[Essential tremor: are we just splitting hairs? Non-motor symptoms and essential tremor-plus]

INTRODUCTION

The existence of non-motor symptoms in essential tremor (ET) and the appearance of a new condition, ET-plus, are two controversial issues.

AIMS

To offer a review of the current status of these two topics.

DEVELOPMENT

We performed an analysis of the studies conducted on non-motor symptoms in ET and of the articles for and against the use of the term ET-plus.

CONCLUSIONS

Non-motor symptoms have gained increased recognition as a feature accompanying ET. Several studies have documented its presence compared to matched controls. It is not clear, however, whether these non-motor symptoms would be part of the spectrum of ET symptoms (a primary phenomenon) or whether they would be symptoms that appear as a consequence of the physical or psychological disability produced by the clinical signs and symptoms of ET itself (a secondary phenomenon). For the time being, their evaluation and treatment are not included within the standard assessment of patients with ET. In view of the heterogeneous phenotype, the term ET-plus aims to improve phenotypic homogeneity for genetic or therapeutic studies. Yet, there is no pathological basis, and epidemiological, genetic and therapeutic research studies have numerous drawbacks. In the absence of clear objective biomarkers, distinguishing between ET and ET-plus by clinical distinction alone is very complex. We should be cautious about using new terms that are not yet backed by sound scientific evidence.

Non-Persistence of Tremorolytic Effect of Perampanel in Essential Tremor: Real-World Experience with 50 Patients

Background

We describe our experience of using perampanel to treat essential tremor (ET) over 12 months.

Methods

We enrolled 50 ET patients in an open-label trial. Perampanel was titrated to 4 mg/day as adjuvant therapy. The main outcome measures were baseline, +1, +3, +6, and + 12 month scores of the Tremor Clinical Rating Scale (TCRS) and the Glass scale (GS).

Results

Twenty patients withdrew because of adverse effects. At +1 month, 27 of 30 patients improved: 68% reduction in both TCRS 1 + 2 (P < 0.001) and TCRS 3 (P < 0.001); TCRS 4 + 1.8 and GS 1.1 point reduction. By +12 months non-persistence of therapeutic effect occurred in 70% of patients: the mean reduction in TCRS 1 + 2 was 33% (P = 0.03), TCRS 3 (0.04), TCRS 4 + 0.8, GS 0.2 points reduction.

Conclusions

We report important peramapanel acute tremorolytic effects, but poor tolerance to adverse effects and a non-sustained therapeutic effect in most patients.

Comparison of the Results of a Parkinson's Holter Monitor With Patient Diaries, in Real Conditions of Use: A Sub-analysis of the MoMoPa-EC Clinical Trial

Background

For specialists in charge of Parkinson's disease (PD), one of the most time-consuming tasks of the consultations is the assessment of symptoms and motor fluctuations. This task is complex and is usually based on the information provided by the patients themselves, which in most cases is complex and biased. In recent times, different tools have appeared on the market that allow automatic ambulatory monitoring. The MoMoPa-EC clinical trial (NCT04176302) investigates the effect of one of these tools—Sense4Care's STAT-ON—can have on routine clinical practice. In this sub-analysis the agreement between the Hauser diaries and the STAT-ON sensor is analyzed.

Methods

Eighty four patients from MoMoPa-EC cohort were included in this sub-analysis. The intraclass correlation coefficient was calculated between the patient diary entries and the sensor data.

Results

The intraclass correlation coefficient of both methods was 0.57 (95% CI: 0.3–0.73) for the OFF time (%), 0.48 (95% CI: 0.17–0.68) for the time in ON (%), and 0.65 (95% CI%: 0.44–0.78) for the time with dyskinesias (%). Furthermore, the Spearman correlations with the UPDRS scale have been analyzed for different parameters of the two methods. The maximum correlation found was −0.63 (p < 0.001) between Mean Fluidity (one of the variables offered by the STAT-dON) and factor 1 of the UPDRS.

Conclusion

This sub-analysis shows a moderate concordance between the two tools, it is clearly appreciated that the correlation between the different UPDRS indices is better with the STAT-ON than with the Hauser diary.

Trial Registration

https://clinicaltrials.gov/show/NCT04176302 (NCT04176302).

Is essential tremor a disorder of primary GABA dysfunction? Yes

Dysfunction in gamma-aminobutyric acid (GABA) neurotransmission has emerged as a prime suspect for the underlying neurochemical dysfunction in essential tremor (ET). This dysfunction has been termed the GABA hypothesis. We review findings to date supporting the 4 steps in this hypothesis in studies of cerebrospinal fluid, pathology, genetics, animal models, imaging, computational models, and human drugs, while not overlooking the evidence of negative studies and controversies. It remains to be elucidated whether reduced GABAergic tone is a primary contributing factor to ET pathophysiology, a consequence of altered Purkinje cell function, or even a result of Purkinje cell death. More studies are clearly needed to confirm both the neurodegenerative nature of ET and the reduction in GABA activity in the cerebellum. Also necessary is to test further therapies to enhance GABA transmission specifically focused on the cerebellar area.

