Anosmia and Ageusia in Parkinson's Disease

α-synuclein inclusions are abundant in non-neuronal cells in the anterior olfactory nucleus of the Parkinson's disease olfactory bulb

Reduced olfactory function (hyposmia) is one of the most common non-motor symptoms experienced by those living with Parkinson's disease (PD), however, the underlying pathology of the dysfunction is unclear. Recent evidence indicates that α-synuclein (α-syn) pathology accumulates in the anterior olfactory nucleus of the olfactory bulb years before the motor symptoms are present. It is well established that neuronal cells in the olfactory bulb are affected by α-syn, but the involvement of other non-neuronal cell types is unknown. The occurrence of intracellular α-syn inclusions were quantified in four non-neuronal cell types - microglia, pericytes, astrocytes and oligodendrocytes as well as neurons in the anterior olfactory nucleus of post-mortem human PD olfactory bulbs (n = 11) and normal olfactory bulbs (n = 11). In the anterior olfactory nucleus, α-syn inclusions were confirmed to be intracellular in three of the four non-neuronal cell types, where 7.78% of microglia, 3.14% of pericytes and 1.97% of astrocytes were affected. Neurons containing α-syn inclusions comprised 8.60% of the total neuron population. Oligodendrocytes did not contain α-syn. The data provides evidence that non-neuronal cells in the PD olfactory bulb contain α-syn inclusions, suggesting that they may play an important role in the progression of PD.

The Promise and Challenges of Developing miRNA-Based Therapeutics for Parkinson's Disease

MicroRNAs (miRNAs) are small double-stranded RNAs that exert a fine-tuning sequence-specific regulation of cell transcriptome. While one unique miRNA regulates hundreds of mRNAs, each mRNA molecule is commonly regulated by various miRNAs that bind to complementary sequences at 3’-untranslated regions for triggering the mechanism of RNA interference. Unfortunately, dysregulated miRNAs play critical roles in many disorders, including Parkinson’s disease (PD), the second most prevalent neurodegenerative disease in the world. Treatment of this slowly, progressive, and yet incurable pathology challenges neurologists. In addition to L-DOPA that restores dopaminergic transmission and ameliorate motor signs (i.e., bradykinesia, rigidity, tremors), patients commonly receive medication for mood disorders and autonomic dysfunctions. However, the effectiveness of L-DOPA declines over time, and the L-DOPA-induced dyskinesias commonly appear and become highly disabling. The discovery of more effective therapies capable of slowing disease progression –a neuroprotective agent–remains a critical need in PD. The present review focus on miRNAs as promising drug targets for PD, examining their role in underlying mechanisms of the disease, the strategies for controlling aberrant expressions, and, finally, the current technologies for translating these small molecules from bench to clinics.

A Case of Logopenic Variant of Primary Progressive Aphasia with Parkinsonism and Anosmia

A 69-year-old right-handed woman developed difficulty naming objects and word-finding. The clinical features of language disorder and predominant atrophy on MRI and predominant hypoperfusion on ¹²³I-IMP SPECT in the left temporo-parietal junction area were consistent with the diagnostic criteria for the logopenic variant of primary progressive aphasia (lvPPA). Neurological examination showed slight right-side rigidity and resting tremor (UPDRS-III: 4). ¹²³I-FP-CIT SPECT showed presynaptic dopamine transporter reduction in the posterior putamina with left-side predominance. The odor-stick identification test for Japanese exhibited complete loss of the sense of smell (anosmia). These findings suggest that lvPPA may be accompanied by parkinsonism and anosmia.

"Smelling and Tasting" Parkinson's Disease: Using Senses to Improve the Knowledge of the Disease

Among non-motor manifestations of Parkinson's Disease (PD), peripheral, sensory symptoms are particularly relevant. Smell dysfunction starts very early and frequently precedes the PD motor symptoms by years (being often a cue to the diagnosis). Moreover, olfactory system could be, together with gut, one of those peripheral sites where PD pathology first develops. Unlike smell loss, the relationship between PD and taste impairment is far less established. It can start early in the course of the disease but more frequently appears in advanced stages, in parallel with the advent of MCI, likely reflecting cortical involvement. Among PD patients has been demonstrated an increase in the frequency of the non-tasters for PROP (prototypical gustatory stimulus, 6- n-propylthiouracil), a genetically determined bitter taste which is mediated by TAS2RS38 receptor, and a significant increase of the recessive non-testing variant of this receptor. TAS2R38 receptors are expressed also in other tissues, such as in the epithelia of the gut and nasal cavities, where they can influence epithelial immunity ad its interaction with microbiota. Those pieces of evidence suggest that not only systematic assessment of taste and smell can be of a remarkable help for clinicians in the early diagnosis, but also that understanding the mechanisms of sensory involvement in PD could increase the knowledge of the pathophysiology of the disease.

