Parkinsonian akinesia, rigidity and tremor in the monkey. Histopathological and neuropharmacological study

Dextran-coated iron oxide nanoparticle-improved therapeutic effects of human mesenchymal stem cells in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a prevalent neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons. With their migration capacity toward the sites of diseased DA neurons in the PD brain, mesenchymal stem cells (MSCs) have the potential to differentiate to DA neurons for the replacement of damaged neurons and to secrete neurotrophic factors for the protection and regeneration of diseased DA neurons; therefore MSCs show promise for the treatment of PD. In this study, for the first time, we demonstrate that dextran-coated iron oxide nanoparticles (Dex-IO NPs) can improve the therapeutic efficacy of human MSCs (hMSCs) in a mouse model of PD induced by a local injection of 6-hydroxydopamine (6-OHDA). In situ examinations not only show that Dex-IO NPs can improve the rescue effect of hMSCs on the loss of host DA neurons but also demonstrate that Dex-IO NPs can promote the migration capacity of hMSCs toward lesioned DA neurons and induce the differentiation of hMSCs to DA-like neurons at the diseased sites. We prove that in vitro Dex-IO NPs can enhance the migration of hMSCs toward 6-OHDA-damaged SH-SY5Y-derived DA-like cells, induce hMSCs to differentiate to DA-like neurons in the conditioned media derived from 6-OHDA-damaged SH-SY5Y-derived DA-like cells and promote the protection/regeneration effects of hMSCs on 6-OHDA-damaged SH-SY5Y-derived DA-like cells. We confirm the potential of MSCs for cell-based therapy for PD. Dex-IO NPs can be used as a tool to accelerate and optimize MSC therapeutics for PD applicable clinically.

Comparison of dystonia between Parkinson's disease and atypical parkinsonism: The clinical usefulness of dystonia distribution and characteristics in the differential diagnosis of parkinsonism

OBJECTIVE

Dystonia is occasionally found in patients with Parkinson's disease (PD) and atypical parkinsonisms. However, systematic comparative analysis of the association between dystonia and parkinsonism have seldom been reported. The goals of this study are to compare the clinical characteristics and distributions of dystonia between PD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD).

METHODS

We prospectively enrolled 176 patients who presented with dystonia and parkinsonism out of 1278 patients with parkinsonism. We analyzed the clinical features of dystonia and parkinsonism.

RESULTS

The frequencies of dystonia were 11.0% in PD, 20.9% in MSA, 40.7% in PSP and 66.7% in CBD. Dystonia symptoms were most frequent in CBD and relatively more frequent in PSP and MSA (p<0.001). Moreover, multiple types of dystonia occurred most frequently in MSA (p=0.034). According to the distribution of dystonia, cranio-facial dystonia (CFD) and cervical dystonia (CD) were more frequently observed in atypical parkinsonism (p=0.001). In contrast, limb dystonia (LD) was more frequently observed in both PD and CBD, and truncal dystonia (TD) was more frequently detected in PD (p<0.001). Levodopa medication related dystonia was markedly more frequent in PD than in atypical parkinsonism (p=0.030).

CONCLUSIONS

In this long-term, observational, prospective study, we concluded that levodopa medication related LD and TD were more frequently observed in PD than in atypical parkinsonism. Conversely, levodopa medication non-related CFD and CD were more frequently observed in atypical parkinsonism, and coexisting of some types of multiple dystonia may be unique features of atypical parkinsonism. TD or multiple types of LD, might be representative of PD rather than atypical parkinsonism.

Multitarget, dual-electrode deep brain stimulation of the thalamus and subthalamic area for treatment of Holmes' tremor

Object

Holmes' tremor (HT) is generally considered to be a symptomatic tremor associated with lesions of the cerebellum, midbrain, or thalamus. Deep brain stimulation (DBS) therapy for essential tremor and parkinsonian tremor has proved quite successful. In contrast, surgical treatment outcomes for HT have often been disappointing. The use of 2 ipsilateral DBS electrodes implanted in parallel within the thalamus for severe essential tremor has been reported. Since dual-lead stimulation within a single target can cover a wider area than single-lead stimulation, it produces greater effects. On the other hand, DBS of the subthalamic area (SA) was recently reported to be effective for refractory tremor.

Methods

The authors implanted 2 DBS electrodes (one at the nucleus ventralis oralis/nucleus ventralis intermedius and the other at the SA) in 4 patients with HT. For more than 2 years after implantation, each patient's tremor was evaluated using a tremor rating scale under the following 4 conditions of stimulation: “on” for both thalamus and SA DBS; “off” for both thalamus and SA DBS; “on” for thalamus and “off” for SA DBS; and “on” for SA and “off” for thalamus DBS.

Results

The tremor in all patients was improved for more than 2 years (mean 25.8 ± 3.5 months). Stimulation with 2 electrodes exerted greater effect on the tremor than did 1-electrode stimulation. Interestingly, in all patients progressive effects were observed, and in one patient treated with DBS for 1 year, tremor did not appear even while stimulation was temporarily switched off, suggesting irreversible improvement effects.

The presence of both resting and intentional/action tremor implies combined destruction of the pallidothalamic and cerebellothalamic pathways in HT. A larger stimulation area may thus be required for HT patients. Multitarget, dual-lead stimulation permits coverage of the wide area needed to suppress the tremor without adverse effects of stimulation. Some reorganization of the neural network may be involved in the development of HT because the tremor appears several months after the primary insult. The mechanism underlying the absence of tremor while stimulation was temporarily off remains unclear, but the DBS may have normalized the abnormal neural network.