Tipping the scales: how clinical assessment shapes the neural correlates of Parkinson's disease mild cognitive impairment

Mild cognitive impairment in Parkinson's disease (PD-MCI) is associated with consistent structural and functional brain changes. Whether different approaches for diagnosing PD-MCI are equivalent in their neural correlates is presently unknown. We aimed to profile the neuroimaging changes associated with the two endorsed methods of diagnosing PD-MCI. We recruited 53 consecutive non-demented PD patients and classified them as PD-MCI according to comprehensive neuropsychological examination as operationalized by the Movement Disorders Task Force. Voxel-based morphometry, cortical thickness, functional connectivity and graph theoretical measures were obtained on a 3-Tesla MRI scanner. 18 patients (32%) were classified as PD-MCI with Level-II criteria, 19 (33%) with the Parkinson's disease Cognitive Rating Scale (PD-CRS) and 32 (60%) with the Montreal Cognitive Assessment (MoCA) scale. Though regions of atrophy differed across classifications, reduced gray matter in the precuneus was found using both Level-II and PD-CRS classifications in PD-MCI patients. Patients diagnosed with the PD-CRS also showed extensive changes in cortical thickness, concurring with the MoCA in regions of the cingulate cortex, and again with Level-II regarding cortical thinning in the precuneus. Functional connectivity analysis found higher coherence within salience network regions of interest, and decreased anticorrelations between salience/central executive and default-mode networks in the PD-CRS classification for PD-MCI patients. Graph theoretical metrics showed a widespread decrease in node degree for the three classifications in PD-MCI, whereas betweenness centrality was increased in select nodes of the default mode network (DMN). Clinical and neuroimaging commonalities between the endorsed methods of cognitive assessment suggest a corresponding set of neural correlates in PD-MCI: loss of structural integrity in DMN structures, mainly the precuneus, and a loss of weighted connections in the salience network that might be counterbalanced by increased centrality in the DMN. Furthermore, the similarity of the results between exhaustive Level-II and screening Level-I tools might have practical implications in the search for neuroimaging biomarkers of cognitive impairment in Parkinson's disease.

Exome-wide rare variant analysis in familial essential tremor

INTRODUCTION

Essential tremor (ET) is one of the most common movement disorders. Despite its high prevalence and heritability, its genetic etiology remains elusive with only a few susceptibility genes identified and poorly replicated. Our aim was to find novel candidate genes involved in ET predisposition through whole exome sequencing.

METHODS

We studied eight multigenerational families (N = 40 individuals) with an autosomal-dominant inheritance using a comprehensive strategy combining whole exome sequencing followed by case-control association testing of prioritized variants in a separate cohort comprising 521 ET cases and 596 controls. We further performed gene-based burden analyses in an additional dataset comprising 789 ET patients and 770 healthy individuals to investigate whether there was an enrichment of rare deleterious variants within our candidate genes.

RESULTS

Fifteen variants co-segregated with disease status in at least one of the families, among which rs749875462 in CCDC183, rs535864157 in MMP10 and rs114285050 in GPR151 showed a nominal association with ET. However, we found no significant enrichment of rare variants within these genes in cases compared with controls. Interestingly, MMP10 protein is involved in the inflammatory response to neuronal damage and has been previously associated with other neurological disorders.

CONCLUSIONS

We prioritized a set of promising genes, especially MMP10, for further genetic and functional studies in ET. Our study suggests that rare deleterious coding variants that markedly increase susceptibility to ET are likely to be found in many genes. Future studies are needed to replicate and further infer biological mechanisms and potential disease causality for our identified genes.

Measuring impulsivity in Parkinson's disease: a correlational and structural neuroimaging study using different tests

BACKGROUND AND PURPOSE

Impulsivity is an aspect of personality and a major component of multiple neuropsychiatric conditions. In Parkinson's disease, it has been associated with the expression of impulse control disorders, a highly prevalent non-motor complication. Even though multiple tests of impulsivity have been used in this context, the impact of test choice has not been addressed. The aim was to evaluate whether different impulsivity measures in Parkinson's disease share substantial inter-scale and anatomical correlations or rather mirror different underlying phenomena.

METHODS

In a consecutive sample of 89 Parkinson's disease patients without impulse control disorders, four common tests were evaluated assessing different aspects of impulsivity: impulsiveness trait, decisions under implicit risk with and without losses, and delay discounting. Correlations among test scores were analysed and each score was used as a regressor in a set of grey matter volume (GMV) voxel-based morphometry analyses to explore their brain structural correlates.

RESULTS

No significant correlations were found between the different impulsivity tests. Furthermore, their structural brain correlates were divergent. Impulsiveness trait appeared to be associated with lower GMV in dorsal-lateral prefrontal cortices, implicit risk (with losses) with higher GMV in the left nucleus accumbens and lower left insular GMV, implicit risk (without losses) with higher GMV in the left lingual gyrus and lower GMV in the gyri recti and delay discounting with higher GMV in the left nucleus accumbens.

CONCLUSIONS

In Parkinson's disease, different impulsivity measures reflect very dissimilar behavioural and brain structural correlates. Our results suggest that parkinsonian impulsivity is not a unitary phenomenon but rather a heterogeneous entity.

Primary Orthostatic Tremor: Experience of Perampanel Use in 20 Patients

Background

Primary orthostatic tremor (POT) is a rare disorder for which current treatments are largely ineffective. Following up on our recent report of complete resolution of POT symptoms in a patient using low doses of perampanel, we describe our experience of perampanel in 20 patients.

Methods

Twenty patients whose neurologists prescribed perampanel were recruited. Initial dose was 2 mg/day, which was increased to 4 mg/day after the first month. Treatment efficacy was self-scored from +3 to -3 at 1 and 3 months.

Results

Eight patients withdrew due to adverse effects. Of the 12 patients who completed the study, 92% indicated that their POT symptoms had improved after 1 month, with 75% indicating moderate to marked improvement (mean score 1.9 ± 0.9). This improvement was not sustained by follow-up at 3 months (mean score 0.9 ± 1.3). A rebound of POT symptoms that lasted 2-6 weeks was observed in most patients who withdrew.

