[Functional anatomy of the basal ganglia]

INTRODUCTION

The cerebral cortex of mammals is massively interconnected with the basal ganglia. The manner in which the basal ganglia process information has been accepted since it was described in the 1980s. It is not a definitive model and many aspects of it still need clarification.

DEVELOPMENT

The corpus striatum (ST) forms the entrance to the basal ganglia circuit (BG) and receives numerous afferent fibres from the cerebral cortex. Similarly, the internal segment of the globus pallidus (GPi) and the substantia nigra pars reticulata (SNpr) form the main nuclei for exit from the circuit and have an inhibitory effect on the pre-motor neurones of the ventral lamina of the thalamus. Between the entrance nucleus and the exit structures are two parallel systems of projection known as the direct and indirect pathways. The direct pathway projects monosynaptically only on the Gpi/SNpr complex. The indirect pathway projects polysynaptically on to the GR/SNpr complex after passing through the external segment of the globus pallidus (Gpe) and subthalamic nucleus. Imbalance in the activity of these two circuits will lead to alterations in discharge from the Gpi/SNpr complex which will cause bradykinesia or hyperkinesia. The bradykinesia or akinesia would be caused by increased gabaergic inhibition of the thalamic premotor neurones as a result of excessive discharge of the Gpi/SNpr complex.

CONCLUSION

Current exploration of the electrophysiology of the basal ganglia and careful analysis of the clinical findings in lesions circumscribed to certain parts of the thalamus, subthalamus and internal globus pallidus in patients with Parkinson's disease, have led to the appearance of paradoxical effects, according to the current basal ganglia model.

Explicit and implicit learning in patients with Alzheimer disease and Parkinson disease with dementia

OBJECTIVE

To examine the differential impairment of implicit and explicit memory systems in cortical and subcortical dementias.

BACKGROUND

Whereas verbal priming was reported to be impaired in patients with Alzheimer Disease (AD), patients with Parkinson Disease (PD) may be relatively more impaired on tasks of motor skill learning.

METHODS

We examined 15 patients with Alzheimer disease, 10 patients with Parkinson disease and dementia (PD-D), 15 patients with PD but no dementia, and 24 age-comparable normal control subjects with a neuropsychologic battery that included tests of explicit memory (Buschke Selective Reminding Test, Benton Visual Retention Test, Digits Span), and tests of implicit memory (Word-Stem Completion task and the Maze Test).

RESULTS

AD and PD-D groups showed similar deficits on all measures of explicit memory, and performed significantly worse than PD patients without dementia and normal control subjects. On the other hand, there were no significant between-group differences in any of the measures of implicit memory.

CONCLUSIONS

Our study demonstrated preserved implicit learning in the context of severe explicit learning deficits in patients with dementia, but could not demonstrate a different profile of memory deficits between so-called cortical and subcortical dementias.

Effect of memantine (NMDA antagonist) on Parkinson's disease: a double-blind crossover randomized study

Our aim was to evaluate the effect of Memantine (1-amino 3,5-dimethyl-adamantane hydrochloride) on cardinal symptoms of Parkinson's disease and on the latency, duration, and magnitude of the response to a single dose of L-Dopa and on drug-induced dyskinesias. Twelve Hoehn-Yahr III-IV patients with idiopathic Parkinson's disease with motor fluctuations and drug-induced dyskinesias were randomized to the NMDA antagonist memantine or placebo in a cross-over design. A single-dose L-Dopa challenge was performed after each medication arm. A significant drug effect on the Unified Parkinson's Disease Rating Scale motor score was observed in "off" and "on" states (F(1,11) = 13.5; p < 0.003). No significant effect on drug-induced dyskinesias was seen. The results suggest that memantine may improve parkinsonian symptoms independently of dopaminergic drugs and, in contrast to recent findings with amantadine, it has no effect on drug-induced dyskinesias.

