Motor features and response to oral levodopa in patients with Parkinson’s disease under continuous dopaminergic infusion or deep brain stimulation

Background: Subthalamic nucleus deep brain stimulation (STN DBS) and continuous dopaminergic infusions (jejunal levodopa or subcutaneous apomorphine) are indicated in complicated Parkinson’s disease (PD), although it remains unsettled how they compare to each other. Methods: We investigated the daytime motor condition in patients with advanced PD under monotherapy with jejunal levodopa, subcutaneous apomorphine, or STN DBS and also measured the motor changes produced by an additional standard morning dose of levodopa. Motor performance was assessed with the UPDRS‐III, hand taps, the AIMS dyskinesia score and patients’ diaries. Outcome measures were time to best motor ‘on’ after start of morning treatment, daytime variability of motor condition, motor scores. Results: The time to ‘on’ was longest in the jejunal levodopa group. DBS and jejunal levodopa treatments produced stable motor conditions without appreciable ‘off’ episodes. Continuous apomorphine infusion was associated with the worst motor scores (UPDRS‐III and taps) and the most frequent off‐states. Jejunal levodopa infusion was associated with the highest AIMS scores. Addition of a levodopa dose produced shortening of time to ‘on’ and a transient motor improvement in the jejunal levodopa group without increase in dyskinesias; in the DBS and apomorphine groups, there was an increase in dyskinesias without changes in UPDRS‐III or taps. Conclusions: STN DBS provided adequate trade‐off between motor improvement and dyskinesia control, although dyskinesias could be elicited by adding oral levodopa. Jejunal levodopa infusion produced adequate motor improvement with slow time to ‘on’ and moderate dyskinesias. Apomorphine infusion produced insufficient motor control and negligible dyskinesias.     

Apomorphine monotherapy in the treatment of refractory motor complications of Parkinson's disease: long-term follow-up study of 64 patients.

Continuous subcutaneous infusion of apomorphine is now increasingly recognized as an effective treatment for refractory off periods and peak-dose dyskinesias in Parkinson's disease. We have reviewed our experience with apomorphine infusions, after a strategy decision in 1995 based on emerging preclinical data, to treat all patients with steady-state plasma levels of apomorphine throughout the waking day, minimizing additional pulsatile stimulation either by oral dopaminergic medication or bolus parenteral injections of apomorphine. Sixty-four patients have been treated with apomorphine pumps and 45 of these successfully converted to monotherapy, managing to discontinue all other forms of dopaminergic stimulation during the daytime treatment period with apomorphine. Patients were followed up for a mean of 33.8 months (range, 4-108 months) and clinical data analyzed retrospectively. The mean maintenance dose of apomorphine was 98 mg per 24 hours (monotherapy group: 103 mg/24 hours; polytherapy group: 93 mg/24 hours), which did not significantly increase at final follow-up. There was a mean maximum dyskinesia reduction of 64% (S.D. = 20) in the monotherapy group, compared to 30% (S.D. = 33) in those continuing on polytherapy (P < 0.001), despite a maintained increase in on time (monotherapy group: 55%, P < 0.005; polytherapy group: 50%, P = 0.05). Fifteen patients failed to successfully convert to monotherapy but benefited nonetheless, and only 3 failed apomorphine infusional therapy altogether. Reasons for failure were mixed, including difficulty with compliance and adverse effects such as daytime somnolence, skin complications, and painful dystonias. There was a significantly higher success rate in patients able to manage the treatment either independently or with the help of their caregiver. These results confirm that subcutaneous apomorphine monotherapy can reset peak-dose dyskinesia threshold in levodopa-treated patients and further reduce off-period disability after all available forms of oral medication, including long-acting dopamine agonists, have been tried.     

