Does a long preclinical period occur in Parkinson's disease?

MPTP Induces Systemic Parkinsonism in Middle-Aged Cynomolgus Monkeys: Clinical Evolution and Outcomes

In this study, we developed a systemic PD model in middle-aged cynomolgus monkeys using individualized low-dose MPTP, to explore effective indicators for the early prediction of clinical outcomes. MPTP was not stopped until the animals showed typical PD motor symptoms on days 10 to 13 after MPTP administration when the Kurlan score reached 10; this abrogated the differences in individual susceptibility to MPTP. The clinical symptoms persisted, peaking on days 3 to 12 after MPTP withdrawal (rapid progress stage), and then the Kurlan score plateaued. A Kurlan score at the end of the rapid progress stage >15 reflected stable or slowly-progressive PD, while a score <15 indicated spontaneous recovery. The entire clinical evolution and outcome of the systemic PD model was characterized in this study, thus providing options for therapeutic and translational research.

Reproducibility of brain dopamine transporter binding with Tc-99m TRODAT-1 SPECT in healthy young men

Single photon emission computed tomography (SPECT) with Tc-99m TRODAT-1 as ligand can be used to evaluate striatal dopamine transporters (DAT) in young subjects. The purpose of this study was to evaluate the reproducibility of (99m)Tc-TRODAT-1 SPECT in DAT binding in healthy young men. Fourteen healthy young men were recruited. The test-retest studies were performed 1week apart. Specific uptake ratios (SUR) of the striatum (ST) and its subregions, the caudate (CA) and the putamen (PU), were measured using the occipital cortex as the reference tissue. The reliability of the two measurements between test and retest, showed significant correlations for the ST, CA and PU, was demonstrated by calculating the intraclass correlation coefficient (ICC). Thus, (99m)Tc-TRODAT-1 SPECT might provide a reproducible and reliable tool in clinical management of young patients with DAT-related disorders.

The mesopontine rostromedial tegmental nucleus: an integrative modulator of the reward system

The mesopontine rostromedial tegmental nucleus (RMTg) is a newly discovered brain structure thought to profoundly influence reward-related pathways. The RMTg is prominently GABAergic, receives dense projections from the lateral habenula and projects strongly to the midbrain ventral tegmental area and substantia nigra compacta. It receives additional afferent connections from widespread brain structures and sends additional strong efferent connections to a number of non-dopaminergic brainstem structures and, to a lesser extent, the forebrain. Projection neurons of the RMTg have been shown to express Fos in response to aversive stimuli and/or reward omission and psychostimulant drug administration. This review will first recount how the RMTg was discovered and then describe in greater detail what is known about its neuroanatomical relationships, including afferent and efferent connections, neurotransmitters, and receptors. Finally, we will focus on what has been reported about its function.

The Value of Semi-Quantitative Analysis of 123I-FP-CIT SPECT in Evaluating Patients with Parkinson's Disease

(123)I-FP-CIT SPECT binding to striatal dopamine transporter (DAT) is markedly reduced in patients with Parkinson's disease (PD) and it may also help in identifyng pre-symptomatic nigrostriatal dysfunction in subjects at risk. This study used semi-quantitative analysis of 123I-FP-CIT SPECT to evaluate the possibility of a more extensive and earlier diagnosis of dopaminergic damage. We used qualitative visual assessment and semiquantitative measures of striatal DAT binding using (123)I-FP-CIT SPECT in 154 patients with suspected PD. A control group comprised 18 people age-matched to the PD group whose follow-up disclosed essential tremor. Abnormal striatal 123I-FP-CIT uptake was evident in 134 out of 154 patients (87%). Qualitative visual assessment showed striatal dopaminergic (123)I-FP-CIT uptake was significantly reduced in 60.4% (controlateral putamen to the symptoms), in 31.3% (caudate nucleus) and in 8.3% (ipsolateral basal ganglia to the symptoms). Semi-quantitative analysis showed the following results: 32.8%, 50.7% and 16.5% respectively. We compared these two assessments and their correlation with PD clinical progression. At 24 month follow-up, patients with greater dopaminergic damage at semiquantitative analysis showed a more severe motor disability. Our findings indicate that (123)I-FP-CIT SPECT with semiquantitative analysis can offer a more accurate characterization of the dopaminergic damage in patients with suspected Parkinson's disease.