GPi firing rate modification during beginning-of-dose motor deterioration following acute administration of apomorphine

We present a patient with clinically evident beginning-of-dose motor deterioration who had undergone posteroventral pallidotomy. This patient underwent an intrasurgical apomorphine test followed by single cell recording of the internal globus pallidus (GPi) to determine changes in GPi firing rate during the occurrence of such phenomenon. A significant increase in GPi firing rate coincident with worsening of patient disabilities prior to improvement was found. This finding suggests that beginning-of-dose motor deterioration may be mediated by enhanced thalamic inhibition.

Comparison of 1-year follow-up evaluations of patients with indication for pallidotomy who did not undergo surgery versus patients with Parkinson's disease who did undergo pallidotomy: a case control study

Many reports published during the past 5 years have shown evidence of the beneficial effect of posteroventral pallidotomy (PVP) in large groups of patients for up to 3 years, but none of them have compared patients who underwent surgery with a control group.

OBJECTIVE

To compare the evolution of Parkinson's disease symptoms at 1-year follow-up between patients who underwent surgery and those who did not.

MATERIAL AND METHODS

Ten patients with idiopathic Parkinson's disease refractory to treatment who were included in the Core Assessment for Intracerebral Transplantation program for PVP did not undergo surgery because financial support was lacking. These patients were followed up for 1 year as if they had been operated on and were finally compared with 10 patients having similar characteristics in whom PVP had been performed during the same period of time.

RESULTS

There were no significant differences at basal evaluation in the motor section scores of the Unified Parkinson's Disease Rating Scale between those patients who underwent surgery and those who did not, but a significant reduction in Unified Parkinson's Disease Rating Scale motor score in the group who underwent surgery at 1-year evaluation was found (P < 0.006). Dyskinesias, which was nonsignificantly different at basal evaluation, showed, at the 1-year follow-up, a significant reduction in the group who underwent surgery (P < 0.04). Scores from the subsets of the Unified Parkinson's Disease Rating Scale addressing rigidity, tremor, and bradykinesia also proved significantly different at the 1-year follow-up. The slope of the line generated by the two evaluations for each group showed a negative value in the group who underwent surgery (value of -0.21) and a positive value in the group who did not (value of 0.148).

CONCLUSION

At the 1-year follow-up, microelectrode-guided PVP produced significant changes in patient motor status and disease progression versus a comparable group of patients who did not undergo surgery during the same period of time.

Apomorphine induces changes in GPi spontaneous outflow in patients with Parkinson's disease

OBJECTIVE

To determine the effect of a single dose of apomorphine on internal globus pallidus (GPi) neuronal discharge in patients with Parkinson's disease (PD).

PATIENTS AND METHODS

Nine PD patients who underwent microelectrode-guided posteroventral pallidotomy (PVP) were studied. After identification of a single GPi unit discharge with sufficient spike S/N ratio to allow reliable thresholding, basal recording was followed by a single 3-mg subcutaneous injection. One-minute samples were recorded 10', 30', and 60' after apomorphine.

RESULTS

In four patients, recording was lost after 5-10 minutes. In two, changes were observed at peak-of-dose but recording was then lost, whereas three completed recording and returned to baseline, all five showing significant reduction in GPi firing rate (mean +/- standard deviation for basal and post-apomorphine were 143+/-55.6 and 52+/-19.2, respectively; p <0.002).

CONCLUSION

In patients with PD, apomorphine induces changes in GPi spontaneous discharge and modifies firing rates resembling recordings in normal primates. These findings show that clinical improvement as well as induction of dyskinesias following DA administration could be mediated by reduction of GPi outflow.

