Neuropsychiatric phenotypes in functional movement disorder.

OBJECTIVE: Functional movement disorder (FMD), the motor-dominant subtype of functional neurological disorder, is a complex neuropsychiatric condition. Patients with FMD also manifest non-motor symptoms. Given that patients with FMD are diagnosed based on motor phenotype, the contribution of non-motor features to the neuropsychiatric syndrome is not well characterized. The objective of this hypothesis-generating study was to explore potential novel, neuropsychiatric FMD phenotypes by combining movement disorder presentations with non-motor comorbidities including somatic symptoms, psychiatric diagnoses, and psychological traits. METHODS: This retrospective chart review evaluated 158 consecutive patients with a diagnosis of FMD who underwent deep phenotyping across neurological and psychiatric domains. Demographic, clinical, and self-report features were analyzed. A data-driven approach using cluster analysis was performed to detect patterns when combining the movement disorder presentation with somatic symptoms, psychiatric diagnoses, and psychological factors. These new neuropsychiatric FMD phenotypes were then tested using logistic regression models. RESULTS: Distinct neuropsychiatric FMD phenotypes emerged when stratifying by episodic vs. constant motor symptoms. Episodic FMD was associated with hyperkinetic movements, hyperarousal, anxiety, and history of trauma. In contrast, constant FMD was associated with weakness, gait disorders, fixed dystonia, activity avoidance, and low self-agency. Pain, fatigue, somatic preoccupation, and health anxiety were common across all phenotypes. CONCLUSION: This study found patterns spanning the neurological-psychiatric interface that indicate that FMD is part of a broader neuropsychiatric syndrome. Adopting a transdisciplinary view of illness reveals readily identifiable clinical factors that are relevant for the development and maintenance of FMD.

Motor Onset Topography and Progression in Parkinson's Disease: the Upper Limb Is First.

OBJECTIVE: To define the motor onset and progression of Parkinson's disease (PD) in a prospective cohort of early unmedicated patients. METHODS: We enrolled a consecutive cohort of recently diagnosed (<18 months) PD patients with unilateral manifestations using age and gender-matched controls. The most affected body region was determined using various clinical standard metrics and objective quantitative kinematic measurements. Parkinson's Progression Markers Initiative data were used for external validation of the results. RESULTS: Twenty-five drug-naive patients and 21 controls were studied. Upper limbs were (92%) the most affected body region at onset as ascertained by patients' self-assessment, neurologists' impression, and Movement Disorders Society Unified Parkinson's Disease Rating Scale score. The upper limb (ie, hand) was the site of onset in 80% of patients. Motor features progressed to involve the lower limb but remained limited to the initially affected body side over a 2-year follow-up. Agreement among the different metrics (96%) confirmed focal upper limb predominant motor impairment at onset. The findings were confirmed by quantitative kinematic analyses and from a cohort of 34 similar patients from the Parkinson's Progression Markers Initiative database. CONCLUSIONS: Motor manifestations in PD start distally in one upper limb. The complexity of the motor repertoire and, consequently, the presumed larger dopaminergic striatal demand for maintaining skillful motor function in the upper limb, may contribute to greater vulnerability of dopaminergic striatal terminals. Recognition of this motor pattern could be used to monitor the evolution of nigrostriatal degeneration and the putative impact of therapies. © 2021 International Parkinson and Movement Disorder Society.

Normal 'heart' in Parkinson's disease: is this a distinct clinical phenotype?

BACKGROUND AND PURPOSE: Reduction of metaiodobenzylguanidine (MIBG) uptake has been observed in almost all patients with Parkinson's disease (PD), associated with hyposmia, orthostatic hypotension and rapid eye movement sleep behavioral disorder (RBD). In contrast, a subgroup of patients with PD with normal MIBG uptake have been reported to have milder disease and preserved cognition compared with those with lower MIBG. The aim of this study was to investigate whether non-motor manifestations of PD differ between patients with normal and abnormal myocardial MIBG uptake. METHODS: Among 160 de-novo cases of PD, 44 had normal MIBG uptake. Twelve candidate non-motor features were evaluated using questionnaires and laboratory tests. RESULTS: Patients with decreased MIBG uptake had more constipation, RBD, cognitive impairment, hyposmia and orthostatic hypotension than did those with normal MIBG uptake. On linear regression analysis, orthostatic hypotension, olfactory function and probable RBD were significantly associated with MIBG uptake in PD. The principal component analysis showed that the group with normal MIBG was not associated with non-motor impairments. CONCLUSIONS: These results suggest that patients with PD with normal MIBG scans have a relatively low disease burden compared with those with abnormal MIBG. Fewer synuclein pathologies in the myocardia and sympathetic ganglia in PD with preserved MIBG uptake might be associated with lower threshold patterns of Braak synuclein pathology for non-motor manifestations compared with PD with decreased MIBG.

