Multiple System Atrophy

Abstract

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder characterized clinically by various combinations of parkinsonian, autonomic, cerebellar, or pyramidal symptoms and signs and pathologically by cell loss, gliosis, and glial cytoplasmic inclusions in several brain and spinal cord structures. The term MSA was introduced in 1969, however cases of MSA were previously reported under the rubrics of striatonigral degeneration, olivopontocerebellar atrophy, Shy-Drager syndrome and idiopathic orthostatic hypotension. In the late 1990s, α-synuclein immunostaining was recognized as most sensitive marker of inclusion pathology in MSA: because of these advances in molecular pathogenesis, MSA has been firmly established as α-synucleinopathy along with Parkinson’s disease (PD) and dementia with Lewy bodies. Recent epidemiological surveys have shown that MSA is not a rare disorder (∼5 cases per 100,000 population), and that misdiagnosis, especially with PD, is still common due to variable clinical presentations of MSA. However, the clinical picture of MSA in its full-blown form is distinctive. The patient is hypomimic with orofacial and anterior neck dystonia resulting in a grinning smile akin to “risus sardonicus” and sometimes disproportionate antecollis. The voice is often markedly impaired with a characteristic quivering high-pitched dysarthria. The motor disorder of MSA is often mixed with parkinsonism, cerebellar ataxia, limb dystonia, myoclonus, and pyramidal features occurring at the same time. However, akinesia and rigidity are the predominating features in 80% of patients, and cerebellar ataxia within the remaining 20%. According to the predominant motor presentation, MSA patients may be labeled as parkinsonian or cerebellar variant (MSA-P, MSA-C). The diagnosis of MSA is largely based on clinical expertise, and this is well illustrated by the consensus diagnostic criteria, which comprise clinical features only (divided into four domains including autonomic dysfunction, parkinsonism, cerebellar dysfunction, and corticospinal tract dysfunction). Nevertheless, several autonomic function, imaging, neurophysiological, and biochemical studies have been proposed in the last decade to help in the differential diagnosis of MSA. No drug treatment consistently benefits patients with this disease. Indeed, parkinsonism often shows a poor or unsustained response to chronic levodopa therapy, however, one-third of the patients may show a moderate-to-good dopaminergic response initially. There is no effective drug treatment for cerebellar ataxia. On the other hand, features of autonomic failure such as orthostatic hypotension, urinary retention or incontinence, constipation, and impotence, may often be relieved if recognized by the treating physician. Novel symptomatic and neuroprotective therapies are urgently required.