Parkinsonism following dystonia in three patients

Hypertonia of the Big Toe Revealing Parkinson's Disease: A Case Report

Despite being less commonly discussed than other motor symptoms such as tremors and bradykinesia, hypertonia of the hallux holds diagnostic and prognostic significance in Parkinson's disease (PD). This motor anomaly is dissected within the context of the broader clinical spectrum of PD symptoms, emphasizing its importance alongside its cardinal symptoms. This case report underscores the importance of accurate clinical assessment especially thorough neurological evaluation in discerning hallux hypertonia, potentially enabling early disease recognition and intervention. By synthesizing these clinical insights, we trust that this case report contributes to an enhanced understanding of hypertonia of the hallux as a distinctive clinical presentation in PD fostering improved diagnostic precision.

New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN

Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.

Dystonia and Parkinson's disease: Do they have a shared biology?

Parkinsonism and dystonia co-occur across many movement disorders and are most encountered in the setting of Parkinson's disease. Here we aim to explore the shared neurobiological underpinnings of dystonia and parkinsonism through the clinical lens of the conditions in which these movement disorders can be seen together. Foregrounding the discussion, we briefly review the circuits of the motor system and the neuroanatomical and neurophysiological aspects of motor control and highlight their relevance to the proposed pathophysiology of parkinsonism and dystonia. Insight into shared biology is then sought from dystonia occurring in PD and other forms of parkinsonism including those disorders in which both can be co-expressed simultaneously. We organize these within a biological schema along with important questions to be addressed in this space.

Parkinsonism and dystonia: Clinical spectrum and diagnostic clues

The links between the two archetypical basal ganglia disorders, dystonia and parkinsonism, are manifold and stem from clinical observations, imaging studies, animal models and genetics. The combination of both, i.e. the syndrome of dystonia-parkinsonism, is not uncommonly seen in movement disorders clinics and has a myriad of different underlying aetiologies, upon which treatment and prognosis depend. Based on a comprehensive literature review, we delineate the clinical spectrum of disorders presenting with dystonia-parkinsonism. The clinical approach depends primarily on the age at onset, associated neurological or systemic symptoms and neuroimaging. The tempo of disease progression, and the response to L-dopa are further important clues to tailor diagnostic approaches that may encompass dopamine transporter imaging, CSF analysis and, last but not least, genetic testing. Later in life, sporadic neurodegenerative conditions are the most frequent cause, but the younger the patient, the more likely the cause is unravelled by the recent advances of molecular genetics that are focus of this review. Here, knowledge of the associated phenotypic spectrum is key to guide genetic testing and interpretation of test results. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Na+ leak-current channel (NALCN) at the junction of motor and neuropsychiatric symptoms in Parkinson's disease

Parkinson's disease (PD) is a debilitating movement disorder often accompanied by neuropsychiatric symptoms that stem from the loss of dopaminergic function in the basal ganglia and altered neurotransmission more generally. Akinesia, postural instability, tremors and frozen gait constitute the major motor disturbances, whereas neuropsychiatric symptoms include altered circadian rhythms, disordered sleep, depression, psychosis and cognitive impairment. Evidence is emerging that the motor and neuropsychiatric symptoms may share etiologic factors. Calcium/ion channels (CACNA1C, NALCN), synaptic proteins (SYNJ1) and neuronal RNA-binding proteins (RBFOX1) are among the risk genes that are common to PD and various psychiatric disorders. The Na⁺ leak-current channel (NALCN) is the focus of this review because it has been implicated in dystonia, regulation of movement, cognitive impairment, sleep and circadian rhythms. It regulates the resting membrane potential in neurons, mediates pace-making activity, participates in synaptic vesicle recycling and is functionally co-localized to the endoplasmic reticulum (ER)-several of the major processes adversely affected in PD. Here, we summarize the literature on mechanisms and pathways that connect the motor and neuropsychiatric symptoms of PD with a focus on recurring relationships to the NALCN. It is hoped that the various connections outlined here will stimulate further discussion, suggest additional areas for exploration and ultimately inspire novel treatment strategies.

Development of parkinsonism after long-standing cervical dystonia - A cohort

INTRODUCTION

Dystonia occurring in the context of parkinsonism is well-known, e.g. as foot dystonia in young-onset Parkinson's disease (PD), anterocollis in multisystem atrophy (MSA) or blepharospasm (levator inhibition) in progressive supranuclear palsy. We have, however, encountered a series of patients whose phenotype differed from the above described entities.

