Parkinson's psychosis

Psychiatric Disorders and Cognitive Fluctuations in Parkinson's Disease: Changing Approaches in the First Decades of the 21st Century

Parkinson's Disease (PD) is a multifaceted neurodegenerative disorder characterized, in addition to the well-recognized motor disturbances, by a complex interplay between cognitive and psychiatric manifestations. We dissect the complex landscape of PD-related psychiatric symptoms, taking into account the impact of functional neurological disorders, somatic delusions, impulse control disorders, and conditions within the bipolar spectrum. The newer entities of somatoform and functional neurological disorders, as well as preexisting bipolar spectrum disorders, are analyzed in detail. Moreover, we emphasize the need for a holistic understanding of PD, wherein the cognitive and psychiatric dimensions are valued alongside motor symptoms. Such an approach aims to facilitate early detection and personalized interventions, and enhance the overall quality of life for individuals suffering from this neurodegenerative disorder.

The effects of chemogenetic targeting of serotonin-projecting pathways on L-DOPA-induced dyskinesia and psychosis in a bilateral rat model of Parkinson's disease

Introduction

Parkinson's disease (PD) is commonly characterized by severe dopamine (DA) depletion within the substantia nigra (SN) leading to a myriad of motor and non-motor symptoms. One underappreciated and prevalent non-motor symptom, Parkinson's disease-associated psychosis (PDAP), significantly erodes patient and caregiver quality of life yet remains vastly understudied. While the gold standard pharmacotherapy for motor symptoms Levodopa (LD) is initially highly effective, it can lead to motor fluctuations like LD-induced dyskinesia (LID) and non-motor fluctuations such as intermittent PDAP. One source of these fluctuations could be the serotonergic raphe nuclei and their projections. Serotonin (5-HT) neurons possess the machinery necessary to convert and release DA from exogenous LD. In DA-depleted brain regions these 5-HT projections can act as surrogates to the DA system initially compensating but chronically leading to aberrant neuroplasticity which has been linked to LID and may also contribute to non-motor fluctuations. In support, recent work from our lab established a positive relationship between LID and PDAP in parkinsonian rats. Therefore, it was hypothesized that normalizing 5-HT forebrain input would reduce the co-expression of LID and PDAP.

Methods

To do so, we expressed 5-HT projection specific inhibitory designer receptor exclusively activated by designer drugs (DREADDs) using Cre-dependent AAV9-hM4di in tryptophan hydroxylase 2 (TPH2)-Cre bilaterally 6-OHDA-lesioned rats. Thereafter we used the designer drug Compound 21 to selectively inhibit 5-HT raphe projections during LD treatment to modulate the expression of PDAP, assayed by prepulse inhibition (PPI) and LID, quantified by the abnormal involuntary movements (AIMs) test.

Results

Our results suggest that chemogenetic inhibition of 5-HT raphe-projecting cells significantly reduces LID without affecting stepping ability or established sensorimotor gating deficits.

Discussion

Overall, this study provides further evidence for the complex influence of 5-HT raphe-projecting neurons on LD's neurobehavioral effects.

Neurophysiological treatment effects of mesdopetam, pimavanserin and clozapine in a rodent model of Parkinson's disease psychosis

Psychosis in Parkinson's disease is a common phenomenon associated with poor outcomes. To clarify the pathophysiology of this condition and the mechanisms of antipsychotic treatments, we have here characterized the neurophysiological brain states induced by clozapine, pimavanserin, and the novel prospective antipsychotic mesdopetam in a rodent model of Parkinson's disease psychosis, based on chronic dopaminergic denervation by 6-OHDA lesions, levodopa priming, and the acute administration of an NMDA antagonist. Parallel recordings of local field potentials from eleven cortical and sub-cortical regions revealed shared neurophysiological treatment effects for the three compounds, despite their different pharmacological profiles, involving reversal of features associated with the psychotomimetic state, such as a reduction of aberrant high-frequency oscillations in prefrontal structures together with a decrease of abnormal synchronization between different brain regions. Other drug-induced neurophysiological features were more specific to each treatment, affecting network oscillation frequencies and entropy, pointing to discrete differences in mechanisms of action. These findings indicate that neurophysiological characterization of brain states is particularly informative when evaluating therapeutic mechanisms in conditions involving symptoms that are difficult to assess in rodents such as psychosis, and that mesdopetam should be further explored as a potential novel antipsychotic treatment option for Parkinson psychosis.

