Age-dependent decline of nigrostriatal dopaminergic function: a positron emission tomographic study of grandparents and their grandchildren

Despite postmortem evidence for an age-related decline in nigrostriatal dopaminergic function, position emission tomography (PET) studies have produced inconsistent results. This may be due to differences in methods or of subject selection. To investigate further the effect of age on dopaminergic function, we performed PET with 6-L-[18F]fluorodopa (FD) on 12 pairs of grandchildren and their grandparents. The FD uptake rate constant (Ki) was calculated using a graphical method for the whole striatum to avoid confounding of the results by striatal atrophy. The mean Ki was significantly lower in grandparents (p = 0.020). These PET observations represent in vivo confirmation of postmortem evidence that nigrostriatal dopaminergic function declines with aging.

Lymphocytes from the site of disease are functionally different from peripheral blood lymphocytes and may demonstrate etiologically related antigen specificity

Over a 12-year period, in vitro synovial lymphocyte responses to microbiological antigen stimulation were measured by the [3H]thymidine uptake method in referred patients with all types of non-crystal, non-septic, inflammatory arthritis. From this large study group comparisons of synovial with peripheral blood lymphocyte (PBL) responses were available in 9 patients with enteric reactive arthritis (ERA), 12 patients with sexually acquired reactive arthritis (SARA) and 18 patients with recurrent or persistent oligoarthritis or with polyarticular 'rheumatoid' arthritis. Employing 2-tailed t tests, analysis of variance (ANOVA) or meta-analysis, as appropriate to the obtained data, significant differences were found between synovial and peripheral blood responses. In only 2 of 9 patients with bacteriologically defined ERA, in only 4 of 12 patients with SARA and in only 2 of 18 patients with oligoarthritis or 'rheumatoid' arthritis did the PBLs show statistically significant responses to the antigen that elicited a significant response from synovial lymphocytes. It is concluded that lymphocytes from the site of disease are often functionally different from PBLs and may demonstrate etiologically related antigen specificity; thus they may be a preferred source of lymphocytes for the investigation of immunologically mediated disease, the etiology of which is not understood. This viewpoint is supported by a recent paper on the specificity of hepatic lymphocytes for a protein of hepatitis C in patients with chronic hepatitis C, and also by the use of tumour-infiltrating lymphocytes for anti-melanoma therapy.

Errors in the diagnosis of visual field progression in normal-tension glaucoma

BACKGROUND

Despite strictly defined criteria for visual field progression in the ongoing Normal-tension Glaucoma Study, the authors noted a surprisingly large number of patients reaching the endpoint. Traditional methods could not be used to check the diagnostic accuracy of their criteria, because no "gold standard" was established for distinguishing true change from physiologic long-term fluctuation.

METHODS

The authors developed a statistical method based on the results of duplicate tests for progression in their subjects. This method allowed the authors to assess the sensitivity, specificity, and predictive values of their diagnostic criterion. It also estimated the true incidence of progression and provided standard errors for the estimates.

RESULTS

The authors found that their original strict criteria for progression, based on duplicate testing, produced false calls of progression 57% of the time. By raising the requirement for deterioration and by repeating the entire sequence of duplicate testing once more, the authors have successfully reduced the rate of false calls to 2%.

CONCLUSION

Accuracy in recognizing progression is improved by not accepting small changes as evidence of progression and by confirming the findings on repeat testing.

Synovial lymphocytes indicate "bacterial" agents may cause some cases of rheumatoid arthritis

OBJECTIVE

To evaluate synovial lymphocyte response data from "rheumatoid" patients, to determine if "bacterial" antigens caused significant stimulation.

METHODS

Two-tailed t tests, analysis of variance, and metaanalysis were applied to 3H-thymidine uptake triplicate/quadruplicate counts, resulting from microbiological antigen stimulation of synovial fluid lymphocytes.

RESULTS

In 5 patients with rheumatoid arthritis, maximal synovial lymphocyte responses to chlamydial (in 3) and salmonella (in 2) antigens were significantly greater than to other tested antigens.

