Effect of levodopa on both verbal and motor representations of action in Parkinson's disease: a fMRI study

Previous studies have demonstrated that non-demented Parkinson's disease (PD) patients have a specific impairment of verb production compared with noun generation. One interpretation of this deficit suggested the influence of striato-frontal dysfunction on action-related verb processing. The aim of our study was to investigate cerebral changes after motor improvement due to dopaminergic medication on the neural circuitry supporting action representation in the brain as mediated by verb generation and motor imagery in PD patients. Functional magnetic resonance imaging on 8 PD patients in "ON" dopaminergic treatment state (DTS) and in "OFF" DTS was used to explore the brain activity during three different tasks: Object Naming (ObjN), Generation of Action Verbs (GenA) in which patients were asked to overtly say an action associated with a picture and mental simulation of action (MSoA) was investigated by asking subjects to mentally simulate an action related to a depicted object. The distribution of brain activities associated with these tasks whatever DTS was very similar to results of previous studies. The results showed that brain activity related to semantics of action is modified by dopaminergic treatment in PD patients. This cerebral reorganisation concerns mainly motor and premotor cortex suggesting an involvement of the putaminal motor loop according to the "motor" theory of verb processing.

Pathological gambling from dopamine agonist and deep brain stimulation of the nucleus tegmenti pedunculopontine

In patients with Parkinson's disease, aberrant or excessive dopaminergic stimulation is commonly indicated as the trigger factor in unmasking impulse control disorders (ICDs) such as pathological gambling. We had the opportunity to follow a patient who experienced Parkinson's disease 7 years ago when he was using pramipexole and again, recently, when he was treated with levodopa (L-dopa) and low frequency stimulation of the nucleus of the pedunculopontine tegmentus (PPTg) but no dopamine agonists. The same patient had shown, when studied with fluorodeoxyglucose-positron emission tomography in the condition PPTg-ON, a peculiar increased activity in the left ventral striatum. This case report confirms that, in a predisposed personality, ICD may arise from the perturbation of endogenous pathways, which connect the brainstem to the basal ganglia.

Deep brain stimulation of the pedunculopontine tegmentum and subthalamic nucleus: effects on gait in Parkinson's disease

OBJECTIVE

This study examines the effects of subthalamic nucleus (STN) deep brain stimulation (DBS) and pedunculopontine tegmentum (PPTg) DBS in advanced Parkinson's disease using gait analysis.

METHODS

Five people underwent bilateral DBS in both the STN and PPTg. Gait analysis was performed one year after neurosurgery using an optoelectronic system. The effects of DBS (STN, PPTg and STN+PPTg) were studied in two clinical conditions: without (Off) and during (On) antiparkinsonian therapy.

RESULTS

PPTg and STN DBS were associated with changes in spatio-temporal and kinematics variables.

CONCLUSIONS

Although experimental data cannot be generalized widely due to the small sample, PPTg DBS appears to affect the neuronal circuits subserving gait.

Deep brain stimulation of CM/PF of thalamus could be the new elective target for tremor in advanced Parkinson's Disease?

Aim of this study was to investigate whether Deep Brain Stimulation (DBS) of the Centre Median Nucleus/Parafascicular (CM/PF) Complex is useful in reducing extrapyramidal symptoms in advanced Parkinson's Disease (PD) patients. In particular, we compared the action of CM/PF and subthalamic nucleus (STN) DBS on resting hand tremor using EMG surface of ulnar and radial right-hand muscles. Our results show that C/M DBS is very effective in reducing tremor, indicating this complex as a new target in advanced PD patients.

Does gait analysis quantify motor rehabilitation efficacy in Parkinson's disease patients?

SUBJECTS

Sixteen rigid-akinetic idiopathic Parkinson's disease patients (PD) and 13 healthy control subjects (controls) were included in this study.

METHODS

Gait analysis was performed using an optoelectronic system. The experimental design involved double evaluation of PD patients (before and after motor rehabilitation program) and a single evaluation of controls. ANOVA was performed in both groups for each gait variable (kinetic and kinematic) and for clinical conditions.

RESULTS

Analysis of kinetic data highlighted a statistically significant difference for all gait variables studied between controls and PD patients either before, or in the same PD patients before and after the motor rehabilitation program. After the rehabilitation program, natural walking speed increased (p<.000). The stance percentage was significantly decreased in the single support (p<.000). After the rehabilitation program, the double support limb phase did not show a reduction in statistical significance. Kinematic data showed statistical differences between controls and PD patients in hip, knee and ankle joint angles, both before and after the motor rehabilitation program.

CONCLUSION

Our results confirm that gait analysis is a valid tool for evaluating changes in PD patients' ability to walk and for quantifying the improvements gained through a motor rehabilitation program.

Global Mobility Task: index for evaluating motor impairment and motor rehabilitation programs in Parkinson's disease patients

OBJECTIVE

In this study, the validity of a motor task, i.e., the Global Mobility Task (GMT), was assessed in a group of Parkinson's disease (PD) patients.