METHODS

We describe a cohort of patients in whom typical idiopathic isolated (primary) late-onset focal or segmental (predominantly cervical) dystonia preceded the development of parkinsonism by several years, sometimes decades.

RESULTS

In a cohort of 450 patients followed in our botulinum toxin injections clinic, we identified 11 (2.4%; 7 women) who developed parkinsonism at a median of 14 years after the onset of dystonia. Median age at onset of parkinsonism was 70 years (range 59-87), usually manifesting with a new tremor or a change of tremor pattern, complaints of 'slowing down' or new walking difficulties. Parkinsonism resembled PD in 5 (one pathologically confirmed); the remainder had atypical parkinsonism of MSA (n = 3) or indeterminate phenotype (n = 3).

CONCLUSION

The relatively frequent occurrence of parkinsonism after long-standing dystonia would suggest a link between the two, in line with evidence from other clinical reports, imaging studies, animal models and genetics. It appears that in some cases of dystonia this could be an antecedent manifestation of a syndrome with parkinsonism developing later, or be a risk factor for parkinsonism. In practice, it is important for clinicians to be alert to new symptoms/signs in patients with long-standing dystonia. From a research point of view, longitudinal case-control studies would be required to further investigate the link between long-standing dystonia and subsequent parkinsonism.

Cervical Dystonia Resolving After the Onset of Parkinson's Disease

Dystonia can occur in Parkinson's disease (PD). Dystonia usually presents during the course of the disease or as a side effect of medication. The development of cervical dystonia (CD) before the onset of PD is uncommon but has been described. Complete resolution of CD has not been described to date. We demonstrate a 71-year-old man with a four-year history of CD, who presented with prodromal PD symptoms. Three years later, he was diagnosed with PD. Shortly after initiating treatment for PD, his cervical dystonia started to improve, and eventually, he had complete resolution of CD approximately after two years of PD treatment. In conclusion, the pathological basis of this association is not well understood, but it is important to note that the globus pallidus internus (GPi) plays an important role in connecting these two disorders at a pathological level and as a target for surgery. Increased activity in the GPi may cause resolution of the CD by decreasing unintentional thalamocortical activity.

Index Finger Pointing (Likely a Subtle Form of Hand Dystonia): Prevalence Across Movement Disorders

Objective: To investigate the prevalence of index finger pointing (IFP) while walking, which is likely a subtle form of hand dystonia, in cranio-cervical focal dystonia syndromes, Parkinson's disease (PD), essential tremor (ET), and controls. Methods: We recruited patients with an established diagnosis of PD, dystonia, or ET and healthy controls. All participants were videotaped while walking. Videotapes were evaluated by the authors, blinded to diagnosis, to assess the presence or absence of IFP. Results: Two-hundred-fifty participants included 50 dystonia, 50 PD, 80 ET and 70 controls. IFP was present in 29/250 (11.6%) participants: 10 dystonia (20.0%), 8 PD (16.0%), 8 ET (10.0%), and 3 controls (3.8%) (p = 0.03). There was a significant evidence of a trend in the odds of having this sign among disorders with higher risk of dystonic features (dystonia>PD>ET>control; test for trend = 0.004). Among the 180 patients (dystonia, PD, and ET, i.e., excluding the 70 controls), IFP was present in 26 (14.4% prevalence). Conclusion: IFP during gait, likely a subtle form of hand dystonia, was observed in 14.4% of movement disorder patients. The highest prevalence was in dystonia, the second highest in a disease that is often accompanied by dystonia (PD), a lower prevalence among individuals with a disease that is rarely accompanied by dystonia (ET), and the lowest in controls.

A case of Parkinson's disease following dystonia

Parkinsonism and dystonia are both disorders of the extrapyramidal motor system, and some patients exhibit a complex of the two symptoms. Although several reports have referred to the coexistence of these disorders as parkinsonian disorders with dystonia, in the majority of cases, dystonia appeared after parkinsonism. DAT-scan is useful for the early diagnosis of Parkinson's disease (PD) and other types of parkinsonism such as dementia with Lewy bodies. This case report describes a 67-year old woman diagnosed with axial dystonia without parkinsonism 6 years previously, which had worsened despite treatment with Botulinum toxin injections, and hindered the patient's gait. The patient visited the hospital because of gait disturbances and DAT-scan showed a levodopa transducer decrease in the putamen. A few weeks later, she was re-admitted to hospital and exhibited Parkinsonism. Levodopa improved the gait disturbances but axial dystonia was unchanged, and a clinical diagnosis of PD was made. In the authors' opinion, this was a rare case of parkinsonian disorders with dystonia, characterized by the development of PD after dystonia. DAT-scan may be helpful for the diagnosis of patients with parkinsonian disorders with dystonia.