CONCLUSION

The data, associated with other published data from similar studies, suggest that Chlamydia and pathogenic Enterobacteriaceae may be etiologically related to the arthritis of some patients with rheumatoid arthritis.

Diagnostic tests: a statistical review

Common measures of the accuracy of diagnostic tests are reviewed. It is shown that the actual performance (predictive value) of these tests depends not only on their sensitivity and specificity, but also on the prevalence of the disease in the population tested (Bayes' theorem). The effect of an inaccurate "gold standard" on the calibration of a new diagnostic test is discussed. Receiver operating characteristic (ROC) curves are introduced as a tool for selecting an optimal cutpoint for a test, and for comparing different tests. Schemes are given for combining tests to improve their accuracy. When multiple continuous measurements are available, methods of discriminant analysis (and logistic regression) are shown to provide measurement combinations with improved accuracy. Examples and key references are provided.

Clinical observations on the rate of progression of idiopathic parkinsonism

The time course of evolution of clinical deficits has been a traditional guide to the nature of the aetiopathogenesis of neurological disease. We studied the influence of ageing and duration of disease on the natural history of idiopathic parkinsonism (IP). Two hundred and thirty-eight patients with IP were examined while off medication. Bradykinesia scores were analysed against patients' age and duration of disease by multiple regression. There was no significant interaction between the effects of age and of duration (P = 0.923). We conclude that age and duration of symptoms influence the natural history of IP additively and independently. Furthermore, the rate of neuronal death is more rapid in the earlier stages of evolution of the pathology; subsequently, the velocity of progression slows down to approach the rate of attrition produced by normal ageing. This time course has implications for possible models of pathogenesis.

A mathematical model of pathogenesis in idiopathic parkinsonism

We used our observations relating clinical deficits in idiopathic parkinsonism (IP) to age and to disease duration (Lee et al, Brain 1994; 117: 501-7), to develop a mathematical model of the temporal profile of neurodegeneration in IP. We also examined other sets of relevant published observations and applied three additional assumptions which permitted the formulation of this model. Our model indicates that accelerating or decelerating processes should be excluded as the driving forces behind neuronal death in IP. Mechanisms in accord with the model include: (i) an event that kills some neurons and damages others in such a way that their life expectation is reduced; or (ii) an event that starts a process which is continuously killing healthy neurons at a constant rate. The model enables us to extrapolate back to estimate when the causal event occurred. It also explains why IP proceeds more rapidly in older patients. The model has potential relevance to other neurodegenerative disorders, such as Alzheimer's disease and amyotrophic lateral sclerosis.

A mathematical model for the prediction of the impact of HIV infection on tuberculosis

A mathematical model is introduced to study the accelerating impact of HIV infection on the incidence rates of tuberculosis (TB) disease. A sexually active population (15-49 years) is followed cross-sectionally over a period of time. Beginning with the year in which HIV infection was probably first present in the population, the model calculates the growing yearly incidence rates of new TB disease in HIV-positive and in HIV-negative individuals. Model equations, derived by an actuarial method, are developed recursively. Input information required for the calculations includes the age distribution of the study population, pre-HIV annual TB infection rates, annual HIV infection and mortality rates, and estimates of annual TB disease breakdown rates in the absence and in the presence of HIV infection. With correct input data, the model provides a useful blueprint for health agencies in designing effective programmes for curbing the future course of these dual epidemics in the population.

Reliability of transcranial magnetic stimulation for mapping the human motor cortex

Motor mapping using transcranial magnetic stimulation has been applied to the study of adaptive and restorative mechanisms of the motor cortex. To date, the reproducibility of mapping techniques has yet to be investigated in detail and/or confirmed. We report a technique used to map the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) motor cortices of 6 normal volunteers, each studied on 2 occasions separated by several weeks (range of 21-132 days). APB and ADM results were analyzed separately, with area and volume characteristics subjected to analysis of variance. Coefficients of variation, which should be low, ranged from 14% to 37% and coefficients of reliability, which should be high, ranged from 63% to 94%, indicating that the described technique for motor mapping is responsible.

