A video-atlas of levodopa-induced dyskinesia in Parkinson's disease: terminology matters

Dyskinesia is a common complication of long-term levodopa therapy in patients with Parkinson's disease (PD), which often worsens the quality of life. It is usually dose-dependent and emerges possibly due to pulsatile stimulation of dopamine receptors. Delineating the pattern of dyskinesia is crucial for determining the most effective therapeutic approach, a task that often presents challenges for numerous neurologists. This article comprehensively describes various patterns of dyskinesia in PD patients and features video demonstration of some of the common forms of dyskinesia. We have used a real case scenario as an example to lead the discussion on the phenomenology, distinguishing features, and management of various types of dyskinesia. A comprehensive literature search was conducted in PubMed using "dyskinesia" as a keyword. The prototype case with videos highlights the differentiating features of dyskinesia along with the treatment strategies. A wide range of descriptive rubrics have been used for certain dyskinesia which are described in detail in this article. The newer types of dyskinesia associated with continuous dopaminergic stimulation in patients with advanced PD and their implications have been described. As there are distinct ways of managing various types of dyskinesia, understanding the phenomenology and chronology of dyskinesia is vital for the optimal management of dyskinetic PD patients. We suggest that dyskinesia should be classified broadly into peak-dose dyskinesia (PDD), biphasic dyskinesia (BD), and OFF-period dystonia. The occurrence of low-dose dyskinesia and complex dyskinesia of continuous dopaminergic treatments should be known to specialists and will require additional studies.

HOMER1 Polymorphism and Parkinson's Disease-Psychosis: Is there an Association?

Objective

Homer1, a postsynaptic protein coded by the HOMER1 gene, presumably has a role in homeostatic plasticity that dampens neuronal responsiveness when the input activity is too high. HOMER1 polymorphism has been studied in major psychiatric disorders such as schizophrenia. The objective of this study is to investigate if polymorphisms of the HOMER1 gene are associated with psychosis in Parkinson's disease (PD-P).

Methods

One hundred patients with Parkinson's disease (PD) and 100 healthy controls were enrolled consecutively in a PD-P biomarker study at the National Institute of Mental Health and Neurosciences, Bangalore, India. Of the 100 PD patients, 50 had psychosis (PD-P) and 50 did not have psychosis (PD-NP). Two single-nucleotide polymorphisms of HOMER1 (rs4704559 and rs4704560) were analyzed from the DNA isolated from peripheral blood. The allele and genotype frequencies in the PD-P and PD-NP groups were compared.

Results

Analysis of HOMER1 rs4704560 revealed a significant difference in both genotype and allele levels between PD-P and PD-NP groups. There was an overrepresentation of T-allele (42% vs. 16%; P < 0.001) and TT genotype (24% vs. 6%; P < 0.001) in the PD-P group compared to PD-NP group. There was no significant difference between PD-P and PD-NP groups when various genotypes and allele frequencies related to HOMER1 rs4704559 were compared.

Conclusion

PD-P is probably associated with overrepresentation of T-allele of HOMER1 rs4704560, and larger studies are warranted to confirm our results.

Cardiac 18F-dopamine positron emission tomography predicts the type of phenoconversion of pure autonomic failure

PURPOSE

Pure autonomic failure (PAF) is a rare disease characterized by neurogenic orthostatic hypotension (nOH), no known secondary cause, and lack of a neurodegenerative movement or cognitive disorder. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease [LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)] or to the non-LBD synucleinopathy multiple system atrophy (MSA). Since cardiac 18F-dopamine-derived radioactivity usually is low in LBDs and usually is normal in MSA, we hypothesized that patients with PAF with low cardiac 18F-dopamine-derived radioactivity would be more likely to phenoconvert to a central LBD than to MSA.

METHODS

We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about 18F-dopamine positron emission tomography (PET).

RESULTS

Nineteen patients (15 with low 18F-dopamine-derived radioactivity, 4 with normal radioactivity) met the above criteria and had follow-up data. Nine (47%) phenoconverted to a central synucleinopathy over a mean of 6.6 years (range 1.5-18.8 years). All 6 patients with low cardiac 18F-dopamine-derived radioactivity who phenoconverted during follow-up developed a central LBD, whereas none of 4 patients with consistently normal 18F-dopamine PET phenoconverted to a central LBD (p = 0.0048), 3 evolving to probable MSA and 1 upon autopsy having neither a LBD nor MSA.

CONCLUSION

Cardiac 18F-dopamine PET can predict the type of phenoconversion of PAF. This capability could refine eligibility criteria for entry into disease-modification trials aimed at preventing evolution of PAF to symptomatic central LBDs.

Developing a Staging Scheme for Essential Tremor: A Discussion of Organizing Principles

Essential tremor (ET) is a chronic, progressive neurological disease that may negatively affect patients' lives. While there has been considerable progress in ET research, some fundamental issues remain unaddressed. One such issue is disease staging. Staging schemes have inherent value and are part of the dialogue that clinicians have with other movement disorders patients. We highlight the value of and challenges with developing a staging system for ET and organize a discussion around the potential steps in developing such a system. Diseases for which there are staging schemes generally have a number of shared characteristics. ET has numerous features that would lend themselves to a staging scheme: emerging evidence supporting the existence of a premotor phase of disease, insidious onset, progressive worsening of arm tremor, spread of tremor to other body regions, the observation that patients seem to be at increased risk for other conditions within the same organ (i.e., emergence of Parkinson's disease and Alzheimer's disease in excessive numbers of ET patients), pathological changes in the cerebellum whose evolution can be ordered from (i) those that compromise the physical integrity and physiological function of Purkinje cells, (ii) subsequent changes that are reparative and regenerative, and (iii) eventual cell death. Challenges to formulating a staging scheme are the absence of both a biological marker and an "end stage" of disease. The sum of combined evidence suggests that a staging scheme would be of value. We provide initial thoughts as to how to begin to structure such a staging scheme.