The Dystonias

Dystonia is a difficult problem for both the clinician and the scientist. It is sufficiently common to be seen by almost all physicians, yet uncommon enough to prevent any physician from gaining broad experience in its diagnosis and treatment. Each case represents a difficult challenge even to the specialist. The basic scientist is faced with investigating a disorder that is without relevant animal models and which is so rare that obtaining suitable tissue for study is a major obstacle. Dystonia may be idiopathic, or associated with lesions from many sources, including a variety of rare diseases. If idiopathic, it may be genetically transmitted or sporadic. If genetically transmitted, it may be generalized or focal, with symptoms varying in different members of the same family. It may be refractory to treatment, or it may respond to any one of a number of individual drugs that have very different mechanisms of action. For idiopathic dystonias, no clear method of genetic transmission has been established and no consistent pathology identified.

Convergent mechanisms in etiologically-diverse dystonias

INTRODUCTION

Dystonia is a neurological disorder associated with twisting motions and abnormal postures, which compromise normal movements and can be both painful and debilitating. It can affect a single body part (focal), several contiguous regions (segmental), or the entire body (generalized), and can arise as a result of numerous causes, both genetic and acquired. Despite the diversity of causes and manifestations, shared clinical features suggest that common mechanisms of pathogenesis may underlie many dystonias.

AREAS COVERED

Shared themes in etiologically-diverse dystonias exist at several biological levels. At the cellular level, abnormalities in the dopaminergic system, mitochondrial function and calcium regulation are often present. At the anatomical level, the basal ganglia and the cerebellum are frequently implicated. Global CNS dysfunction, specifically aberrant neuronal plasticity, inhibition and sensorimotor integration, are also observed in a number of dystonias. Using clinical data and data from animal models, this article seeks to highlight shared pathways that may be critical in understanding mechanisms and identifying novel therapeutic strategies in dystonia.

EXPERT OPINION

Identifying shared features of pathogenesis can provide insight into the biological processes that underlie etiologically diverse dystonias, and can suggest novel targets for therapeutic intervention that may be effective in a broad group of affected individuals.

Dystonia in Parkinson’s disease

Dystonia can occasionally be found in idiopathic Parkinson's disease. It is very uncommon in untreated patients and is more frequently seen as a complication of its treatment. In this review, the various types of dystonia occurring in PD, the differential diagnosis with other parkinsonian syndromes associated with dystonia and treatments available are revised. Dystonia unrelated to treatment can be typical (blepharospasm, torticollis), atypical (parkinsonian writer's cramp, camptocormia, anismus), or occurring in earlyonset Parkinson disease (the so-called kinesigenic foot dystonia, considered a hallmark of early-onset Parkinson's disease). Early and prominent dystonia in untreated patients with parkinsonism should raise the suspicion of other entities other than Parkinson's disease, such as progressive supranuclear palsy, multiple system atrophy or corticobasal degeneration. In patients on chronic dopaminergic treatment, peak-dose dystonia, diphasic dystonia and off-dystonia can be seen. The later constitutes the major dystonic feature of chronic levodopa therapy, and a wide variety of strategies are available to manage this complication. Among them, deep brain stimulation of the subthalamic nucleus has proved to be the most effective one. Dystonic reactions (mainly involving oculomotor cranial nerves and limbs) in operated patients (especially carriers of deep brain stimulation (DBS) devices) are increasingly being reported, constituting a new type of dystonia in patients with Parkinson's disease: dystonia linked to surgical treatment.