Discussion

Our experience with this series of cases points to the potential of low-dose perampanel as a treatment for POT, although poor tolerance and the possibility of a non-persistent therapeutic benefit need to be considered. Controlled studies are needed to confirm these findings.

A divergent breakdown of neurocognitive networks in Parkinson's Disease mild cognitive impairment

Cognitive decline is a major disabling feature in Parkinson's disease (PD). Multimodal imaging studies have shown functional disruption in neurocognitive networks related to cognitive impairment. However, it remains unknown whether these changes are related to gray matter loss, or whether they outline network vulnerability in the early stages of cognitive impairment. In this work, we intended to assess functional connectivity and graph theoretical measures and their relation to gray matter loss in Parkinson's disease with mild cognitive impairment (PD-MCI). We recruited 53 Parkinson's disease patients and classified them for cognitive impairment using Level-1 Movement Disorders Society-Task Force Criteria. Voxel-based morphometry, functional connectivity and graph theoretical measures were obtained on a 3-Tesla MRI scanner. Loss of gray matter was observed in the default mode network (bilateral precuneus), without a corresponding disruption of functional or graph theoretical properties. However, functional and graph theoretical changes appeared in salience network nodes, without evidence of gray matter loss. Global cognition and executive scores showed a correlation with node degree in the right anterior insula. We also found a correlation between visuospatial scores and right supramarginal gyrus node degree. Our findings highlight the loss of functional connectivity and topological features without structural damage in salience network regions in PD-MCI. They also underline the importance of multimodal hubs in the transition to mild cognitive impairment. This functional disruption in the absence of gray matter atrophy suggests that the salience network is a key vulnerable system at the onset of mild cognitive impairment in PD.

Isolated Propriospinal Myoclonus as a Presentation of Cervical Myelopathy

Background

Propriospinal myoclonus is an infrequent type of hyperkinetic movement that can be commonly idiopathic but also may occur after spinal cord lesions.

Phenomenology Shown

We describe an 8-year-old female showing repetitive flexor and extensor arrhythmic brief jerks of the trunk, compatible with propriospinal myoclonus secondary to cervical myelopathy.

Educational Value

Isolated propriospinal myoclonus may be the clinical sign that leads to the diagnosis of incipient myelopathy.

Complete Resolution of Symptoms of Primary Orthostatic Tremor with Perampanel

Background

Primary orthostatic tremor (POT) is an infrequent disorder whose physiopathology is unknown. Current medication is largely ineffective or only offers mild benefits.

Case Report

A 75-year-old female with refractory POT treated with 4 mg/day of perampanel achieved complete symptom resolution. Owing to adverse effects, the patient reduced intake to 2 mg/day, but even at this lower dose the benefit was maintained.

Discussion

We report the complete resolution of POT symptoms using low doses of perampanel, an antiepileptic drug that blocks glutamate-mediated post-synaptic excitation. Further controlled studies are necessary to confirm this finding.

Parkinson's Disease: Impulsivity Does Not Cause Impulse Control Disorders but Boosts Their Severity

Introduction: Impulse control disorders (ICDs) are a common complication of Parkinson's disease (PD) receiving dopamine agonist (DAA) Impulsivity is considered an underlying mechanism but evidence of this relationship is scarce. To explore the relationship between impulsivity and the presence and severity of ICD in PD. Methods: Prospective cross-sectional study of consecutive PD outpatients. Patients with dementia or previously known ICDs were excluded. Two measures of impulsivity were assessed: Barratt Impulsiveness Scale (BIS-11) for impulsiveness trait (main exposure) and commission errors in the Continuous Performance Test (CE) for motor inhibition. Main outcomes were diagnosis of ICD based on a comprehensive clinical interview and severity of ICD based on the Questionnaire for Impulsive-Compulsive Disorders. Results: Of 100 patients (mean [SD] age, 67.2 [8.8], 54 male), 31 had ICD. Patients with ICDs were 5.3 years younger (p = 0.01), used more frequently dopamine agonist (p = 0.02), alcohol (p = 0.009) and tobacco (p = 0.02). They were not more impulsive on BIS-11 (56 vs. 58, p = 0.23, adjusted p = 0.46) and CE (p = 0.96). No relationship was found between dopaminergic medications and impulsivity or ICD severity. Among patients with ICD, impulsivity was correlated with ICD severity (BIS-11 r = 0.33, p = 0.001, adjusted p = 0.002, CE r = 0.53, p = 0.006). Multivariate regression analysis confirmed the independent predictive role of both measures. Conclusions: Impulsivity is not associated with increased prevalence of ICD in PD but it is strongly linked to ICD severity. When considering dopamine replacement therapy, assessment of impulsivity may be a useful approach to detect those patients at risk of severe forms of ICD.

[Movement disorders units and management of motor fluctuations in advanced Parkinson's disease]

INTRODUCTION

Advanced Parkinson's disease (PD) entails complications, such as motor fluctuations. In Spain, medical attention for such cases is often provided in movement disorder units (MDU).

AIM

To gain further knowledge of the diagnostic resources and therapeutic approach of MDU.

SUBJECTS AND METHODS

A descriptive cross-sectional study was conducted. The researchers designed an on-line questionnaire, addressed to neurologists from MDUs, containing 48 questions about the resources they have available, the number of patients with PD and motor fluctuations that have been attended to, as well as the therapeutic approach, according to the Hoehn and Yahr (HY) scale.