Tendon jerks in Parkinson's disease

Tendon reflexes were examined in 119 patients with idiopathic parkinsonism (IP) and 40 spouse controls to estimate the type and frequency of any alterations in the reflexes. Forty one of 119 patients and 2 of 40 controls had reflex ratings of 3+ at two or more sites (p < 0.001). There was no correlation of reflex score with the severity of disease or with the cardinal signs of IP. In 21 patients with asymmetric tendon jerks the side with the more active reflexes correlated with the side with greater parkinsonian signs. We conclude that an increase in tendon jerks is a feature of IP. The pathophysiology of this change in reflexes should be investigated further to establish if it is a heretofore overlooked manifestation of basal ganglia dysfunction or a link with other neurodegenerative diseases.

Reproducibility of fluorine-18-6-fluorodopa positron emission tomography in normal human subjects

Fluorine-18-6-fluorodopa (FD) positron emission tomography (PET) is established for measuring nigrostriatal dopaminergic function. This is despite the absence of data on the reproducibility of results.

METHODS

With an ECAT 953B/31 tomograph, we performed two or three repeated FD PET scans in 10 normal subjects to measure the scan-to-scan variation in the total striatal uptake rate constant (Ki).

RESULTS

We found a scan-to-scan standard deviation (s.d.) of 8.7% of the mean. The between-subject s.d. was 26% of the mean, resulting in a reliability coefficient of 90%. Analysis of the variation in the components contributing to Ki showed a reliability varying from 77% to 86% (depending on the different time points analyzed) for emission data measured by the PET camera. The reliability of the blood radioactivity time course, as reflected by the stretch time, varied from 43% to 81%. The overall reliability for the correction of the blood time course for metabolites of FD was 71%. Variation in the blood radioactivity contributed to the variability of Ki by 50% more than the metabolite correction and by 200% more than the emission data.

CONCLUSION

The striatal Ki is a reliable measurement; it has a 95% chance of lying within +/- 18% of its value for an individual normal subject.

A scoring error in the Mini-Mental State test

A scoring error is identified in the Mini-Mental and the Modified Mini-Mental State test. The major effect of this error is to produce a gap in the total score distribution of the test, resulting in a potential spurious underestimation of the score. Two possible remedies are suggested to resolve this problem.

Anti-glutamate therapy in amyotrophic lateral sclerosis: a trial using lamotrigine

Glutamate excitotoxicity is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). We report the results of a double blind, placebo controlled, trial using 100 mg of oral daily lamotrigine (3,5-diamino-6-(2,3 dichlorophenyl)-1,2,4-triazine) which inhibits glutamate release. 67 patients were entered and at trial termination of 1.5 years 15 had withdrawn (9 active and 6 placebo) and 12 had died (6 active and 6 placebo). Mean age at entry was 57.5 years for the active and 58.6 years for the placebo groups. Patients were seen at 3 monthly intervals and scored according to neurological deficit based upon age of onset, bulbar and respiratory involvement, ambulation and functional disability. The mean change in clinical scores for the active versus placebo groups over the trial period was 7.1 +/- 3.3 and 9.0 +/- 3.3 respectively (0.05 < p < 0.10). Changes in cortical threshold and MEP/CMAP ratios to magnetic stimulation also did not differ significantly between the two groups. We conclude that lamotrigine in the doses administered does not alter the course of ALS.

Receiver operating characteristic curve analysis in the prediction of carpal tunnel syndrome: a model for reporting electrophysiological data

Receiver operating characteristic (ROC) curves were used to predict the risk of carpal tunnel syndrome (CTS). Patients were classified clinically as: (1) normal exam and no symptoms (169 hands); (2) having a motor and/or sensory deficit typical of CTS (115 hands); (3) having a history characteristic of CTS (156 hands); and (4) nondiagnostic symptomatology (122 hands). Electrophysiological studies consisted of median and ulnar motor, sensory, and palmar measurements. Group mean values for group 1 differed significantly from groups 2 and 3 (not 4) for all measurements, but values overlapped considerably. Median distal motor latency (DMML) combined with median-ulnar palmar latency differences (MUPLD) had significantly superior discriminant power than other measurements and correlated highly for all groups (r values = 0.71-0.73). These variables were used to construct ROC curves and prediction tables. The approach used allows one to assign a percentage risk of having a CTS and can be used in outcome studies.