PATIENTS AND METHODS

Fifty-eight PD patients (mean age: 68.7 years) and 18 healthy subjects (mean age: 65.8 years) were enrolled in the study. The GMT measures the ability of an adult to roll over on the floor and stand up in five steps using two parameters: 'Time' and 'Score', i.e., the time needed and the ability to perform each step of the task. As the GMT has never been evaluated before, internal consistency and concurrent and discriminative validity were considered in assessing its characteristics in a group of PD patients at the beginning and at the end of a motor rehabilitation program. To determine whether the GMT could also quantify the extrapyramidal impairment, we compared data collected using this task with data obtained using clinical scales such as the Unified Parkinson's Disease Rating Scale III (UPDRS part III) and Hoehn & Yahr's score.

RESULTS

Results showed that the GMT had good consistency and inter-rater reproducibility, was closely related to clinical scales and was able to detect the amelioration of extrapyramidal symptoms at the end of the motor rehabilitation program.

CONCLUSION

we propose the GMT as a tool for measuring impaired mobility in PD patients and for evaluating the objective effects of motor rehabilitation programs.

Major and minor depression in Parkinson's disease: a neuropsychological investigation

Previous studies have failed to distinguish the differential contribution of major and minor depression to cognitive impairment in patients with idiopathic Parkinson's disease (PD). This study was aimed at investigating the relationships among major depression (MD), minor depression (MiD) and neuropsychological deficits in PD. Eighty-three patients suffering from PD participated in the study. MD and MiD were diagnosed by means of a structured interview (SCID-I) based on the DSM-IV criteria, and severity of depression was evaluated by the Beck Depression Inventory. For the neuropsychological assessment, we used standardized scales that measure verbal and visual episodic memory, working memory, executive functions, abstract reasoning and visual-spatial and language abilities. MD patients performed worse than PD patients without depression on two long-term verbal episodic memory tasks, on an abstract reasoning task and on three measures of executive functioning. The MiD patients' performances on the same tests fell between those of the other two groups of PD patients but did not show significant differences. Our results indicate that MD in PD is associated with a qualitatively specific neuropsychological profile that may be related to an alteration of prefrontal and limbic cortical areas. Moreover, the same data suggest that in these patients MiD and MD may represent a gradual continuum associated with increasing cognitive deficits.

Alexithymia in Parkinson's disease is related to severity of depressive symptoms

The authors investigated the possible relationship between depression and alexithymia in a population of hospitalized patients suffering from Parkinson's disease (PD). Fifty-eight PD patients without dementia participated in the study. Alexithymia was screened using the 20 item version of the Toronto Alexithymia Scale (TAS 20). Depression was diagnosed using a Structured Clinical Interview (SCID I) for DSM-IV. Severity of depression was evaluated with the Beck Depression Inventory (BDI). The prevalence of Alexithymia was about 21%. PD patients with major depression were significantly more alexithymic (TAS 20 average score = 61.4) than PD patients without depression (TAS 20 average score = 47.4) and, also, tended to be more alexithymic than PD patients with minor depression (MiD; TAS 20 average score =50.6), whereas no difference was found between PD patients with MiD and PD patients without depression. Moreover, high scores obtained on the BDI were found to strongly predict high level of alexithymia in these patients. These results extend to a cohort of PD patients previous data from the literature evidencing a strong association between alexithymia and severity of depressive symptoms.

Deep brain stimulation in Parkinson's disease patients: biochemical evidence

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) patients augments STN-driven excitation of the internal globus pallidus (GPi). However, other DBS-induced changes are largely unknown. Here we report the biochemical effects of STN-DBS in two basal ganglia stations (putamen--PUT--and GPi) and in a thalamic relay nucleus, the anteroventral thalamus (VA). In six advanced PD patients undergoing surgery, microdialysis samples were collected from GPi, PUT and VA before, during and after one hour of STN-DBS. cGMP was measured in the GPi and PUT as an index of glutamatergic transmission, whereas GABA was measured in the VA. During clinically effective STN-DBS, we found a significant decrease in GABA extracellular concentrations in the VA (-25%). Simultaneously, cGMP extracellular concentrations were enhanced in the PUT (+200%) and GPi (+481%). DBS differentially affects fibers crossing the STN area: it activates the STN-GPi pathway while inhibiting the GPi-VA one. These findings support a thalamic dis-inhibition, as the main responsible for the clinical effect of STN-DBS. This, in turn, re-establishes a more physiological level of PUT activity.

rTMS of supplementary motor area modulates therapy-induced dyskinesias in Parkinson disease

The neural mechanisms and circuitry involved in levodopa-induced dyskinesia are unclear. Using repetitive transcranial magnetic stimulation (rTMS) over the supplementary motor area (SMA) in a group of patients with advanced Parkinson disease, the authors investigated whether modulation of SMA excitability may result in a modification of a dyskinetic state induced by continuous apomorphine infusion. rTMS at 1 Hz was observed to markedly reduce drug-induced dyskinesias, whereas 5-Hz rTMS induced a slight but not significant increase.

Delayed administration may improve entacapone effects in parkinsonian patients non-responding to the drug

BACKGROUND

Entacapone is a COMT inhibitor used in Parkinson's disease (PD) patients, as an adjunctive therapy to L-dopa in order to prolong its bioavailability and thus its clinical effect. However, previous studies reported entacapone-induced L-dopa to have lower C(max) and delayed t(max) values, coupled with a delayed onset of the clinical effect, possibly suggesting an interference between the two drugs. The aim of our study was to evaluate whether a delayed entacapone administration in association with standard L-dopa/carbidopa, may in some subjects improve the entacapone effects on L-dopa AUC and thus on the clinical 'on time' duration.

