Pramipexole: a nonergot dopamine agonist as drug therapy in Parkinson's disease

Pramipexole is a dopamine agonist that was recently introduced for the treatment of both early and advanced Parkinson's disease. Pramipexole is a synthetic aminobenzothiazole compound with a high affinity to D(3) receptors. It directly stimulates dopamine receptors without requiring metabolic conversion. Pramipexole is rapidly absorbed with bioavailability greater than 90% and is actively secreted by the renal tubules. The drug's plasma half-life is 8-12 h. Shown to be safe and effective as add-on therapy, pramipexole can also be used as initial dopaminergic therapy in Parkinson's disease, delaying the introduction of levodopa thereby postponing levodopa's side-effects.

Apolipoprotein E controls the risk and age at onset of Parkinson disease

BACKGROUND

Similarities between Alzheimer disease (AD) and Parkinson disease (PD) suggest a possible role for apolipoprotein E (APOE) in PD. Most previous studies seeking to establish such a link used case-control datasets and results have been inconsistent.

OBJECTIVE

To investigate APOE's role in PD using family-based association analyses.

METHODS

APOE functional polymorphisms were genotyped for 658 PD affected families, including 282 multiplex and 376 singleton families. The pedigree disequilibrium test (PDT) and the genotype-PDT were used to test the risk effect of APOE. The Monks-Kaplan test was used to evaluate the effect of APOE on age at onset of PD.

RESULTS

APOE was significantly associated with risk of developing PD. Stratified analysis revealed that APOE was most strongly associated with families with a positive PD family history (global p = 0.003). Like AD, the APOE-4 allele increases disease risk while the APOE-3 allele decreases risk. We detected a positive association of APOE-3 (p = 0.019) and a negative association of APOE-4 (p = 0.015) with age at onset in PD.

CONCLUSIONS

The APOE-4 allele increases risk and decreases age at onset of PD, an association that may not be dependent upon cognitive impairment.

Vagus nerve stimulation for essential tremor

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.

Genetic polymorphisms of the N-acetyltransferase genes and risk of Parkinson's disease

Recently, the authors demonstrated linkage in idiopathic PD to a region on chromosome 8p that contains the N-acetyltransferase genes, NAT1 and NAT2. The authors examined NAT1 and NAT2 for association with PD using family-based association methods and single nucleotide polymorphisms (SNPs). The authors did not find evidence for association with increased risk for PD between any individual NAT1 or NAT2 SNP or acetylation haplotype (N = 397 families, 1,580 individuals).

Complete genomic screen in Parkinson disease: evidence for multiple genes

CONTEXT

The relative contribution of genes vs environment in idiopathic Parkinson disease (PD) is controversial. Although genetic studies have identified 2 genes in which mutations cause rare single-gene variants of PD and observational studies have suggested a genetic component, twin studies have suggested that little genetic contribution exists in the common forms of PD.

OBJECTIVE

To identify genetic risk factors for idiopathic PD.

DESIGN, SETTING, AND PARTICIPANTS

Genetic linkage study conducted 1995-2000 in which a complete genomic screen (n = 344 markers) was performed in 174 families with multiple individuals diagnosed as having idiopathic PD, identified through probands in 13 clinic populations in the continental United States and Australia. A total of 870 family members were studied: 378 diagnosed as having PD, 379 unaffected by PD, and 113 with unclear status.

MAIN OUTCOME MEASURES

Logarithm of odds (lod) scores generated from parametric and nonparametric genetic linkage analysis.

RESULTS

Two-point parametric maximum parametric lod score (MLOD) and multipoint nonparametric lod score (LOD) linkage analysis detected significant evidence for linkage to 5 distinct chromosomal regions: chromosome 6 in the parkin gene (MLOD = 5.07; LOD = 5.47) in families with at least 1 individual with PD onset at younger than 40 years, chromosomes 17q (MLOD = 2.28; LOD = 2.62), 8p (MLOD = 2.01; LOD = 2.22), and 5q (MLOD = 2.39; LOD = 1.50) overall and in families with late-onset PD, and chromosome 9q (MLOD = 1.52; LOD = 2.59) in families with both levodopa-responsive and levodopa-nonresponsive patients.

CONCLUSIONS

Our data suggest that the parkin gene is important in early-onset PD and that multiple genetic factors may be important in the development of idiopathic late-onset PD.

Association of single-nucleotide polymorphisms of the tau gene with late-onset Parkinson disease

CONTEXT

The human tau gene, which promotes assembly of neuronal microtubules, has been associated with several rare neurologic diseases that clinically include parkinsonian features. We recently observed linkage in idiopathic Parkinson disease (PD) to a region on chromosome 17q21 that contains the tau gene. These factors make tau a good candidate for investigation as a susceptibility gene for idiopathic PD, the most common form of the disease.

