Multiple System Atrophy

Multiple system atrophy (MSA) is defined as an adult-onset, sporadic, rapidly progressive, multisystem, neurodegenerative fatal disease of undetermined etiology, characterized clinically by varying severity of parkinsonian features; cerebellar, autonomic, and urogenital dysfunction; and corticospinal disorders. Neuropathological hallmarks of MSA are cell loss in the striatonigral and olivopontocerebellar structures of the brain and spinal cord accompanied by profuse, distinctive glia cytoplasmic inclusions (GCIs) formed by fibrillized alpha-synuclein proteins (defined as primary alpha-synucleinopathy). (See Etiology and Pathophysiology, History and Physical Examination, and Workup.)[2]

A consensus statement by the American Autonomic Society and American Academy of Neurology in 2007[3] categorized MSA in MSA-P with predominant parkinsonism and MSA-P with dominant cerebellar features (MSA-C). (See Categories of MSA below.)

The concept of MSA as a unitary diagnosis encompassing several clinical syndromes has a long history. The first cases of MSA were presented as olivopontocerebellar atrophy (OPCA) about a century ago. The Shy-Drager syndrome with features of parkinsonism and autonomic failure with OH was described in 1960. The term MSA was introduced to unify different forms of MSA in 1996. The discovery of GCIs and alpha-synuclein immunostaining as a sensitive marker of MSA were major milestones in the definition of MSA as a clinicopathologic entity. (See Table 1, below).[4]

Table 1. Historical Milestones in the Definition of Terms for MSA (Open Table in a new window)

A consensus conference in 2007[7] simplified the older definition of MSA—as determined by the Consensus Committee representing the American Autonomic Society and the American Academy of Neurology in 1996 and 1998[3] —and incorporated current knowledge for a better assessment of the disease.[8]

Categories of MSA

The 2 categories of MSA are as follows:

• MSA with predominant parkinsonism (MSA-P) - Extrapyramidal features predominate; the term striatonigral degeneration, parkinsonian variant is sometimes used

• MSA with cerebellar features (MSA-C) - Cerebellar ataxia predominates; it is sometimes termed sporadic olivopontocerebellar atrophy

The designation of MSA-P or MSA-C depends on the dominant feature at the time of evaluation, which can change with time.

Shy-Drager syndrome

When autonomic failure predominates, MSA was sometimes termed Shy-Drager syndrome (not defined in the present consensus anymore).

Characteristics of MSA

Features indicating the presence of MSA (tables 2a and 2b) or of another disorder (Table 3) are described below. (Corticospinal tract dysfunction with extensor plantar response with hyperreflexia [pyramidal sign] is not used to categorize MSA.) (See DDx.)

Table 2a. Main Features for the Diagnosis of MSA (Open Table in a new window)

Table 2b. Additional Features for the Diagnosis of Possible MSA* (Open Table in a new window)

 

Table 3. Characteristics That Do Not Support the Diagnosis of MSA (Open Table in a new window)

Levels of certainty of MSA

MSA can be ascertained as possible, probable, or definite MSA (see Table 4, below), based on autonomic and urogenital features, on the presence of parkinsonism, and on cerebellar dysfunction, as well as on additional features (see tables 2a and 2b, above).

Only pathologic findings of high density of alpha-synuclein-positive glial cytoplasmic inclusions (GCIs) and degenerative changes in the striatonigral or olivopontocerebellar pathways can definitively confirm the diagnosis of MSA. (See Workup.)

Table 4. Diagnostic Categories of MSA (Open Table in a new window)

Red flags supporting the diagnosis of MSA include the following:

• Orofacial dystonia

• Disproportionate antecollis

• Severe anterior flexion of the spine (camptocormia)

• Severe lateral flexion of the spine (Pisa syndrome)

• Contractures of hands and feet

• Inspiratory sighs

• Severe dysphonia

• Severe dysarthria

• New or increased snoring

• Cold hands and feet

• Pathologic laughter or crying

• Jerky myoclonic postural/action tremor

Patient education

A variety of resources are available for patient education. These include the Web sites of the Multiple System Atrophy Coalitions, Autonomic Disorder Consortium of the Clinical Rare Diseases Research Network, and Vanderbilt Autonomic Dysfunction Center.