METHODS

Twenty-eight idiopathic advanced PD patients were blindly evaluated in three different test days, following administration of carbidopa/L-dopa or carbidopa/L-dopa plus co-administered entacapone or plus entacapone administered with 30 min of delay.

RESULTS

The AUC, the 'on time' and UPDRS score of the whole group were improved by both modalities of entacapone administration. An ex post analysis showed that the delayed entacapone administration produced a significant improvement in a subgroup of 10 non-responding patients to the co-administration.

CONCLUSION

We suggest that the delayed administration should be attempted in the subjects not improved by entacapone co-administration.

Pergolide effect on cognitive functions in early-mild Parkinson?s disease

In the present study, we evaluated the effect of pergolide, a mixed D1/D2 agonist, on cognitive function in mild Parkinson's disease (PD). After a two-week wash-out phase, twenty patients with a Hoehn and Yahr score </=2.5 entered a 16-week, cross-over study in which the order of administration of pergolide or 1-dopa was randomly assigned. Cognitive assessment was performed after the wash-out phase and repeated after eight weeks (before patients were switched to the other drug) and at the end of the study. There were no significant differences in test scores among the three experimental modalities (off-treatment vs. l-dopa, off-treatment vs. pergolide, pergolide vs. l-dopa). In another cohort of comparably mild PD patients we had previously demonstrated that pramipexole, a mixed D2/D3 agonist, slightly but significantly worsened verbal fluency in comparison to l-dopa; moreover, pramipexole impaired short term verbal memory and attentional-executive functions in comparison to both l-dopa and the off-treatment condition. Taken together, these findings suggest that dopamine agonists may influence cognition in PD according to their pharmacological characteristics. Unlike the D2/D3 agonist pramipexole, pergolide and l-dopa, both of which stimulate D1- and D2-receptor subtypes, do not appear to impair cognitive function.

Time interval of oral feeding recovery as a prognostic factor in severe traumatic brain injury

PRIMARY OBJECTIVES

To assess the outcome of severe traumatic brain injury at least 1 year after trauma, in relation to some early clinical prognostic factors occurring during coma recovery.

RESEARCH DESIGN

Retrospective study conducted at the post-coma unit of a rehabilitation hospital.

METHODS AND PROCEDURES

A total of 43 patients were included. All of the patients sustained severe traumatic brain injury and prolonged coma, i.e. coma lasting at least 15 days. Outcome was assessed by means of Glasgow Coma Scale, Barthel Index and Mini Mental State 1 year after trauma, in relation to some early clinical prognostic factors occurring during coma recovery.

MAIN OUTCOMES AND RESULTS

At the 1 year follow-up, a statistically significant correlation was found with both the Glasgow Outcome Scale and the Barthel Index for the time interval from brain injury to recovery of the following clinical variables: optical fixation, ability to obey commands, spontaneous motor activity and first safe oral feeding. Psychomotor agitation and bulimia were also favourable prognostic factors for the final outcome.

CONCLUSIONS

In the present study, first safe oral feeding during coma recovery represents the clinical feature that better predicts the final outcome of patients with severe traumatic brain injury and prolonged coma.

Pramipexole in comparison to l-dopa: a neuropsychological study

Twenty right-handed patients affected by early/mild Parkinson's disease were evaluated in a randomised study using neuropsychological and clinical assessements during three treatment modalities: when in the off treatment condition, when on pramipexole, and when on l-dopa. In comparison to the off treatment condition, the DA-agonist pramipexole produced a significant impairment of short term verbal memory, attentional-executive functions and verbal fluency, while l-dopa did not. Moreover, pramipexole opposite to l-dopa, failed to improve FAS and Stroop tests. Present findings indicate that pramipexole may worsen cognitive functions although not exceeding normative values.

Emotional processing in Parkinson's disease. A study using functional transcranial doppler sonography

This study evaluated the use of transcranial Doppler ultrasonography for detecting selective changes in cerebral blood flow velocity during emotional processes. The aim was to investigate the possibility of obtaining functional information on the neuropsychology of emotions in patients with Parkinson's disease (PD). For this reason, blood flow velocity changes were investigated in both middle cerebral arteries (MCA) during a rest condition and when viewing non emotional (tasks 1 and 3) and emotional (task 2) slide sequences. The study included 12 PD patients and 12 healthy subjects. All patients were in treatment with levodopa or dopamine agonist. Investigation of PD patients was performed during an on-phase. The three tasks produced significantly different effects on the right and left side in the PD patients compared with the control group. During the two non emotion-related tasks the increase of mean flow velocity (MFV) compared with the basal values was similar in the two middle cerebral arteries in both groups [(PD Patients: Task 1: left MCA = 3.95 % 2.2, Right MCA = 4.33 % +/- 2.3, Task 3: left MCA = 3.04 % +/- 1.9, Right MCA = 2.71 % +/- 2.2) (control group: Task 1: left MCA = 4.57 % +/- 1.4, Right MCA = 4.46 % +/- 1.7, Task 3: left MCA = 2.32 % +/- 0.9, Right MCA = 2.52 % +/- 1.2)] The negative emotional task was accompanied by a significantly higher increase in the right (10.53 % +/- 3.2) than in the left middle cerebral artery (4.52 % +/- 1.51) only in the control group. The PD patients showed a bilateral and symmetrical increase of MFV (left MCA = 4.28 % +/- 2.3 and right MCA 5.77 % +/-3.8). To determine whether there was a dysfunction in cerebrovascular reactivity and a deficit in the ability to activate both hemispheres in response to non emotion-related stimuli in the PD patients, the protocol study included a cerebrovascular reactivity test to apnea, a motor task (thumb-to-finger opposition), a cognitive task (word fluency and visual discrimination of objects), performed by both patients and controls. The pattern of MFV changes during these tasks was not statistically significantly different in the two experimental groups. In order to evaluate the possible influence of drug treatment on cerebrovascular reactivity, seven patients were also evaluated during an off-phase, after a 48-hour wash-out period. Changes in MFV during every task were similar to that observed during the on-phase. These findings show the possibility of obtaining specific functional information from bilateral transcranial Doppler and suggest the selective and specific deficit of PD patients in emotional processing.