Motor features in Parkinson's disease with normal olfactory function.

BACKGROUND: Normosmic Parkinson's disease (PD) might be a unique clinical phenotype with a more benign course when compared with hyposmic PD. OBJECTIVE: The objective of this study was to evaluate motor features and the acute levodopa response according to olfactory function. METHODS: A total of 169 de novo PD patients that underwent olfactory testing and acute levodopa challenge for clinical prediction of sustained long-term dopaminergic response were evaluated. RESULTS: The overall frequency of normosmia was 33%. Normosmic PD patients scored nonsignificantly different to hyposmic/anosmic patients on motor scale and on degree of improvement with levodopa. Motor scores at follow-up were comparable among groups. CONCLUSIONS: Normal olfactory function is common in early PD and was not associated with a different motor phenotype when compared with PD patients with olfactory dysfunction. © 2016 International Parkinson and Movement Disorder Society.

Individual changes in preclinical spinocerebellar ataxia identified via increased motor complexity.

BACKGROUND: Movement changes in autosomal-dominant spinocerebellar ataxias are suggested to occur many years before clinical manifestation. Detecting and quantifying these changes in the preclinical phase offers a window for future treatment interventions and allows the clinician to decipher the earliest dysfunctions starting the evolution of spinocerebellar ataxia. We hypothesized that quantitative movement analysis of complex stance and gait tasks allows to (i) reveal movement changes already at early stages of the preclinical phase when clinical ataxia signs are still absent and to (ii) quantify motor progression in this phase. METHODS: A total of 46 participants (14 preclinical spinocerebellar ataxia mutation carriers [spinocerebellar ataxias 1,2,3,6], 9 spinocerebellar ataxia patients at an early stage; 23 healthy controls) were assessed by quantitative movement analyses of increasingly complex stance and walking tasks in a cross-sectional design. RESULTS: Body sway in stance and spatiotemporal variability in tandem walking differentiated between preclinical mutation carriers and healthy controls (P < .01). Complex movement conditions allowed one to discriminate even those mutation carriers without any clinical signs in posture and gait (SARAposture&gait = 0; P < .04). Multivariate regression analysis categorized preclinical mutation carriers on a single-subject level with 100% accuracy within a range of 10 years to the estimated onset. Movement features in stance and gait correlated significantly with genetically estimated time to onset, indicating a gradual increase of motor changes with increasing proximity to disease manifestation. CONCLUSION: Our results provide evidence for subclinical motor changes in spinocerebellar ataxia, which allow to discriminate patients without clinical signs even on a single-subject basis and may help capture disease progression in the preclinical phase. © 2016 International Parkinson and Movement Disorder Society.

Impact of anger on the health-related quality of life of multiple sclerosis patients.

BACKGROUND: There is evidence of the presence of a disturbed pattern of anger in multiple sclerosis (MS). Emotion changes, including anger, are thought to influence health-related quality of life (HRQoL). However, although deleterious consequences of anger on physical health have been well reported, there are no studies that have analysed the effects of anger on the HRQoL in patients with MS. Our purpose was to assess the extent to which anger impacts on the HRQoL of a cohort of MS patients. METHODS: One hundred and fifty-seven consecutive MS patients were enrolled in the study. Participants were administered affective trait measures (Beck Depression Inventory, Beck Anxiety Inventory) and anger measures (the Spanish adapted version of the State-Trait Anger Expression Inventory-2). HRQoL was quantified using the Functional Assessment of MS. RESULTS: Linear regression analyses revealed that even after controlling for socio-demographic and clinical variables, higher levels of anger expression-in (tendency to handle anger by keeping it inside) independently predicted worse overall HRQoL of MS patients (ß = -0.15, p = 0.04). We further found that this relationship was moderated by gender, showing that anger expression-in is a more influential predictor of the HRQoL in women with MS. CONCLUSION: The present study provides evidence that anger negatively affects the HRQoL of MS patients. Our results may have implications for those involved in treating emotional complications of MS and especially regarding psychotherapeutic interventions to improve HRQoL of MS patients.

Neuropathobiology of non-motor symptoms in Parkinson disease.