OBJECTIVE

To investigate whether the tau gene is involved in idiopathic PD.

DESIGN, SETTING, AND PARTICIPANTS

Among a sample of 1056 individuals from 235 families selected from 13 clinical centers in the United States and Australia and from a family ascertainment core center, we tested 5 single-nucleotide polymorphisms (SNPs) within the tau gene for association with PD, using family-based tests of association. Both affected (n = 426) and unaffected (n = 579) family members were included; 51 individuals had unclear PD status. Analyses were conducted to test individual SNPs and SNP haplotypes within the tau gene.

MAIN OUTCOME MEASURE

Family-based tests of association, calculated using asymptotic distributions.

RESULTS

Analysis of association between the SNPs and PD yielded significant evidence of association for 3 of the 5 SNPs tested: SNP 3, P =.03; SNP 9i, P =.04; and SNP 11, P =.04. The 2 other SNPs did not show evidence of significant association (SNP 9ii, P =.11, and SNP 9iii, P =.87). Strong evidence of association was found with haplotype analysis, with a positive association with one haplotype (P =.009) and a negative association with another haplotype (P =.007). Substantial linkage disequilibrium (P<.001) was detected between 4 of the 5 SNPs (SNPs 3, 9i, 9ii, and 11).

CONCLUSIONS

This integrated approach of genetic linkage and positional association analyses implicates tau as a susceptibility gene for idiopathic PD.

Genome-wide scan for Parkinson's disease: the GenePD Study

A genome-wide scan for idiopathic PD in a sample of 113 PD-affected sibling pairs is reported. Suggestive evidence for linkage was found for chromosomes 1 (214 cM, lod = 1.20), 9 (136 cM, lod = 1.30), 10 (88 cM, lod = 1.07), and 16 (114 cM, lod = 0.93). The chromosome 9 region overlaps the genes for dopamine beta-hydroxylase and torsion dystonia. Although no strong evidence for linkage was found for any locus, these results may be of value in comparison with similar studies by others.

Gene-toxin interaction as a putative risk factor for Parkinson's disease with dementia

We had previously examined environmental, sociodemographic and clinical variables as predictors for Parkinson's disease with dementia (PD + D) and found that lower educational attainment, greater motor impairment and advanced age at disease onset were more common in PD + D than in subjects with Parkinson's disease without dementia (PD-D). We now explore the hypothesis that genetic traits coupled with nongenetic factors may raise the risk of development of PD + D. The study cohort of 43 PD + D and 51 PD-D subjects was analyzed examining environmental, sociodemographic and clinical variables along with 3 candidate gene markers: poor debrisoquine metabolizer allele (CYP 2D6 29B+), monoamine oxidase B allele 1, and apolipoprotein E epsilon 4 allele. Variables were initially entered into a multivariate model singly. Again lower education, age at onset and motor impairment appeared as predictors of PD + D while other variables (including allele status) failed to emerge as significant individual risk factors for dementia. We then examined environmental and genetic variables analyzed in tandem to look for potential variable interactions. Subjects who had pesticide exposure and at least 1 copy of the CYP 2D6 29B+ allele had 83% predicted probability of PD + D (stepwise logistic regression model: p = 0.0491). This case-control study provides preliminary evidence that a gene-toxin interaction may play an etiological role in PD + D. Further assessment of the role of these putative risk factors in incident dementia in PD is indicated.

Test-retest reliability of an epidemiological instrument for Parkinson's disease

Reliability testing was conducted on a survey instrument for a genetic epidemiological study of Parkinson's disease (PD). Information on demographics, medical history, places of residence, and occupations was collected. The instrument was administered to 11 pairs of siblings discordant for PD and then re-administered after 4 weeks. Twenty of 22 (91%) subjects completed and returned the retest questionnaire. Overall reliability of the instrument was acceptable (kappa = 0.88). This instrument could be used to elicit reliable information from similar profiled subjects in future investigations.