Deep brain stimulation (DBS) attentional effects parallel those of l-dopa treatment

Aim of our study was to investigate the different effects on attentional capacity of deep brain stimulation DBS (STN or GPi) and of l-dopa in PD patients. Patients were evaluated on-DBS/off-l-dopa, on-l-dopa/off-DBS, on-l-dopa/on-DBS and off-l-dopa/off-DBS. Our results indicate that DBS effects on attentional functions parallel those of l-dopa. A site independent (both STN and GPi) worsening of verbal fluency was observed, possibly connected to the stimulus effect on the cortico-subcortical-cortical loop.

Subdyskinetic apomorphine responses in globus pallidus and subthalamus of parkinsonian patients: lack of clear evidence for the 'indirect pathway'

OBJECTIVES

Previous studies suggested that the hypo-activity of the external pallidus (GPe) might drive the hyper-activity of subthalamic neurons, which underlies the cardinal symptoms of Parkinson's disease. We have challenged this view, based on the so-called 'indirect pathway', by recording apomorphine effects from both structures of parkinsonian patients, at rest and during passive movements.

METHODS

We performed single-unit recordings from external pallidus (GPe), internal pallidus (GPi) and subthalamic nucleus (STN) during the stereotactic neurosurgery aimed to implant deep brain stimulating electrodes in GPi or STN. First, we verified the firing frequency of each structure in off-state conditions. Then, therapeutic, subdyskinetic concentrations of the dopaminergic agonist apomorphine was delivered to assess each nucleus response.

RESULTS

The firing rate of STN averaged about 40 Hz; a large proportion (75%) of STN units exhibited marked responsiveness to passive movements. Apomorphine reduced the firing discharge of parkinsonian STN in all cells, although electrophysiological recovery was usually incomplete. Movement-related activity was also dramatically reduced. In contrast, apomorphine failed to modify the firing frequency of GPe, despite the amelioration of hypo-kinetic symptoms and the simultaneous inhibition of GPi firing discharge.

CONCLUSIONS

We demonstrate that part of the models on basal ganglia circuitry needs to be revised. The re-balancing of STN hyper-activity, when patients benefit from dopaminergic therapy, is not due to an increased input from GPe, but, instead, due to changes in STN intrinsic firing properties and/or modulation of glutamatergic inputs.

Deep brain stimulation of both subthalamic nucleus and internal globus pallidus restores intracortical inhibition in Parkinson's disease paralleling apomorphine effects: a paired magnetic stimulation study

OBJECTIVE

We investigated the effect of bilateral subthalamic nucleus (STN) and internal globus pallidus (GPi) deep brain stimulation (DBS) on intracortical inhibition (ICI) in patients with advanced Parkinson's disease (PD).

METHODS

The activity of intracortical inhibitory circuits was studied in 4 PD patients implanted with stimulating electrodes both in STN and GPi by means of paired-pulse transcranial magnetic stimulation, delivered in a conditioning-test design at short (1-6 ms) interstimulus intervals (ISI). The effect of apomorphine on the same PD patients was also investigated.

RESULTS

We observed that implanted PD patients showed a significant increase in ICI during either bilateral STN or GPi DBS at 3 ms ISI, and during bilateral STN DBS at 2 ms ISI in comparison to their off DBS condition. The same statistical improvement was observed during apomorphine infusion at 3 and 2 ms ISI. In each condition, the electrophysiological changes were associated with a significant clinical improvement as measured by the Unified Parkinson's Disease Rating Scale motor examination.

CONCLUSIONS

These results are consistent with the hypothesis that basal ganglia DBS can mimic the effects of pharmacological dopaminergic therapy on PD patients cortical activity. We propose that in PD patients, the basal ganglia DBS-induced improvement of ICI may be related to a recovery in modulation of thalamo-cortical motor pathway.