Cardiac 18F-Dopamine Positron Emission Tomography Predicts the Type of Phenoconversion of Pure Autonomic Failure

Background

Pure autonomic failure (PAF) is a rare disease characterized clinically by neurogenic orthostatic hypotension (nOH) and biochemically by peripheral noradrenergic deficiency. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease (LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)) or to the non-LBD synucleinopathy multiple system atrophy (MSA). We examined whether cardiac 18F-dopamine positron emission tomography (PET) predicts the trajectory of phenoconversion in PAF. Since cardiac 18F-dopamine-derived radioactivity always is decreased in LBDs with nOH and usually is normal in MSA, we hypothesized that PAF patients with low cardiac 18F-dopamine-derived radioactivity may phenoconvert to a central LBD but do not phenoconvert to MSA.

Methods

We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about serial 18F-dopamine PET.

Results

Twenty patients met the above criteria. Of 15 with low cardiac 18F-dopamine-derived radioactivity, 6 (40%) phenoconverted to PD or DLB and none to MSA. Of 5 patients with consistently normal 18F-dopamine PET, 4 phenoconverted to MSA, and the other at autopsy had neither a central LBD nor MSA.

Conclusion

In this case series, 40% of patients with nOH and low cardiac 18F-dopamine-derived radioactivity phenoconverted to PD or DLB during follow-up; none phenoconverted to MSA. Cardiac 18F-DA PET therefore can predict the type of phenoconversion in PAF. This capability could refine eligibility criteria for entry into disease-modification trials aiming to prevent evolution of PAF to symptomatic central LBDs.

A multicentre study on grey matter morphometric biomarkers for classifying early schizophrenia and parkinson's disease psychosis

Psychotic symptoms occur in a majority of schizophrenia patients and in ~50% of all Parkinson's disease (PD) patients. Altered grey matter (GM) structure within several brain areas and networks may contribute to their pathogenesis. Little is known, however, about transdiagnostic similarities when psychotic symptoms occur in different disorders, such as in schizophrenia and PD. The present study investigated a large, multicenter sample containing 722 participants: 146 patients with first episode psychosis, FEP; 106 individuals in at-risk mental state for developing psychosis, ARMS; 145 healthy controls matching FEP and ARMS, Con-Psy; 92 PD patients with psychotic symptoms, PDP; 145 PD patients without psychotic symptoms, PDN; 88 healthy controls matching PDN and PDP, Con-PD. We applied source-based morphometry in association with receiver operating curves (ROC) analyses to identify common GM structural covariance networks (SCN) and investigated their accuracy in identifying the different patient groups. We assessed group-specific homogeneity and variability across the different networks and potential associations with clinical symptoms. SCN-extracted GM values differed significantly between FEP and Con-Psy, PDP and Con-PD, PDN and Con-PD, as well as PDN and PDP, indicating significant overall grey matter reductions in PD and early schizophrenia. ROC analyses showed that SCN-based classification algorithms allow good classification (AUC ~0.80) of FEP and Con-Psy, and fair performance (AUC ~0.72) when differentiating PDP from Con-PD. Importantly, the best performance was found in partly the same networks, including the thalamus. Alterations within selected SCNs may be related to the presence of psychotic symptoms in both early schizophrenia and PD psychosis, indicating some commonality of underlying mechanisms. Furthermore, results provide evidence that GM volume within specific SCNs may serve as a biomarker for identifying FEP and PDP.

Dystonia and tremor: Do they have a shared biology?

Dystonia and tremor are the two most commonly encountered hyperkinetic movement disorders encountered in clinical practice. While there has been substantial progress in the research on these two disorders, there also exists a lot of gray areas. Entities such as dystonic tremor and tremor associated with dystonia occupy a major portion of the "gray zone". In addition, there is a marked clinical heterogeneity and overlap of several clinical and epidemiological features among dystonia and tremor. These facts raise the possibility that dystonia and tremor could be having shared biology. In this chapter, we revisit critical aspects of this possibility that may have important clinical and research implications in the future. We comprehensively review the points in favor and against the theory that dystonia and tremor have shared biology from clinical, epidemiological, genetic and neuroimaging studies.

Peripherally-induced Movement Disorders: An Update

Background

Peripherally-induced movement disorders (PIMD) should be considered when involuntary or abnormal movements emerge shortly after an injury to a body part. A close topographic and temporal association between peripheral injury and onset of the movement disorders is crucial to diagnosing PIMD. PIMD is under-recognized and often misdiagnosed as functional movement disorder, although both may co-exist. Given the considerable diagnostic, therapeutic, and psychosocial-legal challenges associated with PIMD, it is crucial to update the clinical and scientific information about this important movement disorder.

Methods

A comprehensive PubMed search through a broad range of keywords and combinations was performed in February 2023 to identify relevant articles for this narrative review.

Results

The spectrum of the phenomenology of PIMD is broad and it encompasses both hyperkinetic and hypokinetic movements. Hemifacial spasm is probably the most common PIMD. Others include dystonia, tremor, parkinsonism, myoclonus, painful leg moving toe syndrome, tics, polyminimyoclonus, and amputation stump dyskinesia. We also highlight conditions such as neuropathic tremor, pseudoathetosis, and MYBPC1-associated myogenic tremor as examples of PIMD.

