Impaired finger dexterity in patients with parkinson's disease correlates with discriminative cutaneous sensory dysfunction

To study the influence of discriminative cutaneous sensory dysfunction on impaired finger dexterity in Parkinson's disease (PD), we evaluated 48 right‐handed PD patients during a practically defined off‐medication period and 24 healthy age‐matched controls. With visual deprivation, a finger tapping task (FTT) was performed to assess the speed of simple repetitive finger movements and a coin rotation task (CRT) was used to assess finger dexterity. The tasks were performed with the right hand. We measured the somesthetic temporal discrimination threshold (sTDT) in the right index finger. The mean ± SD FTT score of the patient group was lower than that of the control group (24.0 ± 8.0 vs. 29.8 ± 7.8; P < 0.01). The patient group performed worse on the CRT than the control group (8.5 ± 3.5 vs. 12.6 ± 1.7; P < 0.001). The mean sTDT value of the patient group was longer than that of the control group (124.0 ± 44.8 vs. 78.1 ± 26.2 ms; P < 0.001). The CRT scores correlated with the sTDT values (Pearson's correlation coefficient = ?0.43; P < 0.01), but not with the Unified Parkinson's Disease Rating Scale (UPDRS) finger bradykinesia scores or FTT scores. Multiple regression analysis showed that the sTDT values (parameter estimate = ?0.03, SE = 0.01; P < 0.01), but not patient age, UPDRS finger bradykinesia score, or FTT score, affected the CRT score. Slowness of simple repetitive finger movements did not have a strong impact on the impaired manual dexterity of PD. Discriminative sensory dysfunction and consequent abnormal sensorimotor integration seem to be involved in the impaired finger dexterity of PD. © 2010 Movement Disorder Society.     

The impact of subthalamic deep brain stimulation on bradykinesia of proximal and distal upper limb muscles in Parkinson's disease

Objective To assess the differential effects of bilateral deep brain stimulation of the subthalamic nucleus on proximal and distal muscle groups of the upper limb in Parkinson's disease. Methods Eight parkinsonian subjects with chronic bilateral stimulation of the subthalamic nucleus performed index finger tapping (differentially drawing upon distal arm muscles), horizontal pointing (differentially drawing upon proximal arm muscles) and a complex reach-to-grasp task with cubes of different sizes, which involved both proximal and distal arm muscles. An ultrasound based system was used for kinematic motion analysis. Subjects were investigated in two clinical conditions: on and off subthalamic nucleus stimulation. Clinical symptom severity was rated with the Unified Parkinson's Disease Rating Scale (UPDRS) motor subscore. Results Stimulation of the subthalamic nucleus improved the UPDRS motor subscore (68 %). Bradykinesia of index finger tapping and horizontal pointing were equally improved by subthalamic nucleus stimulation. In contrast, in a complex reach-tograsp task bradykinesia was differentially ameliorated for the grasp component. Conclusion The data suggest that bilateral stimulation of the subthalamic nucleus improves bradykinesia of both distal and proximal muscles of the arm and hand in Parkinson's disease; however, dependent upon task complexity proximal and distal movement components may be affected differentially. Kinematic motion analysis is an efficient tool to objectively evaluate the beneficial effects of subthalamic nucleus stimulation on dexterity in Parkinson's disease.     

Ultrasound-based motion analysis demonstrates bilateral arm hypokinesia during gait in heterozygous PINK1 mutation carriers