Treatment of Parkinson's disease: levodopa as the first choice

The introduction of levodopa in the 1960s revolutionised the treatment of Parkinson's disease (PD), and it continues to be the most effective symptomatic therapy. The vast majority of PD patients who start treatment with L-dopa experience good to excellent functional benefit. In vitro studies with high doses of L-dopa and absent glia had shown that it may be neurotoxic, but other tissue culture studies show L-dopa to be neuroprotective. Most studies in animal models and clinico-pathological and mortality studies in humans failed to show evidence in favour of accelerated dopaminergic neuronal loss with long-term L-dopa therapy.L-dopa continues to be beneficial throughout the course of PD, although as the disease progresses, escape of some symptoms from adequate control may occur and refractory disabilities such as impaired balance, dysarthria, cognitive decline and hallucinations may emerge. Treatment of advanced PD may also be complicated by the emergence of motor fluctuations and dyskinesias. Studies in animal models and in humans show that these motor complications are not specific to a particular dopaminergic agent, but that they are related both to the extent of the striatal lesion and to the mode of application of dopaminergic agents: Pulsatile administration of L-dopa and of the dopamine agonist apomorphine causes more motor complications than continuous striatal dopaminergic receptor stimulation, and continuous administration can alleviate existing dyskinesias and fluctuations. Several controlled studies comparing levodopa and dopamine agonists as initial treatment have attempted to answer the question whether delaying L-dopa therapy can reduce the occurrence of motor complications. Three medium-term (3-5 years) and one 10-year study showed less dyskinesia in the first five years of treatment in patients who had started therapy with a dopamine agonist. However, these studies also consistently showed that levodopa provided better functional improvement in the first years of treatment. Ten-year follow-up data in patients randomised to L-dopa or bromocriptine also showed a slightly lower incidence of motor complications in the bromocriptine arm. However, this difference was not significant for the clinically relevant moderate and severe forms of dyskinesias and fluctuations, and was achieved at the expense of significantly worse disability scores during the first years of therapy. Furthermore, the relative impact of motor disability and dyskinesias on patients' quality of life remains to be established. Concordance is essential in the optimum treatment of PD and patients should be informed of the various therapeutic options available. Treatment should respect individual patients' needs and take into account their particular functional disabilities and specific handicaps. Low-dose L-dopa therapy (up to 400 mg/day), however, remains the most effective initial treatment of choice for the majority of patients.     

Decreased expression of l-dopa-induced dyskinesia by switching to ropinirole in MPTP-treated common marmosets

Current concepts suggest that pulsatile stimulation of dopamine receptors following L-dopa administration leads to priming for dyskinesia in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-treated primates, while continuous dopaminergic stimulation with long-acting dopamine agonists does not. We investigated whether L-dopa-induced dyskinesia is reduced by switching to a dopamine agonist. MPTP-treated marmosets received chronic treatment with L-dopa or ropinirole in doses producing equivalent motor activity and reversal of motor deficits. Administration of L-dopa led to the rapid onset of moderate to severe dyskinesia, whereas ropinirole produced only mild dyskinesia. Animals initially treated with L-dopa were switched to an equivalent dose of ropinirole and those treated with ropinirole were switched to an equivalent dose of L-dopa for 56 days. L-dopa-primed animals that were switched to ropinirole showed a trend towards a reduction of dyskinesia intensity, whereas animals initially treated with ropinirole and switched to L-dopa showed a trend toward increased dyskinesia intensity. A subsequent, acute L-dopa challenge reversed motor deficits and induced intense dyskinesia in both groups. This suggests that L-dopa leads to the priming and expression of dyskinesia, but that expression is not maintained when switching to a long-acting dopamine agonist. In contrast, dopamine agonists may prime for dyskinesia, but do not lead to its full expression.     

Subcutaneous continuous apomorphine infusion in fluctuating patients with Parkinson's disease: long-term results

Fluctuations in motor disability and dyskinesias are the major problem in the long-term treatment of Parkinson's disease (PD). Many authors and ourselves have shown that by giving patients a continuous infusion of levodopa it is possible to control motor fluctuations. Levodopa can be administered continuously only be intravenous, intragastric or intrajejunal delivery. Continuous dopaminergic stimulation an be achieved more easily by infusing dopamine agonists subcutaneously. Apomorphine is a potent water-soluble dopamine receptor agonist that has been shown to successfully control motor fluctuation when subcutaneously infused in complicated parkinsonian patients. We report the clinical data of 30 PD patients having at least five years of treatment with subcutaneous continuous apomorphine infusion.     

Apomorphintherapie versus tiefe Hirnstimulation Klinische und ökonomische Aspekte bei Patienten mit fortgeschrittenem Morbus Parkinson

Long-term dopaminergic treatment of Parkinson's disease is complicated by the occurrence of dyskinesia and motor fluctuations and is responsible for increasing the costs of treatment. In these patients, continuous subcutaneous therapy with the dopamine agonist apomorphine or deep-brain stimulation represents a promising strategy. While the costs for the treatment with apomorphine are covered by health insurance, separate reimbursement for deep-brain stimulation does not exist in Germany. The case reports (n = 3) presented here emphasize that deep-brain stimulation is less cost-intensive than subcutaneous treatment with apomorphine in selected patients. Even in the first postoperative year costs for medication and hospital stays were reduced by approximately 60%. Moreover, in all three patients, motor complications improved after deep-brain stimulation in comparison to previous subcutaneous application of apomorphine. Thus, to further ensure deep-brain stimulation in parkinsonian patients it is mandatory to find a mode of reimbursement for the institutions concerned.     