Discussion

There is considerable heterogeneity among PIMD in terms of severity and nature of injury, natural course, association with pain, and response to treatment. As some patients may have co-existing functional movement disorder, neurologists should be able to differentiate the two disorders. While the exact pathophysiology remains elusive, aberrant central sensitization after peripheral stimuli and maladaptive plasticity in the sensorimotor cortex, on a background of genetic (two-hit hypothesis) or other predisposition, seem to play a role in the pathogenesis of PIMD.

How should future clinical trials be designed in the search for disease-modifying therapies for Parkinson's disease?

INTRODUCTION

Although there has been substantial progress in research and innovations in symptomatic treatments, similar success has not been achieved in disease-modifying therapy (DMT) for Parkinson's disease (PD). Considering the enormous motor, psychosocial and financial burden associated with PD, safe and effective DMT is of paramount importance.

AREAS COVERED

One of the reasons for the lack of progress in DMT for PD is poor or inappropriate design of clinical trials. In the first part of the article, the authors focus on the plausible reasons why the previous trials have failed and in the latter part, they provide their perspectives on future DMT trials.

EXPERT OPINION

There are several potential reasons why previous trials have failed, including broad clinical and etiopathogenic heterogeneity of PD, poor definition and documentation of target engagement, lack of appropriate biomarkers and outcome measures, and short duration of follow-up. To address these deficiencies, future trials may consider- (i) a more customized approach to select the most suitable participants and therapeutic approaches, (ii) explore combination therapies that would target multiple pathogenetic mechanisms, and (iii) moving beyond targeting only motor symptoms to also assessing non-motor features of PD in well-designed longitudinal studies.

Orthostatic Hypotension In Parkinson Disease: What Is New?

Purpose

of the review: Orthostatic hypotension (OH) is the primary manifestation of cardiovascular autonomic dysfunction in Parkinson’s disease (PD) and can be a prodromal feature of the disease. We review the recent progress in the field of autonomic dysfunction in PD.

Recent findings:

Individuals with isolated neurogenic OH should be followed up frequently as they may evolve into PD, dementia with Lewy bodies, or multiple system atrophy. The prevalence of OH in PD increases with disease stages but the role of levodopa remains unclear. Measurement of supine and standing heart rate and blood pressure allows for accurate identification of neurogenic OH in the clinic.

Summary:

Accurate identification of neurogenic OH in the clinic is crucial for identification of individuals who may benefit from participation in neuroprotective trials in the future. The treatment of OH in PD should be individualized and may reduce the risk of falls, cognitive impairment, and death.

Practical pearls to improve the efficacy and tolerability of levodopa in Parkinson's disease

INTRODUCTION

Levodopa is the most effective medication for the treatment of motor symptoms of Parkinson's disease (PD). Several factors may affect the efficacy and tolerability of levodopa. These include the timing, dosage and administration of levodopa, concomitant drugs, food, PD-associated non motor symptoms, and various neurologic and non-neurologic comorbidities. If not appropriately addressed, these issues may limit levodopa efficacy, tolerability, and compliance.

AREAS COVERED

This article reviews the basics of the metabolism of orally administered levodopa, its side effects, and the factors that may affect its tolerability and efficacy. We provide several practical pearls to improve the tolerability and efficacy of levodopa.

EXPERT OPINION

Protein-rich food delays and reduces levodopa absorption. Hence, levodopa should preferably be administered in a relatively empty stomach. Carbidopa dosing is crucial as it not only enhances the entry of levodopa into the central nervous system, but also reduces levodopa's peripheral adverse effects. Patients experiencing the early side effects such as nausea/vomiting should be prescribed with anti-nausea medications that do not block dopamine receptors. Non-oral routes of administration can be used to obviate persistent gastrointestinal side effects. Implementation of these and other tips may help improve the tolerability and efficacy of levodopa.

Retinal Changes in Parkinson's Disease: A Longitudinal Follow-up Study

BACKGROUND

There is definite evidence for the involvement of retina in Parkinson's disease (PD). However, a specific pattern has not been clear due to the cross-sectional nature of the majority of the previous studies.

OBJECTIVE

The aim of this work was to study the pattern of changes in the retinal layers in patients with PD on longitudinal follow-up.

MATERIALS AND METHODS

Twelve patients with PD (23 eyes) were evaluated at baseline with complete history, clinical examination, Unified Parkinson's Disease Rating Scale (UPDRS) motor part, visual acuity, and retinal imaging with spectral-domain Optical Coherence Tomography. After a mean duration of 3.7 ± 0.46 years, patients were re-evaluated.

RESULTS

The Central Macular Thickness (CMT) of the right eye was found to be significantly thicker during the follow-up (P = 0.002). The outer retinal layer in the temporal quadrant at 0.5 centimeters from the fovea of the left eye was found to be significantly thinner (P = 0.001).

CONCLUSION

The serial evaluation of the retinal layers in patients with PD suggests a progressive loss of thickness of the outer retinal layer. The involvement of non-dopaminergic mechanisms, especially glutamatergic pathways, may be responsible for these changes.

Multimodal Brain Connectomics-Based Prediction of Parkinson’s Disease Using Graph Attention Networks

Background

A multimodal connectomic analysis using diffusion and functional MRI can provide complementary information on the structure–function network dynamics involved in complex neurodegenerative network disorders such as Parkinson’s disease (PD). Deep learning-based graph neural network models generate higher-level embeddings that could capture intricate structural and functional regional interactions related to PD.

Objective

This study aimed at investigating the role of structure–function connections in predicting PD, by employing an end-to-end graph attention network (GAT) on multimodal brain connectomes along with an interpretability framework.