Pre-clinical studies of pramipexole: clinical relevance

This paper reviews the preclinical study of the novel dopamine agonist pramipexole and its use in early Parkinson's disease (PD). Emphasis will be given to those properties distinguishing this drug from other dopamine agonists, the relevance of the preclinical data to clinical trial results in early PD, and the putative neuroprotective properties of the compound. The conventional dopamine agonists are ergot-derived compounds that are most widely used as adjunctive therapies in advancing Parkinson's disease (PD). Examples of conventional agonists are bromocriptine and pergolide. Pramipexole is an aminobenzothiazole compound, recently introduced for the treatment of both early and advanced PD. Its nonergot structure may reduce the risk of side-effects, considered unique to ergot drugs, such as membranous fibrosis. Pramipexole is a full dopamine agonist with high selectivity for the D2 dopamine receptor family. This family includes the D2, D3 and D4 receptor subtypes. Pramipexole has a 5- to 7-fold greater affinity for the D3 receptor subtype with lower affinities for the D2 and D4 receptor subtypes. The drug has only minimal alpha2-adrenoceptor activity and virtually no other receptor agonism or antagonism. The optimal dopamine receptor activation for the safe and effective treatment of PD is not known. Findings in animal models and clinical studies indicate that activation of the postsynaptic D2 receptor subtype provides the most robust symptomatic improvement in PD. Given its pharmacological profile, it is not surprising that pramipexole was found to be effective in ameliorating parkinsonian signs in animal models. This therapeutic effect has been confirmed in clinical trials in both early and advanced PD. In early disease, it provides a clear reduction in the chief motor manifestations of PD and improved activities of daily living. Perhaps most striking is the large number of clinical trial patients who have remained on pramipexole monotherapy for many months. The majority of these subjects have been maintained on pramipexole for an excess of 24 months without requiring additional symptomatic treatment with levodopa. This is in contrast to the general clinical experience with older conventional agonists. Pramipexole also has a favourable pharmacokinetic profile. It is rapidly absorbed with peak levels appearing in the bloodstream within 2 h of oral dosing. It has a high absolute bioavailability of > 90% and can be administered without regard to meals. It has no significant effects on other antiparkinson drugs such as levodopa or selegiline. Its excretion is primarily renal and, thus, has little or no impact on hepatic cytochrome P450 enzymes or other related metabolic pathways. Pramipexole has also been theorized to have 'neuroprotectant' properties. Oxyradical generation is posited as a cause or accelerant of brain nigral cell death in PD. Pramipexole stimulates brain dopamine autoreceptors and reduces dopamine synthesis and turnover which may minimize oxidative stress due to dopamine metabolism. Furthermore, the compound has a low oxidation potential that may serve as an oxyradical scavenger in the PD brain. In summary, pramipexole is a new antiparkinson medication found to have unique dopamine agonist characteristics and putative neuroprotective properties.

Time course of loss of clinical benefit following withdrawal of levodopa/carbidopa and bromocriptine in early Parkinson' s disease

Putative neuroprotective agents for Parkinson's disease can be assessed in untreated patients using progression of clinical disability as an index of disease progression. To avoid the confound associated with symptomatic therapy, progression of the underlying disease can be assessed by evaluating the progression of clinical disability from an untreated baseline to a final visit following wash-out of symptomatic medication. In this type of analysis it is critical to use a washout of sufficient duration to ensure elimination of symptomatic effects. To assess the time course of resolution of symptomatic effects, we evaluated 31 patients at days 1, 8, and 15 following discontinuation of levodopa/carbidopa and bromocriptine. Mean total Unified Parkinson's Disease Rating Scale scores (+/- standard error) increased (worsened) by 7.4+/-1.5 from day 1 to day 15 (p <0.0001), 4.5+/-1.2 from day 1 to day 8 (p = 0.0009), and 2.9+/-1.0 from day 8 to day 15 (p = 0.01). We conclude that a wash-out of at least 2 weeks is required to eliminate the symptomatic effects of levodopa/carbidopa and bromocriptine in patients with early Parkinson's disease.

Novel drugs for Parkinson's disease

Treatment options in PD have expanded remarkably in the past several years. Three new drugs were approved for use in the United States just within the 9 months preceding the preparation of this article. Several new compounds are in the pipeline. Nevertheless, the unmet needs of PD patients are readily apparent in any busy clinical practice. These needs can be posed as three deceivingly simple questions: 1. When and how should L-dopa be started? Despite the fact that L-dopa remains the mainstay of PD therapy after 30 years' time, lacking is a fundamental understanding of proper usage and avoidance of long-term complications. 2. What can be done about cognitive decline and dementia in PD? The current answer is nothing. Efforts are just beginning to fill this large void in knowledge and provide adequate treatment for this disabling problem. 3. How can PD be prevented? This question cannot be answered because the cause of PD remains uncertain. The dearth of substantive information available on this topic is evidenced in this article. The bulk of text appears under the heading Symptomatic Treatments, whereas only a few speculative comments can be offered under the heading Preventive Treatments. The paramount need for expanded resources and dedicated efforts to identify the causes and devise preventions must be met if advances in the treatment of PD are to be made in the twenty-first century.

Aging and the basal ganglia

Age-related changes within the basal ganglia primarily affect the dopaminergic nigrostriatal pathway and related pigmented nuclei. These alterations resemble the pathologic changes of Parkinson's disease, but cell dropout is not as marked or uniquely selective in the aged brain. Histopathologic changes including interneuronal inclusion bodies are associated with aging, but the number and location of these suggest that this is a nonspecific phenomenon, not the harbinger of Parkinson's disease or other specific neuropathology. It appears that aging and Parkinson's disease result in similar brain cell degenerative processes, but the causes and specific triggering mechanisms for these changes are likely to be quite distinct.