Advances in the Diagnosis and Management of Psychotic Symptoms in Neurodegenerative Diseases: A Narrative Review

Background: Approximately 15% of older adults may experience psychotic phenomena. Primary psychiatric disorders that manifest with psychosis (delusions, hallucinations, and disorganized thought or behavior) account for less than half. Up to 60% of late-life psychotic symptoms are due to systemic medical or neurological conditions, particularly neurodegenerative diseases. A thorough medical workup including laboratory tests, additional procedures if indicated, and neuroimaging studies is recommended. This narrative review summarizes current evidence regarding the epidemiology and phenomenology of psychotic symptoms encountered as part of the neurodegenerative disease continuum (including prodromal and manifest stages). Results: Prodromes are constellations of symptoms that precede the onset of overt neurodegenerative syndromes. Prodromal psychotic features, particularly delusions, have been associated with an increased likelihood of receiving a neurodegenerative disease diagnosis within several years. Prompt prodrome recognition is crucial for early intervention. The management of psychosis associated with neurodegenerative diseases includes behavioral and somatic strategies, although evidence is scarce and mostly limited to case reports, case series, or expert consensus guidelines, with few randomized controlled trials. Conclusion: The complexity of psychotic manifestations warrants management by interprofessional teams that provide coordinated, integrated care.

Ulotaront, a Trace Amine-Associated Receptor 1/Serotonin 5-HT1A Agonist, in Patients With Parkinson Disease Psychosis: A Pilot Study

Background and Objectives

Ulotaront (SEP-363856) is a trace amine-associated receptor 1 agonist with 5-HT_1A receptor agonist activity currently in phase 3 clinical development for the treatment of schizophrenia. In this exploratory, flexibly dosed study, ulotaront was evaluated for the treatment of Parkinson disease psychosis (PDP).

Methods

Patients with PDP requiring antipsychotic therapy were randomized, double-blind to ulotaront (25, 50, or 75 mg/d) or placebo. Mixed Model for Repeated Measures was used to assess change from baseline in the Scale for the Assessment of Positive Symptoms for Parkinson Disease (SAPS-PD) at 6 weeks (primary end point).

Results

The efficacy analysis sample comprised 38 patients (ulotaront, n = 24; placebo, n = 14). SAPS-PD total scores were numerically reduced in ulotaront-treated vs placebo-treated patients from week 1 to week 6: Least squares mean (95% confidence interval) difference in change from baseline at week 6 was -1.1 (-6.5, 4.3, p = 0.681). PDP symptom complete remission (≥100% improvement [reduction] from baseline in SAPS-PD total score) was observed in 25% of ulotaront-treated vs 0% of placebo-treated patients. SAPS-PD and Neuropsychiatric Inventory hallucinations subscales were numerically reduced vs placebo, and SAPS-PD total scores were reduced in patients with greater cognitive impairment (baseline Mini-Mental State Examination [MMSE] scores ≤24). Ulotaront improved Scales for Outcomes in Parkinson Disease Sleep Scale - Daytime Sleepiness scores (p = 0.022). There was no worsening of Unified Parkinson Disease Rating Scale Part III motor score, MMSE, or vital signs. Adverse events (≥10%) with ulotaront vs placebo included hallucinations (24% vs 14%), confusional state (20% vs 14%), dizziness (16% vs 7%), nausea (12% vs 7%), and falls (12% vs 21%).

Discussion

In this exploratory pilot study, ulotaront may decrease PDP symptoms without worsening motor function, particularly in patients with cognitive impairment.

Trial Registration Information

ClinicalTrials.gov identifier: NCT02969369; submitted: November 17, 2016; study start date: December 31, 2016.

Classification of Evidence

This Class II study was an exploratory pilot study that was underpowered to detect a statistically significant difference between ulotaront and placebo in the treatment of patients with Parkinson disease psychosis without worsening motor function.