Conclusions

The authors successfully treated patients with severe HT by using dual-electrode DBS over a long period. Such DBS may offer an effective and safe treatment modality for intractable HT.

The role of the cerebellum in the pathophysiology of Parkinson's disease

Parkinson's disease (PD), the most common neurodegenerative movement disorder, has traditionally been considered a "classic" basal ganglia disease, as the most obvious pathology is seen in the dopaminergic cells in the substantia nigra pars compacta. Nevertheless recent discoveries in anatomical connections linking the basal ganglia and the cerebellum have led to a re-examination of the role of the cerebellum in the pathophysiology of PD. This review summarizes the role of the cerebellum in explaining many curious features of PD: the significant variation in disease progression between individuals; why severity of dopaminergic deficit correlates with many features of PD such as bradykinesia, but not tremor; and why PD subjects with a tremor-predominant presentation tend to have a more benign prognosis. It is clear that the cerebellum participates in compensatory mechanisms associated with the disease and must be considered an essential contributor to the overall pathophysiology of PD.

Parkinson's disease tremor-related metabolic network: characterization, progression, and treatment effects

The circuit changes that mediate parkinsonian tremor, while likely differing from those underlying akinesia and rigidity, are not precisely known. In this study, to identify a specific metabolic brain network associated with this disease manifestation, we used FDG PET to scan nine tremor dominant Parkinson's disease (PD) patients at baseline and during ventral intermediate (Vim) thalamic nucleus deep brain stimulation (DBS). Ordinal trends canonical variates analysis (OrT/CVA) was performed on the within-subject scan data to detect a significant spatial covariance pattern with consistent changes in subject expression during stimulation-mediated tremor suppression. The metabolic pattern was characterized by covarying increases in the activity of the cerebellum/dentate nucleus and primary motor cortex, and, to a less degree, the caudate/putamen. Vim stimulation resulted in consistent reductions in pattern expression (p<0.005, permutation test). In the absence of stimulation, pattern expression values (subject scores) correlated significantly (r=0.85, p<0.02) with concurrent accelerometric measurements of tremor amplitude. To validate this spatial covariance pattern as an objective network biomarker of PD tremor, we prospectively quantified its expression on an individual subject basis in independent PD populations. The resulting subject scores for this PD tremor-related pattern (PDTP) were found to exhibit: (1) excellent test-retest reproducibility (p<0.0001); (2) significant correlation with independent clinical ratings of tremor (r=0.54, p<0.001) but not akinesia-rigidity; and (3) significant elevations (p<0.02) in tremor dominant relative to atremulous PD patients. Following validation, we assessed the natural history of PDTP expression in early stage patients scanned longitudinally with FDG PET over a 4-year interval. Significant increases in PDTP expression (p<0.01) were evident in this cohort over time; rate of progression, however, was slower than for the PD-related akinesia/rigidity pattern (PDRP). We also determined whether PDTP expression is modulated by interventions specifically directed at parkinsonian tremor. While Vim DBS was associated with changes in PDTP (p<0.001) but not PDRP expression, subthalamic nucleus (STN) DBS reduced the activity of both networks (p<0.05). PDTP expression was suppressed more by Vim than by STN stimulation (p<0.05). These findings suggest that parkinsonian tremor is mediated by a distinct metabolic network involving primarily cerebello-thalamo-cortical pathways. Indeed, effective treatment of this symptom is associated with significant reduction in PDTP expression. Quantification of treatment-mediated changes in both PDTP and PDRP scores can provide an objective means of evaluating the differential effects of novel antiparkinsonian interventions on the different motor features of the disorder.

Differential involvement of striato- and cerebello-thalamo-cortical pathways in tremor- and akinetic/rigid-predominant Parkinson's disease

Parkinson's disease (PD) presents clinically with varying degrees of resting tremor, rigidity, and bradykinesia. For decades, striatal-thalamo-cortical (STC) dysfunction has been implied in bradykinesia and rigidity, but does not explain resting tremor in PD. To understand the roles of cerebello-thalamo-cortical (CTC) and STC circuits in the pathophysiology of the heterogeneous clinical presentation of PD, we collected functional magnetic resonance imaging (fMRI) data from 17 right-handed PD patients [nine tremor predominant (PDT) and eight akinetic-rigidity predominant (PDAR)] and 14 right-handed controls while they performed internally-guided (IG) sequential finger tapping tasks. The percentage of voxels activated in regions constituting the STC and CTC [divided as cerebellar hemisphere-thalamo-cortical (CHTC) and vermis-thalamo-cortical (CVTC)] circuits was calculated. Multivariate analysis of variance compared the activation patterns of these circuits between study groups. Compared to controls, both PDAR and PDT subjects displayed an overall increase in the percentage of voxels activated in both STC and CTC circuits. These increases reached statistical significance in contralateral STC and CTC circuits for PDT subjects, and in contralateral CTC pathways for PDAR subjects. Comparison of PDAR and PDT subjects revealed significant differences in ipsilateral STC (P=0.005) and CTC (P=0.043 for CHTC and P=0.003 for CVTC) circuits. These data support the differential involvement of STC and CTC circuits in PD subtypes, and help explain the heterogeneous presentation of PD symptoms. These findings underscore the importance of integrating CTC circuits in understanding PD and other disorders of the basal ganglia.