Continuous dopaminergic delivery in Parkinson’s disease

Motor fluctuations and dyskinesias occur in the majority of patients with Parkinson’s disease (PD) and are likely to result from changes in dopamine production, storage and release, occurring as consequences of the nigrostriatal degenerative process. All studies comparing levodopa versus dopamine agonist early therapy indicate that initiation with agonists is associated with a reduced risk of motor complications —in particular, dyskinesias— possibly because agonists’ longer half-lives provide continuous dopaminergic delivery. In advanced PD patients, switching from a pulsatile to continuous dopaminergic delivery may widen patients’ therapeutic window. Currently, this can be accomplished only with subcutaneous apomorphine or duodenal levodopa infusions. Apomorphine is a highly soluble agonist whose effect is similar to dopamine. Conversely, replacing whole oral therapy with levodopa infusion bypasses gastric emptying and avoids peaks and troughs in plasma by releasing levodopa in the duodenum/jejunum.

     

Pulsatile or continuous dopaminomimetic strategies in Parkinson's disease

Levodopa is the most effective treatment for Parkinson's disease (PD) for both motor and non-motor control. Pulsatile levodopa administration likely contributes to the development of motor fluctuations and dyskinesia after a few years. All studies comparing levodopa versus dopamine agonist early therapy indicate that initiation with agonists is associated with a reduced risk of motor complications - in particular, dyskinesias - possibly because agonists' longer half-lives provide continuous dopaminergic delivery. Indeed, this therapeutic strategy may delay the emergence of motor fluctuations and dyskinesia which is essential to maintaining satisfactory quality of life. In advanced disease various levodopa-based strategies may be tried to control motor complications, such as dose fragmentation (smaller, more frequent dosing) or the use of orally administered, liquid levodopa formulations that may reduce off-time intervals or facilitate absorption. More recently introduced, continuous levodopa delivery by duodenal infusion (but also apomorphine infusion) may represent a more effective approach to treat motor complications in advanced PD, and its effect can be perceived by improvement both in clinical scales as well as in health-related items. Infusion therapies may reverse motor complications in complicated patients with significant benefit on quality of life.     

Role of dopamine agonists in Parkinson's disease: an update

At present, dopamine agonists play an important role in antiparkinsonian therapy since they were proved effective in the management of both advanced- and early-stage Parkinson's disease. In the latter, they are often regarded as first-choice medication to delay the introduction of levodopa therapy. Despite sharing the capacity to directly stimulate dopamine receptors, dopamine agonists show different pharmacological properties as they act on different subsets of dopamine receptors. This, in theory, provides the advantage of obtaining a different antiparkinsonian activity or safety profile with each agent. However, there is very little evidence that any of the marketed dopamine agonists should be consistently preferred in the management of patients with Parkinson's disease. Pergolide and cabergoline are now considered a second-line choice after the proven association with valvular fibrosis. Transdermal administration (rotigotine) and subcutaneous infusion (apomorphine) of dopamine receptor agonists are now available alternatives to oral administration and provide continuous dopaminergic stimulation. Continuous subcutaneous apomorphine infusion during waking hours leads to a large reduction in daily 'off' time, dyskinesias and levodopa daily dose. Almost all currently used dopamine agonists are able to provide neuroprotective effects towards dopaminergic neurons during in vitro and in vivo experiments. This neuroprotection may be the result of different mechanisms including antioxidation, scavenging of free radicals, suppression of lipid peroxidation and inhibition of apoptosis. However, the disease-modifying effect of these agents in Parkinson's disease remains to be ascertained.     

Apomorfina w zaawansowanej chorobie Parkinsona

Apomorphine is the most potent dopamine receptor agonist and its symptomatic effectiveness is comparable to levodopa. Subcutaneous apomorphine is rapidly and completely absorbed. Plasma peak concentrations are achieved after 5–15 minutes and onset of clinical effect is within 20 minutes. Apomorphine intermittent subcutaneous injections are effective as rescue therapy for unpredictable off periods in advanced Parkinson disease (PD). More often apomorphine is administered as a subcutaneous infusion which secures the continuous dopaminergic stimulation. The benefit on ‘off’ periods is consistent across all studies, but dyskinesia improvement is not so obvious. Two infusion therapies (apomorphine and intraduodenal levodopa) and deep brain stimulation (DBS) are effective in advanced PD patients with untreatable motor complications. Apomorphine infusions should be considered in patients unable to undergo DBS because of cognitive impairment and neurosurgical contraindications.     