Methods

The proposed GAT model was implemented to generate node embeddings from the structural connectivity matrix and multimodal feature set containing morphological features and structural and functional network features of PD patients and healthy controls. Graph classification was performed by extracting topmost node embeddings, and the interpretability framework was implemented using saliency analysis and attention maps. Moreover, we also compared our model with unimodal models as well as other state-of-the-art models.

Results

Our proposed GAT model with a multimodal feature set demonstrated superior classification performance over a unimodal feature set. Our model demonstrated superior classification performance over other comparative models, with 10-fold CV accuracy and an F1 score of 86% and a moderate test accuracy of 73%. The interpretability framework highlighted the structural and functional topological influence of motor network and cortico-subcortical brain regions, among which structural features were correlated with onset of PD. The attention maps showed dependency between large-scale brain regions based on their structural and functional characteristics.

Conclusion

Multimodal brain connectomic markers and GAT architecture can facilitate robust prediction of PD pathology and provide an attention mechanism-based interpretability framework that can highlight the pathology-specific relation between brain regions.

Essential Tremor: Five New Things

Purpose of the review:

To highlight five new things in the research and clinical aspects of essential tremor (ET).

Recent findings:

The introduction of a new definition of ET and a new category “ET plus” were the major themes of the recent consensus statement. This new change demands a change in the approach to the clinical diagnosis of ET and related diseases. From the pathogenesis standpoint, the cerebellar neurodegenerative model seems to have numerous evidence in its favor compared to the olivary model which has largely fallen out of favor. From the standpoint of therapeutics, magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy has enriched the therapeutic armamentarium.

Summary:

There has been considerable progress in the field of ET. We discuss five new things in this article which include- (i) new definition (ii) ET plus (iii) approach to the diagnosis of ET, (iv) cerebellar degeneration, and (v) MRgFUS thalamotomy.

Tremor Syndromes: An Updated Review

Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathophysiology. The tremor task force of the International Parkinson Disease and Movement Disorders Society has worked toward this goal and proposed a new classification system. This system has remained a prime topic of scientific communications on tremor in recent times. The new classification is based on two axes: 1. based on the clinical features, history, and tremor characteristics and 2. based on the etiology of tremor. In this article, we discuss the key aspects of the new classification, review various tremor syndromes, highlight some of the controversies in the field of tremor, and share the potential future perspectives.

Differential abnormalities of cerebrospinal fluid dopaminergic versus noradrenergic indices in synucleinopathies

The synucleinopathies Parkinson's disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) are characterized by intra-cytoplasmic deposition of the protein alpha-synuclein and by catecholamine depletion. PAF, which manifests with neurogenic orthostatic hypotension (nOH) and no motor signs of central neurodegeneration, can evolve into PD+nOH. The cerebrospinal fluid (CSF) levels of catecholamine metabolites may indicate central catecholamine deficiency in these synucleinopathies, but the literature is inconsistent and incomplete. In this retrospective cohort study we reviewed data about CSF catecholamines, the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the norepinephrine metabolites 3,4-dihydroxyphenylglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG). The compounds were measured in 36 patients with PD, 37 patients with MSA, and 19 patients with PAF and in 38 controls. Compared to the control group, the PD, MSA, and PAF groups had decreased CSF MHPG (p < .0001 each by Dunnett's post hoc test), DHPG (p = .004; p < .0001; p < .0001) and norepinephrine (p = .017; p = .0003; p = .044). CSF HVA and DOPAC were decreased in PD (p < .0001 each) and MSA (p < .0001 each) but not in PAF. The three synucleinopathies therefore have in common in vivo evidence of central noradrenergic deficiency but differ in the extents of central dopaminergic deficiency-prominent in PD and MSA, less apparent in PAF. Data from putamen ¹⁸ F-DOPA and cardiac ¹⁸ F-dopamine neuroimaging in the same patients, post-mortem tissue catecholamines in largely separate cohorts, and review of the neuropathology literature fit with these distinctions. The results suggest a 'norepinephrine first' ascending pathogenetic sequence in synucleinopathies, with degeneration of pontine locus ceruleus noradrenergic neurons preceding the loss of midbrain substantia nigra dopaminergic neurons.

Cardiac 18F-Dopamine PET Distinguishes PD with Orthostatic Hypotension from Parkinsonian MSA

BACKGROUND

Parkinson's disease with orthostatic hypotension (PD + OH) can be difficult to distinguish clinically from the parkinsonian form of multiple system atrophy (MSA-P). Previous studies examined cardiac sympathetic neuroimaging to differentiate PD from MSA but without focusing specifically on PD + OH versus MSA-P, which often is the relevant differential diagnostic issue.

OBJECTIVE

To investigate the utility of cardiac sympathetic neuroimaging by 18F-dopamine positron emission tomographic (PET) scanning for separating PD + OH from MSA-P.

METHODS

Cardiac 18F-dopamine PET data were analyzed from 50 PD + OH and 68 MSA-P patients evaluated at the NIH Clinical Center from 1990 to 2020. Noradrenergic deficiency was defined by interventricular septal 18F-dopamine-derived radioactivity <6000 nCi-kg/cc-mCi in the 5' frame with mid-point 8' after initiation of 3' tracer injection.

RESULTS

18F-Dopamine PET separated the PD + OH from the MSA-P group with a sensitivity of 92% and specificity of 96%.

CONCLUSION

Cardiac 18F-dopamine PET scanning efficiently distinguishes PD + OH from MSA-P.