Intravenous administration of mesenchymal stem cells exerts therapeutic effects on parkinsonian model of rats: focusing on neuroprotective effects of stromal cell-derived factor-1alpha

Background

Mesenchymal stem cells (MSCs) are pluripotent stem cells derived from bone marrow with secretory functions of various neurotrophic factors. Stromal cell-derived factor-1α (SDF-1α) is also reported as one of chemokines released from MSCs. In this research, the therapeutic effects of MSCs through SDF-1α were explored. 6-hydroxydopamine (6-OHDA, 20 μg) was injected into the right striatum of female SD rats with subsequent administration of GFP-labeled MSCs, fibroblasts, (i.v., 1 × 10⁷ cells, respectively) or PBS at 2 hours after 6-OHDA injection. All rats were evaluated behaviorally with cylinder test and amphetamine-induced rotation test for 1 month with consequent euthanasia for immunohistochemical evaluations. Additionally, to explore the underlying mechanisms, neuroprotective effects of SDF-1α were explored using 6-OHDA-exposed PC12 cells by using dopamine (DA) assay and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) staining.

Results

Rats receiving MSC transplantation significantly ameliorated behaviorally both in cylinder test and amphetamine-induced rotation test compared with the control groups. Correspondingly, rats with MSCs displayed significant preservation in the density of tyrosine hydroxylase (TH)-positive fibers in the striatum and the number of TH-positive neurons in the substantia nigra pars compacta (SNc) compared to that of control rats. In the in vitro study, SDF-1α treatment increased DA release and suppressed cell death induced by 6-OHDA administration compared with the control groups.

Conclusions

Consequently, MSC transplantation might exert neuroprotection on 6-OHDA-exposed dopaminergic neurons at least partly through anti-apoptotic effects of SDF-1α. The results demonstrate the potentials of intravenous MSC administration for clinical applications, although further explorations are required.

Subthalamic nucleotomy alleviates parkinsonism in the 1 -methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP)-exposed primate

Research into the neural mechanisms underlying the symptoms of parkinsonism utilizing the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-exposed primate model have shown that the subthalamic nucleus (STN) occupies a central role. As a logical development of this theory, we have studied the effects of thermocoagulative lesions of the STN in the primate model. Such lesions can cause remarkable symptom reversal in the experimental primate model.

Scoliosis in patients with Parkinson's disease

Background and purpose

Scoliosis is more common in patients with Parkinson's disease (PD) than in the general elderly population. We compared clinical characteristics between PD patients with and without scoliosis, to identify the relationship between the direction of scoliosis and the laterality of the dominant symptoms of PD. We also studied the associations between dopaminergic pharmacotherapy and scoliosis (defined by a spinal curvature deviation of 10° or larger).

Methods

The study population comprised 97 patients (42 men and 55 women) with idiopathic PD. All of the patients submitted to a whole-spine scanograph to allow measurement of the degree of scoliosis by Cobb's method.

Results

True scoliosis was found in 32 of the 97 PD patients, and was observed more frequently in women than in men (28 vs. 4, respectively; p=0.006). The age of patients without scoliosis was significantly lower than that of those with scoliosis (66.5±9.2 years vs. 72.8±7.3 years, respectively, mean±SD, p<0.001). There was no correlation between PD symptom laterality and scoliosis. The rate of occurrence of scoliosis did not differ between de novo and levodopa (L-dopa)-treated patients.

Conclusions

We suggest that neither L-dopa treatment nor the laterality of the initial symptoms of PD is related to the appearance of scoliosis.

Norepinephrine loss produces more profound motor deficits than MPTP treatment in mice

Although Parkinson's disease (PD) is characterized primarily by loss of nigrostriatal dopaminergic neurons, there is a concomitant loss of norepinephrine (NE) neurons in the locus coeruleus. Dopaminergic lesions induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are commonly used to model PD, and although MPTP effectively mimics the dopaminergic neuropathology of PD in mice, it fails to produce PD-like motor deficits. We hypothesized that MPTP is unable to recapitulate the motor abnormalities of PD either because the behavioral paradigms used to measure coordinated behavior in mice are not sensitive enough or because MPTP in the absence of NE loss is insufficient to impair motor control. We tested both possibilities by developing a battery of coordinated movement tests and examining motor deficits in dopamine beta-hydroxylase knockout (Dbh-/-) mice that lack NE altogether. We detected no motor abnormalities in MPTP-treated control mice, despite an 80% loss of striatal dopamine (DA) terminals. Dbh-/- mice, on the other hand, were impaired in most tests and also displayed spontaneous dyskinesias, despite their normal striatal DA content. A subset of these impairments was recapitulated in control mice with 80% NE lesions and reversed in Dbh-/- mice, either by restoration of NE or treatment with a DA agonist. MPTP did not exacerbate baseline motor deficits in Dbh-/- mice. Finally, striatal levels of phospho-ERK-1/2 and DeltaFosB/FosB, proteins which are associated with PD and dyskinesias, were elevated in Dbh-/- mice. These results suggest that loss of locus coeruleus neurons contributes to motor dysfunction in PD.