Parkinson disease (PD) is a multisystem disorder associated with α-synuclein aggregates throughout the central, autonomic, and peripheral nervous system, clinically characterized by motor and non-motor (NM) symptoms. The NMS in PD, many of which antedating motor dysfunction and representing a preclinical phase spanning 20 or more years, are linked to widespread distribution of α-synuclein pathology not restricted to the dopaminergic nigrostriatal system that is responsible for core motor features of PD. The pathologic substrate of NM manifestations such as olfactory, autonomic (gastrointestinal, urogenital, cardia, respiratory), sensory, skin, sleep, visual, neuropsychiatric dysfunctions (cognitive, mood, dementia), and others are critically reviewed. In addition to non-nigral brainstem nuclei, α-synuclein pathology involves sympathetic and parasympathetic, enteric, cardiac and pelvic plexuses, and many other organs indicating a topographical and chronological spread, particularly in the prodromal stages of the disease. Few animal models recapitulate NMS in PD. The relationship between regional α-synuclein/Lewy pathology, neurodegeneration and the corresponding clinical deficits awaits further elucidation. Controlled clinicopathologic studies will refine the correlations between presymptomatic and late-developing NM features of PD and neuropathology, and new premotor biomarkers will facilitate early diagnosis of PD as a basis for more effective preventive and therapeutic options of this devastating disease.

The different effects of breaking an object at different time points.

Whether the Object-based Correspondence Effect caused by task-irrelevant handles of graspable objects is attributed to the spatial-based or motor-based accounts, or both, has been controversial thus far. In this study, we investigated this question from the time dynamic perspective with the modified stimulus-response (S-R) compatibility paradigm. Specifically, we used three different types of objects in three behavioral experiments: objects with a handle, symmetrical objects, and objects with unilateral protrusion. The objects were broken or remained intact at three different time points (i.e., 50 ms, 150 ms, and 250 ms). The results showed that the object with an intact handle had the correspondence effect at 150 ms, while the correspondence effect disappeared when the handle was broken (Experiment 1). However, no similar pattern was found for symmetric objects (Experiment 2) and objects with unilateral protrusion (Experiment 3). Meanwhile, similar compatibility effects were found in all three experiments when the breakage occurred at 50 ms, which suggests that spatial-based, attention-related factors play a key role in early visual information representation. Our findings suggest that both early spatial-based and later motor-based mechanisms are necessary for the object-based correspondence effect, corroborating the development of visual information representation over time.

Motor features of abstract verbs determine their representations in the motor system.

Embodied cognition theory posits that concept representations inherently rely on sensorimotor experiences that accompany their acquisitions. This is well established through concrete concepts. However, it is debatable whether representations of abstract concepts are based on sensorimotor representations. This study investigated the causal role of associated motor experiences that accompany concept acquisition in the involvement of the motor system in the abstract verb processing. Through two experiments, we examined the action-sentence compatibility effect, in the test phase after an increase in motor features during the learning phase for abstract verbs with low motor features (Experiment 1) or novel words with no conceptual features at all (Experiment 2). After associated motor experiences were added in the word learning phase, action-sentence compatibility effect was found in the semantic processing tasks during the test phase for abstract verbs (Experiment 1a) and novel words (Experiment 2). This was lacking in the word font color judgment task requiring no semantic processing (Experiment 1b). Coupled with our previous study, these findings suggest that motor features formed during word learning could causally affect embodiment in the motor system for abstract verbs, and reactivation of motor experiences in abstract verb processing depends on a given task's demands. Our study supports the view that conceptual representations, even abstract concepts, can be grounded in sensorimotor experiences.

Nocturnal stridor in multiple system atrophy: Video-polysomnography and clinical features.

INTRODUCTION: Nocturnal stridor, a life-threatening condition linked to respiratory failure and sudden death during sleep, is a serious issue in patients with multiple system atrophy (MSA). However, little is known about polysomnographic findings and clinical features of MSA patients with nocturnal stridor. Hence, we investigated video-polysomnography (VPSG) findings and clinical features associated with nocturnal stridor in patients with MSA. METHODS: We retrospectively analyzed the clinical data of patients with MSA (n = 49) who underwent overnight VPSG for the evaluation of sleep-disordered breathing. The presence of nocturnal stridor was confirmed based on overnight VPSG findings. Clinical data, including VPSG findings and clinical features, were compared between MSA patients with and without nocturnal stridor. RESULTS: Nocturnal stridor was present in 31 (63.3%) patients with MSA. Patients with stridor showed significantly higher apnea-hypopnea, respiratory disturbance, and oxygen desaturation indices than those without stridor (P = 0.024, P = 0.049, and P = 0.006, respectively). Patients with stridor had more severe axial motor features, more impaired activities of daily living, and longer disease duration than those without stridor (P = 0.012, P = 0.036, and P = 0.003, respectively). However, there were no significant between-group differences in sex, age at disease onset, MSA subtype, parkinsonian features, cerebellar ataxia, residual urine volume, or systolic and diastolic blood pressure change. CONCLUSIONS: MSA with nocturnal stridor is related to higher apnea indices in conjunction with higher O2 desaturation index, more severe axial motor features, more impaired activities of daily living, and longer disease duration.