Relapsed granulomatosis with polyangiitis with panhypopituitarism

A man in his early 60s with a medical history of granulomatosis with polyangiitis (GPA) in remission for two decades without maintenance therapy presented with non-specific complaints of profound fatigue and 40-pound weight loss. He was seronegative for antinuclear antibodies and cytoplasmic antineutrophilic antibodies, but erythrocyte sedimentation rate and C reactive protein levels were elevated. Endocrinological testing revealed adrenal insufficiency, hypogonadism, hypothyroidism and diabetes insipidus. An MRI of the head revealed extensive sinonasal inflammation eroding through the floor of the sella turcica and into the pituitary gland and stalk. Biopsy of the sinonasal tissues was inconclusive. On review of his case, a multidisciplinary team diagnosed him with panhypopituitarism secondary to a recurrence of GPA. He responded well to glucocorticoids and methotrexate with marked reduction of pituitary enhancement on imaging and resolution of diabetes insipidus. He will require lifelong testosterone, levothyroxine and glucocorticoids for hormone replacement therapy.

Cardioselective peripheral noradrenergic deficiency in Lewy body synucleinopathies

Objective

Lewy body (LB) synucleinopathies such as Parkinson’s disease (PD) entail profound cardiac norepinephrine deficiency. The status of sympathetic noradrenergic innervation at other extracranial sites has been unclear. Although in vivo neuroimaging studies have indicated a cardioselective noradrenergic lesion, no previous study has surveyed peripheral organs for norepinephrine contents in LB diseases. We reviewed ¹⁸F‐dopamine (¹⁸F‐DA) positron emission tomographic images and postmortem neurochemical data across several body organs of controls and patients with the LB synucleinopathies PD and pure autonomic failure (PAF) and the non‐LB synucleinopathy multiple system atrophy (MSA).

Methods

¹⁸F‐DA–derived radioactivity in the heart, liver, spleen, pancreas, stomach, kidneys, thyroid, and submandibular glands were analyzed from 145 patients with LB synucleinopathies (112 PD, 33 PAF), 74 controls, and 85 MSA patients. In largely separate cohorts, postmortem tissue norepinephrine data were reviewed for heart, liver, spleen, pancreas, kidney, thyroid, submandibular gland, and sympathetic ganglion tissue from 38 PD, 2 PAF, and 5 MSA patients and 35 controls.

Results

Interventricular septal ¹⁸F‐DA–derived radioactivity was decreased in the LB synucleinopathy group compared to the control and MSA groups (P < 0.0001 each). The LB and non‐LB groups did not differ in liver, spleen, pancreas, stomach, or kidney ¹⁸F‐DA–derived radioactivity. The LB synucleinopathy group had markedly decreased apical myocardial norepinephrine, but normal tissue norepinephrine in other organs. The MSA group had normal tissue norepinephrine in all examined organs.

Interpretation

By in vivo sympathetic neuroimaging and postmortem neurochemistry peripheral noradrenergic deficiency in LB synucleinopathies is cardioselective. MSA does not involve peripheral noradrenergic deficiency.

Essential tremor: Is the word "essential" really essential?

Essential tremor (ET) is among the common movement disorders. A surge in research in recent years has considerably improved our understanding of disease etiology and pathogenesis, and its associated clinical phenomenology and natural history. With this progress have emerged a multitude of new questions and conundrums and newly proposed terminologies. Amidst these various related discussions, it is worth revisiting the essence of the nomenclature, "essential tremor", to assess how well it continues to fit the growing understanding of this entity. Here we revisit the historical underpinnings of the nomenclature, its accuracy, pitfalls of eliminating the word, and advantages of removing the word. There are two primary historical bases for using the word "essential": (i) idiopathic or unclear etiology, (ii) a unitary (single-featured) trait perceived as a constitutional feature. Numerous studies indicate that ET is neither truly idiopathic nor is fully isolated, making the use of "essential" technically incorrect. There are pitfalls and advantages of eliminating the term "essential" and both are succinctly described in this article. Yet in the absence of any flawless alternatives at present, we conclude that it is preferable for now to persist with "essential" tremor, thereby respecting the historical continuity of this one-and-a-half-century old nomenclature.

Do We Belittle Essential Tremor by Calling It a Syndrome Rather Than a Disease? Yes

Essential tremor (ET) is among the most prevalent neurological diseases. Appreciation in recent years of a richer tremor phenomenology, additional motor and non-motor features, variability in the natural course of tremor, associations with a host of other neurological conditions, and etiological and pathophysiological heterogeneity have resulted in general awareness of the clinical richness of ET. Along with this evolving view of ET have surfaced several conundrums regarding nomenclature. One of these is whether ET should be labeled a "syndrome" or "disease." Here, we revisit the classical definitions of "syndrome" and "disease" and discuss ET in this context. Considering the characteristics of "disease" and "syndrome" and evaluating the characteristics of ET, it seems to fit more into the "disease" construct. There are several reasons: There is considerable knowledge of the underlying etiologies and pathophysiology of ET, in numerous studies ET has been linked with other neurological conditions, the condition is progressive and deteriorative, and therapeutic approaches are grounded in an understanding of disease mechanisms and its associated neuroanatomy. Moreover, the etiological-pathological-clinical heterogeneity suggests that ET should be regarded as a "family of diseases" more appropriately termed "the essential tremors." This nomenclatural issue is not a mere matter of words; public health implications are numerous. A condition with the label "syndrome" may not be recognized as a serious problem, may be plagued by diminished public awareness, and may not garner funds for research that a condition with the label "disease" or "diseases" would. ET should be regarded as a family of diseases.

Abnormalities in the white matter tracts in patients with Parkinson disease and psychosis

OBJECTIVE

The objective of the current study was to compare the microstructural integrity of the white matter (WM) tracts in patients having Parkinson disease (PD) with and without psychosis (PD-P and PD-NP) through diffusion tensor imaging (DTI).

