Mitochondrial complex I deficiency stratifies idiopathic Parkinson's disease

Idiopathic Parkinson's disease (iPD) is believed to have a heterogeneous pathophysiology, but molecular disease subtypes have not been identified. Here, we show that iPD can be stratified according to the severity of neuronal respiratory complex I (CI) deficiency, and identify two emerging disease subtypes with distinct molecular and clinical profiles. The CI deficient (CI-PD) subtype accounts for approximately a fourth of all cases, and is characterized by anatomically widespread neuronal CI deficiency, a distinct cell type-specific gene expression profile, increased load of neuronal mtDNA deletions, and a predilection for non-tremor dominant motor phenotypes. In contrast, the non-CI deficient (nCI-PD) subtype exhibits no evidence of mitochondrial impairment outside the dopaminergic substantia nigra and has a predilection for a tremor dominant phenotype. These findings constitute a step towards resolving the biological heterogeneity of iPD with implications for both mechanistic understanding and treatment strategies.

Huntingtin CAG repeats in neuropathologically confirmed tauopathies: Novel insights

Previous studies have suggested a relationship between the number of CAG triplet repeats in the HTT gene and neurodegenerative diseases not related to Huntington's disease (HD). This study seeks to investigate whether the number of CAG repeats of HTT is associated with the risk of developing certain tauopathies and its influence as a modulator of the clinical and neuropathological phenotype. Additionally, it aims to evaluate the potential of polyglutamine staining as a neuropathological screening. We genotyped the HTT gene CAG repeat number and APOE-ℰ isoforms in a cohort of patients with neuropathological diagnoses of tauopathies (n=588), including 34 corticobasal degeneration (CBD), 98 progressive supranuclear palsy (PSP) and 456 Alzheimer's disease (AD). Furthermore, we genotyped a control group of 1070 patients, of whom 44 were neuropathologic controls. We identified significant differences in the number of patients with pathological HTT expansions in the CBD group (2.7%) and PSP group (3.2%) compared to control subjects (0.2%). A significant increase in the size of the HTT CAG repeats was found in the AD compared to the control group, influenced by the presence of the Apoliprotein E (APOE)-ℰ4 isoform. Post-mortem assessments uncovered tauopathy pathology with positive polyglutamine aggregates, with a slight predominance in the neostriatum for PSP and CBD cases and somewhat greater limbic involvement in the AD case. Our results indicated a link between HTT CAG repeat expansion with other non-HD pathology, suggesting they could share common neurodegenerative pathways. These findings support that genetic or histological screening for HTT repeat expansions should be considered in tauopathies.

Midbrain and pons MRI shape analysis and its clinical and CSF correlates in degenerative parkinsonisms: a pilot study

OBJECTIVES

To conduct brainstem MRI shape analysis across neurodegenerative parkinsonisms and control subjects (CS), along with its association with clinical and cerebrospinal fluid (CSF) correlates.

METHODOLOGY

We collected demographic and clinical variables, performed planimetric and shape MRI analyses, and determined CSF neurofilament-light chain (NfL) levels in 84 participants: 11 CS, 12 with Parkinson's disease (PD), 26 with multiple system atrophy (MSA), 21 with progressive supranuclear palsy (PSP), and 14 with corticobasal degeneration (CBD).

RESULTS

MSA featured the most extensive and significant brainstem shape narrowing (that is, atrophy), mostly in the pons. CBD presented local atrophy in several small areas in the pons and midbrain compared to PD and CS. PSP presented local atrophy in small areas in the posterior and upper midbrain as well as the rostral pons compared to MSA. Our findings of planimetric MRI measurements and CSF NfL levels replicated those from previous literature. Brainstem shape atrophy correlated with worse motor state in all parkinsonisms and with higher NfL levels in MSA, PSP, and PD.

