Iodine-123-meta-iodobenzylguanidine Myocardial Scintigraphy in Isolated Autonomic Failure: Potential Red Flag for Future Multiple System Atrophy

Abnormal dopamine transporter imaging in pure autonomic failure: a potential biomarker of central nervous system involvement

BACKGROUND AND PURPOSE

Pure autonomic failure (PAF) is a rare progressive neurodegenerative disease characterized by neurogenic orthostatic hypotension at presentation, without other neurological abnormalities. Some patients may develop other central neurological features indicative of multiple system atrophy or a Lewy body disorder. There are currently no biomarkers to assess possible central nervous system involvement in probable PAF at an early stage. A possibility is to evaluate the nigrostriatal dopaminergic degeneration by imaging of dopamine transporter with DaTscan brain imaging. The objective was to evaluate subclinical central nervous system involvement using DaTscan in PAF.

METHODS

We retreospectively reviewed pure autonomic failure patients who were evaluated at the Autonomic Unit between January 2015 and August 2021 and underwent comprehensive autonomic assessment, neurological examination, brain magnetic resonance imaging and DaTscan imaging. DaTscan imaging was performed if patients presented with atypical features which did not meet the criteria for Parkinson's disease or multiple system atrophy or other atypical parkinsonism.

RESULTS

In this cohort, the median age was 49.5 years at disease onset, 57.5 years at presentation, and the median disease duration was 7.5 years. Five of 10 patients had an abnormal DaTscan without neurological features meeting the criteria of an alternative diagnosis. Patients with abnormal DaTscan were predominantly males, had shorter disease duration and had more severe genitourinary symptoms.

DISCUSSION

Degeneration of nigrostriatal dopaminergic neurons measured using DaTscan imaging can present in patients with PAF without concurrent signs indicating progression to widespread α-synucleinopathy. It is advocated that DaTscan imaging should be considered as part of the workup of patients with emerging autonomic failure who are considered to have PAF.

Pure Autonomic Failure-A Localized Alpha Synucleinopathy with a Potential for Conversion to More Extensive Alpha Synucleinopathies

Pure autonomic failure (PAF) is an alpha synucleinopathy with predominant involvement of the autonomic ganglia and peripheral nerves. The hallmark clinical feature is orthostatic hypotension. However, genitourinary, sudomotor, and cardiac involvement is also common. Many patients also develop supine hypertension. Almost a quarter of patients can phenoconvert or evolve into Parkinson's disease, multiple system atrophy, and Lewy body dementia in the future. Early severe bladder involvement, higher supine noradrenaline level, early motor involvement, and dream enactment behavior increase the risk of phenoconversion. The diagnosis is confirmed via autonomic function testing and serum noradrenaline measurement. The treatment is mainly supportive. The non-pharmacological treatment includes adequate fluid, dietary salt, compression stockings, and abdominal binders. The drug therapies to improve blood pressure include midodrine, fludrocortisone, pyridostigmine, and droxidopa. The diagnostic criteria need to be updated to incorporate the recent understandings. The treatment of orthostatic hypotension and supine hypertension is mainly based on case series and anecdotal reports. Randomized control trials are needed to ascertain the best treatment strategies for PAF.

The role of cardiovascular autonomic failure in the differential diagnosis of α-synucleinopathies

The α-synucleinopathies comprise a group of adult-onset neurodegenerative disorders including Parkinson’s disease (PD), multiple system atrophy (MSA), dementia with Lewy bodies (DLB,) and — as a restricted non-motor form — pure autonomic failure (PAF). Neuropathologically, the α-synucleinopathies are characterized by aggregates of misfolded α-synuclein in the central and peripheral nervous system. Cardiovascular autonomic failure is a common non-motor symptom in people with PD, a key diagnostic criterion in MSA, a supportive feature for the diagnosis of DLB and disease-defining in PAF. The site of autonomic nervous system lesion differs between the α-synucleinopathies, with a predominantly central lesion pattern in MSA versus a peripheral one in PD, DLB, and PAF. In clinical practice, overlapping autonomic features often challenge the differential diagnosis among the α-synucleinopathies, but also distinguish them from related disorders, such as the tauopathies or other neurodegenerative ataxias. In this review, we discuss the differential diagnostic yield of cardiovascular autonomic failure in individuals presenting with isolated autonomic failure, parkinsonism, cognitive impairment, or cerebellar ataxia.

Early recognition and diagnosis of multiple system atrophy: best practice and emerging concepts

Introduction: Multiple system atrophy (MSA) is a progressive degenerative disorder of the central and autonomic nervous systems characterized by parkinsonism, cerebellar ataxia, dysautonomia, and pyramidal signs. The confirmatory diagnosis is pathological, but clinical-diagnostic criteria have been developed to help clinicians. To date, the early diagnosis of MSA is challenging due to the lack of reliable diagnostic biomarkers.Areas covered: The authors reappraised the main clinical, neurophysiological, imaging, genetic, and laboratory evidence to help in the early diagnosis of MSA in the clinical and in the research settings. They also addressed the practical clinical issues in the differential diagnosis between MSA and other parkinsonian and cerebellar syndromes. Finally, the authors summarized the unmet needs in the early diagnosis of MSA and proposed the next steps for future research efforts in this field.Expert opinion: In the last decade, many advances have been achieved to help the correct MSA diagnosis since early stages. In the next future, the early diagnosis and correct classification of MSA, together with a better knowledge of the causative mechanisms of the disease, will hopefully allow the identification of suitable candidates to enroll in clinical trials and select the most appropriate disease-modifying strategies to slow down disease progression.