RESULTS

Fifty-five neurologists participated. Structural neuroimaging is available to 100% of them; 89% have access to functional neuroimaging; 89% have acute pharmacological tests available for use; 78% have access to genetic tests; and 53% have transcranial ultrasound at their disposal. There are 2.5 neurologists and 1.2 nurses per unit. Of the patients with PD that they see, 19% of them are in HY stage 1, 59% are in HY stage 2-3 and 22% are in HY stage 4-5. Treatment consists, first of all, in monoamine oxidase type B inhibitors in HY stages 1 and 2, and levodopa in HY stages 3, 4 and 5. Twenty-four per cent of the patients have motor fluctuations, with 5.5 off episodes per day, lasting 44 minutes, with a total of seven off hours per day. Fourteen per cent of the patients under 70 years of age with more than three long-term off episodes per day are receiving invasive treatment for motor fluctuations.

CONCLUSIONS

MDUs are well equipped with diagnostic and pharmacological resources. Pharmacological treatments are tailored to each patient with a wide range of combinations. Despite this optimisation, the prevalence of motor fluctuations is still high in advanced patients, and invasive therapies may be underused.

Visual hallucinations in patients with acute stroke: a prospective exploratory study

BACKGROUND AND PURPOSE

The incidence, underlying physiopathology, features and association with lesion topography of visual hallucinations in acute stroke have scarcely been investigated.

METHODS

Patients with a diagnosis of acute stroke (ischaemic or haemorrhagic) in any vascular territory, admitted within 24 h after the onset of symptoms, were consecutively included in the study. Patients with a previous history of psychosis or cognitive impairment were excluded. They and/or their caregivers answered a structured hallucination and sleep questionnaire at admission, within the first 15 days and at the clinical follow-up 3-6 months after discharge. Lesion location (IMAIOS online atlas) and leukoaraiosis (Wahlund scale) were determined by magnetic resonance imaging or computed tomography scan. Subsets of patients also underwent a neuropsychological evaluation (N = 50) and an electroencephalogram (N = 33) before discharge.

RESULTS

In all, 77 patients with a mean age of 71 ± 12 years were included of whom 57.1% were men. The incidence of visual hallucinations was 16.7%. These hallucinations were mostly complex, in black and white and self-limited. The appearance of hallucinations was not influenced by age, sex, neuropsychological performance during admission or modified Rankin scale score at discharge. Visual hallucinations were associated with occipital cortex lesions (P = 0.04), and with sleep disturbances during and before admission (P = 0.041 and P = 0.03 respectively).

CONCLUSIONS

Visual hallucinations are relatively frequent in patients with acute stroke and they are self-limited. Patients with occipital lesions and sleep disturbances are more likely to suffer them.

Linking Essential Tremor to the Cerebellum: Neurochemical Evidence

The pathophysiology and the exact anatomy of essential tremor (ET) is not well known. One of the pillars that support the cerebellum as the main anatomical locus in ET is neurochemistry. This review examines the link between neurochemical abnormalities found in ET and cerebellum. The review is based on published data about neurochemical abnormalities described in ET both in human and in animal studies. We try to link those findings with cerebellum. γ-aminobutyric acid (GABA) is the main neurotransmitter involved in the pathophysiology of ET. There are several studies about GABA that clearly points to a main role of the cerebellum. There are few data about other neurochemical abnormalities in ET. These include studies with noradrenaline, glutamate, adenosine, proteins, and T-type calcium channels. One single study reveals high levels of noradrenaline in the cerebellar cortex. Another study about serotonin neurotransmitter results negative for cerebellum involvement. Finally, studies on T-type calcium channels yield positive results linking the rhythmicity of ET and cerebellum. Neurochemistry supports the cerebellum as the main anatomical locus in ET. The main neurotransmitter involved is GABA, and the GABA hypothesis remains the most robust pathophysiological theory of ET to date. However, this hypothesis does not rule out other mechanisms and may be seen as the main scaffold to support findings in other systems. We clearly need to perform more studies about neurochemistry in ET to better understand the relations among the diverse systems implied in ET. This is mandatory to develop more effective pharmacological therapies.

Ethosuximide for Essential Tremor: An Open-Label Trial

BACKGROUND

T-type calcium channel activation has been postulated to underlie rhythmicity in the olivo-cerebellar system that is implicated in ET. Ethosuximide reduces T-type calcium currents and can suppress tremor in two animal models of ET. We explored the effects of ethosuximide in subjects with ET in an open-label trial using both clinical scales and accelerometric recordings measures. We initially planned to conduct the trial with 15 patients, but due to lack of efficacy and a high incidence of adverse effects, the trial was stopped after seven patients had participated.

METHODS

Seven patients diagnosed with ET were included in the study. The ethosuximide dose was 500 mg daily (BID). The main outcome measures were: 1) tremor clinical rating scale (TCRS) score, 2) accelerometric recordings, and 3) self-reported disability scale score.

RESULTS

Five patients completed the study, and two dropped out due to adverse effects. There were no significant changes in clinical scores in motor task performance (TCRS 1+2), daily living activities (TCRS 3), or in the patients' subjective assessment (TCRS 4) and global appraisal. There were no differences observed for accelerometry data or disability scale scores. Anxiety, nervousness, headache, and dizziness were reported by two patients while on ethosuximide, causing them to stop the trial. No patient preferred to continue ethosuximide treatment.

DISCUSSION

The results of our exploratory study suggest that ethosuximide is not an effective treatment for ET.

[The essence of essential tremor: neurochemical bases]

INTRODUCTION

Essential tremor is the most frequent movement disorder in adults. It has been considered a benign disease, but can result in significant physical and psychosocial disability. Pharmacological treatment is still not very satisfactory. Its causation, pathophysiology and anatomy remain only partially understood.

AIMS

An understanding of its neurochemical basis is essential to be able to develop more efficient therapies. We review what is currently known in this field in order to motivate further research and ideas that allow an enhanced understanding of the disease and which foster the development of new pharmacological therapies.