Double-blind controlled trial of gabapentin in essential tremor

Gabapentin has been reported to be effective for essential tremor (ET) based on open-label trials. We studied gabapentin (1800 mg/day) and placebo in a double-blind crossover design in 20 ET patients. Eighteen patients completed the study and two patients dropped out as a result of adverse effects which resolved when the medication was discontinued. Tremor was assessed at baseline and after 2 weeks of gabapentin and placebo treatment. One patient was mildly improved and another was moderately improved with placebo. Similarly, one patient reported mild improvement and another patient had marked improvement with gabapentin. All the remaining patients either reported no change or were worse with both treatment arms. There was no significant difference for total tremor score, hand tremor score, handwriting scores, or pouring scores. Sickness Impact Profile scores were no different between placebo and gabapentin. Our results suggest that as an adjuvant therapy in ET, gabapentin has limited benefit.

Gender differences in Parkinson's disease

We examined data from 630 patients entered into the University of Kansas Medical Center's Parkinson's Disease (PD) Registry to determine if gender differences exist in terms of both cognitive and motor symptoms of PD. An analysis of the Mini-Mental State Examination scores indicated slightly higher scores for women relative to men. Although women had significantly better scores than did men on the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS), they had a significantly greater prevalence of dyskinesias compared with men. These motor differences were significant only in patients with PD of greater than 5 years duration. There were no gender differences for age of diagnosis, Hoehn and Yahr Staging, Schwab and England Scale, or the mentation and activities of daily living sections of the UPDRS. We conclude that as PD progresses, gender differences emerge, with men exhibiting more severe parkinsonian motor features and women experiencing more levodopa-induced dyskinesia.

Clinical expression of essential tremor: effects of gender and age

Essential tremor (ET) is considered to be a monosymptomatic disorder consisting primarily of postural hand tremor. Nevertheless, clinical expression can vary based on the body region affected by tremor and the coexistence of other neurologic signs, such as tandem gait disturbance. We conducted a two-part study to test the hypothesis that variability in ET clinical expression is influenced by gender and age. In part 1, we examined a large ET clinical database (n = 450), comparing ratings of postural hand and head/voice tremor based on gender. Head/voice tremor was significantly more frequent and more severe among female ET patients; men had more severe postural hand tremor. In part 2, ET patients (n = 40) had significantly more missteps when tandem walking in comparison to age-matched controls. Poor tandem walk in ET cases was associated with more advanced age, but not gender, disease duration, or ratings of postural hand or head/voice tremor. We conclude that gender influences the body region most affected by ET possibly through the effects of the sex chromosomes or hormones. Ataxia (tandem gait difficulty) is common in ET and may be an accentuation of cerebellar dysfunction due to aging.

Effects of thalamic deep brain stimulation based on tremor type and diagnosis

It has been suggested that deep brain stimulation (DBS) is less effective in alleviating proximal than distal postural arm tremor reduction is said to be less in essential tremor (ET) than in Parkinson's disease (PD). We analyzed blinded rater's tremor scores and subjects' disability ratings at 3-month follow-up to examine the effects of DBS based on tremor type (rest, kinetic, distal postural, proximal postural) and diagnosis (ET, PD). An independent examiner provided tremor scores using randomized videotaped footage of 19 ET and 10 PD subjects at baseline and at follow-up with DBS "on." Subjects provided self-ratings of disability at baseline and at follow-up. Comparisons of baseline and follow-up tremor scores and disability ratings were made using the Mann-Whitney U and Wilcoxon rank sum W test; correlation analyses were performed using Spearman rank order correlation test. There were significant and essentially equal improvements in tremor scores of test, kinetic, distal postural, and proximal postural tremor at follow-up. Only one subject had no improvement in tremor. Tremor improved significantly and to the same extent in ET and PD subjects in each position except "at rest," which was most improved in PD (p = 0.0003). ET and PD subjects did not differ in the extent of disability improvement. Improved disability correlated only with improved postural tremor scores; proximal postural and distal postural (r = 0.41, p = 0.03; r = 0.47, p = 0.01). DBS is effective in alleviating tremor and disability in both ET and PD. Resting, kinetic, distal postural, and proximal postural tremor can be reduced to an equal degree. However, DBS produces the greatest improvement in disability in association with improved postural tremor in both ET and PD.