α-Synuclein Strains and Their Relevance to Parkinson's Disease, Multiple System Atrophy, and Dementia with Lewy Bodies

Like many neurodegenerative diseases, Parkinson's disease (PD) is characterized by the formation of proteinaceous aggregates in brain cells. In PD, those proteinaceous aggregates are formed by the α-synuclein (αSyn) and are considered the trademark of this neurodegenerative disease. In addition to PD, αSyn pathological aggregation is also detected in atypical Parkinsonism, including Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA), as well as neurodegeneration with brain iron accumulation, some cases of traumatic brain injuries, and variants of Alzheimer's disease. Collectively, these (and other) disorders are referred to as synucleinopathies, highlighting the relation between disease type and protein misfolding/aggregation. Despite these pathological relationships, however, synucleinopathies cover a wide range of pathologies, present with a multiplicity of symptoms, and arise from dysfunctions in different neuroanatomical regions and cell populations. Strikingly, αSyn deposition occurs in different types of cells, with oligodendrocytes being mainly affected in MSA, while aggregates are found in neurons in PD. If multiple factors contribute to the development of a pathology, especially in the cases of slow-developing neurodegenerative disorders, the common presence of αSyn aggregation, as both a marker and potential driver of disease, is puzzling. In this review, we will focus on comparing PD, DLB, and MSA, from symptomatology to molecular description, highlighting the role and contribution of αSyn aggregates in each disorder. We will particularly present recent evidence for the involvement of conformational strains of αSyn aggregates and discuss the reciprocal relationship between αSyn strains and the cellular milieu. Moreover, we will highlight the need for effective methodologies for the strainotyping of aggregates to ameliorate diagnosing capabilities and therapeutic treatments.

Non-clinical pharmacology and toxicology studies of LPM6690061, a novel 5-hydroxytryptamine (5-HT)2A receptor inverse agonist

LPM6690061 is a novel compound with 5-HT2A receptor antagonist and inverse agonist activities. To support the clinical trial and marketing application of LPM6690061, a series of pharmacology and toxicology studies have been conducted. In vitro and in vivo pharmacology studies showed that LPM6690061 had high inverse agonism and antagonism activities against human 5-HT2A receptors, and demonstrated significant antipsychotic-like effects in two rat models: the DOI-induced head-twitch model and the MK-801-induced hyperactivity model, which was more effective than the control drug pimavanserin. LPM6690061 did not have detectable side effects on the neurobehavioral activities and respiratory function in rats, or on the ECG or blood pressure in dogs at the doses of 2 and 6 mg/kg. The half maximal inhibitory concentration (IC50) of LPM6690061 for inhibiting hERG current was 1.02 μM. Three in vivo toxicology studies were conducted. In the single dose toxicity study in rats and dogs, the maximum tolerated dose of LPM6690061 was 100 mg/kg. In the 4-week repeat dose toxicity study in rats, the main detectable toxic reactions of LPM6690061 included moderate artery wall hypertrophy, minimal to mild mixed cell inflammation and increased macrophages in the lung, which generally recovered after a 4-week drug withdrawal period. In the 4-week repeat dose toxicity study in dogs, no detectable toxicity was observed. The doses of no-observed-adverse-effect-level (NOAEL) in rats and dogs were 10 mg/kg and 20 mg/kg, respectively. In conclusion, both in vitro and in vivo pharmacological and toxicological studies showed that LPM6690061 was a safe and efficacious 5-HT2A receptor antagonist/inverse agonist which supports the clinical development as a novel antipsychotic drug.

Further characterisation of psychosis-like behaviours induced by L-DOPA in the MPTP-lesioned marmoset

Parkinson's disease (PD) psychosis afflicts over half of patients and poses a significant burden on quality of life. The aetiology of PD psychosis is multifactorial and likely arises from the complex interaction between dopamine replacement therapy and disease state. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned common marmoset is a validated model to predict the efficacy of therapeutic compounds for treatment-related complications, including PD psychosis. In this model, psychosis-like behaviours (PLBs) encompass stereotypies that are idiosyncratic in nature and reproducible with each L-3,4-dihydroxyphenylanaline (L-DOPA) administration. In the present study, we sought to expand upon the existing repertoire of PLBs through the characterisation of novel stereotypical behaviours that appear dependent on the environment. We then discuss our findings in the context of clinical reports on stereotypical behaviours termed "punding" in subjects with PD, which consists of stereotypical repetitive and senseless behaviours. The poor understanding of the pathophysiology governing punding and consequent lack of effective therapies stand to benefit from enhanced characterisation of these stereotypical behaviours in a validated pre-clinical model. We hope that further characterisation of PLBs in the MPTP-lesioned marmoset will be helpful in the evaluation of interventions that seek to alleviate PD psychosis symptoms.