MSA is characterized by progressive loss of neuronal and oligodendroglial cells in numerous sites in the central nervous system (CNS). The cause of MSA remains unclear, although a history of trauma has been suggested. Pesticide exposure as a causative factor in MSA has been suggested but has not been confirmed statistically.[9] Autoimmune mechanisms have also been suggested as potential causes of MSA, but evidence for these is weak.

There is some evidence of genetic predispositions in Japanese cohorts. Autosomal recessive inheritance[10] and genetic alterations with abnormal expansion of 1 allele of the SCA type 3 gene has been reported.[11] Single nucleotide polymorphisms (SNPs) at the SNCA locus coding for alpha-synuclide have been identified. G51D mutation in the SNCA locus has been described, but a connection between SCNA locus and MSA disease could not be confirmed. Associations with COQ2 and C9orf72 have been reported.[12, 13]

Researchers initially assumed that gray-matter damage caused MSA. However, the discovery of oligodendroglial glial cytoplasmic inclusions (GCIs) (see Table 8) indicated that damage primarily affects the white matter.[14] The chronic alterations in glial cells may impair trophic function between oligodendrocytes and axons and cause secondary neuronal damage. Whether the inclusions represent primary lesions or nonspecific secondary markers of cellular injury remains unknown. In addition to the GCIs, extensive myelin degeneration occurs in the brain. Changes in myelin may play an important role in the pathogenesis of MSA. The clinical symptoms of MSA correlate with cell loss in different CNS sites. (See Table 5, below.)

Table 5. Clinicopathologic Correlations (Open Table in a new window)

Occurrence in the United States

The prevalence of MSA is reported to be between 3.4-4.9 cases per 100,000 population. The estimated mean incidence is 0.6-0.7 cases per 100,000 person-years. MSA meets orphan disease status.[16, 17]

Many patients do not receive the correct diagnosis during their lifetime because of the difficulty in differentiating MSA from other disorders (eg, Parkinson disease, pure autonomic failure [PAF], other rare movement disorders). About 29-33% of patients with isolated late-onset cerebellar ataxia and 8-10% of patients with parkinsonism will develop MSA. Therefore, a higher prevalence than that estimated can be assumed.

International occurrence

In the European Union (EU), the prevalence rates show 4-5 cases per 100,000 persons. The incidence rate is about 0.6 cases per 100,000 persons per year.[18]

In the United Kingdom, the crude prevalence of MSA, including all probable and possible cases, is 3.3 per 100,000 population.[19]

In Iceland, the incidence is 0.6 per 100,000 and prevalence is 3.1 per 100,000.[20]

In Japan, the prevalence is 13.1 per 100,000 individuals. The mean annual incidence is 0.68.[21]

Race-, sex-, and age-related demographics

MSA has been encountered in Caucasian, African, and Asian populations. In Western countries, MSA-P predominates, occurring in 66-82% of patients. In Eastern countries (e.g., Japan), MSA-C is common, occurring in 67% of patients.

The disease more often affects men than women. The female-to-male ratio is around 1:2. (A ratio of 1:3-9 has also been reported.) However, the early and easy diagnosis of impotence may have led to the male statistical predominance of MSA. The mean age at onset in MSA is 52.5-55 years. The disease progresses over intervals of 1-18 years.

Patients with MSA have a poor prognosis. The disease progresses rapidly. Median survivals of 6.2-9.5 years from the onset of first symptoms have been reported since the late 20th century. No current therapeutic modality reverses or halts the progress of this disease. MSA-P and MSA-C have the same survival times, but MSA-P shows more rapid dysfunctional progression.

An older age at onset has been associated with shorter duration of survival in MSA. The overall striatonigral cell loss is correlated with the severity of disease at the time of death.

Bronchopneumonia (48%) and sudden death (21%) are common terminal conditions in MSA. Urinary dysfunction in MSA often leads to lower urinary tract infections (UTIs); more than 50% of patients with MSA suffer from recurrent lower UTIs and a significant number die of related complications.[22]

Most patients with multiple system atrophy (MSA) develop the disease when they are older than 40 years (average 52-55y), and they experience fast progression. Usually autonomic and/or urinary dysfunction develops first. Patients with MSA may have parkinsonian symptoms with poor or nonsustained response to levodopa therapy. Only 30% of MSA-P patients have an initial transient improvement. About 90% of patients are nonresponsive to long-term levodopa therapy.