Early morning akinesia in Parkinson's disease: effect of standard carbidopa/levodopa and sustained-release carbidopa/levodopa

We examined the effects of supplemental standard carbidopa/levodopa (Std-L) on early morning akinesia in patients with Parkinson's disease (PD) who were being treated with sustained-release carbidopa/levodopa (L-CR). We compared plasma dopa levels and clinical response in 15 PD patients after a dose of Std-L and L-CR (2 hours later) and after a dose of L-CR and placebo in a double-blind, placebo-controlled, crossover study. Plasma dopa levels, total motor score, walking time, and finger tapping time were assessed every 15 minutes for the first 2 hours and then every 30 minutes for the next 3 hours. The time of onset in clinical benefit was significantly earlier with Std-L (47 minutes, range 15 to 75 minutes) as the first dose as compared with L-CR (58 minutes, range 30 to 105 minutes). Similarly, there was a significant difference in the peak plasma dopa levels (Cmax) and the time to reach peak plasma dopa levels (Tmax) with administration of Std-L (Tmax 36 minutes; Cmax 1,501 micrograms/ml) as compared with L-CR (Tmax 111 minutes, Cmax 1,260 micrograms/ml). There was no significant difference in dyskinesias between the two treatment arms. An initial morning dose of Std-L alleviates the problem of delayed-onset clinical response that commonly occurs with L-CR.

Normal distribution of apolipoprotein E alleles in progressive supranuclear palsy

Apolipoprotein E (Apo E) genotype is a genetic risk factor influencing the development of Alzheimer's disease (AD). Progressive supranuclear palsy (PSP), like AD, is a dementing illness with neurofibrillary tangles. We determined the frequencies of Apo E alleles in 52 PSP patients and 52 age- and gender-matched controls. The distribution of Apo E allele frequencies and genotypes showed no difference between PSP and controls. Apo E allele status does not influence the development of PSP.

Deep brain stimulation for essential tremor

We examined the effects and safety of deep brain stimulation (DBS) as a treatment for essential tremor (ET). Ten ET patients with disabling medication-refractory tremor underwent stereotactic implantation of a DBS lead in the left Vim thalamic nucleus and completed a 6-month follow-up. The Clinical Tremor Rating Scale and disability assessments were performed at baseline, 1-, 3-, and 6-month follow-up. There were significant improvements in dressing, drinking, eating, bathing, and handwriting as reported by the subjects. Tremor severity, writing, pouring, and spiral and line drawing were significantly improved as rated by the examiner. Improvements persisted through the 6-month follow-up period. Although global disability significantly lessened in the group as a whole, one subject with hand-finger tremor accentuated by writing had no change in disability status. In this 6-month open-label study, DBS was effective and safe in reducing tremor and functional disability in ET.

Risk factors for dementia in Parkinson's disease: effect of education

Cognitive deficits are common in Parkinson's disease (PD), but the pathophysiology and relationship to Alzheimer's disease (AD) are not understood. We used a case-control format to investigate putative risk factors for the development of dementia in patients with Parkinson's disease. We compared 52 cognitively intact patients with PD to 43 PD patients with dementia with regard to factors previously suggested as relevant to either AD or PD. Multiple logistic regression yielded the following significant predictors of dementia in PD: lack of education (less than a high school graduate) (OR 21); severity of motor deficit (UPDRS total motor score greater than 20; OR 6.34), and PD onset at greater than 60 years of age (OR 4.12). The predictive probability of dementia in our subjects when all three variables were positive was 97.9%. We conclude that education may modify the risk of cognitive decline in PD. Protective effects of educational attainment, independent of dementia etiology, may be due to greater functional brain reserve.

Nocardia species as an etiologic agent in Parkinson's disease: serological testing in a case-control study

To test the hypothesis that Nocardia spp. may be an etiologic factor in Parkinson's disease (PD), we used a serodiagnostic panel to determine if PD patients had antibodies specific for Nocardia spp. To validate the serological test panel, sera from healthy volunteers and from patients with culture-proven nocardiosis (n = 307) were compared in part 1 of the study. The sensitivity of the panel was 88% for detection of culture-proven nocardial infections, and specificity was 85% (excluding cross-reactive leprosy cases). In part 2, no difference in seropositivity was found when PD patients were compared with their age- and gender-matched controls (n = 140). We found a high exposure rate of humans to nocardial antigens, especially among men and older individuals. Our results offer no support to the hypothesis that Nocardia spp. are causative in PD; however, it is possible that serological testing may not be optimal for detection of nocardial central nervous system infection.