Carriers of a single heterozygous PINK1 (PTEN-induced putative kinase 1) gene mutation provide an ideal opportunity to study the development of parkinsonian motor signs from the very beginning. Measuring tools that reliably represent mild motor symptoms could also facilitate the assessment of future neuroprotective therapies and early diagnosis of Parkinson's disease (PD). We investigated nine family members carrying a heterozygous PINK1 mutation in comparison with 25 age-matched healthy controls. Arm kinematics were quantified during treadmill walking at four different speeds using ultrasound-based motion analysis. Heterozygous PINK1 mutation carriers showed a bilateral reduction of arm swing amplitudes (P = 0.003) and arm anteversion (P = 0.001), which was more pronounced on the predominantly affected body side but also was present, albeit to a lesser degree, contralaterally (amplitude P = 0.01, anteversion P = 0.002, repeated measures analysis of covariance [rmANCOVA]). Single post-hoc comparisons revealed similar results for all speeds on both body sides (P < 0.05) except for 2.0 km/h on the less affected side. A single heterozygous mutation in the PINK1 gene is associated with a bilateral dopaminergic dysfunction in this family. Ultrasound-based three-dimensional motion analysis of arm swing during gait is a suitable tool to quantify even subtle hypokinesia in mildly affected PINK1 mutation carriers, which tends to be easily overlooked on the less affected body side during clinical examination. Therefore, this technique is a promising application in early stage PD and in at-risk populations for the disease. © 2014 International Parkinson and Movement Disorder Society     

Unilateral versus bilateral tasks in early asymmetric Parkinson's disease: differential effects on bradykinesia.

Patients with Parkinson's disease (PD) have an impaired ability to perform two different simultaneous bimanual tasks. The differential effects of unilateral versus bilateral identical tasks on the bradykinesia scores of the more and less affected limbs in PD have not been examined. Twenty-seven patients with early and asymmetric PD underwent blinded, videotaped assessment, independently for each limb, using the bradykinesia items of the Unified Parkinson's Disease Rating Part III, Motor subscale (mUPDRS) and a Modified Bradykinesia Rating Scale (MBRS), which assessed amplitude, speed, and rhythm of movements. We found that the score for finger tapping in mUPDRS and MBRS, the score of amplitude of finger tapping in MBRS, and the lateralized scores of mUPDRS (sum of Items 23 to 25) of the most affected side significantly improved during the bimanual task. The improvement was associated with longer duration of illness, higher total scores in mUPDRS, and higher lateralized bradykinesia scores of the most affected side. There was a simultaneous deterioration of the lateralized bradykinesia scores in MBRS (sum of Items 23 to 25) and Item 25 of mUPDRS (rapid alternating movements) of the least affected side in bimanual tasks. In conclusion, identical bimanual tasks facilitate movement of the most affected side in early asymmetric PD at the cost of motor degradation in the least affected side. This observation also highlights the need to perform tasks of bradykinesia in one limb at a time for best accuracy.     

Visual evoked potentials in Parkinson's disease-correlation with clinical involvement

A total of 18 patients with Parkinson's disease were evaluated clinically and by transient checker-board VEP study. There were significant differences between bradykinesia (P<0.01), rigidity (P<0.02), and tremor (P<0.05) subscores of the more and less severely affected sides. There were no asymmetry of VEP latency or amplitude between the more and less severely affected sides by stimulation of the corresponding eye. There were no significant correlations between the VEP latency or amplitude and any of the clinical features except the bradykinesia scores. The bradykinesia scores on the more severely involved side (r: 0.57; P=0.014) and less severely involved side (r: 0.82; P=0.00003) showed medium to high degree positive correlations with VEP amplitudes by stimulation of the corresponding eye. By studying monocular fullfield responses our data can only suggest that there is no prechiasmal asymmetry. The positive correlation between the VEP amplitude and bradykinesia score might indicate that D2 receptors dominate in the retina.     

Validity of spiral analysis in early Parkinson's disease

Spiral analysis is an objective, easy to administer noninvasive test that has been proposed to measure motor dysfunction in Parkinson disease (PD). We compared overall Unified Parkinson Disease Rating Scale Part III scores to selected indices derived from spiral analysis in seventy‐four patients with early PD (mean duration of disease 2.4 ± 1.7 years, mean age 61.5 ± 9.7 years). Of the spiral indices, degree of severity, first order zero crossing, second order smoothness, and mean speed were best correlated with total motor Unified Parkinson's Disease Rating Scale (UPDRS) score (all P < 0.01), and these indices showed a gradient across worsening tertiles of UPDRS (P < 0.05). Spiral indices also correlated with UPDRS ratings for the worst side and worst arm scores as well. The domains of bradykinesia, rigidity, and action tremor were correlated with first order crossing, second order smoothness, and mean speed, where as rest tremor was most highly correlated with degree of severity. This suggests that the spiral analysis may supplement motor assessment in PD, although further analysis of spiral metrics, a larger sample and longitudinal data should be evaluated. © 2007 Movement Disorder Society     

Correlation of Parkinson's disease severity and duration with 123I-FP-CIT SPECT striatal uptake.