Parkinson's disease: lesions in dorsal horn layer I, involvement of parasympathetic and sympathetic pre- and postganglionic neurons

Clinical signs frequently recognized in early phases of sporadic Parkinson's disease (PD) may include autonomic dysfunctions and the experience of pain. Early disease-related lesions that may account for these symptoms are presently unknown or incompletely known. In this study, immunocytochemistry for alpha-synuclein was used to investigate the first relay stations of the pain system as well as parasympathetic and sympathetic pre- and postganglionic nerve cells in the lower brainstem, spinal cord, and coeliac ganglion in 100 microm polyethylene glycol embedded sections from six autopsy individuals, whose brains were staged for PD-associated synucleinopathy. Immunoreactive inclusions were found for the first time in spinal cord lamina I neurons. Lower portions of the spinal cord downwards of the fourth thoracic segment appeared to be predominantly affected, whereas the spinal trigeminal nucleus was virtually intact. Additional involvement was seen in parasympathetic preganglionic projection neurons of the vagal nerve, in sympathetic preganglionic neurons of the spinal cord, and in postganglionic neurons of the coeliac ganglion. The known interconnectivities between all of these components offer a possible explanation for their particular vulnerability. Lamina I neurons (pain system) directly project upon sympathetic relay centers, and these, in turn, exert influence on the parasympathetic regulation of the enteric nervous system. This constellation indicates that physical contacts between vulnerable regions play a key role in the pathogenesis of PD.

Stanley Fahn Lecture 2005: The staging procedure for the inclusion body pathology associated with sporadic Parkinson's disease reconsidered

The synucleinopathy known as sporadic Parkinson's disease (PD) is a multisystem disorder that severely damages predisposed nerve cell types in circumscribed regions of the human nervous system. A recent staging procedure for the inclusion body pathology associated with PD proposes that, in the brain, the pathological process (formation of proteinaceous intraneuronal Lewy bodies and Lewy neurites) begins at two sites and continues in a topographically predictable sequence in six stages, during which components of the olfactory, autonomic, limbic, and somatomotor systems become progressively involved. In stages 1 to 2, the Lewy body pathology is confined to the medulla oblongata/pontine tegmentum and anterior olfactory structures. In stages 3 to 4, the substantia nigra and other nuclei of the basal mid- and forebrain become the focus of initially subtle and, then, severe changes. During this phase, the illness probably becomes clinically manifest. In the final stages 5 to 6, the lesions appear in the neocortex. This cross-sectional study originally was performed on 168 autopsy cases using material from 69 incidental cases and 41 clinically diagnosed PD patients as well as 58 age- and gender-matched controls. Here, the staging hypothesis is critically reconsidered and discussed.

Phase contrast radiography of Lewy bodies in Parkinson disease

Parkinson's disease (PD), defined as a neurodegenerative disorder, is characterized by the loss of dopaminergic neurons and the presence of Lewy bodies in neurons. Morphological study of Lewy bodies is important to identify the causes and the processes of PD. Here, we investigate a possibility of phase contrast radiography using coherent synchrotron X-rays to explore the microscopic details of Lewy bodies in thick (approximately 3 mm) midbrain tissues. Autopsied midbrain tissues of a PD patient were sliced in 3 mm thickness and then examined using synchrotron X-rays from the 7B2 beamline of the Pohang Light Source. Refraction-enhanced phase contrast radiography and microtomography were adopted to identify dark core and dim edge of Lewy bodies in neurons. The morphology of Lewy bodies was clearly revealed by the phase contrast radiography in very thick (3 mm) midbrain tissues without any staining treatment. Three-dimensional volume rendered microtomography of the autopsied midbrain tissues demonstrates striking evidence that several Lewy bodies are agglomerated by dim edges in a neuron. We suggest that the phase contrast radiography could be a useful tool to morphologically investigate the causes or the processes in PD.

Parkinson's disease, stroke, and related epidemiology

We investigated the prevalence of cerebrovascular disease and other comorbidities in Parkinson's disease (PD) patients compared to the general population. Five hundred PD patients were chosen randomly from one author's (A.H.R.) database. Age- and sex-matched controls were derived from 270 patients with essential tremor from the same database and from 490 patients in a general practitioner's database. Age, hypertensive status, smoking status, coronary artery disease, orthostatic hypotension, diabetes mellitus, and symptomatic cerebrovascular disease (stroke or transient ischemic attack) were assessed. Statistical analysis was performed using Pearson chi(2) testing and binary logistic regression analysis. The prevalence of coronary artery disease, hypertension, diabetes mellitus, and orthostatic hypotension was similar among groups. The PD group had more patients who never smoked and less current smokers than the other groups. While there were similar frequencies of symptomatic cerebrovascular disease among groups, the prevalence of stroke was lower in PD patients. This difference disappeared upon stratification into groups based on smoking status and in the addition of smoking as a covariate in the multivariate analysis. Diminished smoking in PD patients likely plays a role in our finding of decreased stroke in patients with PD. Increased access to appropriate neurological care and subsequent prevention of stroke after a warning transient ischemic attack may also play a role, as may diminished levels of excitotoxic neurotransmitters in PD patients.

Parkinson's disease in diphenyl-exposed workers—A causal association?

We report a cluster of five cases of Parkinson's disease (PD) among paper mill workers exposed to a fungicide, diphenyl. The cause of PD is still unknown, but epidemiological studies have indicated an elevated risk of developing PD after exposure to pesticides. The five cases of PD were found in a group of 255 diphenyl-exposed workers, and the number of expected cases in the exposed group was estimated to be 0.9, resulting in a relative risk of 5.6 (95% CI 1.8-13). Exposure to diphenyl may have contributed to this PD cluster, but chance is an alternative explanation.