Bilateral GPi DBS is useful to reduce abnormal involuntary movements in advanced Parkinson's disease patients, but its action is related to modality and site of stimulation

In Parkinson's disease (PD) patients, internal globus pallidus (GPi) stimulation has been reported to produce good effects on abnormal involuntary movements (AIM); less improvement has been observed in extrapyramidal symptoms. We assessed the effect of monopolar dorsal (uppermost), ventral (lowest) and bipolar (uppermost vs. lowest) bilateral globus pallidus stimulation by quadripolar electrode on extrapyramidal symptoms and AIM induced by a dose of apomorphine. Six PD patients were studied in OFF therapy condition after surgery without stimulation (STIM OFF) and during stimulation (STIM ON) with the three different modalities. All patients were evaluated by the unified Parkinson's disease rating scale, section III (UPDRS) and by the AIM. Our results show that all three bilateral GPi stimulation modalities reduce the UPDRS score (between 49.7 and 31.5%), although the bipolar and lowest stimulation are the most effective. Similarly, bipolar and lowest stimulation were also the most effective in reducing the occurrence and intensity of the apomorphine-induced AIM. On the contrary, uppermost stimulation (UP ON) produced an AIM occurrence similar to that observed in the OFF stimulus condition. We suggest that bilateral GPi stimulation is an useful procedure to ameliorate extrapyramidal signs of advanced PD patients; however, it produces an antidyskinetic effect only if the ventral or the entire GPi is stimulated. On the contrary, the UP ON, most probably located in the external globus pallidus (GPe), does not modify the AIM occurrence.

The effect of deep brain stimulation on the frontal N30 component of somatosensory evoked potentials in advanced Parkinson's disease patients

OBJECTIVES

In the present study we investigated whether in advanced Parkinson's disease (PD) patients the frontal component of short somatosensory evoked potentials (SEPs) to median nerve stimulation may be modified by basal ganglia deep brain stimulation (DBS).

METHODS

We recorded the SEPs in 6 PD patients undergoing bilateral functional neurosurgery in the internal globus pallidus (GPi) (4 patients) and in the nucleus subthalamicus (STN) (two patients) during ineffective and effective bilateral BDS. Pre-operatively, the SEPs were also recorded in off therapy and during apomorphine infusion.

RESULTS

From the evaluation of the latency and the amplitude characteristics of the major parietal (N20 and P25) and frontal (N30) components, we observed that whereas the parietal waves did not vary in any condition, the N30 potential showed a remarkable amplitude increase during apomorphine as well as during effective bilateral GPi or STN DBS. Furthermore, after the stimulators were turned off we noticed that the N30 amplitude potential progressively faded almost in parallel with the attenuation of DBS clinical effects.

CONCLUSIONS

Our results lead to the conclusion that the bilateral DBS of both GPi and STN is really effective in producing a selective increase of frontal N30 amplitude probably improving the supplementary motor area functional activity, but these results do not clarify whether this amelioration is due to a central or a 'long loop' mechanism.

Verbal working memory deficit in Parkinson's disease subjects

The aim of the present work was to evaluate verbal working memory in patients affected by Parkinson's disease (PD). In particular, tests that explore the functionality of the Articulatory Loop and of the Central Executive during verbal tasks were given. PD patients displayed normal phonological similarity, word length and word frequency effects in a Word span task, thus demonstrating adequate retention capacity of the phonological store, normal functioning of the articulatory rehearsal mechanism and a normal contribution of lexical-semantic knowledge to verbal immediate recall. In the Brown-Peterson task, PD patients showed abnormal performance decay on the letter recall task when articulatory rehearsal was inhibited by a serial subtraction concurrent task. These data provide evidence for normal functioning of the Articulatory Loop in PD patients. However, when the verbal recall task is more attention demanding, PD patients show deficient performance levels, presumably due to depleted processing resources by the Central Executive.

Basal ganglia and gait control: apomorphine administration and internal pallidum stimulation in Parkinson's disease

Gait coordination was analyzed (four-camera 100 Hz ELITE system) in two groups of idiopathic Parkinson disease (PD) patients. Five patients underwent continuous infusion of apomorphine and were recorded in two different sessions (APO OFF and APO ON) in the same day. Three patients with a previous chronic electrode implantation in both internal globi pallidi (GPi) were recorded in the same experimental session with the electrodes on and off (STIM ON and STIM OFF). The orientation of both the trunk and the lower-limb segments was described with respect to the vertical in the sagittal plane. Lower-limb inter-segmental coordination was evaluated by analyzing the co-variation between thigh, shank, and foot elevation angles by means of orthogonal planar regression. At least 30 gait cycles per experimental condition were processed. We found that the trunk was bent forward in STIM OFF, whereas it was better aligned with the vertical in STIM ON in both PD groups. The legs never fully extended during the gait cycle in STIM OFF, whereas they extended before heel strike in STIM ON. The multisegmental coordination of the lower limb changed almost in parallel with the changes in trunk orientation. In STIM OFF, both the shape and the spatial orientation of the planar gait loops (thigh angle vs. shank angle vs. foot angle) differed from those of physiological locomotion, whereas in STIM ON the gait loop tended to resume features closer to the control. Switching the electrodes on and off in patients with GPi electrodes resulted in quasi-parallel changes of the trunk inclination and of the planar gait loop. The bulk of the data suggest that the basal-ganglia circuitry may be relevant in locomotion by providing an appropriate spatio-temporal framework for the control of posture and movement in a gravity-based body-centered frame of reference. Pallido-thalamic and/or pallido-mesencephalic pathways may influence the timing of the inter-segmental coordination for gait.