DEVELOPMENT

We review the studies conducted to date in humans and in animal models of neurotransmitters (gamma-aminobutyric acid, glutamate, noradrenalin, serotonin, adenosine), proteins and other neurochemical phenomena, such as T-type calcium channels, in essential tremor.

CONCLUSIONS

Four neurochemical dysfunctions have been described that basically occur in the cerebellum and the inferior olivary nucleus: alteration of the GABAergic system, increased post-inhibitory rebound via T-type calcium currents, decreased neuronal inhibition mechanisms and an increase in excitatory neurotransmitter activity. These neurochemical dysfunctions would involve an increase in the activity of the deep neurons of the cerebellum with an oscillatory activity that would shift to the thalamic nucleus and the motor cortex, which in turn would lead to the appearance of tremor. Further research is needed to be able to confirm these hypotheses and to continue to advance towards achieving more efficient pharmacological treatments for patients with essential tremor.

Minor hallucinations occur in drug-naive Parkinson's disease patients, even from the premotor phase

OBJECTIVES

The description of minor hallucinatory phenomena (presence, passage hallucinations) has widened the spectrum of psychosis in Parkinson's disease (PD). Minor hallucinatory phenomena seem to antedate the development of more severe hallucinations. Early detection of minor hallucinations may be useful for screening patients with more severe endophenotypes. Motivated by the observation of "de novo," drug-naive PD patients reporting minor hallucinations, we aimed to prospectively identify "de novo" untreated PD patients experiencing hallucinatory phenomena, and to compare their clinico-demographic characteristics with those of untreated PD patients without hallucinations and healthy controls.

METHODS

Screening and description of psychosis was assessed by the Movement Disorders Society Unified Parkinson's Disease Rating Scale-Part I and a structured interview covering all types of psychotic phenomena reported in PD. Clinical, neuropsychological, and demographic data of PD patients with and without psychotic phenomena were compared with those of age- and education-matched healthy controls.

RESULTS

Fifty drug-naive, "de novo" PD patients and 100 controls were prospectively included. Minor hallucinations were experienced in 42% (21 of 50) PD patients and 5% controls (P < 0.0001). Coexistence of passage and presence hallucinations was the most common finding. Unexpectedly, 33.3% of patients with minor hallucinations manifested these as a pre-motor symptom, starting 7 months to 8 years before first parkinsonian motor symptoms. The presence of minor hallucinations was significantly associated with presence of rapid eye movement sleep behavior disorder.

CONCLUSIONS

In this first study to prospectively analyze the frequency of minor hallucinatory phenomena in incident, untreated PD patients, hallucinations appeared as a frequent early non-motor symptom that may even predate the onset of parkinsonism.

Missense mutations in TENM4, a regulator of axon guidance and central myelination, cause essential tremor

Essential tremor (ET) is a common movement disorder with an estimated prevalence of 5% of the population aged over 65 years. In spite of intensive efforts, the genetic architecture of ET remains unknown. We used a combination of whole-exome sequencing and targeted resequencing in three ET families. In vitro and in vivo experiments in oligodendrocyte precursor cells and zebrafish were performed to test our findings. Whole-exome sequencing revealed a missense mutation in TENM4 segregating in an autosomal-dominant fashion in an ET family. Subsequent targeted resequencing of TENM4 led to the discovery of two novel missense mutations. Not only did these two mutations segregate with ET in two additional families, but we also observed significant over transmission of pathogenic TENM4 alleles across the three families. Consistent with a dominant mode of inheritance, in vitro analysis in oligodendrocyte precursor cells showed that mutant proteins mislocalize. Finally, expression of human mRNA harboring any of three patient mutations in zebrafish embryos induced defects in axon guidance, confirming a dominant-negative mode of action for these mutations. Our genetic and functional data, which is corroborated by the existence of a Tenm4 knockout mouse displaying an ET phenotype, implicates TENM4 in ET. Together with previous studies of TENM4 in model organisms, our studies intimate that processes regulating myelination in the central nervous system and axon guidance might be significant contributors to the genetic burden of this disorder.

A randomized double-blind crossover trial of deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: a pilot study of relapse prevention

BACKGROUND

To date, antidepressant drugs show limited efficacy, leaving a large number of patients experiencing severe and persistent symptoms of major depression. Previous open-label clinical trials have reported significant sustained improvements with deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG) in patients with severe, chronic treatment-resistant depression (TRD). This study aimed to confirm the efficacy and measure the impact of discontinuation of the electrical stimulation.

METHODS

We conducted a 6-month double-blind, randomized, sham-controlled crossover study in implanted patients with previous severe TRD who experienced full remission after chronic stimulation. After more than 3 months of stable remission, patients were randomly assigned to 2 treatment arms: the ON-OFF arm, which involved active electrode stimulation for 3 months followed by sham stimulation for 3 months, and the OFF-ON arm, which involved sham stimulation for 3 months followed by active stimulation for 3 months. The primary outcome measure was the difference in the 17-item Hamilton Rating Scale for Depression (HAMD-17) total score between sham and active stimulation.

RESULTS

We enrolled 5 patients in our trial. A Friedman repeated-measures analysis of variance revealed a significant effect of treatment (χ(2)1 = 5.0, p = 0.025) in patients with higher depression scores during sham stimulation. At the end of active stimulation, depression was remitted in 4 of 5 patients and none of them had experienced a relapse, whereas at the end of sham stimulation, 2 patients remained in remission, 2 relapsed and 1 showed a progressive worsening without reaching relapse criteria.

LIMITATIONS

The small sample size limited the statistical power and external validity.