Selective blockade of the 5-HT3 receptor acutely alleviates dyskinesia and psychosis in the parkinsonian marmoset

In Parkinson's disease (PD), management of L-3,4-dihydroxyphenylalanine (l-DOPA)-related complications, such as l-DOPA induced dyskinesia and psychosis, remains inadequate, which poses a significant burden on the quality of life of patients. We have shown, in the hemi-parkinsonian rat model of PD, that the selective serotonin type 3 (5-HT₃) receptor antagonists ondansetron and granisetron decreased the severity of established dyskinesia, and ondansetron even attenuated the development of dyskinesia. Here, we seek to confirm these favourable data on dyskinesia and to explore the effect of ondansetron on the severity of psychosis-like behaviours (PLBs) in the gold standard model of PD, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned non-human primate. We first determined the pharmacokinetic profile of ondansetron in the marmoset. Subsequently, six MPTP-lesioned marmosets were administered l-DOPA chronically until they exhibited stable and reproducible dyskinesia and PLBs upon each administration of l-DOPA. On behavioural assessment days, ondansetron (0.01, 0.1 and 1 mg/kg) or vehicle was administered in conjunction with l-DOPA, and the severity of dyskinesia, PLBs and parkinsonism was evaluated. Ondansetron 0.1 mg/kg alleviated global dyskinesia severity by 73% (P < 0.0001) and decreased duration of on-time with disabling dyskinesia by 88% (P = 0.0491). Ondansetron 0.1 mg/kg reduced the severity of global PLBs by 80% (P < 0.0001) and suppressed on-time with disabling PLBs (P = 0.0213). Ondansetron enhanced the anti-parkinsonian action of l-DOPA, reducing global parkinsonism by 53% compared to l-DOPA (P = 0.0004). These results suggest that selective blockade of the 5-HT₃ receptor with ondansetron may be an effective approach to alleviate l-DOPA-related complications.

Hallucinations: diagnosis, neurobiology and clinical management

Hallucinations are important diagnostic symptoms in schizophrenia, but also occur in other medical and neuropsychiatric conditions. Not all patients with hallucinations are psychotic. There has been a surge of interest in the topic of hallucinations, as new research data have begun to reveal their neurobiology. Hallucinogenic molecules may also serve as new scaffolds for the development of new psychotropic drugs. We searched and reviewed recent literature, focusing on the refinement of clinical management, which was inspired by new data regarding the neurobiology of hallucination subtypes. We concluded that the successful management of hallucinations depends on accurate differential diagnosis to identify subtypes, which would then determine the most appropriate treatment.

Pimavanserin for the treatment of Parkinson's disease psychosis: number needed to treat, number needed to harm, and likelihood to be helped or harmed

OBJECTIVE

Our aim was to describe the efficacy and tolerability of pimavanserin, a highly selective serotonin 5-HT2A receptor inverse agonist/antagonist indicated for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis (PDP), using the metrics of number needed to treat (NNT) and number needed to harm (NNH).

METHODS

Categorical efficacy and tolerability data were extracted from the clinical trial databases of the double-blind placebo-controlled studies of pimavanserin in persons with PDP. NNT and NNH values were calculated with their respective 95% confidence intervals. The likelihood to be helped or harmed (LHH) was then calculated contrasting therapeutic response versus discontinuation because of an adverse event.

RESULTS

NNT values for pimavanserin 34 mg/d versus placebo for several definitions of clinical response are 10, and/or are not statistically significant, and/or show an advantage for pimavanserin over placebo (such as for postural hypotension). In terms of LHH, pimavanserin 34 mg/d is about five times more likely to result in clinical response (as measured by a ≥3 point decrease from baseline on the Scale for the Assessment of Positive Symptoms adapted for Parkinson's disease) versus discontinuation due to an adverse event.

CONCLUSIONS

Using the metrics of NNT, NNH, and LHH, pimavanserin 34 mg/d for the treatment of PDP appears to have a compelling benefit/risk profile.

Recognition and treatment of neuropsychiatric disturbances in Parkinson's disease

The non-motor symptoms of Parkinson's disease (PD) have been attracting increasing attention due to their ubiquitous nature and their often devastating effects on the quality of life. Behavioral problems in PD include dementia, depression, apathy, fatigue, anxiety, psychosis, akathisia, personality change, sleep disorders and impulse control disorders. Some of these are intrinsic to the neuropathology while others occur as an interplay between pathology, psychology and pharmacology. While few data exist for guiding therapy, enough is known to guide therapy in a rational manner.