Anomalies of asymmetry of clinical signs in parkinsonism

Parkinson's disease (PD) is characterized by a minimum of two of three features: tremor, rigidity, and bradykinesia. Asymmetry of these features is often considered to support a diagnosis of PD in contrast to other parkinsonian syndromes. All major manifestations of PD are often more pronounced on the side first manifesting features of PD. Significant dissociation of features on the contralateral side, along with other variants of presentation involving the contralateral side, are rarely observed. To determine the frequency and significance of unusual asymmetry in parkinsonism, we retrospectively examined 613 patients clinically diagnosed as idiopathic PD for presence of unusual asymmetries of clinical features. Three groups of patients with unusual asymmetrical clinical findings were identified. Group 1 comprised 10 patients followed for an average of 6 years presenting with rest tremor most prominent in one lower limb and contralateral upper limb. Group 2 comprised 24 patients followed for an average of 5.5 years with action tremor most prominent on the side contralateral to the side of most prominent rest tremor. Group 3 comprised 33 patients followed for an average of 10 years who had parkinsonian signs of greatest severity on one side but subsequently, over an average of 5.4 years, became gradually more prominent on the opposite side. In Group 3, 15 of 33 patients (45%) demonstrated evolution to a rigid form of parkinsonism with disappearance of rest tremor over an average of 7.1 years after presentation. A small percentage (11%) of Parkinson's patients in our clinic demonstrated anomalous asymmetrical clinical findings, which indicates that (1) the disease process may begin in different topographic sites on each side; (2) rest tremor and action tremor may have different anatomical bases; (3) the disease process may progress at different rates on different sides; and (4) tremor becomes less pronounced with progression of disease in some patients with Parkinsonism.

Thalamic stimulation for midbrain tremor after partial hemangioma resection

We describe a patient with disabling medication-resistant midbrain tremor developed after partial hemangioma resection, who responded to deep brain stimulation of the thalamus.

Holmes' tremor following midbrain Toxoplasma abscess: clinical features and treatment of a case

The label Holmes' tremor defines a rare symptomatic movement disorder frequently occurring with midbrain damage. It appears at rest and worsens adopting a posture and on attempting movements. We describe the case of a patient with Holmes' tremor due to a presumed Toxoplasma abscess of the midbrain. The positive response to a combined therapy with levodopa and isoniazid is also reported.

Dystonia and parkinsonism

Parkinsonism and dystonia may coexist in a number of neurodegenerative, genetic, toxic, and metabolic disorders and as a result of structural lesions in the basal ganglia. Parkinson's disease (PD) and the 'Parkinson-plus' syndromes (PPS) account for the majority of patients with the parkinsonism-dystonia combination. Dystonia, particularly when it involves the foot, may be the presenting sign of PD or PPS and these disorders should be suspected when adults present with isolated foot dystonia. Young age, female gender, and long disease duration are risk factors for PD-related dystonia, but dystonia in patients with PD is usually related to levodopa therapy. The mechanism of dystonia in PD is not well understood and the management is often challenging because levodopa and other dopaminergic agents may either improve or worsen dystonia. Other therapeutic strategies include oral medications (baclofen, anticholinergics and benzodiazepines), local injections of botulinum toxin, intrathecal baclofen, and surgical lesions or high frequency stimulation of the thalamus, globus pallidus, or subthalamus.

Tremor is associated with PET measures of nigrostriatal dopamine function in MPTP-lesioned monkeys

Unilateral intracarotid artery (ICA) MPTP infusion, along with sequential systemic doses of MPTP, produces near complete degeneration of the nigrostriatal pathway on the side of infusion (ipsilateral) and variable levels of damage in the contralateral hemisphere accompanied by varying levels of parkinsonism (overlesioned hemiparkinsonian model). Positron emission tomography and the dopamine (DA) metabolism tracer [(18)F]6-fluoro-l-m-tyrosine (FMT) were used to evaluate the relationship between DA metabolism and clinical features of parkinsonism in 14 overlesioned hemiparkinsonian monkeys. Monkeys were rated on a parkinsonian scale that included ratings of bradykinesia, fine motor skills (FMS), and rest tremor. Because the monkeys tended to show more severe clinical signs on the side of the body contralateral to ICA MPTP infusion, we calculated asymmetry scores for each of the clinical features as well as for FMT uptake (K(i)) in the caudate and putamen. Tremor asymmetry was associated with FMT uptake asymmetry in the putamen. No such relationship was observed for FMS or bradykinesia. The overall severity of tremor (mild, moderate/severe) was associated with FMT uptake in the caudate and putamen. Postmortem biochemical analysis for a subset of monkeys showed that the monkeys with moderate/severe tremor had significantly lower DA levels in both caudate and putamen than those with mild tremor. In addition, K(i) values were significantly correlated with DA levels in both caudate and putamen. These findings support the idea that nigrostriatal degeneration contributes to rest tremor.

Thalamic tremor: correlations with three-dimensional magnetic resonance imaging data and pathophysiological mechanisms

Tremor associated with a single focal thalamic lesion has rarely been reported. Furthermore, the exact localization of the lesions is difficult to determine because of the imprecision of "conventional" radiology (computed tomography scan and/or "standard" magnetic resonance imaging). The aim of this study was to identify which thalamic structures are involved in tremor associated with a single focal thalamic lesion. We selected two patients who presented with unilateral postural and kinetic tremor of the upper limb related to a localized thalamic infarction. Three-dimensional T1-weighted magnetic resonance imaging sequence (MP-RAGE sequence) was used to determine the precise topography of the lesions by stereotactic analysis using the atlas of Hassler. The lesions were located within the pulvinar, the sensory nuclei, the mediodorsal nucleus, and the ventral lateral posterior nucleus (according to the classification of Hirai and Jones), the latter including the ventral intermediate nucleus (Vim according to the classification of Hassler). However, the Vim was spared. The subthalamic area, which can induce tremor, was not involved. After having compared the topography of the lesions with the clinical findings, we suggest that thalamic tremors may result from the interruption of the cerebellar outflow tract to the Vim within the thalamus.