Unawareness of dyskinesias in Parkinson's and Huntington's diseases

We performed a clinical study to evaluate the unawareness of dyskinesias in patients affected by Parkinson's disease (PD) and Huntington's disease (HD). Thirteen PD patients with levodopa-induced dyskinesias and 9 HD patients were enrolled. Patients were asked to evaluate the presence of dyskinesias while performing specific motor tasks. The Abnormal Involuntary Movement Scale (AIMS) and Goetz dyskinesia rating scale were administered to determine the severity of dyskinesias. The Unified Parkinson's disease rating scale (UPDRS) and Unified Huntington's Disease Rating Scale (UHDRS) were used in PD and HD patients, respectively. In PD we found a significant negative relationship between unawareness score at hand pronation-supination and AIMS score for upper limbs. In HD we found a significant positive relationship between total unawareness score and disease duration. In PD the unawareness seems to be inversely related with severity of dyskinesias, while in HD it is directly related to disease duration and severity.     

Dopaminergic modulation of visual-spatial working memory in Parkinson's disease

Visual-spatial working memory (WM) impairment is frequently associated with the early stage of Parkinson's disease (PD). The aim of this study was to evaluate the performance of a group of PD patients in visual-spatial and visual-object WM tasks and to investigate the effect of administering the dopaminergic agonist apomorphine (experiment 1) or the dopamine precursor L-dopa (experiment 2) on the performance of tests assessing these functions. To study WM processes, the PD patients and age-matched normal controls were given an n-back task paradigm. In both experiments, the PD patients were submitted to two evaluations: one after a 12-hour therapy washout and the other 15 min after a subcutaneous infusion of apomorphine (average 0.04 mg/kg) or 20/30 min after L-dopa intake (200 mg p.o.). The apomorphine infusion had a worsening effect on reaction times in both visual-spatial and visual-object WM tasks, but it did not influence performance accuracy. Instead, L-dopa administration had a ameliorative effect on accuracy and reaction times in both visual-spatial and visual-object tasks. These results highlight the role of dopamine in the modulation of the WM function in PD patients.     

Dyskinesia: L-dopa-induced and tardive dyskinesia.

Neuroleptic induced tardive dyskinesia and L-dopa-induced dyskinesia are the two most common types of drug-induced abnormal involuntary movements. These two drug-induced dyskinesias are clearly different with respect to the offending drugs and the underlying disease, but they both share a number of intriguing similarities in terms of clinical phenomenology, epidemiology, risk factors, pathophysiological mechanisms and therapeutic responses. In both instances, it is believed that some dysregulation occurring at the level of the striatal dopaminergic receptors, and related non-dopaminergic neurotransmitters systems are playing a crucial role in the development and persistence of the mechanisms causing dyskinesia. These long-lasting functional changes, known as the "priming" phenomenon, are responsible for an impaired balance within the relays of the cortico-subcortical motor loops that release an inadequate output from the basal ganglia leading to an abnormal motor behavior. From a therapeutic perspective, there are also many similarities in the strategies proposed to manage these two dyskinesias. In both cases, unprimed patients not previously exposed to the offending drugs, are offered alternative medications to reduce, at least partly, the risk of occurrence of future dyskinesia: "atypical" neuroleptics in the place of "typical" neuroleptics, and dopamine agonists in the place of L-dopa. In both cases, once dyskinesias are present, in already "primed" patients, both types of dyskinesia appear to be poorly and only partly reversible. Based on limited clinical evidence, it is a common proposal to switch the dyskinetic subject from "typical" to "atypical" neuroleptics for tardive dyskinesia, or to switch from (or more pragmatically to substitute as much as possible) L-dopa to a dopamine agonist for L-dopa-induced dyskinesia. In both cases, efficacious symptomatic antidyskinetic interventions, to reduce the severity of a ready present dyskinesia, are rare. There are some uncontrolled data suggesting that dopamine depleting agents, like tetrabenazine, are possibly useful for tardive dyskinesia; however, there is more clinical evidence to support the efficacy of amantadine and functional surgery in parkinsonian patients with L-dopa-induced dyskinesia.     