Erythrocyte thiolmethyltransferase: another failed marker for Alzheimer's and Parkinson's diseases

There are reports that patients with Parkinson's disease (PD) and Alzheimer's disease (AD) have reduced levels of thiolmethyltransferase (TMT) in erythrocyte membranes. TMT methylates thiols and thiocarbamates, thereby reducing their toxicity. We examined TMT levels in erythrocytes from patients with PD and AD and from age-matched controls. Specific activities of TMT were 564 +/- 199 U/mg protein in PD (n = 32), 513 +/- 118 in AD (n = 13), and 565 +/- 183 in controls (n = 35). There was no difference between any of the groups (p = 0.64). We failed to confirm TMT as a marker for neurodegenerative diseases or for this metabolic defect predisposing to susceptibility to neurotoxins.

Pramipexole in patients with early Parkinson's disease

We evaluated the efficacy, safety, tolerability, and pharmacokinetics of pramipexole, a novel dopamine D2 receptor agonist, in early Parkinson's disease (PD). The study design was a parallel, placebo-controlled trial using an ascending dose of 4.5 mg/day pramipexole maximum. All subjects received selegiline (10 mg/day) but were not treated with levodopa. Of the 55 subjects who received at least one dose of the study medication, all but one, in the placebo group, completed the trial, which was 9 weeks in duration. The primary efficacy endpoints were changes in scores from baseline to final measurement on the Unified Parkinson's Disease Rating Scale (UPDRS) Parts II and III. The pramipexole group had a significantly greater improvement (p = 0.002) than the placebo group on UPDRS Part II (Activities of Daily Living). The change in score from baseline to final measurement on UPDRS Part III (Motor Examination) was not significantly different (p = 0.10) between the pramipexole and placebo groups, although the trend favoured the pramipexole group. All subjects in both the pramipexole and the placebo groups experienced one or more episodes of asymptomatic orthostatic hypotension; there was no significant difference between the pramipexole and the placebo groups in the number of subjects experiencing symptomatic orthostatic hypotension. The adverse events profile of pramipexole was similar, in general, to that of other dopamine receptor agonists. Plasma pramipexole levels increased linearly with dose. Pramipexole appears to be promising agent in the treatment of early PD.

Differentiation of the dementias of Alzheimer's and Parkinson's disease with the dementia rating scale

The Mattis Dementia Rating Scale (DRS) was used to distinguish between 50 dementia of the Alzheimer's type (DAT) and 50 Parkinson's disease (PD) subjects matched for age, education, and DRS total score. Despite a similar level of overall cognitive impairment, the DAT group earned significantly lower scores than did the PD group on the Memory subscale, while the PD group displayed lower scores than did the DAT subjects on the Construction subscale. Ajackknifed, stepwise, linear discriminant function using the five DRS subscales revealed that the Memory, Construction, and Initiation subtests significantly distinguished the groups. These results suggest qualitative differences in the dementias of DAT and PD patients and reveal that such differences can emerge on brief mental status examinations.

Botulinum toxin treatment of essential head tremor

We examined in a double-blind, placebo-controlled study the effects of botulinum toxin in 10 patients with essential head tremor. Each subject received two treatments approximately 3 months apart, one with botulinum toxin injections and another with normal saline injections into the sternocleidomastoid and splenius capitis muscles. The subjects were assessed before each treatment and at 2, 4, and 8 weeks after injections. There was moderate to marked improvement in clinical ratings in five subjects after botulinum toxin injections and in one subject after placebo. There was moderate to marked subjective improvement in five patients with botulinum toxin as compared with three subjects with placebo. Side effects were mild and transient. We conclude that botulinum toxin may be useful for patients with essential head tremor who have failed to benefit from oral medications.

The influence of depression on cognition in Parkinson's disease: a pattern of impairment distinguishable from Alzheimer's disease

Conflicting reports about the effects of depression on cognition in Parkinson's disease (PD) are difficult to interpret because they are based on small sample sizes and confound depression with other variables. We found that a sample of 45 PD patients with current depression was cognitively more impaired than a sample of 45 PD patients without current depression matched for age, education, gender, age at disease onset, disease duration, and disease severity. The domains of cognition impaired in the two PD groups (compared with 45 age-, education-, and gender-matched controls) overlapped considerably, but only the depressed PD group had impaired memory relative to the control group. Our comparison of 22 depressed PD patients and 22 Alzheimer's disease (AD) patients matched for over-all severity of cognitive impairment, age, education, and gender indicated that the depressed PD group performed significantly worse on visuoconstructive tasks and marginally worse on conceptualization tasks. In contrast, the AD group performed significantly worse than the depressed PD group on memory tasks. Together, our results suggest that depression has a negative impact on cognition (and, in particular, memory) in PD, and that the pattern of this cognitive impairment is distinguishable from that associated with AD.