METHODS

This cross-sectional study involved 48 PD-NP and 42 PD-P who were matched for age, sex, and education. Tract-based spatial statistics (TBSS) was used to compare several DTI metrics from the diffusion-weighted MRIs obtained through a 3-Tesla scanner. A set of neuropsychological tests was used for the cognitive evaluation of all patients.

RESULTS

The severity and stage of PD were not statistically different between the groups. The PD-P group performed poorly in all the neuropsychological domains compared with the PD-NP group. TBSS analysis revealed widespread patterns of abnormality in the fractional anisotropy (FA) in the PD-P group, which also correlated with some of the cognitive scores. These tracts include inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, right parieto-occipital WM, body of the corpus callosum, and corticospinal tract.

CONCLUSION

This study provides novel insights into the putative role of WM tract abnormalities in the pathogenesis of PD-P by demonstrating significant alterations in several WM tracts. Additional longitudinal studies are warranted to confirm the findings of our research.

Revisiting the Clinical Phenomenology of "Cerebellar Tremor": Beyond the Intention Tremor

Tremor is an involuntary, rhythmic, oscillatory movement of a body part. It is a central feature of a range of diseases resulting from pathological changes in the cerebellum. Interestingly, in modern times, the terms "cerebellar tremor" and "intention tremor" are often used synonymously and interchangeably. However, "cerebellar tremor" (i.e., tremors of cerebellar origin) do not always present exclusively as intention tremor. In this article, we comprehensively revisit the clinical phenomenology of tremors observed in various diseases that are based in the cerebellum. By this, we mean diseases for which the cerebellum and its various connections are often seen as playing a central and defining role. These include spinocerebellar ataxias, essential tremor, orthostatic tremor, dystonia, acute cerebellitis, cerebellar tumors, paraneoplastic cerebellar degeneration, and cerebellar strokes. The theme of this article is to highlight, through published data available in the current literature, that the clinical phenomenology of tremor of cerebellar origin is heterogeneous, and it extends beyond that of intention tremor to include postural tremors, kinetic tremor, rest tremor, and orthostatic tremor. This heterogeneity is consistent with the seminal work of Gordon Holmes, in which he described a variety of tremors aside from intention tremor in the setting of cerebellar lesions. In the end, it would seem that the notion that intention tremor is the sole signature of cerebellar lesions is an over-simplification and is not correct. Future studies are warranted to identify and further characterize the heterogeneity of tremors arising from the various cerebellar etiologies.

Minor hallucinations in Parkinson disease: A subtle symptom with major clinical implications

OBJECTIVE

Psychosis is one of the most debilitating complications of Parkinson disease (PD). Although research on PD psychosis has been focused on the study of well-structured visual hallucinations (VH), currently accepted National Institute of Neurological Disorders and Stroke-National Institute of Mental Health diagnostic criteria emphasize minor hallucinations (MH) as the most common psychotic phenomena in PD. The objective of this review is to comprehensively describe the clinical and research advances on the understanding of MH and to provide future directions for obtaining further insights into their potential major implications for PD management and prognosis.

METHODS

A PubMed search was done in November 2018 to identify articles on minor psychotic phenomena in PD.

RESULTS

MH often precede the onset of well-structured VH and are associated with other nonmotor symptoms such as REM sleep behavior disorder and depression. The pattern of functional brain connectivity changes associated with MH involve visual-processing areas and attention control networks, which overlap with abnormalities described in patients with well-structured VH. The dysfunction of cortical networks in patients with MH may be an early indicator of a more widespread form of the disease.

CONCLUSION

Although called "minor," MH may have major clinical and prognostic implications. Further research is needed to establish whether MH are associated with a higher risk of disabling psychotic complications, cognitive deterioration, or a more accelerated disease progression. Understanding the early neurobiological underpinnings of MH may provide the background for future studies to identify the progressive dysfunction of neural circuits leading to more severe forms of psychosis in PD.

Spectrum of Movement Disorders in Patients With Neuroinvasive West Nile Virus Infection

Background

West Nile virus (WNV) is a flavivirus that is recognized as one of the common causes of arboviral neurological disease in the world. WNV infections usually manifest with constitutional symptoms such as fever, fatigue, myalgia, rash, arthralgia, and headache. Neuroinvasive WNV infections are characterized by signs and symptoms suggestive of meningitis, encephalitis, meningoencephalitis, and acute flaccid paralysis. In addition, many patients with neuroinvasive WNV infection develop a wide range of movement disorders. This article aims to comprehensively review the spectrum and natural course of the movement disorders observed in patients with neuroinvasive WNV infections.

Methods

A literature search was performed in March 2019 (in PubMed and EMBASE) to identify articles for this review.

Results

Movement disorders observed in the context of WNV infections include tremor, opsoclonus-myoclonus, parkinsonism, myoclonus, ataxia, and chorea. Most often, these movement disorders resolve within a few weeks to months with an indolent course. The commonly observed tremor phenotypes include action tremor of the upper extremities (bilateral > unilateral). Tremor in patients with West Nile meningitis subsides earlier than that in patients with West Nile encephalitis/acute flaccid paralysis. Opsoclonus-myoclonus in WNV infections responds well to intravenous immunoglobulins/plasmapheresis/corticosteroids. Parkinsonism has been reported to be mild in nature and usually lasts for a few weeks to months in the majority of the patients.

Conclusion

A wide spectrum of movement disorders is observed in neuroinvasive WNV infections. Longitudinal studies are warranted to obtain better insights into the natural course of these movement disorders.