Cognitive and behavioral profile of progressive supranuclear palsy and its phenotypes.

BACKGROUND: Although several progressive supranuclear palsy (PSP) phenotypes have recently been described, studies identifying cognitive and neuropsychiatric differences between them are lacking. METHODS: An extensive battery of cognitive and behavioural assessments was administered to 63 PSP patients, 25 PD patients with similar sociodemographic characteristics, and 25 healthy controls. We analysed differences in phenomenology, frequency and severity of cognitive and neuropsychiatric symptoms between PSP, PD and HC, and between PSP subtypes. RESULTS: Regarding phenotypes, 64.6% met criteria for Richardson's syndrome (PSP-RS), 10.7% PSP with predominant Parkinsonism (PSP-P), 10.7% with PSP progressive gait freezing (PSP-PGF), and 10.7% PSP with predominant speech/language disorder (PSP-SL). Impairment was more severe in the PSP group than in the PD and HC groups regarding motor scores, cognitive testing and neuropsychiatric scales. Cognitive testing did not clearly differentiate between PSP phenotypes, but PSP-RS and PSP-SL appeared to have more cognitive impairment than PSP-PGF and PSP-P, mainly due to an increased impairment in frontal executive domains. Regarding neuropsychiatric disturbances, no specific behavior was more common in any of the PSP subtypes. CONCLUSION: Motor deficits delineate the phenotypes included in currently accepted MDS-PSP criteria. Cognition and behavioural disturbances are common in PSP and allow us to distinguish this disorder from other neurological diseases, but they do not differentiate between PSP phenotypes.

Potentials of autophagy enhancing natural products in the treatment of Parkinson disease.

Parkinson disease (PD) is a progressive neurodegenerative movement disorder characterized by motor and non-motor symptoms due to loss of striatal dopaminergic neurons and disruption of degradation signaling leading to the formation of Lewy bodies (aggregation of α-synuclein). Presently, there are no disease modifying therapy for PD despite improvement in the understanding of the disease pathogenesis. However, the drugs currently used in PD management provide symptomatic relieve for motor symptoms without significant improvement in non-motor complications, thus, a public health burden on caregivers and healthcare systems. There is therefore the need to discover disease modifying therapy with strong potential to halt the disease progression. Recent trend has shown that the dysfunction of lysosomal-autophagy pathway is highly implicated in PD pathology, hence, making autophagy a key player owing to its involvement in degradation and clearance of misfolded α-synuclein (a major hallmark in PD pathology). In this review, we described the current drugs/strategy in the management of PD including targeting the autophagy pathway as a novel approach that could serve as potential intervention for PD management. The discovery of small molecules or natural products capable of enhancing autophagy mechanism could be a promising strategy for PD treatment.

Potentials of autophagy enhancing natural products in the treatment of Parkinson disease.

Parkinson disease (PD) is a progressive neurodegenerative movement disorder characterized by motor and non-motor symptoms due to loss of striatal dopaminergic neurons and disruption of degradation signaling leading to the formation of Lewy bodies (aggregation of α-synuclein). Presently, there are no disease modifying therapy for PD despite improvement in the understanding of the disease pathogenesis. However, the drugs currently used in PD management provide symptomatic relieve for motor symptoms without significant improvement in non-motor complications, thus, a public health burden on caregivers and healthcare systems. There is therefore the need to discover disease modifying therapy with strong potential to halt the disease progression. Recent trend has shown that the dysfunction of lysosomal-autophagy pathway is highly implicated in PD pathology, hence, making autophagy a key player owing to its involvement in degradation and clearance of misfolded α-synuclein (a major hallmark in PD pathology). In this review, we described the current drugs/strategy in the management of PD including targeting the autophagy pathway as a novel approach that could serve as potential intervention for PD management. The discovery of small molecules or natural products capable of enhancing autophagy mechanism could be a promising strategy for PD treatment.