The variability in clinical features and the masking effects of drug therapy in Parkinson's disease (PD) can affect clinical assessment of disease severity. The aim of this study was to assess the imaging of dopamine transporters using 123I-FP-CIT SPECT and its correlation with disease staging, severity, and duration. Differences between the clinical severity of the onset and non-onset side and the corresponding striatal uptake ratios were also examined. Forty-one patients with PD (nine unilateral, 32 bilateral clinical features) were studied. Clinical severity was determined by using the Unified Parkinson's Disease Rating Score (UPDRS). Unilateral UPDRS was calculated from unilateral arm and leg resting and action tremor, rigidity, finger taps, hand movements, alternating movements, and leg agility. 123I-FP-CIT striatal uptake was expressed as the ratio of specific:nonspecific (SP:NS) uptake for defined brain areas. Patients with PD who had unilateral symptoms showed a significant difference between the ipsilateral and contralateral SP:NS ratios in both the caudate and putamen, but there was a considerable overlap between between the two sides. This result was repeated in patients with bilateral symptoms and there was overlap of SP:NS ratios between the two groups. For the whole group of patients with PD, striatum, caudate, and putamen SP:NS ratios correlated with disease severity assessed by UPDRS and duration of disease. The SP:NS ratios correlated with the bradykinesia subscore but not with rigidity or tremor subscore. In conclusion, this study provides further evidence that the SP:NS ratio is a robust measure of disease severity correlating with duration of PD. However, variability in uptake values suggest that factors other than nigrostriatal degeneration may contribute to disease severity. Correlation with bradykinesia but not with tremor may indicate an origin for tremor outwith the dopamine transporter system. 123I-FP-CIT SPECT offers significant potential in defining the nigrostriatal changes in PD.     

Nonlinear dynamic analysis of oscillatory repetitive movements in Parkinson's disease and essential tremor

Uncertainty exists on whether Parkinson's disease (PD) and essential tremor (ET) patients have similar degree of impairment during motor tasks. We investigated this problem by analyzing nonlinear dynamics of repetitive movements in 21 control subjects, 33 mild‐moderate PD patients, and 18 ET patients. Accelerometer signals were recorded during finger tapping and unbounded forearm movements between two points, and processed with moving average filtering to generate a new signal consisting of the temporal distance between consecutive cycles. We calculated: mean interpeak interval (slowness), interpeak interval variability (irregularity), and beat decay (BD) of the auto mutual information (AMI) value, which estimates signal predictability by measuring the loss of signal information over a timescale. Both PD and ET had longer interpeak interval (except for finger tapping), higher interpeak interval variability, and higher BD‐AMI values than controls (P ≤ 0.007, all comparisons). ET patients had higher BD‐AMI values than PD (P = 0.003). BD‐AMI was the parameter that discriminated better between subjects (diagnosis accuracies about 80%). No differences existed between PD patients with and without tremor or between PD or ET patients with different disease stages, for any parameter. Evaluation of nonlinear dynamics of oscillatory repetitive movements is a feasible and promising tool for studying movement physiology. Movement performance is more predictable in PD and ET than in controls, even in early disease stages. Slowness and irregularity of movement in PD and ET cannot be fully explained by tremor. Some common pathogenic mechanisms leading to bradykinesia may contribute to this impairment. © 2010 Movement Disorder Society     

Excessive postural sway and the risk of falls at different stages of Parkinson's disease

