Tremor and longevity in relatives of patients with Parkinson's disease, essential tremor, and control subjects

Suggestive linkage to chromosome 19 in a large Cuban family with late-onset Parkinson's disease

The identification of disease genes using family-based approaches has provided important insights into the pathogenesis of Parkinson's disease (PD) demonstrating the importance of genetic studies on monogenic forms of the disease. We studied a large Cuban family with typical, late-onset PD and probable autosomal dominant inheritance. Mean age at onset was 61.2 years (+/- 12.53, 45-76). Other phenotypes such as essential tremor and atypical parkinsonism were observed in this family. We carried out a genome-wide scan and linkage analyses. The genetic data were analyzed using a conservative model in which only patients with clinically definite or likely PD were considered affected, other phenotypes were regarded as "unknown." Multipoint analyses yielded a maximum LOD of 2.26 between markers D19S221 and D19S840. Haplotype analysis showed a region on chromosome 19 shared by six of seven PD patients. The essential tremor phenotype and the atypical parkinsonism do not segregate with this haplotype, suggesting a different etiology. Our findings suggest the presence of a novel locus for PD on chromosome 19p13.3-q12. We propose that an oligogenic model with moderate contribution of two or three genes rather than a "pure" monogenic model might explain better the wide range in age at onset, the reduced penetrance and the phenotypical variability observed in PD families.

Large French-Canadian family with Lewy body parkinsonism: exclusion of known loci

The identification of rare, large families with Parkinson's disease (PD) has provided important clues that have contributed to our understanding of this complex disorder. We have identified a large French-Canadian kindred that spans five generations consisting of more than 90 individuals. A total of 65 individuals now have been examined, had venous blood drawn, and DNA extracted. Two-point and multipoint linkage analysis was performed to assess linkage to known PD genes or loci. Within the third and fourth generations of this family there are 10 living, plus 3 deceased members with well-documented levodopa responsive parkinsonism. Autopsy results on 1 member demonstrated the loss of pigmented neurons in the substantia nigra and the presence of alpha-synuclein positive Lewy bodies. Four of the PD patients have prominent postural and kinetic tremors that preceded their parkinsonism by up to 10 years. Two other individuals within the family have prominent isolated postural and kinetic tremors without parkinsonism. The alpha-synuclein(4q21.3-23), Parkin(6q25.2-27), PARK3 (2p13), PARK4, and ubiquitin carboxy terminal hydrolase-L1 (4p14-16.3) and PARK6 and PARK7 (1p35-36) loci were excluded in this kindred using closely linked markers. The clinical and pathological features of this family are consistent with the diagnosis of PD. This family further demonstrates the known genetic heterogeneity in PD and is large enough that a genome-wide screen has been undertaken in an effort to identify a novel PD gene.

Movement disorders and normal aging

As the population continues to age, it has become increasingly important for clinicians to recognize the clinical characteristics of normal aging. Impaired mobility is one of the most frequent effects of normal aging, and this necessitates a specific understanding of the effects of normal aging on the motor system. This article reviews the physiological basis and clinical manifestations of normal aging as related to movement disorders. The impact of normal aging on major hypokinetic and hyperkinetic movement disorders is also discussed.

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.

Economic and health-related quality of life considerations of new therapies in Parkinson's disease

The progressive disability of Parkinson's disease results in substantial burdens for patients, their families and society in terms of increased health resource use, poorer quality of life, caregiver burden, disrupted family relationships, decreases in social and leisure activities, deteriorating emotional well-being, and direct and indirect costs of illness. Health-related quality of life (HR-QOL) measures have been used successfully in cross-sectional studies to identify and characterise these burdens; however, there is not yet substantial evidence that these instruments will be responsive to changes in patients over time and that the results will provide patients and health professionals with clinically meaningful information useful in making decisions about treatment strategies. The few studies documenting direct and indirect costs indicate increased use of ancillary health and community services, significant adaptations in home and transportation, increased use of mobility and self-care aids, and lack of access to appropriate healthcare providers. Patients with Parkinson's disease incur higher hospital expenses, have increased number of prescriptions, and experience earnings loss; the latter also applies to family caregivers. The choice, intensity and timing of therapy are determined by a variety of factors: presenting symptoms, age, employment status, comorbidity, cognitive impairment and level of functional impairment. Choices must be individually tailored to a patient's physical and personal needs. To be useful for patients with Parkinson's disease in clinical practice, clinicians should be able to use HR-QOL measures to identify appropriate medical interventions or socio-behavioural modifications to modify the HR-QOL deficits. However, while the interplay of interventions and clinical outcomes are often well understood, the effects of interventions on HR-QOL outcomes have not been studied extensively. Little research has been done that explicitly links the signs and symptoms of Parkinson's disease to the HR-QOL outcomes. The only Parkinson's disease cost-effectiveness study as yet performed indicated higher costs for patients receiving pramipexole than for those not taking the drug, but additional quality life-years were gained. Longer term effectiveness of many treatment strategies, and the usefulness of HR-QOL instruments to assess these treatments for individual patients over time, are critical areas for future research.

