Multiple system Atrophy, abbreviated MSA defines a
specific syndrome within the larger less well defined category of multiple system degenerations. The features of the MSA include: parkinsonism, cerebellar or corticospinal signs, orthostatic hypotension,
impotence, and urinary incontinence or retention, usually preceding or within two years after the onset of the motor symptoms. The previous division into Shy Drager Syndrome (SDS), Striato Nigral
Degeneration (SND), and Olivopontocerebellar Atrophy (OPCA) has been dropped. Immunohistochemistry demonstrates that these three disorders share a common pathology.
The latest diagnostic criteria are shown in the table below.
Wenning et. al. determined that the
combination of autonomic insufficiency, speech or bulbar dysfunction, absence of dementia, postural instability with falls, poor response to levodopa, and absence of levodopa-induced confusion gave a
diagnostic sensitivity and specificity greater than 90%.
Median age of onset of MSA is about age 55
years (range of 33 to 76). It affects men slightly more than women. Nearly half of patients are disabled or wheelchair bound within 5 years of the onset of motor symptoms. Mean survival is 6 to 7 years.
80% of MSA patients develop predominant parkinsonism (MSA-P) and 20% develop predominant cerebellar signs (MSA-C). The latter statistics are likely skewed by referral patterns to movement disorder
centers. There is considerable overlap. Cerebellar features are present in over 40% of patients with SND type, and parkinsonism is detectable in 50% of OPCA type patients.
30% and 65% of MSA patients had a good
levodopa response at some stage. Between 13% and 30% maintained some response through the course of the illness. 25% to 50% of those treated with levodopa had dyskinesias (particularly orofacial) and
dystonia, even if they did not experience improvement in motor state.
Autonomic symptoms were the initial
feature in 41% of patients, but ultimately 97% of patients developed some degree of autonomic dysfunction. The most frequent autonomic symptom in men was impotence and in women urinary incontinence.
Orthostatic hypotension occurred in 68%.
A mild restriction of downgaze may develop
in about 10% of MSA cases.. Anterior horn cell loss may occur but is uncommon. Anal sphincter EMG (90% have an abnormality) is a sensitive and specific diagnostic test for MSA. Even less frequently seen
is a mild sensory neuropathy. Classic rest tremor is uncommon (29%).
Cerebellar signs occurred in 54% of patients and upper motor neuron signs in 49% of the cases. MSA-P type generally demonstrates more tremor, pyramidal signs, and myoclonus than MSA-C type. Severe dementia is uncommon
Respiratory stridor (which ultimately
occurs in 1/3 of cases) in combination with parkinsonism is highly suggests MSA until proven otherwise; although stridor can also occur in PD, it is exceptionally rare.