The effect of lens opacity on the resolution visual field in normal subjects

The sensitivity of the visual field declines with age. The density of the crystalline lens increases with age and may be partly responsible for the decline in sensitivity. To determine whether lens opacity influences the mean threshold of the visual field, 82 normal subjects were enrolled. All had their lens opacity measured with the Interzeag Lens Opacity Meter 701 and the visual field assessed with the Ring Resolution Perimeter. Lens opacity was highly correlated with age, while mean visual field threshold was also correlated with age but showed much greater variation. Multiple regression failed to show any influence of lens opacity measurements on the mean field threshold after age had been accounted for.

Lymphocytes from the site of disease suggest adenovirus is one cause of persistent or recurrent inflammatory arthritis

The assessment of synovial lymphocyte reactivity to adenovirus antigen stimulation was undertaken in patients with persistent or recurrent inflammatory arthritis. The 3H-thymidine uptake procedure was employed, incorporating multiple microbiological antigens. Five patients were found with repeated maximal responses to adenovirus antigen; in one of these adenovirus nucleotide sequences were present in a synovial biopsy specimen. It is concluded that adenovirus may be one cause of persistent or recurrent inflammatory arthritis.

Reproducibility of topographic parameters obtained with the heidelberg retina tomograph

The Heidelberg retina tomograph is a confocal scanning laser ophthalmoscope that permits recording of topographic information related to the optic nerve and retina. We studied the reproducibility of the topographic parameters obtained by recording five times sequentially the images obtained from one eye of five healthy people and five glaucoma patients. The reproducibility coefficients ranged from 60.5 to 99.4%. The results indicate that, for the parameters examined, the instrument has a high level of reproducibility.

Duration of amyotrophic lateral sclerosis is age dependent

Since 1985, we prospectively followed 246 patients with ALS. The relationship between the age of developing neurological impairment and disease duration was analyzed in 138 patients (86 men and 52 women) who died. Mean disease duration was 4.0 +/- 3.8 years for men and 3.2 +/- 2.5 years for women. There was an inverse, exponential, relationship between onset age and duration (goodness-of-fit P > 0.05). Mean duration at onset age < or = 40 years was 8.2 +/- 5.0 years compared with 2.6 +/- 1.4 years for patients aged 61 to 70 years (P > 0.001). The ratio of young (< or = 40 years) men to women was 3.6:1. When matched for age, disease duration was the same for patients with bulbar and nonbulbar onsets. We conclude that onset age, but not sex, is the most significant predictor determining disease duration in ALS. Longer survival in younger patients probably reflects their greater neuronal reserve.

Clinical spectrum of nonmenstrual toxic shock syndrome (TSS): comparison with menstrual TSS by multivariate discriminant analyses

To further characterize the clinical spectrum of nonmenstrual toxic shock syndrome (NMTSS), we constrasted and compared the clinical and laboratory features of 24 patients with NMTSS with those of 21 patients with menstrual TSS (MTSS), using univariate and stepwise discriminant analyses. In contrast to patients with MTSS, those with NMTSS comprised a heterogeneous group with varying host factors and clinical presentations. The NMTSS group differed from the MTSS group in terms of the frequency of prior antimicrobial treatment (46% vs. 16%; P = .05), the rate of nosocomial acquisition (65% vs. 0; P = .0001), and the time of onset of fever and rash in relation to the initial symptoms (P = .005 and .03, respectively, with earlier onset in the NMTSS group). In addition, NMTSS patients experienced more frequent renal and CNS complications and less frequent musculoskeletal involvement (P = .07 in all three cases). Stepwise discriminant analysis identified four variables (delayed onset of TSS symptoms after precipitating injury or event, more frequent CNS manifestations, less frequent musculoskeletal involvement, and higher degree of anemia) differentiating NMTSS patients from MTSS produced TSS toxin 1 (TSST-1) with comparable frequency (62% vs. 84%; P = .2), but production of staphylococcal enterotoxin A (SEA) was less common in NMTSS than in MTSS (33% vs. 74%; P = .01). Furthermore, MTSS-associated isolates more commonly coexpressed TSST-1 and SEA than did NMTSS-associated isolates (68% vs. 28%; P = .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral glucose metabolism in Parkinson's disease with and without dementia