Extradural motor cortex stimulation in Parkinson's disease.

Extradural motor cortex stimulation (EMCS) is a surgical procedure proposed for patients with advanced Parkinson's disease (PD) who cannot undergo deep brain stimulation (DBS). Five PD patients with motor fluctuations and dyskinesia underwent EMCS of the left hemisphere. All fulfilled CAPSIT criteria for DBS, with the exception of age > 70 years. Patients were assessed preoperatively and 6 months after surgery on and off medications, with stimulator on, and 2 weeks later with stimulator off. Outcome measures included changes in mean medication dosage (levodopa and dopamine agonists), Unified Parkinson's Disease Rating Scale (UPDRS Parts II-III and Item 39), and dyskinesias (Abnormal Involuntary Movements Scale [AIMS]). We found no significant mean changes following EMCS. However, there was a trend for a reduction of mean daily medication intake (-30%) and AIMS (-19%). There were 3 patients who reported reduced OFF time (UPDRS Item 39) and 4 of 5 who felt a subjective benefit in stability and gait. In our PD cohort, EMCS induced no objective benefit, although some subjective improvement was reported mostly on axial symptoms.     

Continuous subcutaneous waking day apomorphine in the long term treatment of levodopa induced interdose dyskinesias in Parkinson's disease

OBJECTIVES—To determine whether continous wakingday dopaminergic stimulation with the dopamine agonist apomorphine canreduce levodopa induced dyskinesias in Parkinson's disease
METHODS—19 patients with severe unpredictablerefractory motor fluctuations and functionally disabling levodopainduced dyskinesias were treated with continuous subcutaneoiusapomorphine monotherapy for a minimum duration of 2.7 years
RESULTS—A mean 65% reduction in dyskineticseverity and a mean 85% reduction in frequency and duration occurred.On discontinuing levodopa a concomitant reduction in off period timewas also seen (35% of waking day "off" reduced to 10%)
CONCLUSION—Continuous waking day dopaminergicstimulation with apomorphine reset the threshold for dyskinesias andled to a pronounced reduction in their frequency.Apomorphine should be considered as a less invasive alternative topallidotomy or deep cerebral stimulation in controlling levodopainduced interdose dose dyskinesias.

     

Clinical and neuropsychological follow up at 12 months in patients with complicated Parkinson's disease treated with subcutaneous apomorphine infusion or deep brain stimulation of the subthalamic nucleus

BACKGROUND: The clinical condition of advanced Parkinson's disease (PD) patients is often complicated by motor fluctuations and dyskinesias which are difficult to control with available oral medications. OBJECTIVE: To compare clinical and neuropsychological 12 month outcome following subcutaneous apomorphine infusion (APO) and chronic deep brain stimulation of the subthalamic nucleus (STN-DBS) in advanced PD patients. METHODS: Patients with advanced PD and medically untreatable fluctuations underwent either APO (13 patients) or STN-DBS (12 patients). All patients were clinically (UPDRS-III, AIMS, 12 h on-off daily) and neuropsychologically (MMSE, Hamilton-17 depression, NPI) evaluated at baseline and at 12 months. APO was discontinued at night. RESULTS: At 12 months APO treatment (74.78+/-24.42 mg/day) resulted in significant reduction in off time (-51%) and no change in AIMS. Levodopa equivalent medication doses were reduced from 665.98+/-215 mg/day at baseline to 470+/-229 mg/day. MMSE, NPI, and Hamilton depression scores were unchanged. At 12 months STN-DBS resulted in significant clinical improvement in terms of reduction in daily off time (-76%) and AIMS (-81%) as well as levodopa equivalent medication doses (980+/-835 to 374+/-284 mg/day). Four out of 12 patients had stopped oral medications. MMSE was unchanged (from 28.6+/-0.3 to 28.4+/-0.6). Hamilton depression was also unchanged, but NPI showed significant worsening (from 6.58+/-9.8 to 18.16+/-10.2; p<0.02). Category fluency also declined. CONCLUSIONS: Both APO and STN-DBS resulted in significant clinical improvement in complicated PD. STN-DBS resulted in greater reduction in dopaminergic medications and provided 24 h motor benefit. However, STN-DBS, unlike APO, appears to be associated with significant worsening on NPI resulting from long term behavioral problems in some patients.     