Classification of normal and pathological tremors using a multidimensional electromagnetic system

A new multidimensional movement analysis system was used to record limb tremor over six degrees-of-freedom, and signal processing techniques were explored to develop a suitable classification method to distinguish between different types of tremor. The specific aims were to investigate the ability of the system to screen for differences between normal subjects and a group of neurological patients, and then to differentiate between three diagnostic groups of patients. Postural tremor at the hand was recorded in normal subjects (n=24) and patients with essential tremor (n=21), multiple sclerosis (n=17) and parkinsonism (n=19). Data were collected using a 3Space Fastrak((R)) (Polhemus, Inc.) over six degrees-of-freedom (three translational directions and three rotations). Spectral estimates produced measures of tremor frequency and amplitude. Mathematical models of the data, using autoregressive modelling and K-nearest neighbour classification, produced parameters used to classify, (1) the normal subjects and 24 patients (using the three rotational movements), and (2) the three patient groups (using all six movement directions). Results were given in terms of the probability of each subject belonging to the groups being classified. 70%). The diagnostic classification produced clear differences between the patient groups (60% for essential tremor, 80% for multiple sclerosis and 60% for parkinsonism). The ability of this assessment technique to distinguish between postural tremor in normal subjects and neurological patients suggests that it could be developed as a screening tool. Classification of tremors between the patients groups, with a high degree of sensitivity, indicates the potential for further development of the system as a diagnostic aid.

Visuomotor performance in patients with essential tremor

Essential tremor (ET) is the most prevalent extrapyramidal disorder, yet its diagnosis is still controversial. This article introduces new findings that pertain to this diagnostic problem. Twenty-three patients with ET were studied. Patients with parkinsonism, cerebellar signs, severe head injury, or those under neuroleptic medication were excluded. Twenty-five normal subjects served as control subjects. Visuomotor tests involving tracking and tracing along three different paths with both the right and left hands, were used. Performance was assessed by measuring test duration, directional error, the proportion of the cumulative test time during which directional error exceeded half the maximal possible level (PT50%), the mean distance from the model path, the velocity of the hand movement, and the number of tracking interruptions. In 15 of 23 patients performance was the same as in the control subjects. These patients were defined as having a "simple condition" of ET (ETs). Considerable visuomotor impairment was found in eight patients who were regarded as having a "complex condition" of ET (ETc). Patients with ETc had significantly lower tracking speed, more tracking interruptions, longer test duration, greater directional error, greater PT50%, and greater distance from path than patients with ETs or control subjects. Most patients with ET appear to have normal visuomotor capabilities (ETs) but some display significant visuomotor disturbances (ETc). Considering the presence of similar impairments in patients with early Parkinson's disease and the increased prevalence of parkinsonism in patients with ET, it is possible that preclinical parkinsonism exists in patients with ETc. Further follow up of patients with ETc is necessary to verify this possibility.

Essential Tremor

Multiple pharmacologic treatments have been studied, but propranolol and primidone have proven to be the most effective medications. It is unlikely that a patient will respond miraculously to another medication if his or her response to propranolol and primidone is minimal. Some subsets of essential tremor, however, such as the kinetic predominant type, may respond better to other medications. Mildly affected patients may not need treatment at all, and the potential benefits must always be weighed against the possible side effects. The main benefit of botulinum toxin injection is for head tremor, whereas its efficacy in hand tremor is variable. If a patient does not respond to adequate doses of propranolol or primidone, deep brain stimulation should be considered because it carries the lowest risk of the available surgical procedures; usually, it should be given preference over thalamotomy. It is important for the physician to realize the multitude of symptomatic treatments available. Beyond the conventional and often effective oral medications, use of newer treatments such as botulinum toxin, thalamotomy, and deep brain stimulation can often reduce tremor and lead to a greater quality of life for patients with ET.