CONCLUSION

Atypical parkinsonisms present different brainstem shape patterns which correlate with clinical severity and neuronal degeneration. In MSA, shape analysis could be further explored as a potential diagnostic biomarker. By contrast, shape analysis appears to have a rather limited discriminant value in PSP.

KEY POINTS

• Atypical parkinsonisms present different brainstem shape patterns. • Shape patterns correlate with clinical severity and neuronal degeneration. • In MSA, shape analysis could be further explored as a potential diagnostic biomarker.

Diagnostic Accuracy of Magnetic Resonance Imaging Measures of Brain Atrophy Across the Spectrum of Progressive Supranuclear Palsy and Corticobasal Degeneration

Importance

The accurate diagnosis of progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) is hampered by imperfect clinical-pathological correlations.

Objective

To assess and compare the diagnostic value of the magnetic resonance parkinsonism index (MRPI) and other magnetic resonance imaging-based measures of cerebral atrophy to differentiate between PSP, CBD, and other neurodegenerative diseases.

Design, Setting, and Participants

This prospective diagnostic study included participants with 4-repeat tauopathies (4RT), PSP, CBD, other neurodegenerative diseases and available MRI who appeared in the University of California, San Francisco, Memory and Aging Center database. Data were collected from October 27, 1994, to September 29, 2019. Data were analyzed from March 1 to September 14, 2021.

Main Outcomes and Measures

The main outcome of this study was the neuropathological diagnosis of PSP or CBD. The clinical diagnosis at the time of the MRI acquisition was noted. The imaging measures included the MRPI, cortical thickness, subcortical volumes, including the midbrain, pons, and superior cerebellar peduncle volumes. Multinomial logistic regression models (MLRM) combining different cortical and subcortical regions were defined to discriminate between PSP, CBD, and other pathologies. The areas under the receiver operating characteristic curves (AUROC) and cutoffs were calculated to differentiate between PSP, CBD, and other diseases.

Results

Of the 326 included participants, 176 (54%) were male, and the mean (SD) age at MRI was 64.1 (8.0) years. The MRPI showed good diagnostic accuracy for the differentiation between PSP and all other pathologies (accuracy, 87%; AUROC, 0.90; 95% CI, 0.86-0.95) and between 4RT and other pathologies (accuracy, 80%; AUROC, 0.82; 95% CI, 0.76-0.87), but did not allow the discrimination of participants with CBD. Its diagnostic accuracy was lower in the subgroup of patients without the canonical PSP-Richardson syndrome (PSP-RS) or probable corticobasal syndrome (CBS) at MRI. MLRM combining cortical and subcortical measurements showed the highest accuracy for the differentiation between PSP and other pathologies (accuracy, 95%; AUROC, 0.98; 95% CI, 0.97-0.99), CBD and other pathologies (accuracy, 83%; AUROC, 0.86; 95% CI, 0.81-0.91), 4RT and other pathologies (accuracy, 89%; AUROC, 0.94; 95% CI, 0.92-0.97), and PSP and CBD (accuracy, 91%; AUROC, 0.95; 95% CI, 0.91-0.99), even in participants without PSP-RS or CBS at MRI.

Conclusions and Relevance

In this study, the combination of widely available cortical and subcortical measures of atrophy on MRI discriminated between PSP, CBD, and other pathologies and could be used to support the diagnosis of 4RT in clinical practice.

Characterization of sleep in six patients with pantothenate kinase-associated neurodegeneration

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare neurologic disorder included in the group of neurodegeneration with brain iron accumulation diseases (NBIA). Information regarding sleep in patients with PKAN is limited.

OBJECTIVES

To describe the clinical and polysomnographic characteristics of sleep in six patients with genetically confirmed PKAN.

METHODS

The evaluation included a clinical interview, sleep questionnaires -Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI) and Hospital Anxiety and Depression Scale (HADS)- and a video-polysomnography (VPSG). In addition to standard sleep measures we manually quantified sleep spindle density in stage N2 and rapid eye movements in REM sleep comparing the results with matched controls. Quantification of EMG activity in REM sleep was performed following standard criteria.