CONCLUSION

These preliminary findings indicate that DBS of the SCG is an effective and safe treatment for severe forms of TRD and that continuous electrical stimulation is required to maintain therapeutic effects.

TRIAL REGISTRATION

NCT01268137 (ClinicalTrials.gov).

Severity stages in essential tremor: a long-term retrospective study using the glass scale

Background

Few prospective studies have attempted to estimate the rate of decline of essential tremor (ET) and these were over a relatively short time period (less than 10 years). We performed a long-term study of severity stages in ET using the Glass Scale scoring system.

Methods

Fifty consecutive patients with severe ET were included. We retrospectively obtained Glass Scale scores throughout the patient's life. Common milestone events were used to help recall changes in tremor severity.

Results

According to the Glass Scale, the age distributions were as follows: score I, 40±17 years, score II, 55±12 years, score III, 64±9 years, and score IV, 69±7 years. A significant negative correlation between age at first symptom and rate of progression was found (r = −0.669, p<0.001). The rate of progression was significantly different (p<0.001) when the first symptom appeared at a younger age (under 40 years of age) compared with older age (40 years or older).

Discussion

Our results support the progressive nature of ET. Age at onset was a prognostic factor. The Glass Scale may be a useful tool to determine severity stages during the course of ET in a manner similar to the Hoehn and Yahr Scale for Parkinson's disease.

The role of executive control in bilingual language production: A study with Parkinson's disease individuals

The basal ganglia are critically involved in language control (LC) processes, allowing a bilingual to utter correctly in one language without interference from the non-requested language. It has been hypothesized that the neural mechanism of LC closely resembles domain-general executive control (EC). The purpose of the present study is to investigate the integrity of bilingual LC and its overlap with domain-general EC in a clinical population such as individuals with Parkinson's disease (PD), notoriously associated with structural damage in the basal ganglia. We approach these issues in two ways. First, we employed a language switching task to investigate the integrity of LC in a group of Catalan-Spanish bilingual individuals with PD, as compared to a group of matched healthy controls. Second, to test the relationship between domain-general EC and LC we compared the performances of individuals with PD and healthy controls also in a non-linguistic switching task. We highlight that, compared to controls, individuals with PD report decreased processing speed, less accuracy and larger switching costs in terms of RT and errors in the language switching task, whereas in the non-linguistic switching task PD patients showed only increased switching cost in terms of errors. However, we report a positive correlation between the magnitudes of linguistic and non-linguistic mixing costs in individuals with PD. Taken together, these results support the notion of a critical role of the basal ganglia and connected structures in LC, and suggest a possible link between LC and domain-general EC.

[Complications related with implanted devices in patients with Parkinson's disease treated with deep brain stimulation. A study of a series of 124 patients over a period of 16 years]

INTRODUCTION

Establishing protocols of the best candidates for deep brain stimulation in patients with Parkinson's disease and a greater knowledge of the technique have increased its safety profile. Yet, the complications related with implanted devices still occur with a far-from-negligible frequency and have both an economic and clinical impact.

AIM

From a broad series of patients undergoing deep brain stimulation included consecutively for the treatment of their Parkinson's disease, data concerning the complications related with implanted devices were gathered and compared with those in the literature.

PATIENTS AND METHODS

Altogether 124 patients with a total of 242 implanted electrodes and 252 generator replacements were included in the study. Mean follow-up time was 8.4 years (range: 3-16 years). Data on all the complications related with implanted devices were collected retrospectively.

RESULTS

Findings showed that 23 implanted device-related complications occurred (17.7% of the patients): 12 (9.6%) had culture-positive ulcers, five (4%) had culture-negative ulcers, four (3.2%) were left with infections following generator replacement, one (0.8%) had a generator malfunction, and electrode migration took place in one (0.8%). Significant differences were observed as regards the effectiveness of the treatment involving surgical revision of the ulcers, which suggests that the culture-negative ulcers responded to the surgical revision better than the culture-positive ulcers (80% healing versus 16.6%; p = 0.028).

CONCLUSIONS

The results observed in the series were comparable to those in the existing literature. The presence of culture-positivity in the ulcers is a factor forecasting surgical revision.

The GABA Hypothesis in Essential Tremor: Lights and Shadows

Background

The gamma-aminobutyric acid (GABA) hypothesis in essential tremor (ET) implies a disturbance of the GABAergic system, especially involving the cerebellum. This review examines the evidence of the GABA hypothesis.

Methods

The review is based on published data about GABA dysfunction in ET, taking into account studies on cerebrospinal fluid, pathology, electrophysiology, genetics, neuroimaging, experimental animal models, and human drug therapies.

Results

Findings from several studies support the GABA hypothesis in ET. The hypothesis follows four steps: 1) cerebellar neurodegeneration with Purkinje cell loss; 2) a decrease in GABA system activity in deep cerebellar neurons; 3) disinhibition in output deep cerebellar neurons with pacemaker activity; and 4) an increase in rhythmic activity of the thalamus and thalamo-cortical circuit, contributing to the generation of tremor. Doubts have been cast on this hypothesis, however, by the fact that it is based on relatively few works, controversial post-mortem findings, and negative genetic studies on the GABA system. Furthermore, GABAergic drug efficacy is low and some GABAergic drugs do not have antitremoric efficacy.

Discussion

The GABA hypothesis continues to be the most robust pathophysiological hypothesis to explain ET. There is light in all GABA hypothesis steps, but a number of shadows cannot be overlooked. We need more studies to clarify the neurodegenerative nature of the disease, to confirm the decrease of GABA activity in the cerebellum, and to test more therapies that enhance the GABA transmission specifically in the cerebellum area.