Excessive postural sway may result in falls in Parkinson's disease (PD). We measured postural sway using the sensory organization test (SOT) of dynamic posturography in static (platform still) and dynamic (sway referenced platform) conditions with normal, no and inappropriate visual feedback in 102 subjects with PD, off medication. Twenty‐five healthy subjects were used as age‐matched controls. Eighteen very early stage PD subjects had never used dopaminergic medication. Postural sway was normal in those subjects in all conditions, but was abnormal in subjects with more advanced symptoms (UPDRS III > 20, P < 0.01). Postural sway increased with disease severity in all conditions except static, eyes closed (P < 0.0001). We developed the SOT Fall Severity Scale (SOTFSS) from the number of times postural sway was so large that the subject had to take a step (registered as a “fall”) and showed that falls mainly occurred in dynamic conditions, and were correlated with disease severity (P < 0.0001). In dynamic conditions the SOTFSS was correlated with the retropulsion score from the UPDRS III (N = 102, P < 0.0001) and with the subjects' self‐reported fall frequency from the UPDRS II (N = 62, SOT5: P = 0.0419, SOT6: P = 0.0034). © 2008 Movement Disorder Society     

Differential response of speed, amplitude, and rhythm to dopaminergic medications in Parkinson's disease

Although movement impairment in Parkinson's disease includes slowness (bradykinesia), decreased amplitude (hypokinesia), and dysrhythmia, clinicians are instructed to rate them in a combined 0–4 severity scale using the Unified Parkinson's Disease Rating Scale motor subscale. The objective was to evaluate whether bradykinesia, hypokinesia, and dysrhythmia are associated with differential motor impairment and response to dopaminergic medications in patients with Parkinson's disease. Eighty five Parkinson's disease patients performed finger‐tapping (item 23), hand‐grasping (item 24), and pronation–supination (item 25) tasks OFF and ON medication while wearing motion sensors on the most affected hand. Speed, amplitude, and rhythm were rated using the Modified Bradykinesia Rating Scale. Quantitative variables representing speed (root mean square angular velocity), amplitude (excursion angle), and rhythm (coefficient of variation) were extracted from kinematic data. Fatigue was measured as decrements in speed and amplitude during the last 5 seconds compared with the first 5 seconds of movement. Amplitude impairments were worse and more prevalent than speed or rhythm impairments across all tasks (P < .001); however, in the ON state, speed scores improved exclusively by clinical (P < 10^?6) and predominantly by quantitative (P < .05) measures. Motor scores from OFF to ON improved in subjects who were strictly bradykinetic (P < .01) and both bradykinetic and hypokinetic (P < 10^?6), but not in those strictly hypokinetic. Fatigue in speed and amplitude was not improved by medication. Hypokinesia is more prevalent than bradykinesia, but dopaminergic medications predominantly improve the latter. Parkinson's disease patients may show different degrees of impairment in these movement components, which deserve separate measurement in research studies. © 2011 Movement Disorder Society     

Quadrupedal coordination of bipedal gait: implications for movement disorders

During recent years, evidence has come up that bipedal locomotion is based on a quadrupedal limb coordination. A task-dependent neuronal coupling of upper and lower limbs allows one to involve the arms during gait but to uncouple this connection during voluntarily guided arm/hand movements. Hence, despite the evolution of a strong cortico-spinal control of hand/arm movements in humans, a quadrupedal limb coordination persists during locomotion. This has consequences for the limb coordination in movement disorders such as in Parkinson’s disease (PD) and after stroke. In patients suffering PD, the quadrupedal coordination of gait is basically preserved. The activation of upper limb muscles during locomotion is strong, similar as in age-matched healthy subjects although arm swing is reduced. This suggests a contribution of biomechanical constraints to immobility. In post-stroke subjects a close interactions between unaffected and affected sides with an impaired processing of afferent input takes place. An afferent volley applied to a leg nerve of the unaffected leg leads to a normal reflex activation of proximal arm muscles of both sides. In contrast, when the nerve of the affected leg was stimulated, neither on the affected nor in the unaffected arm muscles EMG responses appear. Muscle activation on the affected arm becomes normalized by influences of the unaffected side during locomotion. These observations have consequences for the rehabilitation of patients suffering movement disorders.     

Poor dopaminergic response of impaired dexterity in Parkinson's disease: Bradykinesia or limb kinetic apraxia?