Low dosage clozapine effects on L-dopa induced dyskinesias in parkinsonian patients

Objectives – The aim of this study was to investigate the clinical efficacy of clozapine, an atypical neuroleptic, on L-dopa induced dyskinesias of Parkinson's disease. Material and methods – In an open study, a group of 10 PD patients was treated with low dosage clozapine (mean 30 mg/day) for a 4-month period and L-dopa dyskinesias were evaluated in basal conditions and during clozapine treatment after the usual morning dose of clozapine. We utilized the AIMS for evaluation of dyskinesias and UPDRS for the assessment of motor performances. Results – Clozapine produced a significant ( P < 0.05) reduction of dyskinesias 1 week after the therapy onset. This effect was more pronunced at the end of the 2nd week and remained stable through the following months. We did not observe significant variations of motor performances. Conclusion – A low dose of clozapine appears to be beneficial for patients with L-dopa induced dyskinesias that do not respond to other drugs and therapeutic measures.     

Motor response following repeated apomorphine administration is reduced in Parkinson's disease

Ten patients with Parkinson's disease (PD) with motor fluctuations under levodopa treatment were given repeated equal subcutaneous injections of apomorphine [minimal effective dose (MED)] in 1 day. The MED was defined as the dose of apomorphine necessary to induce at least 60% reduction of motor disability for a minimum period of 10 min. MED was found for each patient in previous study days. In eight a subcutaneous infusion of apomorphine was performed on a different day. Four patients with simple fluctuations ("wearing off") showed a progressive reduction of the motor response to apomorphine injections, but three of the four had a stable response (continuous "on") to apomorphine infusion. Six patients with complicated fluctuations also exhibited a decreasing response to successive apomorphine injections and often completely failed to respond to some of the boluses. The response to a subcutaneous infusion of apomorphine was unstable in three of four cases. These findings indicate that a reduction of striatal dopaminergic receptor sensitivity is associated with repeated "pulsatile" apomorphine administration in parkinsonian patients with oscillations of motor performance. It is suggested that altered regulation of dopaminergic receptor sensitivity following pulsatile stimulation with levodopa may be a relevant phenomenon in the pathogenesis of motor fluctuations in PD.     

Focal striatal dopamine may potentiate dyskinesias in parkinsonian monkeys

Striatal neurons convert L-dopa to dopamine (DA) following gene transfer of aromatic L-amino acid decarboxylase (AADC) via adeno-associated virus (AAV) in parkinsonian monkeys. We investigated whether AAV-AADC could reduce or eliminate L-dopa-induced dyskinesias (LIDs) and side effects in MPTP-treated monkeys. Five monkeys were made parkinsonian by bilateral MPTP lesions. The optimal therapeutic dose of L-dopa was determined using an acute dose response regimen. After 3 weeks of chronic L-dopa treatment, AAV-AADC or control vector was bilaterally injected into the striatum. Animals were assessed for 6 months with the same L-dopa dosing as presurgery as well as chronic oral L-dopa treatment. Presurgery LID was observed at doses greater than 5 mg/kg. The AAV-AADC-treated animals displayed an average 7.3-fold decrease in the therapeutic dose of L-dopa throughout the 6-month follow-up period. Only AAV-AADC-treated monkeys were susceptible to dyskinesias even at sub-clinical doses. Immunohistochemical analysis revealed well-delineated foci of AADC within the striatum. These results suggest that high levels of focal DA were generated in response to L-dopa administration and may be responsible for the exacerbation of dyskinesias. This may be similar to focal dopaminergic activity in PD patients that developed off-drug or "runaway" dyskinesias following fetal mesencephalic grafts.     

The pharmacological therapeutic management of levodopa-induced dyskinesias in patients with Parkinson’s disease

The clinical management of levodopa-induced dyskinesia is difficult. Once present, dyskinesias are only partially improved by lowering the daily dose of levodopa and co-administering a D2 dopamine agonist. Therefore it appears to be necessary to use an NMDA-antagonist, such as amantadine, as an antidyskinetic agent. Clozapine may also improve dyskinesia without worsening akinesia, but it requires strict haematological monitoring. A long-term continuous subcutaneous infusion of apomorphine significantly reduces the dose of levodopa required, thereby markedly reducing dyskinesia, but this is difficult from a practical point of view. If none of these pharmacological strategies is successful, surgery should then be considered. Since the management of established levodopa-induced dyskinesia is difficult and often disappointing, efforts should be encouraged to try to prevent the occurrence of dyskinesia, before levodopa priming. This seems to be best achieved by the use of D2 dopamine agonists in the early stages of the disease, before, or in combination with, levodopa.