Can Autonomic Testing and Imaging Contribute to the Early Diagnosis of Multiple System Atrophy? A Systematic Review and Recommendations by the Movement Disorder Society Multiple System Atrophy Study Group

Background

In the current consensus diagnostic criteria, the diagnosis of probable multiple system atrophy (MSA) is based solely on clinical findings, whereas neuroimaging findings are listed as aid for the diagnosis of possible MSA. There are overlapping phenotypes between MSA-parkinsonian type and Parkinson's disease, progressive supranuclear palsy, and dementia with Lewy bodies, and between MSA-cerebellar type and sporadic adult-onset ataxia resulting in a significant diagnostic delay and misdiagnosis of MSA during life.

Objectives

In light of an ongoing effort to revise the current consensus criteria for MSA, the Movement Disorders Society Multiple System Atrophy Study Group performed a systematic review of original articles published before August 2019.

Methods

We included articles that studied at least 10 patients with MSA as well as participants with another disorder or control group for comparison purposes. MSA was defined by neuropathological confirmation, or as clinically probable, or clinically probable plus possible according to consensus diagnostic criteria.

Results

We discuss the pitfalls and benefits of each diagnostic test and provide specific recommendations on how to evaluate patients in whom MSA is suspected.

Conclusions

This systematic review of relevant studies indicates that imaging and autonomic function tests significantly contribute to increasing the accuracy of a diagnosis of MSA.

The natural history of idiopathic autonomic failure: The IAF-BO cohort study

OBJECTIVE

To retrospectively describe clinical and instrumental features of a cohort of patients with at least a 5-year history of idiopathic autonomic failure (IAF) longitudinally evaluated at the Autonomic Unit of the University of Bologna (IAF-Bo cohort).

METHODS

We identified patients with at least a 5-year history of IAF who were referred to our department from 1989 to 2016 and evaluated at least once a year during the disease course. Clinical and instrumental data were collected from medical records. Clinical variables were categorized as early if presenting within 3 years from disease onset. Predictors associated with conversion to other synucleinopathies were identified in a Cox regression analysis.

RESULTS

The IAF-Bo cohort included 50 patients (39 male, 19 deceased at the last follow-up). At the last follow-up visit, 34 patients retained IAF phenotype (ncIAF group), while 16 developed a CNS synucleinopathy (converters group). Specific clinical and instrumental features were represented differently in the converters and ncIAF groups. The converters group showed a higher risk of death than the ncIAF group. Early onset of urinary dysfunction, early onset of REM sleep behavior disorder, and a Valsalva ratio ≥1.25 were identified as variables associated with phenoconversion.

CONCLUSIONS

This is one of the largest studies on the natural history of a cohort of patients with at least a 5-year history of IAF, showing a percentage of phenoconversion of 32%. We demonstrated that specific clinical and instrumental features entail an increased probability of phenoconversion. These findings could contribute to a better definition of the nature of IAF and to the identification of early markers of phenoconversion.

Multiple System Atrophy: An Oligodendroglioneural Synucleinopathy1

Multiple system atrophy (MSA) is an orphan, fatal, adult-onset neurodegenerative disorder of uncertain etiology that is clinically characterized by various combinations of parkinsonism, cerebellar, autonomic, and motor dysfunction. MSA is an α-synucleinopathy with specific glioneuronal degeneration involving striatonigral, olivopontocerebellar, and autonomic nervous systems but also other parts of the central and peripheral nervous systems. The major clinical variants correlate with the morphologic phenotypes of striatonigral degeneration (MSA-P) and olivopontocerebellar atrophy (MSA-C). While our knowledge of the molecular pathogenesis of this devastating disease is still incomplete, updated consensus criteria and combined fluid and imaging biomarkers have increased its diagnostic accuracy. The neuropathologic hallmark of this unique proteinopathy is the deposition of aberrant α-synuclein in both glia (mainly oligodendroglia) and neurons forming glial and neuronal cytoplasmic inclusions that cause cell dysfunction and demise. In addition, there is widespread demyelination, the pathogenesis of which is not fully understood. The pathogenesis of MSA is characterized by propagation of misfolded α-synuclein from neurons to oligodendroglia and cell-to-cell spreading in a "prion-like" manner, oxidative stress, proteasomal and mitochondrial dysfunction, dysregulation of myelin lipids, decreased neurotrophic factors, neuroinflammation, and energy failure. The combination of these mechanisms finally results in a system-specific pattern of neurodegeneration and a multisystem involvement that are specific for MSA. Despite several pharmacological approaches in MSA models, addressing these pathogenic mechanisms, no effective neuroprotective nor disease-modifying therapeutic strategies are currently available. Multidisciplinary research to elucidate the genetic and molecular background of the deleterious cycle of noxious processes, to develop reliable biomarkers and targets for effective treatment of this hitherto incurable disorder is urgently needed.