Animal models of tremor

Animal models of tremor have been widely used in experimental neurology, because they are an indispensable requirement for understanding the pathophysiology of human tremor disorders and the development of new therapeutic agents. This review focuses on three approaches to produce tremor in animals (application of tremorgenic drugs, experimental central nervous system lesions, study of genetic mutants) and their use in simulating tremor syndromes of humans. Whereas harmaline induces a postural/kinetic tremor in animals that shares some features with human essential tremor/enhanced physiological tremor, MPTP tremor is the best model available for rest tremor in people. The tremor following experimental lesion of the ventromedial tegmentum in primates closely resembles Holmes tremor in humans, whereas cerebellar intention tremor is mimicked by cooling of the lateral cerebellar nuclei. The "campus syndrome," discovered in a breed of Pietrain pigs, might be a useful model of human orthostatic tremor. However, no animal model has yet been generated that exactly recreates all features of any of the known tremor disorders in humans. Problems encountered when comparing tremor in animals and humans include differing tremor frequencies and the uncertainty, if specific transmitter abnormalities/central nervous system lesions seen in animal tremor models are characteristic for their human counterparts. The search for adequate tremor models continues.

Physiology of MPTP tremor

Rhesus and vervet monkeys respond differently to treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride neurotoxin (MPTP). Both species develop akinesia, rigidity, and severe postural instability. However, rhesus monkeys only develop infrequent, short episodes of high-frequency tremor, whereas vervet monkeys have many prolonged episodes of low-frequency tremor. After MPTP treatment, the spiking activity of many pallidal neurons became oscillatory and highly correlated. Oscillatory autocorrelation functions were dominated by lower frequencies, cross-correlograms by higher frequencies. The phase shift distribution of the oscillatory cross-correlograms of pallidal cells in MPTP-treated vervet monkey were clustered around 0 phase shift, unlike the oscillatory correlograms in the MPTP-treated rhesus monkey, which were widely distributed between 0 degrees and 180 degrees. Analysis of the instantaneous phase differences between tremors of two limbs in the MPTP monkeys and human parkinsonian patients showed short periods of tremor synchronization. We thus concluded that the rhesus and the vervet models of MPTP-induced parkinsonism may represent the tremulous and nontremulous variants of human parkinsonism. We suggest that the tremor phenomena of Parkinson's disease (PD) are related to the emergence of synchronous neuronal oscillations in the basal ganglia. Finally, the oscillating neuronal assemblies in the pallidum of tremulous parkinsonian primates are more stable (in time and in space) than those of parkinsonian primates without overt tremor.

Pathology of symptomatic tremors

Symptomatic tremors are labeled in the literature under different names including rubral tremor, midbrain tremor, thalamic tremor, myorhythmia, Holmes' tremor, cerebellar tremor, and goal-directed tremor. The most common tremor is a delayed-onset postural and action tremor with a low frequency of 3 Hz and a proximal distribution. Resting irregular tremor is sometimes present. Mild cerebellar dysmetria is often detected. The lesions are mainly located in the thalamus, the brain stem, and the cerebellum, with secondary interruption and degeneration of various pathways and olivary hypertrophy. The more consistent lesions are found in the cerebello-thalamo-cortical and dentato-rubro-olivary pathways. The role of superimposed dysfunction of the nigrostriatal system may account for the rest component. The role of the basal ganglia in the emergence and control of tremor is poorly understood.

Anti-ataxic effects of TRH and its analogue, TA-0910, in Rolling mouse Nagoya by metabolic normalization of the ventral tegmental area

1. The mechanism of the anti-ataxic action of thyrotropin-releasing hormone (TRH) and its analogue. TA-0910, in the Rolling mouse Nagoya (RMN), an ataxic mutant mouse, has been investigated. 2. TRH (30 mg kg-1, i.p.) and TA-0910 (3 mg kg-1, i.p.) reduced the fall index (number of falls/spontaneous motor activity), an index of ataxia, 10-30 and 10-60 min after administration, respectively. 3. Relative local cerebral glucose utilization (LCGU) in the cerebellum and ventral tegmental area (VTA) of the rolling mouse was significantly smaller than that in normal animals. TRH (30 mg kg-1, i.p.) and TA-0910 (3 mg kg-1, i.p.) increased the relative LCGU value of the VTA but not of the cerebellum in rolling mice to the level of normal animals. 4. These results suggest that the ataxia of the rolling mouse may be due to dysfunction of the cerebellum and VTA, and that amelioration by TRH and TA-0910 could result from metabolic normalization of the VTA.

Hemibody tremor related to stroke

BACKGROUND

Hemibody tremor is an uncommon manifestation of stroke. We describe a case investigated by both brain magnetic resonance imaging and positron emission tomography using [18F]fluorodeoxyglucose.