Electrophysiological and clinical desensitization to apomorphine administration in parkinsonian patients undergoing stereotaxic neurosurgery

A decreased motor response after repeated doses of apomorphine is observed in severely affected Parkinson's disease patients. We simultaneously studied clinical symptoms and internal pallidus single unit activity in three parkinsonian patients underlying stereotaxic neurosurgery for deep brain stimulation. In each patient, two closely spaced doses of intraoperatory apomorphine were administered, while recording the same extracellular unit. The reduced clinical effect of the second administration was correlated to a lessened inhibition of the pallidal single unit recorded throughout the double administration. Our data support the proposition that fast postsynaptic desensitization to dopamine agonists may take place in the basal ganglia nuclei and play a role in the physiopathology of levodopa long-term treatment syndrome.

A mixed D1 and D2 antagonist does not replay pattern electroretinogram alterations observed with a selective D2 antagonist in normal humans: relationship with Parkinson's disease pattern electroretinogram alterations

The human retina produces a tuned response to stimuli of increasing spatial frequency reversed at a steady state. The peak amplitude response, at medium spatial frequencies, is decreased in Parkinson's disease and in normal subjects (n = 18) treated with a D2 dopaminergic antagonist (l-sulpiride). Here, we report that a mixed D1-D2 receptor antagonist (haloperidol) in normal subjects (n = 18) does not produce an amplitude decrease of medium spatial frequencies (SFs) responses but it decreases low-frequency response. It could argued that the increased dopamine release produced by the presynaptic D2 antagonistic action of haloperidol is subsequently counteracted at postsynaptic level by its D1 antagonistic effect, producing a net counterbalance at medium SFs. These data suggest that the two dopamine receptors may play different roles in the retinal function and in the origin of visual alterations in Parkinson's disease.

Does pattern electroretinogram spatial tuning alteration in Parkinson's disease depend on motor disturbances or retinal dopaminergic loss?

Systemic decrease of dopaminergic cells, such as in Parkinson's disease may produce visual alterations in humans. In order to show possible pattern electroretinogram (PERG) spatial tuning function (STF) alterations due to impaired dopaminergic transmission in humans, we studied a group of Parkinson's disease patients before and during treatment with the dopamine precursor, levodopa, and compared their performances with those of an age-matched control group. Moreover, in order to exclude the possible involvement of motor disabilities to produce PERG alterations, we also investigated PERG responses in post-traumatic parkinsonian patients who exhibited motor abnormalities as a consequence of focal lesions of basal ganglia, in the absence of systemic dopaminergic degeneration. Our results showed a clear decrease of PERG responses in Parkinson's disease patients particularly at medium spatial frequency range (2.7-4.0 cycles/degree) with a substantial preservation of responses at low frequencies. Levodopa therapy reversed these alterations in Parkinson's disease patients, resulting in the recovery of a normal tuning function shape. In contrast to Parkinson's disease, the tuning function appeared to be preserved in post-traumatic parkinsonian patients. Our results clearly establish a relationship between retinal alteration in PD patients and dopaminergic retinal function.

D1 agonist CY208-243 attenuates the pattern electroretinogram to low spatial frequency stimuli in the monkey

We investigated whether or not the D1 agonist, CY 208-243, affects the spatial tuning function of pattern electroretinogram (PERG). Two lightly anaesthetised monkeys were studied before and after CY 208-243 or placebo administration. The results show that the PERG response to 0.5 cycles/degree (c/d; coarse), but not to 2.3 c/d (medium) spatial frequency stimuli disappears following systemic administration of this drug. Since previous results show that D2 blockers attenuate the PERG only above 2.3 c/d, foremost the peak of the normal spatial frequency response function, the current results suggest that dopamine itself, via D1 receptors, may be responsible for the low spatial frequency decline of normal spatial PERG tuning function. We infer that the synergistic activation of D1 and D2 receptors is needed to shape the spatially tuned primate ERG.

Age and stage dependency of P300 latency alterations in non-demented Parkinson's disease patients without therapy

Acoustic P300 was recorded from Fz, Cz and Pz by means of an 'odd-ball' paradigm in 44 non-demented de novo Parkinson's disease patients (PD) or PD patients under treatment withdrawal, and in 31 age-matched normal subjects, to evaluate whether a P300 latency increase was present in PD patients. The influence of age and disease stage on latency was successively verified by subgrouping PD patients according to different age ('young' and 'old') and disease stage ('early' or 'advanced'). PD patient data were compared to data of normal subjects subgrouped into 'young' and 'old' or, to eliminate the age-dependent shift of latency, this latter was adjusted to 60 years in all the examined subjects. A significant increase of latency has been found in Fz and Cz in the 'old' group of PD patients (n = 23) but not in the 'young' group (n = 21) utilising both methods. Moreover, a significant latency increase was also present in Fz and Cz in the group of 'advanced' PD patients (n = 8), but not in the group of 'early' PD patients (n = 36) utilising age-adjusted measurements. When the 'early' PD patient group was divided into 'young' (n = 20) and 'old' (n = 16), the 'early old' group displayed significantly increased latencies in Fz compared with normal subjects. Abnormal P300 latencies were observed, at least in one electrode, by analysing the raw data, in 5.0% of the 'early young', 43.7% of the 'early old' and up to 62.7% of the 'advanced' patients. Fz represented the site in which abnormal P300 latencies were most often observed. Moreover, in the total group of PD patients, the P300 delay was significant only on the frontal (Fz) site when compared with normal subjects. The reported findings were interpreted as if PD produces a sort of 'accelerated effect of age' on the cognitive functions, presumably produced by a mechanism different from that producing motor impairment since no clear correlation could be detected between P300 latency and motor score. The frontal impairment of P300 is in line with previous neuropsychological findings obtained in these patients. Considering that about 30% of PD patients develop dementia during their disease progression, a border-line or abnormal P300 latency observed at disease onset may represent a predictive marker of this evolution.