Unilateral radiofrequency lesion versus electrostimulation of posteroventral pallidum: a prospective randomized comparison

Microelectrode-guided posteroventral pallidotomy (PVP) has shown to be an effective method in the treatment of a group of patients with advanced Parkinson's disease. A nonlesioning approach by means of deep brain electrodes connected to a programmable neuropacemaker has also been used to inhibit the internal segment of globus pallidus (posteroventral stimulation [PVS]) reporting comparable clinical efficacy to the one obtained with the ablative method. Nevertheless, no controlled studies have been performed to compare the efficacy of both procedures. A prospective series of 13 patients with a clinical indication for globus pallidus surgery was randomized either to a pallidotomy or stimulator implantation, and comparisons on motor and neuropsychologic measurements were made on a 3-month follow-up basis. Primary measurements of efficacy showed a comparable effect on Unified Parkinson's Disease Rating Scale and activities of daily living score after both procedures. Secondary measurements of efficacy showed that although both techniques improve hand tapping score and dyskinesia score, the bilateral improvement in the former was greater after PVS whereas the latter improved more significantly after PVP. No significant changes in neuropsychologic parameters were observed after either PVP or PVS. Side effects and surgery complications occurred in six of 13 patients (three after PVP and three after PVS): they were mild, transient, and unrelated to optic tract injury. In conclusion, the short-time effect and safety of both procedures is comparable.

Confirmation of the antidyskinetic effect of posteroventral pallidotomy by means of an intraoperative apomorphine test

We present a series of six consecutive Parkinson's disease patients undergoing posteroventral pallidotomy (PVP), who received an apomorphine injection after thermolesioning the posteroventral region of the internal globus pallidus (GPi) to evaluate the effect of the lesion on drug-induced dykinesias and therefore to proceed with further lesions or to conclude the surgery. Five of six patients failed to present dykinesias or did so to a significantly lesser degree (F [2,10] 42.6; p < 0.0001) so that surgery was concluded. One patient continued having contralateral dyskinesia despite an improvement in rigidity and bradykinesia, therefore, a new track was performed followed by a new lesion. No differences were found between intrasurgical and 1-month postoperative apomorphine test values. This report indicates that the use of an apomorphine test after thermolesioning may provide a reliable tool to check lesion efficacy on dyskinesia. The development of techniques that provide additional clinical information to the electrophysiological recording could help improve the outcome of patients undergoing pallidotomy.

Changes in the motor response to acute L-dopa challenge after unilateral microelectrode-guided posteroventral pallidotomy

To determine the effect of unilateral posteroventral pallidotomy (PVP) on latency and duration of response to L-dopa ipsilateral and contralateral to the side of the lesion, six severe fluctuating Hoehn-Yahr IV patients with Parkinson's disease were evaluated 2 days before and after unilateral PVP. After an overnight drug holiday in a fasting state, patients were challenged with a single dose of 200/50 mg of L-dopa/ carbidopa. Sequential tapping tests every 5 minutes in both hands were used to measure changes in motor status. Duration of L-dopa effect was significantly longer after PVP (p < 0.03). Mean latency of the effect improved by 50% without reaching statistical significance. Despite a clear, asymmetric improvement of cardinal Parkinson's disease symptoms after unilateral PVP, changes in the dose-response L-dopa profile occurred symmetrically, suggesting that mechanisms underlying the two effects are distinct.

Depression in classic versus akinetic-rigid Parkinson's disease

We examined the prevalence of major depression and dysthymia in 78 patients with the classic variant of Parkinson's disease (PD) (that is, tremor plus rigidity and/or bradykinesia), and in 34 patients with the akinetic-rigid variant. Although the prevalence of dysthymia was similar in both groups (classic PD, 31%; and akinetic-rigid PD, 32%), patients with akinetic-rigid PD had a significantly higher prevalence of major depression (38% versus 15%, respectively; p < 0.01). A stepwise regression analysis demonstrated that bradykinesia was the extrapyramidal sign with the highest correlation with Hamilton depression scale scores. Our findings demonstrate a significant association between major depression and the akinetic-rigid type of PD.

Involuntary movements during thermolesion predict a better outcome after microelectrode guided posteroventral pallidotomy

Eight of the first 15 patients with advanced Parkinson's disease who underwent microelectrode guided posteroventral pallidotomy developed transient abnormal involuntary movements during thermolesion, four of whom also did so during high frequency macrostimulation. Abnormal involuntary movements found before thermolesion were choreic, ballistic, or choreoathetoid in nature, usually persisted less than 60 minutes, and were contralateral to the site of thermolesion in six and bilateral in two of them. The appearance of abnormal involuntary movements during macrostimulation or thermolesion of the internal globus pallidus correlated with better surgical outcome as measured by UPDRS motor items and CAPIT timed test, so that they seem to be of prognostic value.