CASE DESCRIPTION

Three months after a pure motor stroke, a 65-year-old man developed a right arm and leg tremor. The tremor was of large amplitude, intermittent at rest; its frequency was 5 to 6 Hz. Neither rigidity nor akinesia was detected, and administration of L-dopa was ineffective. Brain magnetic resonance imaging revealed an ischemic lesion in the left centrum semiovale and a left caudate lacunar infarction. We suspected that the resting unilateral tremor was related to this lacunar lesion. Positron emission tomography demonstrated glucose hypermetabolism in the left sensorimotor cortex.

CONCLUSIONS

This case suggests that unilateral tremor may be related to a lacunar stroke in the caudate nucleus and may be accompanied by an increased glucose metabolism in the contralateral sensorimotor cortex.

MR imaging findings of tremors associated with lesions in cerebellar outflow tracts: report of two cases

Two cases with severe tremors were studied by means of electromyograms using surface electrodes and also by magnetic resonance (MR) imaging. The first case was associated with multiple sclerosis and demonstrated a severe postural cerebellar tremor and an alternate activation of antagonist muscles in the right arm. The second case, with hemorrhage in the brainstem, demonstrated a severe tremor at rest and mixed synchronous and alternating activation of antagonist muscles in the left forearm. MR imaging studies localized lesions possibly responsible for these tremors. In the first case a lesion was located in the superior cerebellar peduncle just under the decussation, and in the second case a lesion was found between the red nucleus and the thalamus, with possible involvement of both the cerebellothalamic and nigrostriatal pathways. The first case accords with the theory that a lesion located in the dentate nucleus and its projection can cause severe postural cerebellar tremor. The lesion demonstrated in the second case may be responsible for "cerebellar tremor at rest" or "static (resting) cerebellar tremor."

Parkinson's disease-like effects of S-: Effects of l-Dopa

The major symptoms of Parkinson's disease (PD) are due to degeneration of the nigrostriatal pathway and depletion of dopamine (DA). Tyrosine hydroxylase (TH), norepinephrine (NE), serotonin (5-HT), and melanin pigments are also decreased and acetylcholinergic activity increased. Biochemically, increased methylation can cause the depletion of DA, NE, 5-HT, and melanin pigments and also an increase of acetylcholine; thus, increased methylation can present a biochemical picture that resembles the biochemical changes that occur in PD. During the therapy of PD with L-dopa, it is well known that L-dopa reacts avidly with S-adenosyl-L-methionine (SAM), the biologic methyl donor, to produce 3-O-methyl-dopa. Correspondingly, L-dopa has been shown to deplete the concentration of SAM, and SAM has been found to induce PD-like motor impairments in rodents; therefore, an excess of SAM-dependent methylation may be associated with Parkinsonism. To further study the effects of methylation, SAM was injected into the lateral ventricle of rats. SAM caused tremors, rigidity, abnormal posture, and dose-related hypokinesia. Doses of 9.38, 50, and 400 nM/rat caused 61.9, 73.4, and 94.8% reduction, respectively, of motor activity. A 200-mg/kg IP dose of L-dopa, given before 50 nM SAM, blocked the SAM-induced hypokinesia. SAM also caused a decrease in TH immunoreactivity, apparent degeneration of TH-containing fibers, loss of neurons, and the accumulation of phagocytic cells in the substantia nigra. These results showed that excess SAM in the brain, probably due to its ability to increase methylation, can induce symptoms that resemble some of the changes that occur in PD.

Animal models of parkinsonism

The discovery of profound dopamine depletion of basal ganglia in patients with Parkinson's disease and the development of antiparkinsonian drug therapy were largely based on animal models. The behavioural changes caused by cholinergic drugs, reserpine and related agents, and unselective neuronal lesions were the first widely used animal models for Parkinson's disease. The crucial breakthrough was the observation of the circling behaviour in rodents after unilateral intranigral injection of 6-hydroxydopamine. This Ungerstedt model still is one of the basic animal models of Parkinson's disease. It is suitable for the screening of new potential antiparkinsonian agents with the classic spectrum. The parkinsonism induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse and the monkey is the latest and the best animal model for Parkinson's disease. Especially when given to the monkey, MPTP causes biochemical, behavioural and neuropathological changes which largely mimick those of Parkinson's disease in man. The MPTP-induced parkinsonism in the monkey can be used for the study of the neurobiology and new forms of drugs therapy of Parkinson's disease. However, because the MPTP monkey model is expensive and laborious, it is not particularly convenient for the screening of new drugs. Recently, a new approach in the treatment of Parkinson's disease is to develop drugs which might prevent or retard the disease progression. The prevention of behavioural changes of aged rodents is used as an animal model and promising results with selegiline have been obtained.