Spectroscopic changes associated with mild cognitive impairment and dementia in Parkinson's disease

Frontal subcortical cognitive defects are predominant in Parkinson's disease (PD). Temporal lobe dysfunction seems more relevant for progression to dementia. We aimed to study the relative importance of temporal lobe defects versus executive impairment in the progression to dementia in PD by using proton magnetic resonance spectroscopy ((1)H-MRS). The (1)H-MRS features of PD patients with intact cognition (PD-CgInt; n = 16), mild cognitive impairment (MCI; n = 15) and dementia (PDD; n = 15) were compared, to delineate the metabolic alterations correlating with cognitive status. Metabolite concentrations were acquired from voxels localized to the hippocampus and dorsolateral prefrontal cortex (DL-PFC). Cognitive status was established following the Movement Disorder Society PDD criteria, administering the Clinical Dementia Rating Scale and Mattis Dementia Rating Scale. The Parkinson's Disease Cognitive Rating Scale (PD-CRS) was used to correlate (1)H-MRS with neuropsychology. N-acetylaspartate (NAA) concentrations in the right DL-PFC were decreased in PD-MCI compared with PD-CgInt patients (p = 0.002), and correlated with frontal subcortical tasks. Decreased NAA concentrations in the left hippocampus in PDD compared to PD-MCI (p = 0.03) correlated with confrontation naming. The present findings support that executive impairment is related to dorsolateral prefrontal dysfunction from the early stages, while progression to dementia is linked to the additional impairment of temporal lobe structures. The PD-CRS was able to capture the differential impairment of prefrontal versus temporal cortical areas.

Fused in Sarcoma (FUS) gene mutations are not a frequent cause of essential tremor in Europeans

FUS/TLS (denoting fused in sarcoma/translocated in liposarcoma [MIM 137070]) codifies an RNA binding protein. Mutations in this gene cause amyotrophic lateral sclerosis (ALS; MIM 608030). Essential tremor (ET [MIM 190300]) is the most frequent movement disorder. Despite its strong familiar aggregation, recently a whole exome sequencing study has identified FUS mutations as a cause of familial ET. To determine whether mutations in FUS are also common in other populations, we sequenced FUS gene in 178 unrelated Spanish subjects with ET. We detected only an intronic single-pair nucleotide deletion (c.1293-37delC), which was predicted to affect mRNA splicing. However, leukocyte mRNA analysis showed no changes in FUS expression. In conclusion, coding or splicing FUS mutations are not a frequent cause of ET in the Spanish population.

[Descriptive analysis of the activity in a movement disorder unit in a tertiary hospital in Catalonia]

INTRODUCTION

Movement disorders are an important part of the activity of a Neurology service, but there are few studies examining their health care demand.

AIMS

To analyze the first visits of the Movement Disorders Unit of the Hospital de la Santa Creu i Sant Pau in Barcelona and to compare the results with those of previous studies.

PATIENTS AND METHODS

Prospective study of the first neurological assessments carried out during 2010. Demographic variables of patients were collected and diagnoses were reviewed 12 months later.

RESULTS

423 first visits were done (application rate of 1.41 per 1000 inhabitants-year): 54% females, median age 68.8 ± 14.2 years-old. 74.3% of referrals came from the family doctor. The most frequent reasons for consultation were tremor (40%) and parkinsonism-motor clumsiness (26%). The most prevalent diagnoses were Parkinson's disease (36%) and essential tremor (19%). After the first assessment, 84% of patients continued controls in the Unit. One year later, in the 8% of cases there was a change in the initial diagnosis. Taking into account the incidence of each disorder, the number of patients seen was fewer compared to the estimated (19.5 times lower), especially marked in cases of restless legs syndrome, essential tremor and Tourette syndrome.

CONCLUSIONS

In our Unit the most frequent reason for consultation is tremor and the most prevalent diagnosis is Parkinson's disease. The number of patients treated is clearly lower than the estimated according to the incidence of the diseases in the population.

Gaba and serotonin molecular neuroimaging in essential tremor: a clinical correlation study

BACKGROUND

Essential tremor is the most common movement disorder in adults, but its exact etiology and pathophysiology are still not fully understood. There is some consensus, however, about the involvement of the cerebellum and accumulating evidence points towards a dysfunction of the gabaergic system. We hypothesize that the serotonin neurotransmission system may also play a role as it does in tremor in Parkinson disease. This study aimed to investigate the association between the severity of tremor symptoms and the gabaergic and serotoninergic neurotransmission systems in essential tremor.

MATERIAL AND METHODS

We measured the tremor clinical rating scale score and acquired DASB and Flumazenil PET scans in 10 patients who presented with essential tremor at different stages of clinical severity. Statistically significant correlations were sought between the scale scores and parametric binding potential images.

RESULTS

The correlation analysis of cerebellar Flumazenil uptake and tremor clinical rating scale scores reached statistical significance (R2 = 0.423, p = 0.041), whereas no association was detected in the DASB scans.

CONCLUSIONS

The severity of tremor correlated with the abnormalities found in GABA receptor binding, suggesting a primary gabaergic deficiency or a functional abnormality at the level of GABA(A) receptor subtypes. These results may assist in the rational development of new pharmacological treatments for essential tremor.