Auditory Dysfunction in Parkinson's Disease

PD is a progressive and complex neurological disorder with heterogeneous symptomatology. PD is characterized by classical motor features of parkinsonism and nonmotor symptoms and involves extensive regions of the nervous system, various neurotransmitters, and protein aggregates. Extensive evidence supports auditory dysfunction as an additional nonmotor feature of PD. Studies indicate a broad range of auditory impairments in PD, from the peripheral hearing system to the auditory brainstem and cortical areas. For instance, research demonstrates a higher occurrence of hearing loss in early-onset PD and evidence of abnormal auditory evoked potentials, event-related potentials, and habituation to novel stimuli. Electrophysiological data, such as auditory P3a, also is suggested as a sensitive measure of illness duration and severity. Improvement in auditory responses following dopaminergic therapies also indicates the presence of similar neurotransmitters (i.e., glutamate and dopamine) in the auditory system and basal ganglia. Nonetheless, hearing impairments in PD have received little attention in clinical practice so far. This review summarizes evidence of peripheral and central auditory impairments in PD and provides conclusions and directions for future empirical and clinical research. © 2020 International Parkinson and Movement Disorder Society.

Dysbiosis in Parkinson's disease might be triggered by certain antibiotics

Parkinson's disease (PD) is a neurodegenerative amyloid disorder with debilitating motor symptoms due to the loss of dopamine-synthesizing, basal ganglia-projecting neurons in the substantia nigra. An interesting feature of the disease is that most of PD patients have gastrointestinal problems and bacterial dysbiosis, years before the full expression of motor symptoms. We hypothesized that antibiotic consumption might be a contributing factor of gut microbiome dysbiosis in PD, favoring curli-producing Enterobacteria. Curli is a bacterial α-synuclein (αSyn) which is deposited first in the enteric nervous system and amyloid deposits are propagated in a prion like manner to the central nervous system. In addition, antibiotics result in a low-grade systemic inflammation, which also contributes to damage of neurons in enteric- and central nervous system. To support our hypothesis, by comparing PD prevalence change with antibiotic consumption data in EU countries, we found significant positive correlation between use narrow spectrum penicillin + penicillinase resistant penicillin and increased prevalence of the disease.

Open questions on the nature of Parkinson's disease: from triggers to spreading pathology

Parkinson's disease (PD) is a movement disorder identified more than 200 years ago; today it is defined by specific motor symptoms that together receive the name of parkinsonism. PD diagnosis is reached with the full parkinsonian syndrome, but in recent years, a series of non-motor symptoms have arisen as intrinsic components of PD. These non-motor symptoms are variable, creating a widely heterogenous disease presentation. Some non-motor symptoms appear in late disease stages and are explained as the natural progression of PD pathology into other brain centres, including the frontal cortex. Other symptoms can appear a decade or earlier preceding PD diagnosis, particularly hyposmia (loss of smell) and constipation. These early symptoms and the accompanying protein pathology have stimulated a lively conversation about the origin and nature of PD and other related conditions: some authors propose that PD starts in the olfactory mucosa and the gut due to direct exposure to toxins or pathogens. This pathology then travels by anatomically interconnected networks to the midbrain to cause motor symptoms and the cortex to cause late complications. Other models propose that PD develops in multiple independent foci that do not require pathology spread. We will review these hypotheses in the context of recent developments regarding the spread of amyloids and propose a mixed model where a multifocal origin explains the variable presentation of PD, while cell-to-cell spread explains stereotypical disease progression.