A Cross-Cultural Validation of the Filipino and Hiligaynon Versions of the Parts IIIB (Non-Motor Features) and IV (Activities of Daily Living) of the X-Linked Dystonia-Parkinsonism- MDSP Rating Scale.

INTRODUCTION: X-linked dystonia-parkinsonism (XDP) is a progressive movement disorder which also encompasses non-motor features and alterations in activities of daily living. The study aims to translate the Parts IIIB (Non-Motor Features) and IV (Activities of Daily Living) of the XDP-Movement Disorder Society of Philippines Rating Scale to Filipino and Hiligaynon and subsequently validate these versions, which are more understandable to the natives given that XDP originated from the Panay Islands in the Philippines. METHODS: This is a cross-cultural, cross-sectional validation study, composed of the following steps: forward translation, backward translation, panel reconciliation, pretesting, and field testing. Two sets of 10 XDP patients were recruited to the Filipino and Hiligaynon groups for pretesting and cognitive debriefing while another 2 sets of 50 XDP patients were assigned for field testing. RESULTS: The Filipino version had a good internal consistency with a Cronbach's alpha of 0.951 during the pretesting and 0.886 during the field testing. Similar results were seen in the Hiligaynon version (0.837; 0.900). Both also had good conceptual equivalence as demonstrated by significant Pearson r values of 0.384 to 0.814 for the Filipino and 0.355 to 0.800 for the Hiligaynon versions. CONCLUSION: The Filipino and Hiligaynon versions of the Parts IIIB and IV of the XDP-MDSP scale are internally valid and reliable. These scales are considered acceptable to assess the severity of the non-motor features and difficulties in activities of daily living among XDP patients.

Functional motor phenotypes: to lump or to split?

INTRODUCTION: Functional motor disorders (FMDs) are usually categorized according to the predominant phenomenology; however, it is unclear whether this phenotypic classification mirrors the underlying pathophysiologic mechanisms. OBJECTIVE: To compare the characteristics of patients with different FMDs phenotypes and without co-morbid neurological disorders, aiming to answer the question of whether they represent different expressions of the same disorder or reflect distinct entities. METHODS: Consecutive outpatients with a clinically definite diagnosis of FMDs were included in the Italian registry of functional motor disorders (IRFMD), a multicenter data collection platform gathering several clinical and demographic variables. To the aim of the current work, data of patients with isolated FMDs were extracted. RESULTS: A total of 176 patients were included: 58 with weakness, 40 with tremor, 38 with dystonia, 23 with jerks/facial FMDs, and 17 with gait disorders. Patients with tremor and gait disorders were older than the others. Patients with functional weakness had more commonly an acute onset (87.9%) than patients with tremor and gait disorders, a shorter time lag from symptoms onset and FMDs diagnosis (2.9 ± 3.5 years) than patients with dystonia, and had more frequently associated functional sensory symptoms (51.7%) than patients with tremor, dystonia and gait disorders. Patients with dystonia complained more often of associated pain (47.4%) than patients with tremor. No other differences were noted between groups in terms of other variables including associated functional neurological symptoms, psychiatric comorbidities, and predisposing or precipitating factors. CONCLUSIONS: Our data support the evidence of a large overlap between FMD phenotypes.

Treatment Responsiveness of Motor Features in Parkinson's Disease: A Matched Case-Control Analysis.

BACKGROUND: Treatment response in PD is important clinically and for research diagnostic criteria, but few objective data show treatment-responsiveness of PD motor features. OBJECTIVES: To evaluate the treatment response of motor features to moderate treatment doses in a "real-world" PD cohort. METHODS: We analyzed data from a community-based incident cohort of PD in North-East Scotland (PINE study). We assessed change in the UPDRS motor scale and its individual items over a period of up to 13 months comparing (1) patients with an increase of at least 300 mg of levodopa-equivalent dose (LED) and (2) patients without treatment change, matched for age, sex, and disease duration. RESULTS: We identified 101 matched pairs of patients with and without a treatment increase. LED increases were mostly 300 to 375 mg/day. Forty-two percent with treatment increase had ≥30% improvement in overall UPDRS motor score, a further 35% had substantial subjective improvement, but only 1 had an objective excellent (>70%) treatment response. Women responded better than men by 5.4 points (95% confidence interval [CI]: 2.7-8.1). All motor features improved with treatment, but after adjustment for age, sex, and initial score, only rest tremor (P < 0.001), rigidity (P = 0.01), bradykinesia (<0.001), posture (P = 0.01), and gait (P = 0.03) had significant improvements, compared to those with no treatment change. Dopa-less-responsive motor items, taken together, had small statistically significant relative improvements (1.1-point difference [95% CI: 0.4-1.8]; P = 0.004). CONCLUSIONS: Motor items sometimes previously considered dopa unresponsive have small improvements with moderate LED increases. Women respond better than men. Excellent treatment responses are uncommon. These data can inform clinical decisions about treatment.