Patients with Parkinson's disease (PD) often show impaired manual dexterity even when being only minimally bradykinetic, suggesting that they may have limb kinetic apraxia (LKA), that is, a loss of fine motor skill not explained by elemental motor deficits. To explore this dissociation, we investigated the differential dopaminergic responsiveness of dexterity and bradykinesia in PD. Twelve patients with PD (4 women, age 64.4 ± 8.3, mean + SD) and 12 matched healthy controls (64.8 ± 8.9) were tested twice in ON vs. OFF and 1st vs. 2nd trial, respectively. A coin rotation (CR) task was applied to assess dexterity and a finger tapping (FT) task to assess bradykinesia. Performance was followed by video recording and analyzed by measuring the frequency of CR and FT during three 10‐second periods. Statistical analysis was done by a mixed factorial design with group (PD vs. controls) as between‐subject factor and medication (ON‐ vs. OFF‐state or 1st vs. 2nd trial), task (FT vs. CR), and handedness (dominant vs. nondominant) as within‐subject factors. In patients with PD, regardless of hand involved, dopaminergic treatment only mildly improved CR performance, in contrast to the strong increase in FT scores (up to the level of controls), as demonstrated by the significant triple interaction of the factors group, medication, and task (F_1,22 = 7.9, P = 0.01; η² = 0.26). Furthermore, CR scores were considerably lower, both in OFF and ON, than in normal controls, pointing to a substantial impairment of dexterity in PD (P < 0.001). In conclusion, impaired manual dexterity showing significantly diminished response to dopaminergic treatment suggests that dextrous deficits in PD are related to LKA rather than bradykinesia. © 2008 Movement Disorder Society     

Perception of heaviness in Parkinson's disease

The present study investigated whether a specific aspect of proprioception, the sense of heaviness or weight is affected in PD. We determined detection thresholds for the perception of a gravito‐inertial load in 10 PD patients and 11 age‐matched control subjects. A gradually increasing weight was applied to the index finger by means of two slings of different width (low vs. high skin pressure). For the controls, mean detection thresholds were 31.3 g at skin high pressure and 33.0 g under low pressure. PD patients revealed significantly higher thresholds than the control group in both pressure conditions (mean high pressure,47.7 g; mean low pressure, 52.3 g; group effect, P = 0.001). Thresholds of PD patients tended to increase with disease severity as measured by the Unified Parkinson's Disease Rating Scale Motor score (r = 0.55) but did not correlate significantly with levodopa equivalent dosage. The results demonstrate that the perception of heaviness or weight is already affected in the early stages of PD. These findings underline the growing evidence that proprioceptive and possibly haptic dysfunction is a common feature of PD. © 2006 Movement Disorder Society     

Factors predicting response to dopaminergic treatment for resting tremor of Parkinson's disease

We aimed to evaluate the clinical factors predicting response to dopaminergic treatment for resting tremor in patients with Parkinson's disease (PD). Eighty‐five PD patients with prominent resting tremor, defined as tremors of score greater than 3 in at least one limb on the Unified Parkinson's Disease Rating Scale (UPDRS), were divided into those responsive or nonresponsive to dopaminergic treatment. Responsiveness was defined as a reduction of at least two points for more than 3 months in the UPDRS tremor score. Of the 85 patients, 36 (42.4%) were responsive and 49 (57.6%) were nonresponsive to dopaminergic treatment. Initial UPDRS III score (P = 0.015) and Hoehn and Yahr stage (P = 0.010) were each significantly higher in the RG than in the NRG. UPDRS subscores for rigidity (P = 0.012), bradykinesia (P = 0.021) and postural impairment (P = 0.018) also correlated with responsiveness to dopaminergic treatment. Resting tremor in PD patients was more responsive to dopaminergic treatment when accompanied by moderate degrees of bradykinesia and rigidity than in patients without other prominent parkinsonian features. © 2007 Movement Disorder Society     

Development of a prediction formula of Parkinson disease severity by optical coherence tomography

