tremor, including medical and surgical approaches

Essential tremor (ET) is one of the most common neurological disorders among adults. For many years, ET was viewed as a benign monosymptomatic condition, characterized by a kinetic arm tremor, yet over the last 10 years, a growing body of evidence suggests that this disorder is a progressive condition that is heterogeneous. Tremor may have a negative impact on health-related quality of life in some patients. Pharmacotherapy is initiated when the tremor interferes with the patient's ability to perform daily activities or when the tremor becomes embarrassing or affects health-related quality of life. For severe tremor, deep-brain stimulation of the thalamus may improve function.

Parkinsonism and tremor disorders. A clinical approach

Differentiation of idiopathic Parkinson's disease from other causes of Parkinsonism, such as Multiple System Atrophy, Progressive Supranuclar Palsy and Vascular Parkinsonism can be difficult. Clinicopathological studies suggest that the clinical diagnosis of idiopathic Parkinson's disease is 76% reliable. Also, clinical differentiation of tremor prominent Parkinsonism from Essential Tremor or Drug induced Parkinsonism may be problematic, especially in the early stages of the disease. Since these disorders are obviously different in clinical progress, it is important for the clinician to address the patient's and family's concerns about prognosis from a firm diagnostic footing. In this article the clinical features of the common and important causes of Parkinsonism and tremor disorders are reviewed and a practical approach is suggested.

Essential Tremor

BACKGROUND

Essential tremor (ET) is the most common adult tremor disorder and is characterized by postural and kinetic tremor. Symptoms are typically progressive and potentially disabling, often forcing patients to change jobs or seek early retirement. Proper treatment is contingent on a correct diagnosis, and other possible causes of tremor must be excluded.

REVIEW SUMMARY

Although primidone and propranolol have been regarded as the mainstays of pharmacologic therapy for ET, additional agents may be useful in reducing tremor. Surgical procedures are available that effectively ameliorate tremor that is refractory to medical management. This article reviews the epidemiology, pathophysiology, and treatment options for ET.

CONCLUSIONS

Despite a range of treatment options currently available, further research is necessary to manage this syndrome most effectively. Double-blind, controlled trials are needed to determine whether primidone, propranolol, or a combination of these medications is superior in the initial management of ET. Other pharmacologic agents have shown potential to reduce tremor and should be investigated further. Additional studies are also needed to determine the best treatment of head and voice tremor with pharmacologic and surgical interventions. With proper treatment, tremor is sufficiently reduced in the majority of patients.

Role of dopamine transporter imaging in the diagnosis of atypical tremor disorders

Dopamine transporter (DAT) imaging detects presynaptic dopamine neuronal dysfunction and thereby assists differentiation of conditions with and without dopamine deficit. In atypical tremor disorders, DAT imaging can differentiate between Parkinson's disease (PD), where dopamine deficit is demonstrated on DAT imaging, and essential tremor, where no dopamine deficit is found. DAT imaging may be particularly informative in monosymptomatic rest tremors, benign tremulous Parkinson's syndrome, and in the elderly in whom essential tremor may be accompanied by pseudoparkinsonism.

Tremor--easily seen but difficult to describe and treat

Tremor is a common movement disorder yet many physicians struggle with its terminology as well as with its treatment. Attempts have been made to develop standard terminology and criteria for tremors but this process continues to evolve. In this review, a summary of the currently-proposed phenomenology and syndromic classification of all types of tremor is presented. The diagnosis and management of essential tremor is presented in more detail, as it is the most commonly encountered tremor.

Management of essential tremor

Essential tremor (ET) is the most prevalent tremor syndrome. It commonly affects the hands, head, voice, and other body parts. Appropriate management begins with correct diagnosis. Primidone and propranolol are the first-line medications for the treatment for ET, but several other medications may also provide benefit. In patients with medically refractory tremor, alternative therapies, including surgery or injections of botulinum toxin, may be considered.

Phenomenology and treatment of tremor disorders

Tremor is classified according to anatomic distribution among body parts, and by frequency and amplitude during rest, postural maintenance, movement, intention, and the performance of specific tasks. Key historical features include age at onset, progression over time, family history, exacerbating and remitting factors and behaviors, response to alcohol and medications, and additional neurological signs and symptoms. Accurate diagnosis is a critical factor in predicting the natural history and response to treatment.