Typically, 60% of patients experience objective decline in motor function within 1 year. Motor impairment can be caused by cerebellar dysfunction. Corticospinal tract dysfunction also can occur but is not often a major symptomatic feature of MSA. Table 2a provides an overview of the clinical domains and their main features. More details are described in subsequent sections.[23]

Autonomic and/or urinary dysfunction

Autonomic symptoms are the initial feature in 41-74% of patients with MSA; these symptoms ultimately develop in 97% of patients. Genitourinary dysfunction is the most frequent initial complaint in women, and erectile dysfunction is the most frequent initial complaint in men.

Severe orthostatic hypotension

Severe orthostatic hypotension is defined as a reduction in systolic blood pressure (BP) of at least 30mm Hg or in diastolic BP of at least 15mm Hg, within 3 minutes of standing from a previous 3-minute interval in the recumbent position. This form of hypotension is common in MSA, being present in at least 68% of patients. Most patients do not respond with an adequate heart rate increase. The definition of severe orthostatic BP fall as a diagnostic criterion for MSA is stricter than the definition of orthostatic hypotension as a physical finding as defined by the American Autonomic Society.[24]

Symptoms associated with orthostatic hypotension include the following:

• Light-headedness

• Dizziness

• Dimming of vision

• Head, neck, or shoulder pain

• Altered mentation

• Weakness - Especially of the legs

• Fatigue

• Yawning

• Slurred speech

• Syncope

Some patients have fewer orthostatic symptoms. In 51% of patients with MSA, syncope is reported at least once. In 18% of patients with severe hypotension, more than 1 syncopal episode is documented. Because of dysautonomia-mediated baroreflex impairment and consequent debuffering, patients respond in an exaggerated fashion to drugs that raise or lower their BP.

Orthostatic hypotension must be distinguished from postural tachycardia syndrome, which is defined as an increase in heart rate of greater than 30 beats per minute (bpm) and maintained BP (absence of orthostatic hypotension).

Postprandial hypotension

Patients are also susceptible to postprandial hypotension. Altered venous capacitance and baroreflex dysfunction have been reported as a cause.[25]

Supine hypertension

Approximately 60% of patients with MSA have orthostatic hypotension and supine hypertension. The supine hypertension is sometimes severe (>190/110mm Hg) and complicates the treatment of orthostatic hypotension.

Parkinsonism

Parkinsonism can be the initial feature in 46% of patients with MSA with predominant parkinsonism (MSA-P); it ultimately develops in 91% of these MSA-P patients. Although akinesia and rigidity predominate, tremor is present at rest in 29% of patients; however, a classic pill-rolling parkinsonian rest tremor is recorded in only 8-9%. Patients with MSA-P have a poor response to levodopa.

About 28-29% of patients have a good or even excellent levodopa response early in their disease. However, only 13% maintain this response. Patients with early onset (at < 49 y) MSA-P tend to have a good levodopa response.

Patients sometimes complain of stiffness, clumsiness, or a change in their handwriting at the onset of the disease.

Cerebellar dysfunction

Cerebellar symptoms or signs are the only initial feature in 5% of MSA patients. MSA with cerebellar features (MSA-C) most commonly causes gait and limb ataxia; tremor, pyramidal signs, and myoclonus are less common findings.

Additional symptoms

Other symptoms of MSA are based on mixed dysfunction. When the disorder results in nonautonomic features, imbalance caused by cerebellar or extrapyramidal abnormalities is the most common feature.

If the cerebellar, extrapyramidal, and pyramidal systems are involved, the movement disorder is usually the most profound disability.

Vocal cord paralysis may lead to hoarseness and stridor. A neurogenic and obstructive mixed form of sleep apnea can occur.

Multiple system atrophy (MSA) is a difficult diagnosis, especially early in the clinical course, and the initial physician often misdiagnoses the condition. The most common initial diagnosis is idiopathic Parkinson disease.[1]

The diagnosis of MSA is based mainly on clinical features (see tables 2a, 2b, 3, and 4). The presence of MSA can be definitively established only on postmortem examination. MSA is confirmed by the presence of a high density of glial cytoplasmic inclusions (GCIs) in association with degenerative changes in the striatonigral and olivopontocerebellar pathway.