Sleep benefit in Parkinson's disease

Sleep benefit (SB) In Parkinson's disease (PD) is not well characterized. To determine SB frequency, as well as to characterize and correlate it with other disease variables, we evaluated prospectively a consecutive series of 312 PD patients by means of a structured questionnaire: 55% reported having SB and 35% reported that awakening was their best time of the day. Because of SB, 21% of the entire population were able to skip or delay medication. The mean duration of the phenomenon was 85.4 +/- 67 min. Patients with SB were significantly older (p < 0.0002), had disease longer (p < 0.05), and were often men (chi 2 = 3.5, df 1, p = 0.05). Patients with SB took sleep medication with similar frequency as those without SB. There were no differences in hours of sleep or sleep latency. Sleep problems such as nightmares or somnambulism, but not the number of sleep awakenings, were similar in both groups. In conclusion, SB is a frequent phenomenon, especially in men, elderly patients, and patients with longer disease duration. SB enables the morning L-dopa dose to be postponed in approximately 50% of patients.

Comparison of subcutaneous apomorphine versus dispersible madopar latency and effect duration in Parkinson's disease patients: a double-blind single-dose study

Twelve parkinsonian patients with severely fluctuating symptoms were given a single dose of apomorphine or Dispersible Madopar on 2 consecutive days, to confirm the latter drug's usefulness in "off" period rescue. According to our results, apomorphine proved faster in reverting "off" periods and should still be regarded as the drug of choice for this treatment modality.

Apraxia in Parkinson's disease, progressive supranuclear palsy, multiple system atrophy and neuroleptic-induced parkinsonism

We studied 45 non-demented patients with Parkinson's disease (PD), 12 with progressive supranuclear palsy (PSP), 10 with multiple system atrophy (MSA) and 12 with neuroleptic-induced parkinsonism (NIP) for the presence of apraxia. Our aim was to determine whether a standard comprehensive assessment of different praxic functions would demonstrate specific types of errors not attributable to bradykinesia, rigidity, tremor or any other abnormal elementary motor deficit. PD patients on chronic levodopa treatment were examined in the 'on' and 'off' (treatment) states. Based on apraxia assessment scores, bilateral ideomotor apraxia for transitive movements was found in eight (75%) and 12 (27%) of PSP and PD patients, respectively. Ideomotor apraxia was mainly characterized by spatial errors (i.e., external and internal configuration, body-part-as-object and trajectory). Four PSP but no PD patients exhibited ideomotor apraxia for intransitive movements. PSP as well as PD patients with ideomotor apraxia also had difficulties in imitating hand and finger postures, but none of them failed on pantomime comprehension and pantomime recognition/discrimination. Some PSP patients exhibited, in addition, a limbkinetic type of apraxia and a minority of them displayed deficits on tasks involving multiple steps. Neither MSA nor NIP patients showed any disturbance of praxic functions. There were no differences in age, disease duration, Mini Mental State Examination (MMSE), Unified Parkinson's disease Rating Scale and Hoehn-Yahr scores between apraxic and non-apraxic PD patients, and ideomotor apraxia scores were similar in the 'on' and 'off' states. A correlation was found between ideomotor apraxia scores in PD patients and deficits in frontal lobe-related neuropsychological tasks such as the Tower of Hanoi, verbal fluency and the Trail Making Test. Furthermore, PD patients with apraxia showed higher Hamilton depression scores than non-apraxic PD patients. In PSP patients, ideomotor apraxia scores correlated significantly with cognitive deficit as measured with MMSE. The presence or absence of cortical involvement, and its severity and distribution might determine the presence and type of apraxia in PD and PSP. Apraxia in these conditions would therefore reflect combined cortico-striatal dysfunction.