Pathology associated with sporadic Parkinson's disease--where does it end?

Parkinson's disease (PD) is a multisystem disorder in which predisposed neuronal types in specific regions of the human peripheral, enteric, and central nervous systems become progressively involved. A staging procedure for the PD-related inclusion body pathology (i.e., Lewy neurites and Lewy bodies) in the brain proposes that the pathological process begins at two sites and progresses in a topographically predictable sequence in 6 stages. During stages 1-2, the inclusion body pathology remains confined to the medulla oblongata, pontine tegmentum, and anterior olfactory structures. In stages 3-4, the basal mid- and forebrain become the focus of the pathology and the illness reaches its symptomatic phase. In the final stages 5-6, the pathological process is seen in the association areas and primary fields of the neocortex. To date, we have staged a total of 301 autopsy cases, including 106 cases with incidental pathology and 176 clinically diagnosed PD cases. In addition, 163 age-matched controls were examined. 19 of the 301 cases with PD-related pathology displayed a pathological distribution pattern of Lewy neurites and Lewy bodies that diverged from the staging scheme described above. In these cases, olfactory structures and the amygdala were predominantly involved in the virtual absence of brain stem pathology. Most of the divergent cases (17/19) had advanced concomitant Alzheimer's disease-related neurofibrillary changes (stages IV-VI).

123I-FP-CIT semi-quantitative SPECT detects preclinical bilateral dopaminergic deficit in early Parkinson's disease with unilateral symptoms

BACKGROUND AND AIM

123I-FP-CIT SPECT has been successfully used to detect the loss of dopaminergic nigrostriatal neurons in Parkinson's disease at an early stage. In this study we evaluated the capacity of 123I-FP-CIT SPECT to assess bilateral dopamine transporter (DAT) loss in de-novo hemi-Parkinson's disease (PD) patients with one-sided clinical symptoms.

PATIENTS AND METHODS

Twenty-nine de-novo hemi-PD patients at an early stage (Hoehn & Yahr stage 1) and 18 gender and age matched healthy subjects were studied. SPECT imaging was always performed at 4 h post-injection. The ratios of striatal (S) to non-specific occipital (O) binding for the entire striatum (S/O), caudate nuclei (C/O), putamina (P(put)/O), and the putamen to caudate nucleus index (P(put)/C) were calculated in both the basal ganglia.

RESULTS

In PD patients S/O, C/O and P(put)/O ratio values contralateral to the clinically affected side were significantly lower (P<0.001) than in the control group (-38%, -34% and -42%, respectively). A significant reduction (P<0.001) of the striatal binding ratios was also found ipsilaterally (S/O, -31%; C/O, -28%; P(put)/O, -33%). The P(put)/C index was also bilaterally significantly reduced (P<0.01). DAT loss was significantly greater (P<0.001) in the contralateral than in the ipsilateral S; and putamen bilaterally presented a higher dopaminergic deficit than did caudate.

CONCLUSION

Our results indicate that semi-quantitative 123I-FP-CIT SPECT detects a bilateral dopaminergic deficit in early PD with unilateral symptoms and preclinical DAT loss in the ipsilateral striatal binding, corresponding to the side not yet affected by motor signs. Semi-quantitative analysis may thus be used to diagnose PD at an early stage as well as to identify individuals developing bilateral dopaminergic damage.

Test–retest repeatability of self-reported environmental exposures in Parkinson's disease cases and healthy controls

There is substantial disagreement among published epidemiological studies regarding environmental risk factors for Parkinson's disease (PD). Differences in the quality of measurement of environmental exposures may contribute to this variation. The current study examined the test-retest repeatability of self-report data on risk factors for PD obtained from a series of 32 PD cases recruited from neurology clinics and 29 healthy sex-, age- and residential suburb-matched controls. Exposure data were collected in face-to-face interviews using a structured questionnaire derived from previous epidemiological studies. High repeatability was demonstrated for 'lifestyle' exposures, such as smoking and coffee/tea consumption (kappas 0.70-1.00). Environmental exposures that involved some action by the person, such as pesticide application and use of solvents and metals, also showed high repeatability (kappas>0.78). Lower repeatability was seen for rural residency and bore water consumption (kappa 0.39-0.74). In general, we found that case and control participants provided similar rates of incongruent and missing responses for categorical and continuous occupational, domestic, lifestyle and medical exposures.

Amphetamine treatment similar to that used in the treatment of adult attention-deficit/hyperactivity disorder damages dopaminergic nerve endings in the striatum of adult nonhuman primates

Pharmacotherapy with amphetamine is effective in the management of attention-deficit/hyperactivity disorder (ADHD), now recognized in adults as well as in children and adolescents. Here we demonstrate that amphetamine treatment, similar to that used clinically for adult ADHD, damages dopaminergic nerve endings in the striatum of adult nonhuman primates. Furthermore, plasma concentrations of amphetamine associated with dopaminergic neurotoxicity in nonhuman primates are on the order of those reported in young patients receiving amphetamine for the management of ADHD. These findings may have implications for the pathophysiology and treatment of ADHD. Further preclinical and clinical studies are needed to evaluate the dopaminergic neurotoxic potential of therapeutic doses of amphetamine in children as well as adults.