In a patient with autonomic failure and orthostatic hypotension, the combination of a normal supine norepinephrine level that does not rise significantly with upright position suggests MSA.

Autonomic function testing

This can used to evaluate the distribution and severity of parasympathetic and sympathetic dysfunction. Findings include the following:

• Diminished respiratory sinus arrhythmia

• Abnormal response to Valsalva maneuver (no BP recovery in late phase II and/or no overshoot in phase IV, reduced Valsalva ratio for heart rate)

• Reduced response to isometric exercise (handgrip)

• Diminished response to cold pressor test

Sphincter electromyography (EMG)

Sphincter electromyography (EMG) can be used to detect hyperreflexia of the detrusor.

Measurement of urine residual volume by ultrasonography

Incomplete bladder emptying of greater than 100ml can be detected through ultrasonography.

Detrusor contractions

Impaired detrusor contractility is the pathognomonic urodynamic finding that distinguishes MSA from PD.[32]

Scintigraphy

Scintigraphy with iodine-123 metaiodobenzylguanidine (123 I MIBG) appears to be a useful tool for differentiation between Parkinson disease and MSA early after onset of autonomic dysfunction (90% sensitivity, 95% specificity).

Patients with Parkinson disease have significantly lower cardiac123 I MIBG uptake than do some patients with MSA and controls. However, studies have shown imperfect reliability.[33, 34]

Brain images may be normal in MSA. However, olivopontocerebellar atrophy (OPCA), cerebellar atrophy, and the putaminal lesions of striatonigral degeneration are often detected using MRI techniques. The slight hyperintensity of the lateral margin of the putamen on T2-weighted MRI is a characteristic finding in patients with MSA involving the extrapyramidal system.[35]

Expected MRI findings in MSA are as follows:

• Atrophy of cerebellum and brainstem in OPCA and striatonigral degeneration (SND)

• No vascular damage

• No multi-infarct pattern in brain

• No other lesions

• Hyperintensity in the pons, peduncles, and cerebellum on T2-weighted and proton density–weighted MRI scans

• Slitlike hyperintensity on T2-weighted and proton density–weighted MRI scans; a cruciform hyperintensity in the pons on T2-weighted MRI, known as the hot cross bun sign, is diagnostically helpful, but it is not specific to MSA.[36]

In addition, MRI and proton MR studies can be used to exclude other conditions, such as multi-infarct syndromes.

Trace (D)

A study using diffusion-weighted MRI showed that patients with MSA with predominant parkinsonism (MSA-P) had significantly higher Trace (D) values in the entire and anterior putamen, whereas patients with MSA with cerebellar features (MSA-C) had significantly higher Trace (D) values in the cerebellum and middle cerebellar peduncle. Furthermore, increased disease duration correlated significantly with increased Trace (D) values in the pons of patients with MSA-P and in the cerebellum and middle cerebellar peduncle of patients with MSA-C.[37]

MSA can be differentiated from Parkinson disease with the use of FDG-PET scanning. The caudate-putamen index, which is calculated using a formula based on the difference in the uptakes in the caudate and putamen divided by the caudate uptake, is lower in patients with MSA than in patients with Parkinson disease.[38]

Expected findings in MSA are as follows:

• Reduced putaminal FDG uptake

• Reduced [11 C]raclopride and [11 C]diprenorphine levels

• Reduced cerebellar glucose metabolism in OPCA

Absence of parkinsonian features but evidence of striatonigral dopaminergic denervation may point to MSA.