Diagnosis and management of essential tremor and dystonic tremor

Essential tremor (ET) is the most common adult movement disorder. Traditionally considered as a benign disease, it can cause an important physical and psychosocial disability. Drug treatment for ET remains poor and often unsatisfactory. Current therapeutic strategies for ET are reviewed according to the level of discomfort caused by tremor. For mild tremor, nonpharmacological strategies consist of alcohol and acute pharmacological therapy; for moderate tremor, pharmacological therapies (propranolol, gabapentin, primidone, topiramate, alprazolam and other drugs); and for severe tremor, the role of functional surgery is emphasised (thalamic deep brain stimulation, thalamotomy). The more specific treatment of head tremor with the use of botulinum toxin is also discussed. Several points are discussed to guide the immediate research into this disease in the near future. Dystonic tremor is a common symptom in dystonia. Diagnostic criteria for dystonic tremor and differential diagnosis with psychogenic tremor and ET are described. Treatment of dystonic tremor matches the treatment of dystonia. In cases of symptomatic dystonic tremor similar to ET, therapeutic strategies would be the same as for ET.

"Preclinical" MSA in definite Creutzfeldt-Jakob disease

Multiple system atrophy (MSA) is a sporadic alpha-synucleinopathy clinically characterized by variable degrees of parkinsonism, cerebellar ataxia and autonomic dysfunction. The histopathological hallmark of MSA is glial cytoplasmic inclusion (GCI). It is considered to represent the earliest stage of the degenerative process in MSA and to precede neuronal degeneration. Sporadic Creutzfeldt-Jakob disease (sCJD) is a fatal, rapidly progressive dementia generally associated with ataxia, pyramidal and extrapyramidal symptoms and myoclonus. Definite diagnosis needs neuropathological demonstration of variable degrees of spongiform degeneration of neuropil, neuronal loss, astro- and microgliosis, and the presence of abnormal deposits of the misfolded prion protein PrP(res) . Both diseases, CJD and MSA are infrequent among neurodegenerative diseases. In the present report we describe clinical and neuropathological findings of a previously healthy 64-year-old woman who developed symptoms of classical CJD. At post mortem examination, the brain showed in addition to classical methionine/methionine PrP(res) type 1 (MM1) sCJD changes and moderate Alzheimer-type pathology, features of "preclinical" MSA with minimal histopathological changes. These were characterized by discrete amounts of alpha-synuclein immunoreacive glial cytoplasmic inclusions in the striato-nigral system, isolated intraneuronal inclusions in pigmented neurons of the substantia nigra, as well as some vermiform intranuclear inclusions. To our knowledge, this is the first report on the coexistence of definite sCJD and "minimal changes" MSA in the same patient.

The Glass scale: a simple tool to determine severity in essential tremor

BACKGROUND

The method for measuring disease severity in essential tremor (ET) is not consistent among neurologists in routine clinical practice.

METHODS

We have developed a new scale, called Glass scale, which is easy and quick to administer to ET patients with upper limb involvement. Using the scale involves asking the patient one question: "Over the last week, when you were sitting down at the table, how did you drink water from a glass?" Scores: I - I have no difficulties. II - I can drink with one hand, but I have to fill the glass with less liquid to avoid spills. III - I cannot drink with one hand, I need both hands. IV - I cannot drink with my hands, I need a straw. The score is followed by "A" if tremor involves only the upper limbs, and "B" if not. Construct validity of the Glass scale was tested against the Tremor Clinical Rating Scale (TCRS) and the Bain disability scale. A second neurologist blinded to the Glass scale score assessed inter-rater reliability.

RESULTS

The Glass scale displayed strong construct validity compared to TCRS (w. kappa = 0.907) and to the Bain scale (w. kappa = 0.868). High inter-rater validity was also observed (w. kappa = 0.937).

CONCLUSION

The Glass scale appears to be a reliable and valid tool to determine tremor severity in ET. The simplicity of the scale makes it appropriate for use in routine clinical practice.

Facial emotion recognition impairment in patients with Parkinson's disease and isolated apathy

Apathy is a frequent feature of Parkinson's disease (PD), usually related with executive dysfunction. However, in a subgroup of PD patients apathy may represent the only or predominant neuropsychiatric feature. To understand the mechanisms underlying apathy in PD, we investigated emotional processing in PD patients with and without apathy and in healthy controls (HC), assessed by a facial emotion recognition task (FERT). We excluded PD patients with cognitive impairment, depression, other affective disturbances and previous surgery for PD. PD patients with apathy scored significantly worse in the FERT, performing worse in fear, anger, and sadness recognition. No differences, however, were found between nonapathetic PD patients and HC. These findings suggest the existence of a disruption of emotional-affective processing in cognitive preserved PD patients with apathy. To identify specific dysfunction of limbic structures in PD, patients with isolated apathy may have therapeutic and prognostic implications.

[Head tremor]

INTRODUCTION

Head tremor, either as an isolated symptom or as part of a symptomatic complex, occurs in patients with different neurological diseases. Little research has been carried out to analyse the clinical features of this neurological symptom.

AIM

To review the symptomatology, aetiology and therapeutics of brain tremors.

DEVELOPMENT

Two main types of brain tremor can be distinguished: tremor of the whole brain (holocephalic tremor) and segmented brain tremor (tremor of the jaw, tongue, chin, soft palate, task-specific, orthostatic orolingual and undetermined). Essential tremor, the main cause of brain tremor, and dystonic tremor give rise to holocephalic-type tremor in the vast majority of cases. Brain tremor in Parkinsonism is characteristically of the segmented type. The effectiveness of the pharmacological treatment of brain tremor is very limited. Botulinum toxin is a promising therapy for brain tremors of any causation. In severe cases of brain tremor, functional surgery by means of deep brain stimulation of the intermediate ventral thalamic nucleus is useful, but must be performed bilaterally.

CONCLUSIONS

The semiological characteristics of brain tremor are a valuable aid in the aetiological diagnosis. Pharmacological therapy is very limited. Botulinum toxin and functional surgery of the intermediate ventral thalamic nucleus are useful in selected patients.