Apolipoprotein E genotypes in Parkinson's disease with and without dementia

The apolipoprotein E gene (Apo E) type 4 allele is a genetic risk factor influencing the development and age of onset of Alzheimer's disease. Because Parkinson's disease shares many characteristics of Alzheimer's disease, we studied the frequencies of Apo E genotypes in a cohort of 52 Parkinson's disease patients with dementia and 61 patients without dementia. Dementia was determined per National Institute of Neurological and Communicative Disorders and Stroke criteria and Mattis Dementia Rating Scale (DRS) < 126. Normal cognition was defined as DRS > 132. Apo E genotype and allele frequencies did not differ between demented and nondemented parkinsonian patients. Neither group's genotype and allele frequencies differed from that of a nondemented population of 78 controls. We conclude that the Apo E epsilon 4 allele influences neither the development of Parkinson's disease nor the dementia associated with Parkinson's disease.

Influence of demographic variables on the Dementia Rating Scale

Demographic characteristics influence many cognitive assessment tools. We evaluated the impact of age, education, and gender on the Dementia Rating Scale (DRS) in a sample of 212 normal people. Separate regression analyses revealed that age was the most potent demographic factor, whereas education and gender had little impact. However, the amount of variance accounted for by age was small (less than 20%). Clinical utility of age-adjusted DRS total score cut-offs was investigated in samples of Alzheimer's and Parkinson's disease patients. Hit rate analysis revealed greater sensitivity for a single cut-off value than age-corrected cut-off scores. Overall, these findings revealed the lack of a clinically meaningful relationship between demographic characteristics and DRS scores, suggesting that age, education, and gender can be ignored for interpretative purposes based on cut-off scores.

Enhanced MPTP neurotoxicity after treatment with isoflurophate or cholinergic agonists

Administration of the irreversible cholinesterase inhibitor isoflurophate (diisopropylfluorophosphate, DFP) before 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) enhanced the loss in tyrosine hydroxylase activity and dopamine and 3,4-dihydroxy-phenylacetic acid content in the striatum of mice in a dose-dependent manner. The effect of DFP on the MPTP-induced changes of dopaminergic markers was evident 30 days after initiating treatment, suggesting augmented neurotoxicity. Neurotoxicity was also enhanced by prior treatment with nicotine, carbachol or oxotremorine. We conclude that activation of either muscarinic or nicotinic receptors enhances the neurotoxicity of MPTP.

Personality and depression in Parkinson's disease

The Parkinson's disease (PD) patient has been characterized as having a distinctive personality with introverted features. These personality traits are said to predate motor symptoms and are theorized to serve as a subtle clue to latent PD. To examine this hypothesis, we compared remote and current personality features in 35 PD subjects and 35 controls. Subjects' spouses completed a personality inventory (PI) characterizing patients' premorbid and current status. The premorbid PI of PD subjects differed from that of controls in being more "quiet," "generous," "cautious," and "even-tempered," and less "flexible." The characterization of the PD subjects' current personality differed greatly from reported premorbid personality features, i.e., significant change in 13 of 24 PI items. Personality inventory responses regarding both the PD subjects' premorbid and current personality correlated to symptoms of depression and disease severity. Cognition, tobacco use, alcohol consumption, and rural versus urban residency did not correlate with PI responses. We conclude that PD patients are apt to be viewed as introverts premorbidly, and, with disease onset, more striking personality changes are recognized. These perceptions appear to be closely linked to depressed affect and correlate with motor impairment to a lesser extent.

Risk factors for Parkinson's disease

Parkinson's disease (PD) has been associated with rural living, well-water consumption, and pesticide exposure; however, the individual risk contribution of these variables has not been established. We examined social and medical histories of predominantly rural populations to determine relative risk factors for PD. Patients and controls were surveyed regarding residency, occupation, medical history, and social and dietary habits. An initial multiple logistic regression model was confounded by excessive variable colinearity. Principal factor analysis yielded three factors: rural living (including years of rural residency and ground-water use), pesticide use, and male lifestyle (male gender, head trauma, male-dominated occupations). Other variables did not load in factor analysis and were entered separately, with the three factor scores, in a second multiple logistic regression model. Significant predictors of PD emerged (in order of strength): pesticide use, family history of neurologic disease, and history of depression. The predicted probability of PD was 92.3% (odds ratio = 12.0) with all three predictors positive. Pesticide use (distinguishable from rural living) can be considered a risk factor for the development of PD, with family history of neurologic disease and history of depression serving as weaker predictors of PD.