Dystonia and parkinsonism

Parkinsonism and dystonia may coexist in a number of neurodegenerative, genetic, toxic, and metabolic disorders and as a result of structural lesions in the basal ganglia. Parkinson's disease (PD) and the 'Parkinson-plus' syndromes (PPS) account for the majority of patients with the parkinsonism-dystonia combination. Dystonia, particularly when it involves the foot, may be the presenting sign of PD or PPS and these disorders should be suspected when adults present with isolated foot dystonia. Young age, female gender, and long disease duration are risk factors for PD-related dystonia, but dystonia in patients with PD is usually related to levodopa therapy. The mechanism of dystonia in PD is not well understood and the management is often challenging because levodopa and other dopaminergic agents may either improve or worsen dystonia. Other therapeutic strategies include oral medications (baclofen, anticholinergics and benzodiazepines), local injections of botulinum toxin, intrathecal baclofen, and surgical lesions or high frequency stimulation of the thalamus, globus pallidus, or subthalamus.

A family with hereditary juvenile dystonia-parkinsonism

We report a family with autosomal dominant type hereditary juvenile dystonia-parkinsonism in which eight members in three generations exhibited parkinsonism, sleep benefit, marked efficacy of levodopa, wearing-off phenomenon, and dopa-induced choreic dyskinesia. However, one case showed mainly dystonic movement that worsened after administration of levodopa. The patients in this family showed neck dystonia, such as torticollis and retrocollis, in addition to foot dystonia and other dystonic movement, such as frequently lifting the thigh. From the family history and clinical findings, these patients are considered to have a specific form of hereditary dystonia-parkinsonism.

Genetic mapping of "Lubag" (X-linked dystonia-parkinsonism) in a Filipino kindred to the pericentromeric region of the X chromosome

"Lubag" is an X-linked disorder causing dystonia and parkinsonism that has only been described in families from the Philippines, principally from the island of Panay. We have established linkage between the disease phenotype "lubag" and DNA markers which span the Xp11.22-Xq21.3 region by using a large Filipino family with 8 affected men in three generations. These DNA markers define an interval of about 20 centimorgans in the pericentromeric region of the X chromosome as the most likely site of the disease locus XDPD (X-linked dystonia-parkinsonism). XDPD has a maximum multipoint log likelihood ratio score (Zmax) of about 4.6 over the interval from Xq12 to Xq21.31 (DXS159-DXYS1X). The co-occurrence of dystonia and parkinsonism in lubag and in other known disorders suggests there may be a common pathogenetic mechanism. Identification of the genetic defect in this family may provide an important clue toward understanding the pathogenesis and pathophysiology of both dystonia and parkinsonism.

Ocular movements in essential blepharospasm

In essential blepharospasm histopathologic and electrophysiologic evidence supports the existence of lesions in proximity to brainstem nuclei controlling ocular movements. We studied horizontal ocular movements in eight patients who had been treated previously with surgery or botulinum toxin injection to control essential blepharospasm (mean age, 58 years) and compared these with seven control subjects who did not have blepharospasm (mean age, 68 years). We examined fixation stability, saccades, the vestibulo-ocular reflex, visual enhancement and suppression of the vestibulo-ocular reflex, optokinetic nystagmus, and pursuit by using digitally sampled, direct current electro-oculography. Patients with blepharospasm exhibited no ocular movement abnormalities. Since quantitative aspects of ocular movements are sensitive to nonspecific brainstem lesions, the absence of abnormal ocular movements suggests that the lesion in blepharospasm is specifically limited to neurons regulating the facial muscles.

New approaches in the treatment of the dystonias

At this point the treatment of dystonias remains highly empirical. Secondary dystonias, especially those related to specific drug treatment, have to be ruled out carefully. A few dystonic subgroups respond well to levodopa medication. In the other syndromes, anticholinergics are the usual first choice. In focal conditions botulinum toxin injections seem to be the most effective regimen, although there are only a few long-term studies. Surgical procedures are an ultimate option.

Clinical variants of idiopathic torsion dystonia

Some patients with dystonic movements and postures not known to be caused by environmental or degenerative disorders can be segregated from classical-appearing idiopathic torsion dystonia on the basis of distinctive clinical and pharmacologic features. Many of them should be considered within the family of dystonia, as clinical variants of idiopathic torsion dystonia, while others are better classified as being part of other families of dyskinesias. In the former group are paradoxical dystonia, myoclonic dystonia, diurnal dystonia, and dopa-responsive dystonia. The latter group consists of dystonic tics and the various entities comprising paroxysmal dystonia, namely kinesigenic, nonkinesigenic and hypnogenic dystonia.