Effects of kappa receptor agonists on D1 and D2 dopamine agonist and antagonist-induced behaviors

Striatal dynorphin-containing neurons receive dopaminergic inputs from the substantia nigra pars compacta and project primarily to the substantia nigra pars reticulata and entopeduncular nucleus. These neurons mainly express dopamine (DA) D1 receptors and thus dynorphin system stimulation might be expected largely to influence D1 receptor agonist or antagonist effects on motor function. It is well known the interaction existing between DA D1 and D2 drugs in the induction of behavioral effects. However, the effects of dynorphin on selective D1 and D2 DA agonist and antagonist-induced behaviors have not yet been investigated. Administration of the kappa agonists spiradoline (0.5, 1 and 5 mg/kg) or U50,488H (1, 10 and 25 mg/kg) decreased non-stereotyped grooming induced by the selective D1 agonist SKF38393. This effect was inhibited by the non-selective opioid receptor antagonist naloxone (20 mg/kg) and by the selective kappa antagonist nor-binaltorphimine (nor-BNI, 20 mg/kg). Stereotypies induced by the selective D2 agonist quinpirole were decreased by spiradoline (1 and 5 mg/kg) and by U50,488H (1, 10 and 25 mg/kg), while jerking movements of a type associated with increased D2 receptor and decreased D1 receptor stimulation emerged. Kappa agonist effects were inhibited by the prior administration of SKF38393 (10 mg/kg); these inhibitory effects were blocked by prior administration of the D1 antagonist SCH23390 (5 mg/kg). Naloxone reversed the effects of both kappa agonists on quinpirole-induced stereotypies. Kappa agonists increased D1 antagonist-induced catalepsy, but had no effect on D2 antagonist-induced catalepsy. Naloxone and nor-BNI inhibited this effect. These results suggest that the motoric effects of D1 receptor antagonists in part reflect stimulation of striatal dynorphin containing efferents.

Increasing doses of l-sulpiride reveal dose- and spatial frequency-dependent effects of D2 selective blockade in the human electroretinogram

The amplitude and phase of the second harmonic (15 Hz) of the electroretinographic responses to three different spatial frequency grating stimuli (0.25, 1 and 4 c/deg), reversed at 7.5 Hz, were studied i normal human subjects, before and 30 min after the systemic administration of three doses (0.071, 0.357 or 1.428 mg/kg) of a selective D2 blocker, l-sulpiride, to three populations of 18, 19, or 20 subjects. The effect of the drug on the pattern electroretinogram (PERG) was clearly dose-dependent, being greatest on the responses to 4 c/deg. The mean decrease in second harmonic amplitude was -13.8% after 0.071 mg/kg of l-sulpiride, -23.5% after 0.357 mg/kg and -28.5% after 1.428 mg/kg. The last two variations were significant at P < 0.01 and P < 0.01 respectively. These data suggest that a dose-dependent effect on the human retinal response to 4 c/deg stimuli exists, probably mediated by a coupling between l-sulpiride and D2 receptors. Lastly, our data suggest that D2 receptors may play an important role in the pathophysiology of visual dysfunction in Parkinson's disease, that has been described to be more significant at medium spatial frequency (2-5 c/deg).

Visual alterations in de novo Parkinson's disease: pattern electroretinogram latencies are more delayed and more reversible by levodopa than are visual evoked potentials

There are increased latencies of pattern-reversal visual evoked potentials (VEPs) and electroretinograms (PERGs) in Parkinson's disease (PD) patients who have not received therapy. This study aimed to evaluate whether these delays are present in the early stage of PD and whether they are dopamine-sensitive. The results show that both PERG P50 and VEP P100 latencies are increased (p < 0.0001) in a group of patients with de novo PD (13 subjects; 13.3 +/- 5.6 months' mean disease duration) before therapy in comparison with an age-matched control group (eight subjects). A larger latency increase (9.9% at the 47% contrast level and 7.8% at the 96% contrast level) was present in PERG recordings than in VEPs (6.2% at the 47% contrast level and 3.9% at the 96% contrast level). Levodopa therapy produced recovery of both PERG and VEP latency increases at both contrast levels, but only the PERG recovery at 47% of contrast was statistically significant. Before therapy, five eyes from PD patients showed no reproducible PERG at the 47% contrast level although the simultaneously recorded VEP was present. Both potentials were recordable in the same eyes at the 96% contrast level. During therapy, four of those five eyes showed a clear PERG even at the 47% contrast level. We conclude that, using an adequate midspatial frequency, both VEPs and PERGs are delayed even in the early stage of PD, and that PERGs are more sensitive if low contrast (47%) is used. The larger alterations, as well as the larger recovery during levodopa therapy, seem to correlate the PERG response more than the VEP response to dopaminergic transmission.