Nonmotor symptoms in Parkinson's disease

The recognition and treatment of nonmotor symptoms are increasingly emphasized in the care of Parkinson's disease (PD) patients. This manuscript will review signs and symptoms localized, generally, to the cortex, basal ganglia, brainstem, spinal cord, and peripheral nervous system. Cortical manifestations include dementia, mild cognitive impairment, and psychosis. Apathy, restlessness (akathisia), and impulse control disorders will be linked as basal ganglia symptoms. Symptoms attributed to the brainstem comprise depression, anxiety, and sleep disorders. Peripheral nervous system disturbances may lead to orthostatic hypotension, constipation, pain, and sensory disturbances.

Adenosine A(2A) Receptor Antagonists Do Not Disrupt Rodent Prepulse Inhibition: An Improved Side Effect Profile in the Treatment of Parkinson's Disease

Parkinson's disease (PD) is characterized by loss of dopaminergic neurons in the substantia nigra. Current treatments for PD focus on dopaminergic therapies, including L-dopa and dopamine receptor agonists. However, these treatments induce neuropsychiatric side effects. Psychosis, characterized by delusions and hallucinations, is one of the most serious such side effects. Adenosine A_2A receptor antagonism is a nondopaminergic treatment for PD with clinical and preclinical efficacy. The present studies assessed A_2A antagonists SCH 412348 and istradefylline in rodent prepulse inhibition (PPI), a model of psychosis. Dopamine receptor agonists pramipexole (0.3–3 mg/kg), pergolide (0.3–3 mg/kg), and apomorphine (0.3–3 mg/kg) significantly disrupted PPI; ropinirole (1–30 mg/kg) had no effect; L-dopa (100–300 mg/kg) disrupted rat but not mouse PPI. SCH 412348 (0.3–3 mg/kg) did not disrupt rodent PPI; istradefylline (0.1–1 mg/kg) marginally disrupted mouse but not rat PPI. These results suggest that A_2A antagonists, unlike dopamine agonists, have an improved neuropsychiatric side effect profile.

Levodopa-carbidopa intestinal gel for treatment of advanced Parkinson's disease

BACKGROUND

Levodopa is the mainstay of Parkinson's disease (PD) treatment, but is often eventually associated with disabling motor complications in patients with advanced PD. The inability of perorally administered levodopa to provide more physiologic continuous dopaminergic stimulation (CDS) is a leading hypothesis to explain these complications.

OBJECTIVE

To investigate the cumulative efficacy and safety, and re-evaluate the role, of levodopa-carbidopa intestinal gel (LCIG) infusion in treatment of advanced PD patients experiencing levodopa-associated motor complications, through its purported mechanism for providing CDS.

METHODS

Literature searches in the MEDLINE/PubMed database were used to identify peer-reviewed publications examining the role of CDS in levodopa-associated motor complications and pharmacologic strategies for CDS, focusing on LCIG infusion for advanced PD patients.

RESULTS

LCIG, an aqueous gel, is continuously infused (daytime only or 24 h) via a portable pump and tube permanently inserted into the duodenum through percutaneous endoscopic gastrostomy (PEG). LCIG infusion provides stable levodopa plasma levels, which are significantly less variable than those with oral levodopa. Clinical trials indicate LCIG may significantly improve motor complications (reduction of time in 'off' and time in 'on with dyskinesias'), motor scores using the Unified Parkinson's Disease Rating Scale (UPDRS), non-motor symptomatology (Non-motor Symptom Scale) and health-related quality of life (HRQOL) in advanced PD patients. The adverse-event profile of LCIG is similar to that of oral levodopa, although technical problems with the infusion device have occurred in up to 70% of patients.

CONCLUSION

LCIG has demonstrated efficacy in reducing levodopa-associated motor complications in patients with advanced PD, and improving UPDRS and HRQOL scores. Because it involves PEG and its associated risks, LCIG is recommended for patients in whom motor fluctuations and dyskinesias are inadequately treated with traditional peroral medication. For these patients, LCIG can be a valuable alternative to deep brain stimulation (DBS), especially when DBS is contraindicated. These conclusions are limited by the modest number and size of completed randomized, controlled trials of LCIG.