The flavor test is a sensitive tool in identifying the flavor sensorineural dysfunction in Parkinson's disease

Gustatory perception has been poorly explored in Parkinson's disease (PD). Aim of this study was to assess the flavor ability in PD patients, using the "flavor test" (FT), a new standardized and validated tool to examine the flavor perception. Thirty-eight patients (17 F and 21 M) and 36 control subjects (15 F and 21 M) comparable for age and gender were enrolled. All the subjects underwent the flavor test (FT), the Sniffin' Sticks test (SST), and the gustometry test (GT), based on the basic four tastants ("salty," "sour," "sweet," and "bitter"). PD patients presented a FT score significantly lower than controls (p < 0.001). Olfaction (SST) was impaired in PD in comparison with controls (p < 0.001), and the patients also showed a mild reduction of basic tastant identification at the GT (p = 0.08), with a trend toward statistical significance. There was no correlation between SST, FT, and GT. GT performance was negatively correlated with disease severity (p = 0.004) and stage (p = 0.024). The SST and FT resulted abnormal in PD in comparison with controls, independently of disease duration and severity. The ability to identify the basic four tastants was correlated with the disease severity and stage in PD patients suggesting that it might occur later in the course of the disease. FT might be a sensitive tool in identifying the sensorineural perception dysfunction in PD, even in the early stage and regardless of the disease severity.

Essential Tremor and Parkinson's Disease: Exploring the Relationship

Background

There is longstanding controversy surrounding the possible link between essential tremor (ET) and Parkinson's disease (PD). Inconsistent and unreliable diagnostic criteria may in part account for some of the difficulties in defining the relationship between these two common movement disorders.

Methods

References for this systematic review were identified using PubMed with the search terms "essential tremor" AND "Parkinson's disease" with articles published in English between 1960 and September 2018 included.

Results

In this review we provide evidence that some patients diagnosed with ET have an increased risk of developing PD years or decades after onset of action tremor. There are several still unresolved questions about the link between the two disorders including lack of verifiable diagnostic criteria for the two disorders and marked overlap in phenomenology. Here we review clinical, epidemiologic, imaging, pathologic, and genetic studies that address the ET-PD relationship. Several lines of evidence support the association between ET and PD, including overlapping motor and non-motor features, relatively high prevalence of rapid eye movement sleep behavior disorder (26-43%) in ET patients, increased prevalence of PD in patients with longstanding antecedent ET, increased prevalence of ET in family members of patients with PD, and the presence of Lewy bodies in the brains of some ET patients (15-24%).

Discussion

There is a substantial body of evidence supporting the association between ET and PD within at least a subset of patients, although the nature and possible pathogenic mechanisms of the relationship are not well understood.

Frequency of non-motor symptoms in Parkinson's disease presenting to tertiary care centre in Pakistan: an observational, cross-sectional study

OBJECTIVE

To determine the frequency of non-motor symptoms (NMS) in patients of Parkinson's disease (PD) presenting to a movement disorder clinic at a tertiary care centre in Pakistan, and how frequency of NMS is different in male and female patients.

STUDY DESIGN

Observational, cross-sectional study.

SETTING

Tertiary care centre.

PARTICIPANTS

Out of 102 patients, 85 were included. Inclusion criteria were patients with PD diagnosed according to the UK Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria, age ≥18 years, able to give consent and have no difficulty in answering questions. Exclusion criteria were diseases that resemble PD, stroke, dementia, patients unable to provide information and history of antipsychotic use.

RESULTS

The NMSQuest revealed a mean of nearly seven different NMS per patient. Autonomic problems such as constipation (56%) and nocturia (49%) were the most common NMS, while urinary urgency was reported by 35% of patients. Low mood and feeling sad were reported by 47%, whereas feeling anxious/panicky was reported by 36%. Problem with memory was reported by 45% of patients. Feeling of light-headedness and dizziness was reported by 40% of patients. Problems with sexual relationship were reported by 30% of patients. The most common sleep problem was difficulty falling sleep (29%). Pain not related to the musculoskeletal system was reported by 30% of patients. Loss or change in the ability to taste or smell was reported by 29% of patients. The rest of NMS were less than 25% in frequency. Feeling sad or blue, feeling light-headed/dizzy, unexplained pain, unpleasant sensations in the legs, difficulty in swallowing and faecal incontinence were more common in female participants, while problems with sex were more common in male participants.

CONCLUSION

NMS are quite prevalent in PD in our population. Certain NMS are more common in women as compared with men. There is a need for a large-scale study to look for the association of different NMS with sex.