Statins, cholesterol, Co-enzyme Q10, and Parkinson's disease

'Statins', drugs that lower cholesterol are widely used. Statins block cholesterol in the body and brain by inhibiting HMG-Co-A reductase. This pathway is shared by CoQ-10. An unintended consequence of the statins is lowering of CoQ-10. As CoQ-10 may play a role in PD, its possible statins may worsen PD. Such a report has appeared. Statins came into wide use in 1997-1998, 6 years before our study began. Thus 74% of our patients on a statin had a PD duration of 1-6 years versus 56% of our patients not on a statin. A direct comparison of patients on a statin and not on a statin would bias the study in favor of the statins: patients on a statin would have a shorter disease duration and less advanced PD. Therefore we divided the patients into two groups. Group I consisted of 128 patients on a statin, and 252 not on a statin who had PD for 1-6 years. In this group, disease severity (Hoehn & Yahr Stage), levodopa dose, Co-enzyme Q10 use, prevalence of 'wearing off', dyskinesia and dementia were similar. Group II consisted of 45 patients on a statin and 200 patients not on a statin who had PD for 7-22 years. In this group disease severity, levodopa dose, Co-enzyme Q10 use, prevalence of wearing off, dyskinesia and dementia were similar. Statins although they may affect Co-enzyme Q10 levels in the body and the brain, do not worsen PD at least as assessed by stage, and prevalence of wearing-off, dyskinesia, and dementia.

Detection of presymptomatic Parkinson's disease: combining smell tests, transcranial sonography, and SPECT

Olfactory loss is among the early signs of Parkinson's disease (PD). We investigated whether "idiopathic" olfactory dysfunction might relate to signs of nigral degeneration. Olfactory tests were combined with transcranial sonography of the substantia nigra and single photon emission computed tomography (SPECT) imaging. Thirty patients diagnosed with idiopathic olfactory loss participated. Eleven of these patients exhibited an increased echogenicity of the SN in the transcranial sonography. In 10 of these 11 patients, SPECT scans with (123)I-FP-CIT were performed. Median uptake ratios in the basal ganglia were pathological in 5 patients, 2 patients exhibited borderline findings, and 3 patients had normal results. Considering patients with idiopathic olfactory dysfunction, noninvasive transcranial sonography seems to be helpful in identifying patients potentially at risk to develop PD. Longitudinal follow-up studies are necessary to estimate the ratio of patients with dopaminergic cell loss in the basal ganglia who will develop PD in the future.

Presymptomatic diagnosis of experimental Parkinsonism with 123I-PE2I SPECT

Presymptomatic diagnosis of the loss of nigrostriatal neurons that characterises Parkinson's disease, is a crucial issue for future neuroprotective therapies as degeneration exceeds 70 to 80% when symptoms appear. Here we propose an early diagnosis method that utilises single photon emission computerized tomography (SPECT) coupled to the iodine-123-labelled selective dopamine transporter ligand N-(3-ioprop-2E-enyl)-2-beta-(4-methylphenyl)nortropane ((123)I-PE2I), applying Logan's graphical method for quantification. Sequential (123)I-PE2I SPECT acquisitions were performed in nonhuman primates chronically treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine according to a regimen that consistently produces a progressive Parkinsonian state. While classical neurological examination only allows detection of Parkinsonian signs at Day 12 of the protocol of intoxication, the mean distribution volume ratio calculated according to Logan's graphical method is significantly decreased from Day 6 onward, i.e., when animals are clinically normal. (123)I-PE2I SPECT is a very sensitive method to detect presymptomatic lesions of nigrostriatal neurons and the first to be experimentally validated. It could now be used clinically for early diagnosis and follow-up of neuroprotective treatment.

Diet and Parkinson's disease: a potential role of dairy products in men

Diet may play a causative role in Parkinson's disease (PD), but potential associations between diet and PD risk rarely have been assessed in prospective studies. We investigated associations between food intakes and PD risk in two large prospective cohorts in which 210 incident PD cases in men and 184 in women were documented. A positive association was found between dairy intake and PD risk in men (relative risk [RR] comparing extreme categories, 1.8; p trend = 0.004), but not in women (RR, 1.1; p trend = 0.9). No other food groups were associated with PD risk in either men or women. Further analyses among men showed significant positive associations with PD risk for intakes of several dairy foods as well as dairy calcium (RR, 1.5; p trend = 0.02), dairy vitamin D (RR, 1.6; p trend = 0.004), dairy protein (RR, 1.6; p trend = 0.01), and lactose (RR, 1.8; p trend = 0.002), but not dairy fat (RR, 1.1; p trend = 0.4). Intakes of calcium, vitamin D, and protein from other dietary or supplemental sources were not related to PD risk in men. Our results suggest that higher intake of dairy products may increase the risk of PD in men; however, this finding needs further evaluation, and the underlying active components need to be identified.