The role of Optical Coherence Tomography in Parkinsonism: A critical review

Optical coherence tomography (OCT) has been evaluated as a tool to assess retinal changes in various neurodegenerative disorders. Parkinson's disease (PD), is a neurodegenerative disorder wherein dopaminergic deficiency results in some of the symptoms. As retina also has high concentration of dopamine, it would be of interest for both the clinician as well as the basic scientist to know if there is a correlation between the clinical features and the retinal changes. The objective of this review is to critically evaluate the literature and study the utility of OCT as a tool to evaluate retinal changes in PD.

A Comparative Study of Early and Late Onset Freezing of Gait in Parkinson's Disease

BACKGROUND

Freezing of gait (FOG) is a common and debilitating symptom in Parkinson's disease (PD); the pathogenesis and natural course of which has not been fully understood.

OBJECTIVES

This study was performed to evaluate patients with FOG in PD and ascertain factors contributing to an early onset of FOG in patients with PD.

METHODOLOGY

A chart review of 100 patients with PD (FOG [+] 50, FOG [-]: 50) was performed. FOG (+) patients were subdivided by a median split of time from motor onset to development of FOG (median: 6 years) into early onset FOG (EOFOG [n = 24]) and late onset FOG (n = 26).

RESULTS

The FOG (+) group had a significantly longer duration of motor symptoms, a higher Hoehn and Yahr stage, and greater severity of disease. Festination, falls, and wearing off were more prevalent in the FOG (+) group. Several nonmotor symptoms (NMS) such as constipation, psychosis, fatigue, weight loss, drooling, excessive sweating, depression, and postural giddiness were significantly higher in the FOG (+) group. The EOFOG group had a later age at onset of motor symptoms. There were no significant differences observed in the NMS, with the exception of fatigue in EOFOG.

CONCLUSIONS

FOG is associated with longer disease duration and higher severity of disease. FOG (+) patients have distinct NMS which are contributory to disease morbidity. EOFOG might be associated with an accelerated disease progression and is linked with older patients and shorter disease duration.

Implications of secondary unresponsiveness to dopaminergic drugs with preserved response to subthalamic nucleus stimulation in Parkinson's disease

Improvement in motor symptoms with levodopa is one of the hallmark features of Parkinson's disease (PD). The response to levodopa may reduce during the course of the illness. Few studies have also reported reduced response to levodopa in patients with PD several years after deep brain stimulation (DBS) of the subthalamic nucleus (STN) on both the sides. In this study, we report an extreme unresponsiveness to levodopa in the presence of a good response to STN stimulation in a patient 5 years after the DBS proceudre had been carried out. The implications of this phenomenon are also discussed.

Three-dimensional neuromelanin-sensitive magnetic resonance imaging of the substantia nigra in Parkinson's disease

BACKGROUND AND PURPOSE

The aim was to investigate the diagnostic utility of signal intensity measurement of the substantia nigra pars compacta (SNc) using three-dimensional (3D) neuromelanin-sensitive magnetic resonance imaging (MRI), for discrimination of patients with Parkinson's disease (PD) from healthy controls.

METHODS

T1-weighted neuromelanin-sensitive images of 16 patients with PD and 15 controls were quantitatively analyzed by placing circular 10 mm² regions of interest over the central and lateral parts of the bilateral SNc and anterior to the cerebral aqueduct at three levels of the midbrain. Signal intensities and contrast ratios (CRs) were calculated, after which significant differences, correlations, sensitivity and specificity were calculated.

RESULTS

The CRs of the central and lateral SNc were significantly lower in patients with PD. Lateral CRs were lower than the central CRs in both groups and significantly correlated with duration of illness. CRs of central and lateral parts of the SNc also correlated with the Unified Parkinson's Disease Rating Scale III OFF state scores. Receiver operating characteristic analysis revealed lateral CRs to be more sensitive and central CRs to be more specific for the discrimination of patients with PD from controls.

CONCLUSIONS

Contrast ratio analysis of the SNc using 3D neuromelanin-sensitive MRI may serve as a quick and accurate tool to discern between patients with PD and healthy controls.

Impaired frontal lobe functions in patients with Parkinson's disease and psychosis

INTRODUCTION

Patients with Parkinson's disease (PD) may develop several non-motor symptoms (NMS). Psychosis is one of the debilitating NMS of PD. The neurobiology of psychosis is not fully understood. This study aims to compare the frontal lobe functions of PD patients with and without psychosis using the Frontal Assessment Battery (FAB).

METHODOLOGY

This study included 69 patients with PD; 34 with psychosis (PD-P) and 35 without psychosis (PD-NP). Mini Mental Status Examination (MMSE) was used to screen for cognitive impairment. Unified Parkinson's disease Rating scale part-III (UPDRS-III) was used to measure the severity and Hoehn and Yahr score (H&Y) was used to measure the stage of PD. Frontal lobe functions were assessed by FAB.

RESULTS

The PD-P and PD-NP groups were comparable for age (58.7±8.4 vs 55.7±8.2, p=0.14), age at onset of symptoms (51.4±8.1 vs 50.0±8.8, p=0.48), gender distribution (men: 88%vs 80%, p=0.51), MMSE (28.2±1.9 vs 28.7±1.2 p=0.12), levodopa equivalent dose/day (736.0±376.3 vs 625.2±332.2, p=0.19), UPDRS-III OFF-score (36.7±8.8 vs 35.4±13.2, p=0.64), UPDRS-III ON-score (13.2±5.4 vs 12.4±6.6, p=0.44) and H&Y stage (2.3±0.3 vs 2.3±0.3, p=0.07). PD-P group had lower total FAB score compared to PD-NP group (13.9±2.2 vs 16.5±1.8, p<0.01). On the FAB, PD-P group had lower scores compared to PD-NP in lexical fluency (FAB-2), programming (FAB-3), sensitivity to interference (FAB-4) and inhibitory control (FAB-5).