Motor impairments and neurochemical changes after unilateral 6-hydroxydopamine lesion of the nigrostriatal dopaminergic system in monkeys

Unilateral lesions of the nigrostriatal dopaminergic system were induced in five monkeys by intranigral injections of the neurotoxin 6-hydroxydopamine. Following the lesion, all monkeys showed a transient reluctance in using the contralateral forelimb, accompanied, in two monkeys by semi-flexed posture of the disabled forelimb. Three of the monkeys that had been conditioned to perform a visually triggered goal-directed arm movement, showed an increase in latency and duration of contralateral arm movements. Task performance recovered spontaneously to preoperative levels within four months in two monkeys despite significant reductions of endogenous dopamine and dihydroxyphenylacetic acid contents in the caudate nucleus, putamen and globus pallidus ipsilateral to the neurotoxic nigral injection. The third monkey exhibited a persistent increase in movement latency associated with a near complete loss of dopamine in both the putamen and the caudate nucleus. In all cases, an increase the dihydroxyphenyl-acetic acid to dopamine ratio was detected in the striatum and pallidum suggesting a compensatory increase in dopamine turnover in remaining intact dopaminergic nerve terminals. The level of serotonin was changed in all monkeys consisting of either a decrease or an increase, depending on the striatopallidal regions studied. Changes in choline acetyltransferase and glutamic acid decarboxylase activities in the same regions were only seen in some cases. The present results show that 6-hydroxydopamine-induced partial unilateral lesion of nigral dopaminergic neurons produced predominantly contralateral hypokinesia, accompanied by reductions of dopamine content in the ipsilateral striatum and pallidum. The use of this locally applied neurotoxin appears to be a suitable method for investigating neurophysiological mechanisms underlying hypokinesia since deficits in both initiating and executing movements can be expressed independently of other behavioral symptoms. The results show more persistent deficits in starting movements than in their execution and thus suggest that motor initiation is more dependent upon the functional integrity of the nigrostriatal dopamine system than movement completion.

Differential time-course of reaction time recovery depending on variations in the amplitude of a goal-directed movement after nigrostriatal lesion in monkeys

Unilateral striatal dopamine depletion induced by 6-hydroxydopamine injections into the substantia nigra of behaving monkeys was found to increase the latency of a visually guided pointing movement performed by the contralateral forelimb. The time-course of recovery of the movement latency was faster in small displacements of the limb than in movements with larger amplitudes. The efficiency of putative compensatory mechanisms that may develop progressively in response to the striatal dopamine deficit depends on the amplitude of the movement to be initiated.

Recent physiological and pathophysiological aspects of Parkinsonian movement disorders

Deficits in the neural control of limb movements constitute a major part of Parkinsonian symptoms and are linked to a decay of dopaminergic neurotransmission. In animal models, Parkinsonian-like hypokinesia is consistently reproduced with large nigrostriatal dopamine depletions, while tremor and rigidity are less readily obtained. Lesions leading to a less than 70% striatal dopamine depletion are largely compensated by an increased activity of dopamine terminals. With more important lesions, supersensitivity of striatal non-adenylate cyclase-linked dopamine receptors occurs. Electrophysiological studies in Parkinsonian patients demonstrate increased reaction times and a reduced build-up of movement-related muscular activity underlying hypokinesia and provide circumstantial evidence for a central origin of tremor and rigidity. Single cell activity in unlesioned, behaving monkeys shows an increasingly direct relationship to movements when following the neural connections from mid-brain dopamine cells via striatum, globus pallidus, thalamus to pyramidal tract neurons of motor cortex. These data corroborate experimentally the concept that Parkinsonian hypokinesia is due to a failure of basic behavioral activating mechanisms.

Behaviour correlates of neurotransmitter activity

Most disorders of motor activity including disturbances of muscle tone and of locomotor activity observed in patients with neurological disorders have been reproduced experimentally in animals. Most motor disorders of the extrapyramidal type including those associated with Parkinson's disease and choreiform and athetoid involuntary movements, have been reproduced exclusively in primates. This is most likely related to the highly complex organization of the extrapyramidal and related nervous mechanisms subserving the corresponding peculiar type of motor control in the primate brain. Other types of motor disturbances including cervical and trunkal dystonias, ataxia, hypotonicity, spasticity and intention tremor, however, have been successfully induced in various mammalian species. The latter types of motor disorders are related to disturbances of central nervous mechanisms which show similar patterns in the brains of different animal species. Histopathological and neurochemical changes associated with extrapyramidal disorders have been discovered and more precisely determined as a consequence of the development of new technical approaches. Therefore numerous morphological, physiological and neurochemical data concerning the extrapyramidal system are now available but a better knowledge of their precise and subtle interrelationship is greatly needed in order to develop more efficient therapeutic procedures.

Defective utilization of sensory input as the basis for bradykinesia, rigidity and decreased movement repertoire in Parkinson's disease: a hypothesis

From a review of the anatomical relationships and single unit activity in the components of the basal ganglia related to limb movement, it is concluded that the major outflow from basal ganglia circuits is via the motor cortex (area 4). Recent results of recording from area 4 neurons revealed that they preferentially "encode" the higher derivatives of movement, i.e. acceleration and jerk. In the parkinsonian (PK) patient and in the monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), EMG responses to imposed loads show a markedly increased gain of the "M2" component which depends upon the integrity of area 4 and which correlates with the severity of PK rigidity. The above observations are considered, along with those of others (demonstrating prolonged movement times, a decreased "repertoire" of voluntary movements fractionation of voluntary movements, inability in tracking movements without visual input, and failure to improve performance in PK's) in relation to a model of the interactions between sensory input and motor programs. Using this model, it is hypothesized that the above PK movement deficits, as well as rigidity, can be accounted for by abnormal processing of the mechanoreceptor sensory input utilized in the generation and execution of movements. The MPTP treated monkey is suggested as a model in which to directly test the hypothesis.