Environmental factors in Parkinson's disease

Evidence discussed in this review article lends strong support in favor of an etiologic role of environmentalfactors in Parkinson's disease. First, thanks to the discovery of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), it is now clear that, by targeting the nigrostriatal system, neurotoxicants can reproduce the neurochemical and pathological features of idiopathic parkinsonism. The sequence of toxic events triggered by MPTP has also provided us with intriguing clues concerning mechanisms of toxicant selectivity and nigrostriatal vulnerability. Relevant examples are (i) the role of the plasma membrane dopamine transporter in facilitating the access of potentially toxic species into dopaminergic neurons; (ii) the vulnerability of the nigrostriatal system to failure of mitochondrial energy metabolism; and (iii) the contribution of inflammatory processes to tissue lesioning. Epidemiological and experimental data suggest the potential involvement of specific agents as neurotoxicants (e.g. pesticides) or neuroprotective compounds (e.g. tobacco products) in the pathogenesis of nigrostriatal degeneration, further supporting a relationship between the environment and Parkinson's disease. A likely scenario that emerges from our current knowledge is that neurodegeneration results from multiple events and interactive mechanisms. These may include (i) the synergistic action of endogenous and exogenous toxins (e.g. the ability of the pesticide diethyldithiocarbamate to promote the toxicity of other compounds); (ii) the interactions of toxic agents with endogenous elements (e.g. the protein alpha-synuclein); (iii) the tissue response to an initial toxic insult; and, last but not least, (iv) the effects of environmental factors on the background of genetic predisposition and aging.

Olfactory function in Parkinsonian syndromes

The study aimed to compare olfactory function in idiopathic Parkinson's disease (IPD) and nonidiopathic Parkinson's syndrome (PS). At their first visit 50 PS patients (age 38-80 years) received testing for odor threshold, olfactory discrimination and identification. All patients underwent extensive neurological diagnostics including PET scans. Patients were followed up for 6-12 months. Most of IPD patients were functionally anosmic (n=19), the remaining IPD patients had severe/moderate hyposmia (n=18). PS patients diagnosed with multiple system atrophy had less severe olfactory deficits (7 hyposmia, 1 normosmia). With the exception of 1 hyposmic patient, other PS patients had no olfactory deficits (progressive supranuclear palsy, corticobasal degeneration, psychogenic PS, essential tremor). This study added to previous findings: (1) there was no major difference betwesen olfactory function in IPD subtypes; (2) all olfactory tests differentiated IPD from nonIPD. These data suggest that olfactory probes improve the diagnostic armamentarium in IPD.

Do risk factors for Alzheimer's disease predict dementia in Parkinson's disease? An exploratory study

The extent to which concomitant Alzheimer's disease (AD) is etiologically related to the development of dementia in Parkinson's disease (PD) remains controversial. We explored the association of four risk factors associated with AD, including head injury, smoking, hypertension, and diabetes mellitus, with incident dementia in PD. A cohort of 180 nondemented PD patients from the Washington Heights community in northern Manhattan, New York, completed a risk factor questionnaire at baseline and was followed annually with neurological and neuropsychological evaluations. The association of baseline variables with incident dementia was analyzed by using Cox proportional hazards models. All analyses controlled for age at baseline, gender, years of education, duration of PD, and total Unified Parkinson's Disease Rating Scale (UPDRS) motor score at baseline. Of 180 patients (mean age, 71.0 +/- 10.3 years), 52 (29%) became demented during a mean follow-up period of 3.6 +/- 2.2 years. Head injury risk ratio ([RR] 0.9; 95% confidence interval [CI], 0.4-2.2; P = 0.9), hypertension (RR, 0.7; 95% CI, 0.4-1.4, P = 0.3), and diabetes mellitus (RR, 0.8; 95% CI, 0.3-2.3; P = 0.7) were not significantly associated with incident dementia in the Cox models. Patients who reported having ever smoked were at increased risk for the development of dementia compared with nonsmokers (RR, 2.0; 95% CI, 1.0-3.9; P = 0.05). Current smoking was significantly associated with incident dementia (RR, 4.5; 95% CI, 1.2-16.4; P = 0.02), whereas past smoking approached significance (RR, 1.9; 95% CI, 0.9-3.7; P = 0.07). Although an inverse association between smoking and PD has been reported in several studies, our study showed a positive association between smoking and dementia in the setting of PD. The association of smoking with incident dementia in PD deserves further study.