Clinical and electromyographic examinations of Parkinsonian tremor

Background: The clinical presentations of postural Parkinsonian tremor are variable and different types of tremors have been described. The aim of this study was to re-evaluate the clinical and electromyographic (EMG) pattern of different tremors in Parkinsonian patients.Methods: One hundred and ten patients with Parkinsonian tremor were included in the study. Patients were subdivided into four groups according to the presence or absence of postural tremor, in addition to a resting tremor and its EMG pattern. The first group consisted of patients without postural tremor. The second group consisted of patients with fast postural tremor (>7Hz). The third group consisted of patients with slow postural tremor with alternating EMG activity. Patients with slow postural tremor with synchronous EMG activity were included in the fourth group. In each limb position, the tremor of the most involved body part was graded on the Webster Tremor Scale. Surface EMG recordings of the most involved limb in all positions were performed.Results: Postural tremor in addition to the rest one was found in 84% of the patients. The postural tremor was with lower amplitude than the rest one. The frequencies and EMG patterns of the postural tremors were different and correlated with some specific clinical symptoms. Patients with alternating postural tremor had a kinetic and intention tremor in addition.Conclusions: Four different subtypes of Parkinsonian tremor were found according to the presence and type of postural tremor. These subtypes had some differing clinical characteristics and probably different relationships to essential tremor.

Functional imaging of tremor

We review the insight that has been obtained from positron emission tomography (PET) and magnetic resonance imaging (MRI) activation studies on the functional anatomy underlying different forms of tremor. The effects of treatment, both pharmacologic and interventional approaches, on the dysfunctional cerebral systems involved in tremor, also are considered. Finally, we speculate on the neuropharmacologic basis of different types of tremor based on available in vivo PET evidence.

Classification of tremors

Until there is a greater understanding of basic tremorgenic mechanisms in the central nervous system, current classifications of tremors rely heavily on the behavioural characteristics, putative sites of origin, and/or the underlying disease process. Careful clinical evaluation remains the centrum of tremor classification. Few tremors do show specific neurophysiological features that will clinch diagnosis, e.g., primary orthostatic tremor and dystonic tremor. With the exception of dopaminergic drugs in Parkinson's disease, drug effects in tremors are unpredictable and nonspecific. Drug side effects should be considered in the differential diagnosis of any unexplained tremor.

Tremors

In this article, normal tremor and common types of pathologic tremors seen in the elderly are defined and described along with a review of current treatments. Problems of differential diagnosis are emphasized.

Ineffective treatment of essential tremor with an alcohol, methylpentynol

Six patients with essential tremor tested in the therapeutic effectiveness of a 6-carbon alcohol, methylpentynol, 200 mg/day, against placebo in a randomised double-blind clinical cross-over trial. The effect of methylpentynol on postural tremor amplitude was not different from that of placebo.

Writing tremor: its relationship to benign essential tremor

Nine patients with tremor on writing and one patient with tremor only on swinging a golf club were investigated. None of the patients had any other neurological symptoms or signs. The frequency of the tremor ranged from 5 to 6 Hz. Rapid passive supination or pronation of the forearm by a torque motor evoked a short burst of alternating tremor in seven patients. The tremor was improved by alcohol or propranolol in six patients. These characteristics of writing tremor (and of other isolated action tremors) suggest that it is a variant of benign essential tremor.

Essential tremor in Rochester, Minnesota: a 45-year study

A 45-year (1935-79) retrospective study of essential tremor based on original medical records on residents of Rochester, Minnesota, is presented. The age and sex adjusted incidence for the most recent 15 year period was 23.7 per 100 000 for US white population. The prevalence rate, age and sex adjusted to 1970 US white population on January 1, 1979 was estimated at 305.6 per 100 000. Survival after diagnosis of essential tremor is comparable to age and sex matched population of West North Central United States. Mean age at diagnosis was 58 (range 2-96) years. Age adjusted annual incidence rate was not different in males (18.3/100 000) and females (17.1/100 000). Functional handicap was reported by four (1.5%) of the 266 incidence cases in school, 13 (5%) cases at work and five cases (2%) retired prematurely. Excessive use of alcohol was noted in 16% and 6% were diagnosed as alcoholic. Torticollis was diagnosed in 3% cases and an additional diagnosis of Parkinson's disease after the index date was made in 2% of incidence cases. Subsequent emergence of Parkinsonism was regarded as incidental. Diagnosis of hypertension was made at some time in 30% of incidence cases during the period (mean 37 years) for which the medical records were available. Risk of hypertension after onset of essential tremor in the cases was not different from that in a control group.