Neuropathologic changes in MSA consist of the development of a high density of GCIs in association with degenerative changes in some or all of the following structures (Table 5 provides an overview of the clinicopathologic correlation):

• Putamen

• Caudate nucleus

• Globus pallidus

• Thalamus

• Subthalamic nucleus

• Substantia nigra

• Locus ceruleus

• Dorsal vagal nucleus

• Vestibular nuclei

• Pontine nuclei

• Inferior olives

• Pontine nuclei

• Cerebellar Purkinje cells

• Autonomic nuclei of the brainstem

• Intermediolateral cell columns

• Anterior horn cells

• Onuf nuclei in the spinal cord and pyramidal tracts

GCIs, which can be stained using the Gallyas silver technique, range from sickle shaped to flame shaped to ovoid, on occasion, superficially resembling neurofibrillary tangles. GCIs are loosely aggregated filaments with cross-sectional diameters of 20-30 nm. These filaments often entrap cytoplasmic organelles (eg, mitochondria, secretory vesicles), have no limiting membrane, and have tubular profiles and electrodense granules along much of their lengths. GCIs are ubiquitin-positive, tau-positive, and alpha-synuclein ̶ positive oligodendroglial inclusions. They are different from Lewy bodies and neurofibrillary structures in Alzheimer disease. (See Table 8, below.)

Table 8. Differences Between GCIs in MSA and Other Pathologic Inclusions and Structures (Open Table in a new window)

The cause of multiple system atrophy (MSA) remains unknown, and no current therapy can reverse or halt progression of the disease. The extrapyramidal and cerebellar aspects of the disease are debilitating and difficult to treat.

Nonpharmacologic treatment

See the list below:

• Constipation - A high-fiber diet, bulk laxative, lactulose, and suppositories can prevent constipation

• Stridor - Speech therapy is often useful to improve swallowing and communication

• Deconditioning - Physical therapy and an aquatic exercise program (hypotension does not occur while patients are in water) prevent physical deconditioning of the patient unless the movement disorder aspect of the illness so impairs balance that this is not advisable

• Urinary incontinence - Intermittent self catheterization or suprapubic or urethral catheterization can improve symptoms of urinary incontinence

• Falls - As the disease progresses, the risk of falls increases; proper gait instruction and precautions are critical to prevent falls and resultant injury

Pharmacologic treatment

Drug therapy is directed mainly toward alleviation of symptoms of the movement disorder and orthostatic hypotension. Urinary incontinence, constipation, erectile dysfunction, and supine hypertension can also be addressed through pharmacologic therapy. (See Table 9.)

Surgical care

An atrial pacemaker may be used in patients with profound bradycardia in addition to orthostatic hypotension as a means of preventing the hypotension. However, this treatment is rarely undertaken and is rarely helpful.

Consider tracheostomy with the utmost care for intermittent respiratory stridor. Cricopharyngeal myotomy or gastrostomy has been used in patients with severe dysphagia, but its value is uncertain.

Consultations

Physical therapists, occupational therapists, speech therapists, and social workers can offer considerable practical help.

Diet

An essentially normal diet is recommended, with the following guidelines:

• Increased salt and fluid intake maintains plasma volume

• Small, frequent meals may help patients for whom postprandial hypotension is a significant problem

• A high-fiber diet, bulk laxatives, and suppositories prevent constipation

Activity

Exercise of muscles of the lower extremities and abdomen, water aerobics at hip level (not swimming, as it causes polyuria), and postural training, in combination with drug therapy, are useful.

Inpatient evaluation and tailoring of therapy are often important. However, if patients are restricted to bedrest, their functional mobility can decrease rapidly. Therefore, initiate physical therapy if the patient must remain in the hospital for longer than 2 days.

Orthostatic hypotension

The earliest symptom that brings patients to medical attention usually is orthostatic hypotension. Orthostatic hypotension leads to curtailing of physical activity, with all of the problems of deconditioning that consequently occur. Without an adequate upright BP, keeping patients active and on an exercise regimen is extremely difficult; therefore, management of orthostatic hypotension is one of the major tasks in the treatment of patients with MSA.

Mechanical maneuvers, such as leg-crossing, squatting, abdominal compression, bending forward, and placing 1 foot on a chair, can be effective in preventing episodes of orthostatic hypotension. Wearing an external support garment that comes to the waist improves venous return and preload to the heart during standing but loses effectiveness if the patient also wears it while supine. Increased salt and fluid intake and tilted sleeping with the head elevated increase the circulatory plasma volume.

Postprandial hypotension

Small, frequent meals attenuate BP drop after eating. Intake of water half an hour before meals or drinking coffee can counteract postprandial hypotension.