Drug treatment effects on disease progression

Degenerative diseases are characterized by a worsening of disease status over time. The rate of deterioration is determined by the natural rate of progression of the disease and by the effect of drug treatments. A goal of drug treatment is to slow disease progression. Drug treatments can be categorized as symptomatic or protective. Symptomatic treatments do not affect the rate of disease progression whereas protective treatments have the ability to slow disease progression down. Many current methods for describing disease progression have two common drawbacks: a linear relationship between time and disease status is assumed, and within- and between-subject variability is ignored. Disease progress models combined with pharmacokinetic pharmacodynamic models and hierarchical random effects statistical models provide insights into understanding the time course and management of degenerative disease.

Emission tomography contribution to clinical neurology

The role of functional neuroimaging techniques in furthering the understanding of pathophysiological mechanisms of neurological diseases and in the assessment of neurological patients is increasingly important. Here, we review data mainly from emission tomography techniques, namely positron emission tomography (PET) and single photon emission computerized tomography (SPECT), that have helped elucidate the pathophysiology of a number of neurological diseases and have suggested strategies in the treatment of neurological patients. We also suggest possible future developments of functional neuroimaging applied to clinical populations and briefly touch on the emerging role of functional magnetic resonance imaging (fMRI) in clinical neurology and neurosurgery.

Experimental models of Parkinson's disease: from the static to the dynamic

The experimental models of Parkinson's disease (PD) available today can be divided into two categories according to the mode of action of the compound used: transient pharmacological impairment of dopaminergic transmission along the nigrostriatal pathway or selective destruction by a neurotoxic agent of the dopaminergic neurons of the substantia nigra pars compacta. The present article looks at the relative merits of each model, the clinical symptoms and neuronal impairment it induces, and the contribution it could make to the development of a truly dynamic model. It is becoming more and more clear that there is an urgent need for a chronic model integrating all the clinical features of PD including resting tremor, and reproducing the gradual but continuous nigral degeneration observed in the human pathology. Discrepancies have been reported several times between results obtained in classic animal models and those described in PD, and it would seem probable that such contradictions can be ascribed to the fact that animal models do not, as yet, reproduce the continuous evolution of the human disease. Dynamic experimental models which come closer to the progressive neurodegeneration and gradual intensification of motor disability so characteristic of human PD will enable us to investigate crucial aspects of the disease, such as compensatory mechanisms and dyskinesia.

Autosomal dominant progressive syndrome of motor-speech loss without dementia

This patient report describes a 68-year-old man with progressive dissolution in motor-speech without concomitant language or cognitive decline, with presumed autosomal dominant inheritance. Motor-speech impairments included marked difficulty in articulating words and in coordinating articulation, phonation, and respiration. Brain imaging results revealed severe focal atrophy of the posterior frontal region extending to the anterior parietal and superior temporal regions bilaterally on structural (MRI) and functional (single photon emission computed tomography) brain imaging studies. The involved neural substrate represented the primary motor cortex, premotor cortex (supplementary motor area), and the postcentral gyrus. Familial history included similar difficulties in his mother, her sister, and his own sister. The isolated involvement of the motor-speech processes alone indicated that this syndrome was distinguishable from progressive aphasia associated with prominent loss of language and from Alzheimer's disease.

Symptoms and duration of the prodromal phase in Parkinson's disease

To investigate the duration of a prodromal phase before the onset of the classic symptoms of idiopathic Parkinson's disease, the authors conducted a retrospective case-control study of 60 patients with Parkinson's disease and 58 age- and sex-matched control subjects, covering the decade preceding the onset of classic Parkinson's disease. The symptoms were derived from files of the patients' general practitioners. Compared with control subjects, patients pre-Parkinson's disease had more central nervous system, psychologic, musculoskeletal, and cardiovascular (i.e., autonomic) symptoms. Patients pre-Parkinson's disease also made more visits to general practitioners and medical specialists. The results indicate that the onset of classic parkinsonism is frequently preceded by a prodromal phase lasting from 4-6 years.

Rats with partial striatal dopamine depletions exhibit robust and long-lasting behavioral deficits in a simple fixed-ratio bar-pressing task

It is widely accepted that enduring parkinsonian symptoms are only evident if there are few remaining dopaminergic neurons in the substantia nigra and dopamine levels in the basal ganglia are very low [26,41]. In the present study, partial dopamine depletions were produced by infusing 6-OHDA bilaterally into the ventrolateral striatum as previously described [11,12,44]. Consistent with previous studies, behavioral deficits were detectable in rats with partial lesions with a simple fixed-ratio bar-pressing task. The present study demonstrated that these behavioral deficits were long-lasting, and that the sensitivity of this bar-pressing task could be increased by manipulating the level of difficulty of the task-higher fixed ratios were more sensitive to partial dopamine depletions. Deficits in rats with partial dopamine depletions could also be detected using non-automated neurological tests of parkinsonian symptoms developed for rats with severe unilateral dopamine depletions, but these deficits were transient and not as robust as those detected with the bar-pressing task. Oral Sinemet (L-DOPA:carbidopa) did not attenuate behavioral deficits related to partial dopamine depletions in this simple fixed-ratio bar-pressing task, but the present results suggest that Parkinson's patients might be identifiable earlier in the disease process, at a time when they could benefit from treatment with neuroprotective/neurotrophic agents. In addition, the results of the present study demonstrate that robust behavioral deficits may emerge with age. Mild dopamine depletions that were not detectable behaviorally at the time of the insult became clearly evident 10 months after the lesion with this bar-pressing task, and this may represent a more clinically relevant rodent model of Parkinson's disease.

