Morphological substrate of autonomic failure and neurohormonal dysfunction in multiple system atrophy: impact on determining phenotype spectrum

Papp-Lantos inclusions and the pathogenesis of multiple system atrophy: an update

Multiple systemic atrophy (MSA) is a progressive, adult-onset neurodegenerative disorder of undetermined aetiology characterized by a distinctive oligodendrogliopathy with argyrophilic glial cytoplasmic inclusions (GCIs) and selective neurodegeneration. GCIs or Papp-Lantos inclusions, described more than 20 years ago, are now accepted as the hallmarks for the definite neuropathological diagnosis of MSA and suggested to play a central role in the pathogenesis of this disorder. GCIs are composed of hyperphosphorylated alpha-synuclein (alphaSyn), ubiquitin, LRRK2 (leucin-rich repeat serine/threonine-protein) and many other proteins, suggesting that MSA represents an invariable synucleinopathy of non-neuronal type, a specific form of proteinopathies. The origin of alphaSyn deposition in GCIs is not yet fully understood, but recent findings of dysregulation in the metabolism of myelin basic protein (MBP) and p25alpha, a central nervous system-specific protein, also called TPPP (tubulin polymerization promoting protein), strengthened the working model of MSA as a primary glial disorder and may explain frequent alterations of myelin in MSA. However, it is unknown whether these changes represent an early event or myelin dysregulation occurs further downstream in MSA pathogenesis. The association between polymorphisms at the SNCA gene locus and the risk for developing MSA also points to a primary role of alphaSyn in its pathogenesis, while in a MBP promoter-driven alphaSyn transgenic mouse model gliosis accompanied the neurodegenerative process originating in oligodendrocytes. Because alphaSyn represents a major component in both oligodendroglial and neuronal inclusions in MSA, some authors suggested both a primary oligodendrogliopathy and a neuronal synucleinopathy, but current biomolecular data and animal models support a crucial role of the Papp-Lantos inclusions and of aberrant alphaSyn accumulation as their main constituent, causing oligodendroglial pathology, myelin disruption and, finally, neuronal degeneration in MSA. The relationship between oligodendrocytes involved by Papp-Lantos inclusions and those in degenerating neurons in the course of MSA needs further elucidation.

An autopsy report on multiple system atrophy diagnosed immunohistochemically despite severe ischaemic damage: a new approach for investigation of medical practice associated deaths in Japan

A 60-year old man with a 10-year history of multiple system atrophy (MSA) was found in respiratory arrest. After 4 months of respiratory support with two episodes of septic shock, he died. Autopsy disclosed severe atrophy of the mesencephalon, brainstem, medulla oblongata and cerebellum. Gallyas–Braak, α-synuclein and ubiquitin-positive inclusions in the cytoplasm of glial cells were evident, despite the severe ischaemic damage due to respiratory arrest and subsequent respiratory support for 4 months. The cause of respiratory arrest was not identified, but could be explained by the natural history of MSA. The bereaved family, who had suspected malpractice, was satisfied with the explanation based on the investigation performed by eight expert doctors, one expert nurse, two coordinator nurses and two lawyers in the model project promoted by the Japanese government.

Recent developments in multiple system atrophy

Multiple system atrophy (MSA) is a rare late onset neurodegenerative disorder which presents with autonomic failure and a complicated motor syndrome including atypical parkinsonism, ataxia and pyramidal signs. MSA is a glial alpha-synucleinopathy with rapid progression and currently poor therapeutic management. This paper reviews the clinical features, natural history and novel diagnostic criteria for MSA as well as contemporary knowledge on pathogenesis based on evidence from neuropathological studies and experimental models. An outline of the rationale for managing symptomatic deterioration in MSA is provided together with a summary of novel experimental therapeutic approaches to decrease disease progression.

Multiple system atrophy: a primary oligodendrogliopathy

To this day, the cause of multiple system atrophy (MSA) remains stubbornly enigmatic. A growing body of observations regarding the clinical, morphological, and biochemical phenotypes of MSA has been published, but the interested student is still left without a clue as to its underlying cause. MSA has long been considered a rare cousin of Parkinson's disease and cerebellar degeneration; it is rich in acronyms but poor in genetic and environmental leads. Because of the worldwide research efforts conducted over the last two decades and the discovery of the alpha-synuclein-encoding SNCA gene as a cause of rare familial Parkinson's disease, the MSA field has seen advances on three fronts: the identification of its principal cellular target, that is, oligodendrocytes; the characterization of alpha-synuclein-rich glial cytoplasmic inclusions as a suitable marker at autopsy; and improved diagnostic accuracy in living patients resulting from detailed clinicopathological studies. The working model of MSA as a primary glial disorder was recently strengthened by the finding of dysregulation in the metabolism of myelin basic protein and p25alpha, a central nervous system-specific phosphoprotein (also called tubulin polymerization promoting protein, TPPP). Intriguingly, in early cases of MSA, the oligodendrocytic changes in myelin basic protein and p25alpha processing were recorded even before formation of glial cytoplasmic inclusions became detectable. Here, we review the evolving concept that MSA may not just be related to Parkinson's disease but also share traits with the family of demyelinating disorders. Although these syndromes vary in their respective cause of oligodendrogliopathy, they have in common myelin disruption that is often followed by axonal dysfunction.

Multiple system atrophy

BACKGROUND

It has been almost 4 decades since the descriptions of the 3 parts of multiple system atrophy (MSA) have taken place, characterized clinically by dysautonomia, parkinsonism, and cerebellar dysfunction. The discovery of a distinctive pathologic maker has finally provided the conceptual synthesis of these 3 entities into the universal designation of MSA as a distinct disease process with a complex combination of clinical presentations. Although advances have been made in terms of awareness and knowledge concerning the clinical features and pathophysiology of MSA, it remains challenging for neurologists who treat these patients to differentiate MSA from its mimics as well as providing them with effective treatment.

REVIEW SUMMARY

The aim of this review is to provide an overview of the advances in the knowledge of the disease, to highlight typical features useful for the recognition of its entity, and to enlist different treatment options.

CONCLUSION

Despite the fact that there is still no treatment modality that can alter the disease progression, a number of useful symptomatic treatment measures are available and should be offered to patients to ameliorate the nonmotor features of MSA and even the motor features that may at least transiently respond to treatment.