RESULTS

All the patients reported at least one sleep complaint, most commonly sleep fragmentation (4/6) and sleep onset insomnia (3/6). ESS and PSQI were abnormal in 3/6 and 4/6, respectively. VPSG showed in 4/6 decreased ocular movements during REM sleep, an increase in sleep spindles in 3/6 (all of them with deep brain pallidal stimulation), an absence of slow wave sleep in 2 and undifferentiated NREM sleep and delayed sleep phase in one. Three patients had an abnormal sleep apnea/hypopnea index, and 2 periodic limb movements of sleep. REM sleep muscular atonia was preserved in all.

CONCLUSIONS

Sleep disorders are common in patients with PKAN. Although our sample is small and heterogeneous, with different symptomatic treatments possibly influencing the results, it suggests that evaluation of sleep should be considered in their management.

Video-tutorial for the Movement Disorder Society criteria for progressive supranuclear palsy

BACKGROUND

The International Parkinson and Movement Disorder Society-endorsed Progressive Supranuclear Palsy Study Group published clinical diagnostic criteria for progressive supranuclear palsy in 2017, aiming to optimize early, sensitive and specific diagnosis.

OBJECTIVE

To assist physicians in the application of these criteria, we developed a video-based tutorial in which all core clinical features and clinical clues are depicted and explained.

METHODS

Patients provided written informed consent to the publication of their videos. High-quality videos along with essential descriptions were collected by the study group members. Most educational videos were selected in a structured consensus process.

RESULTS

We provide 68 videos of all core clinical features and clinical clues defined by the diagnostic criteria, along with instructive descriptions of the depicted patients, examination techniques and clinical findings.

CONCLUSIONS

This comprehensive video-based tutorial will support physicians in the application of the diagnostic criteria of progressive supranuclear palsy.

Management of rare movement disorders in Europe: outcome of surveys of the European Reference Network for Rare Neurological Diseases

Background and purpose

The diagnosis of rare movement disorders is difficult and specific management programmes are not well defined. Thus, in order to capture and assess care needs, the European Reference Network for Rare Neurological Diseases has performed an explorative care need survey across all European Union (EU) countries.

Methods

This is a multicentre, cross‐sectional study. A survey about the management of different rare movement disorders (group 1, dystonia, paroxysmal dyskinesia and neurodegeneration with brain iron accumulation; group 2, ataxias and hereditary spastic paraparesis; group 3, atypical parkinsonism; group 4, choreas) was sent to an expert in each group of disorders from each EU country.

Results

Some EU countries claimed for an increase of teaching courses. Genetic testing was not readily available in a significant number of countries. Regarding management, patients’ accessibility to tertiary hospitals, to experts and to multidisciplinary teams was unequal between countries and groups of diseases. The availability of therapeutic options, such as botulinum toxin or more invasive treatments like deep brain stimulation, was limited in some countries.

Conclusions

The management of these conditions in EU countries is unequal. The survey provides evidence that a European care‐focused network that is able to address the unmet rare neurological disease care needs and inequalities is highly warranted.

Head and voice tremor improving with immunotherapy in an anti-NF155 positive CIDP patient

Chronic inflammatory demyelinating polyradiculoneuropathy with NF155 antibodies (anti-NF155+) constitutes a specific chronic inflammatory demyelinating polyradiculoneuropathy subset with a high incidence of limb's tremor and poor response to conventional therapies. We report a patient with chronic inflammatory demyelinating polyradiculoneuropathy anti-NF155+ with a severe tremor involving limbs, head and voice that responded very well to rituximab. This response correlated with a sharp decrease in the anti-NF155 titers. This case is the first report associating head and voice tremor to chronic inflammatory demyelinating polyradiculoneuropathy, reinforces the hypothesis of the cerebellar origin of this tremor and provides indirect evidence that the antibodies may be the cause of the tremor in these patients.