Akinesia in Parkinsonism. Relation between spontaneous movement (other than tremor) and voluntary movements made on command

In eleven patients with Parkinsonism there was a strong inverse relationship between the frequency of spontaneous activity of the arms and the degree of fatiguing of repetitive finger movements made upon command. The prevalence of spontaneous arm movement was related inversely (but more weakly) to the time taken to complete a pegboard test or to move clothespegs by hand; it had little association with the speed of linear movement or with simple motor reaction time involving the arm.

Galloping induced by pontine tegmentum damage in rats: a form of "Parkinsonian festination" not blocked by haloperidol

Localized lesions or local applications of gamma-aminobutyric acid (GABA) in the nucleus reticularis tegmenti pontis (NRTP) of rats cause rapidly accelerating forward locomotion. Such "festination" can coexist with blockade of the dopamine system. We suggest that (i) the akinesia produced by dopamine deficiency results at least in part from release of excessive inhibition of locomotion by a neural system whose final common inhibitory path includes the region of the NRTP and (ii) when it occurs in addition to nigrostriatal damage, destruction in the region of the NRTP might be the cause of a form of festination seen in some patients suffering from Parkinsonism.

Parkinsonism: If surgery is necessary, can it help spontaneous movement and motor fatiguing?

Eleven patients with Parkinsonism had unilateral sterotaxic lesions made in the vicinity of the ventrolateral thalamus to reduce contralateral tremor and rigidity. The results indicate that a lesion of this sort allows motor fatiguing to improve in those limbs in which rigidity is reduced. It increases contraletral spontaneous movement if it relieves rigidity by a sufficient amount. Otherwise spontaneous movement is reduced. The lesion affects the spontaneous movement of the ipsilateral arm in parellel with its effect on the contralateral one.

The effects of reserpine on motor activity and pallidal discharge in monkeys: implications for the genesis of akinesia

1. A reversible disturbance of basal ganglia function was produced in monkeys by the intramuscular administration of reserpine.2. Pallidal discharge was then compared with that recorded in the same animals during movement performance and following passive manipulation of the limbs.3. Akinesia, loss of postural support of the trunk, head and neck and absent postural reflexes were the predominant motor abnormalities produced by reserpine administration.4. Occasionally, postural tremor and catatonia were apparent. Rigidity and resting tremor were absent.5. Recordings made in the pallidum during the presence of akinesia revealed a marked reduction in natural neuronal discharge.6. Some pallidal neurones that remained active were driven in an uncharacteristic manner by peripherally generated afferent inputs from wide territories and by a variety of peripheral stimuli.7. The findings suggest the hypothesis that the akinesia in these animals was due to the diminished pallidal activity, and that pallidal discharge is normally a prerequisite for the performance of spontaneous motor activity. Pallidal neuronal firing may provide a background excitability to motor regions involved in the maintenance and elaboration of natural motor activity.

Effects of interruption of the nigrostriatal pathway and of dopaminergic agents on the spontaneous activity of globus pallidus neurons in the awake monkey

Interruption of the nigrostriatal pathway has been shown to change parameters of striatal activity. These changes are often difficult to explain because the functional structure of the striatum is not understood sufficiently. The function of the globus pallidus appears to be simpler. It transmits the output of the striatum to the thalamus and to the midbrain. Yet the effects of interruption of the nigrostriatal pathway on the activity of pallidal neurons are unknown. To study these effects the spontaneous activity of globus pallidus neurons was recorded in intact monkeys and in monkeys with lesions of the ventromedial midbrain tegmentum. The two groups of animals were studied with and without administration of dopaminergic agents. In intact monkeys medial pallidal neurons discharge uninterruptedly at high firing rates, while the discharge of most lateral pallidal neurons is interrupted by relatively long periods of silence. Lesions involving the nigrostriatal pathway change the firing patterns but not the mean firing rates of pallidal neurons. In lesioned monkeys pallidal neurons fire in bursts continuously: during movement, rest and sleepiness. Two lines of evidence strongly suggest that the bursting pallidal activities are a consequence of the interruption of the nigrostriatal dopaminergic pathway: (1) the percentage of bursting pallidal neurons is proportional to the amount of degeneration in the pars compacta of the ipsilateral substantia nigra; (2) chronic administration of dopamine antagonists, haloperidol and reserpine, reproduces in intact monkeys the bursting activities observed in lesioned animals. On the other hand, single injections of dopamine agonists, apomorphine and piribedil, silence the medial pallidum and concomittantly abolish the signs of parkinsonism displayed by lesioned monkeys.

Alterations in forebrain catecholamine metabolism produced by cerebellar lesions in the rat

Projections from the midline cerebellar nuclei to norepinephrine (NE) and dopamine (DA) cell groups in the brain stem have been demonstrated histologically. To determine if these connections are significant biochemically, unilateral electrolytic lesions were placed in either vermis or paravermis and levels of DA, NE and gamma-aminobutyric acid (GABA) were measured in each half of the forebrain at 1 1/2, 3 or 6 weeks. In the cerebral hemisphere ipsilateral to a vermis lesion, there was a decrease in NE levels at 3 and 6 weeks. Relative to the opposite side DA was also reduced at 3 and 6 weeks. Paravermal lesions caused a contralateral reduction in DA at 3 weeks but no change in NE. GABA was only slightly altered. These results suggest that the cerebellum can modify levels and turnover of catecholamines in the brain, possibly via direct anatomic connections as well as by functional interaction with catecholaminergic pathways.