CONCLUSION

Patients with PD-P had significant frontal lobe dysfunction compared to PD-NP. FAB may be a simple and useful bedside tool to assess frontal dysfunction in patients with PD in a busy neurological set up.

Pathogenesis of Primary Orthostatic Tremor: Current Concepts and Controversies

Background

Orthostatic tremor (OT), a rare and complex movement disorder, is characterized by rapid tremor of both legs and the trunk while standing. These disappear while the patient is either lying down or walking. OT may be idiopathic/primary or it may coexist with several neurological conditions (secondary OT/OT plus). Primary OT remains an enigmatic movement disorder and its pathogenesis and neural correlates are not fully understood.

Methods

A PubMed search was conducted in July 2017 to identify articles for this review.

Results

Structural and functional neuroimaging studies of OT suggest possible alterations in the cerebello-thalamo-cortical network. As with essential tremor, the presence of a central oscillator has been postulated for OT; however, the location of the oscillator within the tremor network remains elusive. Studies have speculated a possible dopaminergic deficit in the pathogenesis of primary OT; however, the evidence in favor of this concept is not particularly robust. There is also limited evidence favoring the concept that primary OT is a neurodegenerative disorder, as a magnetic resonance spectroscopic imaging study revealed significant reduction in cerebral and cerebellar N-acetyl aspartate (NAA) levels, a marker of neuronal compromise or loss.

Discussion

Based on the above, it is clear that the pathogenesis of primary OT still remains unclear. However, the available evidence most strongly favors the existence of a central oscillatory network, and involvement of the cerebellum and its connections.

Abnormalities of Eye-Hand Coordination in Patients with Writer's Cramp: Possible Role of the Cerebellum

Background

Writer's cramp (WC) is one of the commonly observed focal dystonias. The pathophysiology of WC has not been fully understood. The role of the cerebellum has been increasingly recognized in the pathogenesis of dystonia. As the cerebellum is crucial for maintaining accurate eye-hand coordination (EHC), its role in the pathogenesis of WC can be investigated by studying the EHC in patients with WC.

Methods

Fifteen patients with WC (women:men, 3:12) and 15 age- and gender-matched controls performed oculomotor and EHC tasks. A visually guided stimulus (VGS) task was first performed with eye-only condition (EOC) and then with EHC.

Results

A significant interaction between the groups (controls and patients) and tasks (EOC and EHC) with age as a covariate confirmed that the two groups reacted differently to the tasks in saccadic latency (F(1,27) = 4.8; p = 0.039) and average saccade acceleration (F(1,27) = 10.6; p = 0.003). The curvature index of acceleration of the hand was significantly more in patients compared to controls (patients vs. controls, 2.4±0.4 vs. 1.8±0.2, p = 0.01). While performing the EHC task, there was a significant correlation of the Writer's Cramp Rating Score with the average saccadic speed (-0.61, p = 0.016), peak saccadic deceleration (0.59, p = 0.019) and average saccadic acceleration (-0.63, p = 0.012).

Discussion

Saccadic acceleration and latency are abnormal while performing EHC tasks in patients with WC. Our study gives further insights into the possible role of the cerebellum in the pathogenesis of WC.

Orofacial Involuntary Movements in Neurosyphilis: Beyond the Candy Sign

Background

Involvement of the central nervous system in patients with syphilis (neurosyphilis) may result in several neuropsychiatric symptoms. Rarely, patients with neurosyphillis may develop movement disorders with different phenomenology. Subtle orofacial dyskinesias have been reported in patients with neurosyphilis, known as the candy sign.

Case Report

We describe a patient with neurosyphilis who presented with severe orofacial involuntary movements.

Discussion

Our patient had orofacial movements at presentation and severity of the movements was much higher than the candy sign that has been reported in patients with neurosyphilis. This report contributes towards the ever-expanding clinical spectrum of neurosyphilis.

Handwriting Analysis in Parkinson's Disease: Current Status and Future Directions

BACKGROUND

The majority of patients with Parkinson's disease (PD) have handwriting abnormalities. Micrographia (abnormally small letter size) is the most commonly reported and easily detectable handwriting abnormality in patients with PD. However, micrographia is perhaps the tip of the iceberg representing the handwriting abnormalities in PD. Digitizing tablet technology, which has evolved over the last 2 decades, has made it possible to study the pressure and kinematic features of handwriting. This has resulted in a surge of studies investigating graphomotor impairment in patients with PD.

METHODS

The objectives of this study were to review the evolution of the kinematic analysis of handwriting in PD and to provide an overview of handwriting abnormalities observed in PD along with future directions for research in this field. Articles for review were searched from the PubMed and SCOPUS databases.

RESULTS

Digitizing tablet technologies have resulted in a shift of focus from the analysis of only letter size to the analysis of several kinematic features of handwriting. Studies based on the kinematic analysis of handwriting have revealed that patients with PD may have abnormalities in velocity, fluency, and acceleration in addition to micrographia. The recognition of abnormalities in several kinematic parameters of handwriting has given rise to the term PD dysgraphia. In addition, certain kinematic properties potentially may be helpful in distinguishing PD from other parkinsonian disorders.

CONCLUSION

The journey from micrographia to PD dysgraphia is indeed a paradigm shift. Further research is warranted to gain better insight into the graphomotor impairments in PD and their clinical implications.