Although cognitive impairment is commonly associated with Parkinson's disease, the relative importance of cortical and subcortical pathologic changes to the development of dementia is controversial. Characteristic abnormalities in cortical glucose metabolism have been reported previously in Alzheimer's disease, a disease in which cortical changes predominate. We measured cerebral glucose metabolism with positron emission tomography in 20 control subjects and in 14 patients with PD with mental status ranging from normal to severely demented to determine whether changes in cortical glucose metabolism occur in early PD and whether the degree and pattern of metabolic change relate to the severity of dementia. The patients were divided into demented and nondemented groups according to the results of neuropsychological assessment. Age-adjusted covariance analyses were performed, since the age distribution varied between groups. The nondemented patients with PD showed widespread cortical glucose hypometabolism without any selective temporoparietal defects. The pattern of glucose hypometabolism seen in the demented patients with PD resembled that described in patients with Alzheimer's disease; ie, there was a global decrease in glucose metabolism, with more severe abnormalities observed in the temporoparietal regions.

The antiparkinson efficacy of deprenyl derives from transient improvement that is likely to be symptomatic

We undertook an analysis of the hazard functions derived from results published by the Parkinson Study Group following their investigation of deprenyl. Our findings indicate that the action of deprenyl is transient rather than sustained. We also infer that this effect may be mediated through alleviation of symptoms rather than by neuroprotection.

Intraocular pressure reduction in normal-tension glaucoma patients. The Normal Tension Glaucoma Study Group

BACKGROUND

In a collaborative study, patients with untreated normal-tension glaucoma were randomly assigned to a marked intraocular pressure reduction group or to a no therapy group. It was anticipated that medical therapy and laser trabeculoplasty would generally not achieve adequate pressure lowering and that fistulizing surgery would be required. This hypothesis was examined using current observations in the study.

METHODS

Patients randomized to the therapy group had a pressure reduction of at least 30% from their last prerandomization level. This was achieved within 6 months by means of fistulizing surgery or with pilocarpine and/or laser trabeculoplasty. Beta-blockers and adrenergic agonists were excluded from both eyes.

RESULTS

Of 30 patients with documented stable 30% pressure reduction, 17 (57%) achieved this with topical medication and/or laser trabeculoplasty: 8 with pilocarpine alone, 2 with laser trabeculoplasty alone, and 7 with laser trabeculoplasty after initial topical medication. The remaining 13 (43%) patients required a single fistulizing procedure. There was no statistically significant difference between the mean follow-up time for the nonfistulized group (533.8 +/- 437.6 days) and for the fistulized group (502.7 +/- 344.7 days). Both treatment groups had similar baseline profiles.

CONCLUSION

Marked pressure reduction can be achieved and maintained on a long-term basis by means other than fistulizing surgery in a large proportion of patients with untreated normal-tension glaucoma.

An electronic method for measuring joint tenderness in rheumatoid arthritis

OBJECTIVE

To test the precision of a new electronic method for measuring joint tenderness.

METHOD

Joint tenderness was measured in 30 patients with rheumatoid arthritis, using an electronic dolorimeter. The results were compared with joint tenderness counts, which were made according to the American Rheumatism Association (ARA) methods.

RESULTS

The intra-observer variability using the electronic method was significantly decreased compared with the conventional ARA joint tenderness counts.

CONCLUSION

The electronic method is more efficient for use in clinical trials than is the conventional ARA joint tenderness count.