Epidemiology and genetics of essential tremor

Essential tremor (ET) is one of the most common movement disorders. However, the etiology and pathogenesis are as yet unknown. Continued research will give us clues to understanding the impact on society, identifying genetic and environmental contributors to the disease, understanding the significance of a sporadic case, the phenotypic spectrum and timing of presentation, and the relationship with other neurologic disorders. Because the condition is both clinically and genetically heterogeneous and there is overlap with these other disorders, such as dystonia, parkinsonism, peripheral neuropathy, and migraine, the definition of phenotype plagues research in this area. Advances in understanding the genetic and molecular underpinnings of tremor should provide additional tools to unravel the clinical phenotype (including physiology), genotype-phenotype relationships, and the epidemiology of tremor.

Evidence that a gene for essential tremor maps to chromosome 2p in four families

In this Journal, we previously reported genetic linkage between loci on chromosome (chr)2p(ETM) and dominantly inherited essential tremor (ET) in a large American kindred of Czech ancestry. Other investigators reported another ET susceptibility locus on chr 3q (FET1) which accounted for over half of the Icelandic families that were studied. We now report evidence for linkage to the ETM locus in three additional, unrelated American families with ET and exclude the FET1 locus in these families. Fine mapping results, using an "affecteds-only" model in all four American families, demonstrate positive combined pairwise lod scores (Z) at the ETM locus with aZ(max) = 5.94 at a recombination fraction (theta) = 0.00 for locus D2S220. Haplotype reconstruction places the ETM gene in a 9.10 cM interval between the D2S224 and D2S405 loci. Multipoint linkage analysis suggests that the ETM gene is in the 2.18 cM interval between loci D2S2150 and D2S220 with a Z(max) = 8.12. These findings may facilitate the search for a gene that causes ET and may further our understanding of other disorders that are associated with tremor [corrected].

Mapping of a familial essential tremor gene, FET1, to chromosome 3q13

Essential tremor (ET), the most common movement disorder in humans, appears to be inherited as an autosomal dominant trait in many families. The familial form is called familial essential tremor (FET), which seems similar to sporadic essential tremor. ET is a cause of substantial disability, particularly in the elderly. The prevalence of Parkinson's disease and dystonia may be increased in families with ET, but other movement disorders are seldom encountered in these families. Here we report the results of a genome-wide scan for FET genes in 16 Icelandic families with 75 affected individuals, in whom FET was apparently inherited as a dominant trait. The scan, which was performed with a 10-cM framework map, revealed one locus on chromosome 3q13 to which FET mapped with a genome-wide significance when the data were analysed either parametrically, assuming an autosomal dominant model (lod score = 3.71), or non-parametrically (NPL Z score = 4.70, p < 6.4 x 10(-6).

Concordance of common movement disorders among familial cases

Multicase families are frequently utilized in studies of movement disorders (MDs). We report families with two or more MD cases seen at the Movement Disorder Clinic, Saskatoon (MDCS). In 30% of the MD probands, there was either a history or documentation of at least one secondary MD case in the family. Only those MD cases that were seen at the MDCS were considered in this study. A total of 56 probands and 77 secondary MD cases were seen at the MDCS between 1968 and 1996. In 24 (31.2%) of the secondary cases, the diagnosis was different from that in the proband. In 46 families (82%), only one secondary case was seen, and the diagnosis was concordant with the proband in 71.7%. In the remaining 10 families with two or more secondary cases, the diagnosis was concordant in 64.5% of cases. The largest subgroup was Parkinson's disease (PD)--40 probands and 53 secondary cases. of these secondary cases, 73.6% had PD. The concordance rate was 91% in essential tremor, but only 12.5% if the proband had essential tremor + parkinsonism. Considering that a large proportion of secondary cases have a diagnosis discordant with the proband, we recommend that, whenever possible, MD diagnosis in secondary cases be based on clinical assessment.