The late stage of Parkinson's -results of a large multinational study on motor and non-motor complications.

INTRODUCTION: There is little information on the late stages of parkinsonism. METHODS: We conducted a multicentre study in 692 patients with late stage parkinsonism in six European countries. Inclusion criteria were disease duration of ≥7 years and either Hoehn and Yahr stage ≥4 or Schwab and England score of 50 or less. RESULTS: Average disease duration was 15.4 (SD 7.7) years and mean total UPDRS score was 82.7 (SD 22.4). Dementia according to MDS-criteria was present in 37% of patients. Mean levodopa equivalence dose was 874.1 (SD 591.1) mg/d. Eighty two percent of patients reported falls, related to freezing (16%) or unrelated to freezing (21% of patients) or occurring both related and unrelated to freezing (45%), and were frequent in 26%. Moderate-severe difficulties were reported for turning in bed by 51%, speech by 43%, swallowing by 16% and tremor by 11%. Off-periods occurred in 68% and were present at least 50% of the day in 13%, with morning dystonia occurring in 35%. Dyskinesias were reported by 45% but were moderate or severe only in 7%. Moderate-severe fatigue, constipation, urinary symptoms and nocturia, concentration and memory problems were encountered by more than half of participants. Hallucinations (44%) or delusions (25%) were present in 63% and were moderate-severe in 15%. The association with overall disability was strongest for severity of falls/postural instability, bradykinesia, cognitive score and speech impairment. CONCLUSION: These data suggest that current treatment of late stage parkinsonism in the community remains insufficiently effective to alleviate disabling symptoms in many patients.

An update on MSA: premotor and non-motor features open a window of opportunities for early diagnosis and intervention.

In this review, we describe the wide clinical spectrum of features that can be seen in multiple system atrophy (MSA) with a focus on the premotor phase and the non-motor symptoms providing an up-to-date overview of the current understanding in this fast-growing field. First, we highlight the non-motor features at disease onset when MSA can be indistinguishable from pure autonomic failure or other chronic neurodegenerative conditions. We describe the progression of clinical features to aid the diagnosis of MSA early in the disease course. We go on to describe the levels of diagnostic certainty and we discuss MSA subtypes that do not fit into the current diagnostic criteria, highlighting the complexity of the disease as well as the need for revised diagnostic tools. Second, we describe the pathology, clinical description, and investigations of cardiovascular autonomic failure, urogenital and sexual dysfunction, orthostatic hypotension, and respiratory and REM-sleep behavior disorders, which may precede the motor presentation by months or years. Their presence at presentation, even in the absence of ataxia and parkinsonism, should be regarded as highly suggestive of the premotor phase of MSA. Finally, we discuss how the recognition of the broader spectrum of clinical features of MSA and especially the non-motor features at disease onset represent a window of opportunity for disease-modifying interventions.

Auditory and Olfactory Deficits in Essential Tremor - Review of the Current Evidence.

Background: Essential tremor (ET) is the most common adult movement disorder, characterized by several motor and increasingly well recognized non-motor symptoms. Sensory deficits, such as hearing impairment and olfactory dysfunction, are amongst them. This review analyzes the available evidence of these sensory deficits and their possible mechanistic basis in patients with ET. Method: A PubMed literature search on the topic was performed in the May 2019 database. Results: Nineteen articles on hearing impairment and olfactory dysfunction in ET patients were identified. The prevalence of hearing impairment is higher in ET patients than healthy controls or Parkinson disease. Cochlear pathologies are suggested as the underlying cause, but there is still a lack of information about retrocochlear pathologies and central auditory processing. Reports on olfactory dysfunction have conflicting results. The presence of mild olfactory dysfunction in ET was suggested. Conflicting results may be due to the lack of consideration of the disease's heterogeneity, but according to recent data, most studies do not find prominent evidence of olfactory loss in ET. Conclusion: Although there is increasing interest in studies on non-motor symptoms in ET, there are few studies on sensory deficits, which are of particularly high prevalence. More studies are needed on to investigate the basis of non-motor symptoms, including sensory deficits.