Relationship between clinical features of Parkinson's disease and presynaptic dopamine transporter binding assessed with [123I]IPT and single-photon emission tomography

IPT [N-(3-iodopropen-2-yl)- 2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane] is a new cocaine analogue which allows the presynaptic dopamine transporters to be imaged with single-photon emission tomography (SPET) as early as 1-2 h post injection. In the present study [123I]IPT SPET was performed in patients with Parkinson's disease (PD) to analyse the relationship between specific dopamine tansporter binding and clinical features of the disease. Twenty-six PD patients (Hoehn and Yahr stages I-IV, age range 40-79 years) and eight age-matched controls were studied. SPET imaging was performed 90-120 min after injection of 160-185 MBq [123I]IPT using a triple-head camera. For semiquantitative evaluation of specific [123I]IPT binding, ratios between caudate, putamen and background regions were calculated. Specific [123I]IPT uptake was significantly reduced in PD patients compared to controls. Most patients showed a marked asymmetry with a more pronounced decrease in [123I]IPT binding on the side contralateral to the predominant clinical findings. The putamen was always more affected than the caudate. [123I]IPT binding was significantly correlated with disease duration (r=-0.7, P<0.0001) but not with the age of PD patients (r=-0.10, P=0. 61). Specific [123I]IPT uptake in the caudate and putamen, and putamen to caudate ratios, decreased with increasing Hoehn and Yahr stage. Our findings indicate that [123I]IPT SPET may be a useful technique to estimate the extent of nigrostriatal degeneration in PD patients. Close relationships between striatal [123I]IPT binding and clinical features of the disease suggest that this method can be used to objectively follow the course and progression of PD. The reduced putamen to caudate ratios observed even in patients with mild, newly recognized symptoms indicate that particularly this parameter may help to establish the correct diagnosis in the early course of PD.

Origin and functional consequences of the complex I defect in Parkinson's disease

The mitochondrial electron transport enzyme NADH:ubiquinone oxidoreductase (complex I), which is encoded by both mitochondrial DNA and nuclear DNA, is defective in multiple tissues in persons with Parkinson's disease (PD). The origin of this lesion and its role in the neurodegeneration of PD are unknown. To address these questions, we created an in vitro system in which the potential contributions of environmental toxins, complex I nuclear DNA mutations, and mitochondrial DNA mutations could be systematically analyzed. A clonal line of human neuroblastoma cells containing no mitochondrial DNA was repopulated with mitochondria derived from the platelets of PD or control subjects. After 5 to 6 weeks in culture, these cytoplasmic hybrid (cybrid) cell lines were assayed for electron transport chain activities, production of reactive oxygen species, and sensitivity to induction of apoptotic cell death by 1-methyl-4-phenyl pyridinium (MPP+). In PD cybrids we found a stable 20% decrement in complex I activity, increased oxygen radical production, and increased susceptibility to 1-methyl-4-phenyl pyridinium-induced programmed cell death. The complex I defect in PD appears to be genetic, arising from mitochondrial DNA, and may play an important role in the neurodegeneration of PD by fostering reactive oxygen species production and conferring increased neuronal susceptibility to mitochondrial toxins.

Childhood chronic inflammatory demyelinating neuropathies: clinical course and long-term follow-up

Chronic inflammatory demyelinating neuropathy (CIDP) is a rare disease in childhood. We reviewed the clinical characteristics, response to therapy, and long-term prognosis in 13 children (1.5 to 16 years of age) diagnosed with CIDP at Washington University Medical Center, St. Louis, and the Royal Children's Hospital, Melbourne, Australia, between 1979 and 1994. The most common presenting symptom (in 11/13 [85%]) was lower extremity weakness associated with difficulty in walking. Preceding events within 1 months of onset, mostly intercurrent infections or vaccinations, occurred in seven children (54%). The disease was monophasic in three children (23%). One relapse occurred in four (30%) and multiple relapses in six (46%). All patients had at least short-term response to steroids. Three children (23%) recovered completely during the first year. Ten children (77%) had residual weakness after an average follow-up of 6 years. There seems to be two populations of children with CIDP. One subgroup, with a favorable prognosis, progressed to peak disability over less than 3 months; these children often have a monophasic course with complete resolution of symptoms and signs and withdrawal from all medications by 1 year after onset. A second subgroup progressed for 3 months or longer; these children all required substantial does of prednisone for prolonged periods and had considerable long-term morbidity with persistent weakness.