Hypokinesia and rigidity as clinical manifestations of mitochondrial encephalomyopathy: report of three cases

Three patients are reported with a neurological disorder in which hypokinesia and rigidity were the most prominent clinical signs. On CT scan and MRI, two were found to have bilateral lesions in the striatum, mainly in the putamen, and the third had bilateral lesions in the posterior limb of the internal capsule. Laboratory investigations suggested abnormal pyruvate metabolism in all three cases, which was confirmed to skeletal muscle in two cases. In the third the cause was a NADH dehydrogenase defect. The signs and symptoms, the bilateral striatal lesions in two of the patients, and the abnormal pyruvate metabolism justify a classification of mitochondrial encephalomyopathy, resembling Leigh syndrome. This diagnosis must be considered for infants and children presenting with Parkinsonian signs, and mitochondrial energy metabolism should be investigated.

Paraneoplastic degeneration of the substantia nigra with dystonia and parkinsonism

A 42-year-old woman suffered unexplained weight loss followed by action tremor and difficulty initiating gait. Three months after onset of symptoms, infiltrating ductal carcinoma of the breast, metastatic to liver and lymph nodes, was diagnosed and treated briefly with cyclophosphamide, methotrexate, and 5-flourouracil (5FU). Severe symmetric action and postural tremor with a myoclonic component developed, with minimal rest tremor, severe dysarthria and dysphagia, small-stepped and slightly ataxic gait progressing to a bedbound state, and severe widespread dystonic posturing. The latter began as a typical parkinsonian posture of trunk and upper extremities and progressed to a fixed and painful flexion of the elbows and wrists and extension of fingers and neck. Sinemet, anticholinergics, baclofen, diazepam, and plasmapheresis gave no benefit. The patient died of complications of immobility 5 months after neurologic symptom onset. Autopsy revealed many pigment-laden macrophages in substantia nigra and moderate loss of pigmented neurons. Inflammation, Lewy bodies, and tumor were absent. Cerebellar Purkinje cells were moderately depleted. Mild neuronal loss and gliosis were present in globus pallidus and cerebellar cortex. Stains for anti-human IgG, IgM, kappa, and lambda were negative. This, to our knowledge, is the first report of paraneoplastic degeneration of substantia nigra or paraneoplastic parkinsonism.

Constipation and paradoxical puborectalis contraction in anismus and Parkinson's disease: a dystonic phenomenon?

Anismus, or constipation due to functional obstruction at the pelvic outlet by paradoxical contraction of the striated sphincter muscles during defaecation straining, is described in ten constipated patients and four patients with Parkinson's disease and constipation. The dysfunctional pattern of muscle recruitment resembled that characteristic of dystonia elsewhere in the body and was indistinguishable in patients with idiopathic anismus and those with extrapyramidal motor disturbance due to Parkinson's disease. These findings suggest that anismus may be a focal dystonic phenomenon.

Meige syndrome: neuropathology of a case

Primary Meige syndrome is a form of cranial dystonia of unknown cause. Only three postmortem studies have been reported, and the results of these studies have not been consistent. We have examined the brain of a 72-year-old man with typical primary Meige syndrome and found mild to moderate cell loss in the zona compacta of the substantia nigra, locus ceruleus, midbrain tectum, and dentate nucleus of the cerebellum. Also frequent Lewy bodies were present in pigmented nuclei of the brainstem. No abnormalities were detected elsewhere. These pathological findings support the notion that brainstem pathology is important in the pathophysiology of cranial dystonia.

Dystonia in Parkinson's disease: clinical and pharmacological features

We studied the features of dystonia in 9 patients with untreated idiopathic Parkinson's disease and in 56 patients on sustained treatment with L-dopa. Dystonia was seen as an initial symptom in patients with both early- and late-onset Parkinson's disease and included action dystonia of the limbs and cranial dystonia. Although the coexistence of parkinsonism and dystonia suggests a common pathophysiology, antiparkinsonian drugs did not consistently influence dystonic spasms. L-dopa-induced dystonia was seen as an off-period, biphasic, or peak-dose phenomenon. Each type showed a distinctive pattern of localization of dystonic spasms, possibly reflecting neurochemical aspects of basal ganglia somatotopy. Neuropharmacological studies performed in 12 patients suggest that off-period dystonia is genuinely induced by L-dopa and best relieved by antiparkinsonian agents.