Interactive video conferencing: a means of providing interim care to Parkinson's disease patients

Inequity in health care delivery is attributable to a variety of factors including geographic isolation. Patients living far from major urban centers have limited access to medical specialists. In the instance of Parkinson's disease (PD), optimal assessment and care may depend upon availability of specialty health care providers. In order to broaden health care access, interactive video conference (IVC) units are being developed for medical use. IVC allows a patient at a distant site to be "seen and heard" by a hospital-based physician; simultaneously, the patient can "see and hear" the doctor. To establish the validity of this technology in the evaluation of PD, nine patients were independently examined and scored (UPDRS) by two movement disorder specialists. One examination was performed in-person by the usual physician. The other examination was performed on the same day via IVC over a distance of 350 miles by an examiner previously unfamiliar with the patients. Individual patient scores did not differ based on examiner (Spearman Rho Correlation Coefficients: UPDRS total scores r = 0.933, p < 0.0002; Hoehn and Yahr Scale r = 0.883, p < 0.001). A standardized exit interview was conducted to assess patients' perceptions of this application of video technology. Responses were favorable and virtually all patients viewed this as a means of accessing better health care. We conclude that valid motor assessments of PD patients can be made via IVC.

Aromatic L-amino acid decarboxylase activity of mouse striatum is modulated via dopamine receptors

Aromatic L-amino acid decarboxylase (AAAD) activity is enhanced in the striatum of control and MPTP-treated mice after administration of a single dose of the dopamine receptor antagonists haloperidol, sulpiride, and SCH 23390. MPTP-treated mice appear more sensitive to the antagonists, i.e., respond earlier and to lower doses of antagonists than control mice. The rise of AAAD activity induced by the antagonists is prevented by pretreatment with cycloheximide. The apparent Km values for L-3,4-dihydroxyphenylalanine (L-DOPA) and pyridoxal 5-phosphate appear unchanged after treatment with the antagonists. Increased AAAD activity was observed also after subchronic administration of dopamine receptor antagonists or treatment with reserpine. A single dose of a selective dopamine receptor agonists had no effect on AAAD activity. In contrast, administration of L-DOPA, quinpirole, or SKF 23390 for 7 days lowers AAAD activity in the striatum. We conclude that AAAD is modulated in striatum via dopaminergic receptors.

Clinical experience with controlled-release carbidopa/levodopa in Parkinson's disease

We converted 158 Parkinson's disease (PD) patients on stable doses of standard carbidopa/levodopa (Std-L) to controlled-release carbidopa/levodopa (L-CR). Of the 141 patients who completed the study, 103 (73%) preferred L-CR, 26 (18.5%) preferred Std-L, and 12 (8.5%) had no preference. One hundred fourteen patients elected to continue L-CR, and we performed the primary data analysis on this group. Following conversion to L-CR, patients reported an increase in length of benefit from each dose and an increased "kick-in" time. There was a decrease in the total number of doses, "off" periods, sleep interruptions per night, dose failures, and sleep disturbances. Conversion to L-CR resulted in a significant increase in total levodopa dose. There was no significant change in the dyskinesias. However, early-morning dystonia resolved in eight of 14 patients. Our findings suggest that L-CR is particularly effective in decreasing motor fluctuations, reducing nocturnal problems, and minimizing levodopa dose failures in PD.

Effects of selegiline dosing on motor fluctuations in Parkinson's disease

To examine selegiline's dosing effects, we studied 16 Parkinson disease patients with motor fluctuations in a double-blind, crossover trial of selegiline at 0, 5, and 10 mg daily. Patients' motor diaries, disability scores, and walking speed were marginally improved, with no advantage of 10 mg over 5 mg found. We conclude that in patients with motor fluctuations, selegiline provides modest symptomatic effects, with daily dosing of 5 mg being indistinguishable from 10 mg.

Osteomyelitis of the skull base

Three cases of osteomyelitis of the skull base with associated problems in diagnosis and therapy are discussed. Patients with atypical skull base osteomyelitis are difficult to diagnose as they have no ear abnormalities, but they often develop multiple cranial nerve deficits mimicking symptoms of a posterior fossa mass. We conclude that computed tomographic scans, magnetic resonance imaging studies, bone scans indium-labeled white blood cell scans, and gallium scans are useful in making the diagnosis. A biopsy of the bony lesion often is needed to identify the causative organism and to rule out a tumor. Intravenously administered antibiotics are the mainstay of therapy and should be continued until 1 week after the gallium scan shows no abnormalities. Follow-up gallium scans then are done at 1 week and 3 months after the cessation of antibiotic therapy to search for a recurrence.

Is essential tremor benign?

We analyzed the results of the Sickness Impact Profile, a self-reporting measure of sickness-related dysfunction in 753 essential tremor (ET) patients, 87 controls from the general population, and 145 patients with Parkinson's disease (PD). Compared with the general population, ET patients had significantly greater dysfunction in all but one category. Communication, Work, Emotional Behavior, Home Management, and Recreation and Pastimes were particularly impaired in ET. The PD patients had significantly higher dysfunction in all categories as compared with ET patients. We conclude that significant disability can occur in ET and, compared with PD, ET tends to be less severe but causes relatively greater psychosocial dysfunction.