[123I] beta-CIT/SPECT imaging demonstrates bilateral loss of dopamine transporters in hemi-Parkinson's disease

We have used in vivo single-photon emission computed tomography (SPECT) of the dopamine transporter with 2 beta-carboxymethoxy-3 beta-(4-iodophenyl)tropane ([123I] beta-CIT) to investigate striatal dopamine transporter loss in patients with early Parkinson's disease (PD). Striatal uptake of ([123I] beta-CIT was compared in eight early-PD patients with exclusively hemi-parkinsonism and eight age- and sex-matched healthy subjects. [123I] beta-CIT striatal uptake was reduced by approximately 53% contralateral and by 38% ipsilateral to the clinically symptomatic side in the hemi-PD patients, compared with the mean striatal uptake in age- and sex-matched healthy subjects. The relative reduction in [123I] beta-CIT uptake in the hemi-PD patients was greater in the putamen than in the caudate. These data demonstrate that SPECT imaging of the dopamine transporter with [123I] beta-CIT can identify patients with PD at the onset of motor symptoms and suggest that this technique also may be useful in identifying individuals with developing dopaminergic pathology before onset of motor symptoms.

Pilot trial of immunoglobulin versus plasma exchange in patients with Guillain-Barré syndrome

We compared intravenous immunoglobulin (IVIG) and plasma exchange (PLEX) in the treatment of 50 patients with Guillain-Barré syndrome (GBS). Standard outcome measures did not differ for the two groups. Sixty-one percent of the PLEX-treated group and 69% of the IVIG-treated group improved by one disability grade at 1 month. The complication rate was higher in the PLEX-treated group. We conclude that the efficacy of IVIG in the treatment of GBS is comparable with that of PLEX and that it can be used safely, although we had a small number of patients. We did not observe a higher relapse rate with IVIG. The usefulness of combination therapy is unknown at this time.

Cognitive deficits in asymptomatic first-degree relatives of Alzheimer's disease patients

The present study was designed to determine whether neuropsychological deficits exist in asymptomatic first-degree relatives of Alzheimer's disease (AD) patients. The neuropsychological performances of 20 first-degree asymptomatic relatives of NINCDS-ADRDA diagnosed AD patients were compared to 20 normal controls without family history of AD. Cognitive functions assessed included intelligence, memory, overall brain function, verbal learning, and language and constructional abilities. Significant statistical differences were found between the groups across several cognitive areas indicating lower functioning in the first-degree relatives of AD patients. Fifty percent of the first-degree subjects but only 20% of controls showed a pattern of significant neuropsychological deficit. The results demonstrate neuropsychological deficits in asymptomatic first-degree relatives of AD patients, suggesting that preclinical markers for AD may be present long before the clinical manifestation of the disease.

The relationship of essential tremor to other movement disorders: report on 678 patients. Essential Tremor Study Group

We examined 678 essential tremor patients in specialty, university, and private practice clinics. The mean age of patients was 65.2 years with a similar number of men and women. Six percent of patients were left-handed. A positive family history of tremor was reported in more than 60% of patients. Alcohol ingestion was reported to decrease tremor in 74% of patients who were cognizant of the effect of alcohol on tremor. Mean age at tremor onset was 45.3 years. An earlier onset of tremor was observed in those patients having a positive family history of tremor. Tremor affected the hands in 90% of patients, head in 50%, voice in 30%, and legs and chin in 15%. Functional disability was common and impairment at work occurred in 18%. Propranolol and primidone were the most frequently used drugs and were effective in 40% of patients. Six and one-tenth percent of essential tremor patients had concomitant Parkinson's disease, 6.9% had a coexisting dystonia, and 1.8% had myoclonus. It is concluded that the frequency of Parkinson's disease in essential tremor is more than would be reported in the general population and that other movement disorders are infrequently observed in essential tremor.

The genetics of Parkinson's disease

The possibility of a major contribution of hereditary factors to the cause of Parkinson's disease (PD) is being reconsidered by many. The studies preceding the 1980s presented conflicting evidence and suffered from procedural difficulties. The emergence of the MPTP hypothesis and the failure of three twin studies to document a strong hereditary component in the early 1980s turned attention toward an environmental cause of PD. However more recent descriptions of deficiencies in genetically-coded biochemical functions in PD, more sophisticated clinical family analyses, re-analysis and extension of the twin studies and the emergence of several large autopsy-proven PD kindreds raise the possibility of an important heritable factor in PD.

Positron emission tomography with 18F-dopa: interpretation and biological correlates in nonhuman primates

Positron emission tomography (PET) was carried out, with 18F-DOPA as a ligand, in normal control monkeys and "parkinsonian" monkeys who had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. The following approaches were used in data analysis: ratio of 18F accumulation in specific to nonspecific brain areas and 18F-DOPA influx constant obtained using either the actual plasma 18F-DOPA or the 18F activity in a nonspecific brain area as the input function. The results from these analyses were compared to one another and to biological parameters relevant to dopaminergic function. The striatum/cortex ratio and the rate constant calculated from plasma 18F-DOPA appeared to be the most sensitive analytic techniques.