The aims of this study were to assess the peripapillary retinal nerve fiber layer (RNFL) thickness in patients with Parkinson's disease (PD), to determine its correlation with disease severity, and to define a simple biomarker for predicting clinical severity. One hundred two eyes from 52 patients affected by PD were compared with 97 eyes from 50 age‐comparable controls. In all patients, peripapillary RNFL thickness was measured by optical coherence tomography (OCT). We used the Unified Parkinson's Disease Rating Scale (UPDRS) total score and measured responses in the on medication state. Eyes from patients with PD had a statistically significant decrease in average peripapillary RNFL thickness compared with control eyes (P < 0.001). This reduction was observed in every quadrant (inferior, superior, nasal [P < 0.001], and temporal [P = 0.017]) in patients with PD. Furthermore, a strong inverse correlation was found between the PD severity measured according to the UPDRS score and the average peripapillary RNFL thickness (r = ?0.615; P < 0.001) and PD duration (r = ?0.303; P = 0.002). From these results, we defined a regression equation that predicts the UPDRS score from the above‐mentioned variables: UPDRS = 81.6 + 29.6 * log PD duration (years) ? 0.6 * RFNL thickness (μm). We observed that, as the evolution and severity of PD progress, the peripapillary RNFL layer thickness, as evaluated by OCT, gradually diminishes. These results suggest that the average peripapillary RNFL thickness measured by OCT might be useful as a biomarker to detect the early onset and progression of PD. © 2013 International Parkinson and Movement Disorder Society     

Body side and predominant motor features at the onset of Parkinson's disease are linked to motor and nonmotor progression

Patients with Parkinson's disease most often have asymmetric motor features at onset, and specific motor signs (ie, tremor versus bradykinesia and rigidity) frequently characterize the first few years of disease evolution. Some previous clinical evidence has suggested that body side and a predominance of motor manifestations at disease onset are linked to long‐term evolution and disease progression. We prospectively analyzed 206 patients with Parkinson's disease according to the most affected side and predominant motor signs at onset. Patients were divided into left‐side rigid‐akinetic (n = 71), right‐side rigid‐akinetic (n = 59), left‐side tremor (n = 41), and right‐side tremor (n = 35) subgroups. These subgroups were compared in terms of motor and cognitive functions, mean motor deterioration per year (calculated as the motor score divided by disease duration), total equivalent doses of dopaminergic drugs, and the presence of hallucinations and rapid eye movement sleep behavior disorder. Disease duration was similar in all groups. Motor fluctuations were more likely to occur in rigid‐akinetic patients. In a multiple model analysis adjusted for potential confounders, faster disease progression was associated with right‐side (P = 0.045) and rigid‐akinetic onset (P = 0.001). With respect to nonmotor symptoms, the rigid‐akinetic type was associated with increased risk of cognitive decline (P = 0.004) compared with the tremor type. A trend was noticed toward an increased risk of developing visual hallucinations in rigid‐akinetic patients and toward an increased frequency of rapid eye movement sleep behavior disorder in those who had left‐sided onset of symptoms. Our findings corroborate that body side and type of motor signs at the time of diagnosis affect the evolution of motor severity and may also have an impact on some nonmotor manifestations. © 2013 Movement Disorder Society     

Assessment of movement time in patients with essential tremor

Background We have observed mild bradykinesia in essential tremor (ET) patients, which do not satisfy the criteria of Parkinson’s disease (PD). Objective To compare the mean movement time for repetitive movements around distal and proximal joints in ET patients with normal controls by using a simple test paradigm. Patients and methods Seventeen patients with ET and 14 control subjects were instructed to tap with the index finger sequentially on push–button microswitches. Movement times around metacarpophalangeal, wrist, elbow, and shoulder joints of the right side were tested. The data collected were stored on a computer and the time elapsed between sequential taps on two keys (ms) and number of taps on the left key for 15 seconds were evaluated offline. Results Movement times of the patients with ET were not found to be significantly different from those of the controls at all joints tested despite slight prolongation for movements around the shoulder joint. Conclusion The simple test paradigm we have used showed that there is no difference in the movement time for repetitive movements around four joints of the upper extremity between patients with ET and normal control subjects. The slightly prolonged movement time around the shoulder joint noted in patients with ET may be ascribed to tremor, not bradykinesia. Tremor may cause these patients to pay more attention to the performance of goal–directed finger movements and consequently prolong movement time slightly or it may simply delay the time elapsed to reach the goal in the absence of overt intention tremor.     

