(See also Overview of the Autonomic Nervous System.)
Multiple system atrophy affects about twice as many men as women. Mean age at onset is about 53 years; after symptoms appear, patients live about 9 to 10 years.
There are 2 types of multiple system atrophy (MSA); types are based on the initial symptoms that predominate:
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MSA-C: Characterized by ataxia and postural instability (cerebellar dysfunction)
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MSA-P: Similar to Parkinson disease but often without tremor and often unresponsive to levodopa (parkinsonian symptoms)
Both types involve autonomic nervous system dysfunction. Although multiple system atrophy begins as one type, symptoms of the other type eventually develop. After about 5 years, symptoms tend to be similar regardless of which disorder developed first.
Etiology
Etiology of multiple system atrophy is unknown, but neuronal degeneration occurs in several areas of the brain; the area and amount damaged determine initial symptoms. A characteristic finding is cytoplasmic inclusion bodies containing alpha-synuclein within oligodendroglial cells.
Multiple system atrophy is a synucleinopathy (due to synuclein deposition); synuclein can also accumulate in patients with Parkinson disease, pure autonomic failure, or dementia with Lewy bodies. Synuclein is a neuronal and glial cell protein that can aggregate into insoluble fibrils and form Lewy bodies.
Symptoms and Signs
Initial symptoms of multiple system atrophy vary but include a combination of
Parkinsonian symptoms
Parkinsonian symptoms predominate in striatonigral degeneration. They include rigidity, bradykinesia, postural instability, and jerky postural tremor. High-pitched, quavering dysarthria is common.
In contrast to Parkinson disease, multiple system atrophy usually does not usually cause resting tremor and dyskinesia, and symptoms respond poorly and transiently to levodopa.
Cerebellar abnormalities
Autonomic symptoms
Typically, autonomic insufficiency causes orthostatic hypotension (symptomatic fall in blood pressure (BP) when a person stands, often with syncope), urinary retention, urinary incontinence, constipation, and erectile dysfunction.
Other autonomic symptoms, which may occur early or late, include decreased sweating, difficulty breathing and swallowing, fecal incontinence, and decreased tearing and salivation.
Rapid eye movement (REM) sleep behavior disorder (eg, speech or skeletal muscle movement during REM sleep), respiratory stridor, and sleep apnea are common. Patients are often unaware of REM sleep behavior disorder.
Patients may have nocturnal polyuria; contributing factors may include a circadian decrease in arginine vasopressin and treatments used to increase blood volume.
Diagnosis
Diagnosis of multiple system atrophy is suspected clinically, based on the combination of autonomic insufficiency and parkinsonism or cerebellar symptoms. Similar symptoms may result from Parkinson disease, dementia with Lewy bodies, pure autonomic failure, autonomic neuropathies, progressive supranuclear palsy, multiple cerebral infarcts, or drug-induced parkinsonism.
No diagnostic test is definitive, but some (eg, MRI, nuclear imaging with 123I-metaiodobenzylguanidine [MIBG], autonomic tests) help confirm clinical suspicion of multiple system atrophy—for example, if
Treatment
There is no specific treatment for multiple system atrophy, but symptoms are managed as follows:
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Orthostatic hypotension: Treatment includes intravascular volume expansion with salt and water supplementation and sometimes fludrocortisone 0.1 to 0.4 mg orally once a day. Use of compression garments for the lower body (eg, abdominal binder, compression stockings) and alpha-adrenoreceptor stimulation with midodrine 10 mg orally 3 times a day may help. However, midodrine also increases peripheral vascular resistance and supine blood pressure (BP), which may be problematic. Raising the head of the bed about 10 cm reduces nocturnal polyuria and supine hypertension and may reduce morning orthostatic hypotension. Alternatively, droxidopa may be used; its action is similar to that of midodrine, but duration of action is longer.
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Parkinsonism: Levodopa/carbidopa 25/100 mg orally at bedtime may be tried to relieve rigidity and other parkinsonian symptoms, but this combination is usually ineffective or provides modest benefit.
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Urinary incontinence: If the cause is detrusor hyperreflexia, oxybutynin chloride 5 mg orally 3 times a day or tolterodine 2 mg orally 2 times a day may be used. Tamsulosin 0.4 to 0.8 mg once a day may be effective for urinary urgency. Alternatively, the beta-3 adrenergic agonist mirabegron 25 to 50 mg once a day can be used; unlike tamsulosin, mirabegron does not worsen orthostatic hypotension.
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Urinary retention: Many patients must self-catheterize their bladder.
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Constipation: A high-fiber diet and stool softeners can be used; for refractory cases, enemas may be necessary.
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Erectile dysfunction: Drugs such as sildenafil 50 mg orally as needed or tadalafil 2.5 to 5 mg once a day and various physical means can be used.
Patients require supportive therapy because the disorder is progressive and fatal.
Key Points
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Multiple system atrophy can include parkinsonian symptoms, cerebellar abnormalities, and autonomic insufficiency in various degrees of severity.
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Diagnose this disorder based on clinical, autonomic, and MRI findings, but consider Parkinson disease, dementia with Lewy bodies, pure autonomic failure, autonomic neuropathies, progressive supranuclear palsy, multiple cerebral infarcts, and drug-induced parkinsonism, which can all cause similar symptoms.
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Use treatments specific for the symptoms present.