Visual and visual perceptual disorders in neurodegenerative diseases

Optic neuropathy is reported to occur in 10-30% of patients, while retinopathy is characteristic of type III OPCA. The use of visual and visual electrophysiological tests in early diagnosis and classification is promising. The relationship between visual impairment and other manifestations of these diseases has not been explored.

D1 and D2 dopamine receptor-mediated mechanisms and behavioral supersensitivity

The contribution of D1 and D2 dopamine (DA) receptor mechanisms to the behavioral supersensitivity and receptor upregulation induced by chronic DA antagonist administration were compared. Rats received either the selective D1 DA receptor antagonist SCH23390, the selective D2 DA receptor antagonist raclopride, their combination, or haloperidol, a predominantly D2 antagonist, for 21 days. Equivalent cataleptogenic doses of all drugs and drug combinations were employed. Tolerance to the cataleptic response was observed only in the haloperidol-treated group. Apomorphine-induced stereotypies were significantly enhanced in SCH23390-, raclopride-, and haloperidol-treated rats. In contrast, coadministration of both SCH23390 and raclopride had no effect on apomorphine-induced stereotypy. These findings suggest that neuroleptics blocking in equal proportion D1 and D2 receptor sites might be less likely to induce tardive dyskinesia and drug tolerance than those acting selectively on one or the other of these receptor subtypes.

Low contrast stimuli enhance PERG sensitivity to the visual dysfunction in Parkinson's disease

The pattern electroretinogram (PERG) was recorded at different contrast levels (96%, 71%, 47%) in 10 Parkinson's disease patients before and during dopaminergic monotherapy. The data were compared to a control group of 8 normal subjects recorded with the same procedure. PERG P50 latency progressively increased as contrast was decreased both in normal subjects and patients; however, this trend was much more pronounced in PD patients without therapy; consequently in this group the difference between P50 latency obtained with 96% and 47% contrast was statistically significant (P = 0.01, analysis of variance corrected by post-hoc Tukey test). By contrast this was not seen in the control group. Statistical analysis (Bonferroni's t test) showed at the 47% contrast level a significant P50 latency increase (P less than 0.01) in PD patients without therapy if compared with the control group. Dopaminergic monotherapy induced a P50 latency recovery in PD patients. We conclude that low contrast stimuli enhance PERG sensitivity to the visual dysfunction of PD patients. Moreover, the effects observed after therapy confirm that abnormal contrast response functions in PD patients are linked to dopaminergic deficiency.

[Intravenous infusion of L-dopa: current prospective therapies]

Most of Parkinson's disease patients treated with Levodopa develop the Long Treatment Levodopa Syndrome. Many authors showed a correlation between clinical features and plasma level of Levodopa. In our study, five parkinsonian patients with severe clinical response fluctuations, oral levodopa treatment was replaced by repeated continuous infusions of Levodopa (with oral carbidopa). Our results confirm that repeated intravenous infusion are very effective in PD patients with LTS.

[Miller Fisher syndrome: review of the literature and presentation of 2 cases]

Miller Fisher Syndrome (MFS), which is characterized by ophthalmoplegia, ataxia and tendon areflexia, is generally considered as a clinical variant of Guillain-Barré Syndrome. However some features of the disease are still debated, particularly regarding possible central nervous system involvement. After presenting two new cases of MFS, the authors provide a critical review of the literature and discuss the nosographical position of the disease. The main conclusions can be summarized as follows: MFS is a predominantly axonal inflammatory neuropathy with prevailing involvement of oculomotor nerves. It is associated to spinal multi or polyneuropathy, which in mildly affected cases is manifested by areflexia, while in severe ones it can be responsible of sense and/or motor impairment. In addition to peripheral neuropathy CNS involvement, exclusive or more marked in posterior fossa, occurs not infrequently. The prognosis of the disease is often benign, but disabling or even fatal outcome is possible. Corticosteroid treatment, possibly because of antiinflammatory and/or immunosuppressive action, could be effective in some patients. Finally, in spite of some similarities with GBS, MFS should be considered as a separate entity with its own nosographical position.

Antiepileptic effects of a calcium antagonist (nimodipine) on cefazolin-induced epileptogenic foci in rabbits

The epileptogenic properties of cefazolin (CFZ) were utilized to induce an electrophysiological pattern of epilepsy in the rabbit. CFZ, cortically applied in different concentrations (2 or 4%), produced epileptic activity in a degree proportional to the concentration of the substance. In this experimental epilepsy model, we evaluated the effects of increasing doses (0.025, 0.05, and 0.1 mg/kg i.v.) of the calcium antagonist nimodipine (Bay e 9736). In the evaluation of nimodipine effects, the spike-and-wave burst frequency per minute was taken into account. These data were compared with those of placebo-treated (Bay e 9736 control test) control groups and statistically evaluated by two-tailed t test. In 2% CFZ-induced epilepsy, nimodipine at the 0.025- and 0.05-mg/kg doses did not produce significant changes in the EEG pattern. A statistically significant reduction (p less than 0.001) in epileptic activity was observed at the 0.1-mg/kg nimodipine dose. This reduction was seen first in the contralateral focus leads and persisted for the entire time of observation. In the more intense epileptic form (4% CFZ), nimodipine at the doses employed did not induce noteworthy EEG modifications. These data indicate that nimodipine exerts an antiepileptic effect. The possible mechanisms involved in this activity of a calcium antagonist are discussed.