Corticomotor excitability in drug-naive patients with Parkinson disease

Background and purposeThis study aimed to assess the indices of corticomotor excitability (CE) in drug-naive Parkinson disease (PD) patients and to investigate its relationship with asymmetry and severity of clinical symptoms.Material and methodsEleven (4 men) drug-naive PD patients (mean age: 53.1 ± 9.8 years) and 13 (7 men) healthy controls (mean age: 51.7 ± 4.2 years) were included. All PD patients were rated on the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS) with measurement of the side-specific score separately for arms and legs. Resting motor threshold (RMT), central silent period (CSP), amplitude of motor evoked potential (MEP) and central motor conduction time (CMCT) evoked by a single pulse of the transcranial magnetic stimulation were recorded in all subjects from the left and right abductor digiti minimi (ADM) and extensor digitorum brevis (EDB).ResultsParkinson disease patients showed higher MEP (1.8 ± 0.9 vs. 1.1 ± 0.8 mV, p < 0.05) and shorter CMCT (6.1 ± 0.9 vs. 7.4 ± 1.0 ms, p < 0.05) recorded from the ADM on the more affected side. CSP recorded from the more affected ADM was under the normal range in five and from the less affected ADM in four PD patients. For CSP recorded from the EDB, respective values are four for the more affected side and three for the less affected side. The rigidity from the more affected arm and leg correlated negatively with the respective CSP recorded from the ADM (r = –0.74, p < 0.01) and EDB (r = –0.68, p < 0.04).ConclusionsIn the early stage of untreated PD the CE parameters are altered only on the more affected side. The shortening of CSP reflects the severity of rigidity on the more affected side.     

Factors associated with drug–induced visual hallucinations in Parkinson's disease

Aims Visual hallucinations are common in medicationtreated Parkinson's disease (PD) patients. Although their etiology is unknown several factors seem to be involved in their pathogenesis. The aim of this study was to identify possible risk factors and determine clinical characteristics associated with the development of visual hallucinations in PD. Methods 166 consecutive patients fulfilling clinical criteria for PD were studied. During a semi–structured interview, demographic characteristics and clinical variables were recorded. Motor, cognitive and psychiatric status was also assessed. Patients with and without visual hallucinations were compared using non–parametric tests, and logistic regression was applied to significant data. Results During the month before evaluation 20.4% of our patients experienced visual hallucinations (11.4% benign, 9% malignant). Logistic regression analysis identified three factors independently associated with visual hallucinations: long duration of Parkinson's disease, dementia, and disease severity as measured by the UPDRS total score. Conclusions Our findings indicate that apart from well established risk factors such as cognitive impairment and disease duration, disease severity is also important for the development of visual hallucinations in PD. Furthermore, the presence of bradykinesia and instability, the absence of tremor and the severity of rigidity and bradykinesia (limb and axial) may act as cofactors.     

Stimulation of the subthalamic region at 20 Hz slows the development of grip force in Parkinson's disease

Excessive synchronization of basal ganglia neuronal activity at ~ 20 Hz is characteristic of patients with untreated Parkinson's disease (PD). Correlative evidence suggests that this activity may contribute to bradykinesia. Attempts to demonstrate causality through stimulation imposed synchronization at 20 Hz in the region of the subthalamic nucleus (STN) have had limited success. Finger-tapping is slowed by about 8% and only in those PD patients that have a relatively normal baseline performance in this task. Here we investigate whether greater performance decrements might be seen in a reaction time grip task. We studied 32 sides in 16 patients with PD after overnight withdrawal of medication. Patients were asked to grip as hard and as fast as possible without STN stimulation and during bilateral stimulation at 5 Hz, 10 Hz, 20 Hz, 50 Hz and 130 Hz. Stimulation at 20 Hz slowed the development of force by 14.7 ± 8.3% (P = 0.044) across all patients. Slowing increased by 22 ± 7% (P = 0.005) in those patients with the best performance in the task without stimulation. The effect was frequency specific. These data provide direct interventional evidence of a mechanistic link between excessive neuronal synchronization in the beta range and motor impairment in PD.