Supine hypertension

The management of patients with orthostatic hypotension and supine hypertension can be challenging, but adequate BP control is often achieved with the following treatment strategy:

• Use of over-the-counter medication with pressor effects

• Avoidance of fluid intake at bedtime

• Not using elastic stockings when supine

• Not using pressor agents before bedtime

• Raising the head of the bed 6-9 inches

• Resting on a semirecumbent chair with feet on the floor during the day

• Snacking before bedtime

As previously mentioned, pharmacologic therapy for multiple system atrophy (MSA) is directed mainly toward alleviation of symptoms of the movement disorder and orthostatic hypotension (see Table 9, below). Medications can also be used to treat urinary incontinence, constipation, erectile dysfunction, and supine hypertension. In recent years, neuroprotective therapy has been successfully applied in the mouse model.[39] But studies in humans (e.g., rifampicin rasagiline) did not show beneficial effects on slowing down the disease.[40, 41] Transgenic MSA mouse models do not have the same human phenotype but may be the best choice to explore new therapies.[42]

Medical therapy of movement disorder

The movement-disorder component of MSA is usually treated with levodopa, dopaminergic agonists, anticholinergic agents, or amantadine, but results are rarely as favorable in MSA as in classic Parkinson disease.

Drugs that now are not commonly used in patients with MSA include nonsteroidal anti-inflammatory drugs (NSAIDs), antihistamines, somatostatin analogues, and caffeine.

Medical therapy of orthostatic hypotension

Many agents have been advocated for the management of orthostatic hypotension. Table 9, below, shows some of the most widely used drugs. However, drug therapy of orthostatic hypotension is limited by supine hypertension, which affects about 60% of patients with MSA.[43]

In February 2014, droxidopa was approved by the FDA for the treatment of orthostatic hypotension. It is a synthetic amino precursor prodrug and is converted to norepinephrine.[44]

Water is a uniquely powerful pressor agent in the management of orthostatic hypotension in patients with MSA. It acts by increasing sympathetic activity. On average, 16 ounces of water will raise BP about 30 mm Hg. Patients may understandably be skeptical that something so commonplace could help raise their BP, so it does require patient education. No other beverage (not juice or coffee or even Gatorade) is as good as a pressor agent as water in patients with autonomic dysfunction. Its major limitations are a short (1-hour) half-life and increased urination (inconvenient when autonomic impairment makes urination difficult).

Patients should drink 16 ounces of water on awakening each morning, even before they get out of bed. Patients should learn to use water prophylactically; they will be able to do much more in the hour after ingesting water than at other times. A repeat dosing midmorning or at lunch and at midafternoon may give the patient additional capacity for activity during this part of the day. Conversely, since patients with autonomic failure commonly have supine hypertension, we discourage them from drinking large amounts of water within the 2 hours prior to bedtime, although we allow them to drink when they are thirsty.

Table 9. Drugs Used to Manage Orthostatic Hypotension in MSA (Open Table in a new window)

Medical therapy of supine hypertension

The presence of supine hypertension can complicate the pharmacologic management of patients with MSA, but a rational approach to its treatment is often successful. Simply avoiding the supine position is often enough to control hypertension during the day. Treatment of supine hypertension is required at night. Elevating the head of the bed is useful but rarely sufficient. Short-acting vasodilators are effective in controlling hypertension.

The management of patients with orthostatic hypotension and supine hypertension can be challenging, but adequate BP control is often achieved by combining the nonpharmacologic approach, as previously described, with the following medications:

• Nitrates, transdermal nitroglycerin (0.1–0.2 mg/h)

• Hydralazine (50 mg)

• Nifedipine; short-acting calcium blocker (10-30 mg)

• Clonidine (0.1 mg), early in the evening[45]

Class Summary

Patients with MSA may have an initial response to levodopa, but this response usually diminishes over time. Withdrawal of levodopa can cause a patient's condition to deteriorate, but this is much more prominent in Parkinson disease than in MSA. In modern practice, levodopa is administered in combination with a dopa decarboxylase inhibitor.

Levodopa/Carbidopa (Sinemet, Parcopa)

In this combination, levodopa is administered with a dopa decarboxylase inhibitor. When levodopa is administered alone, it is largely decarboxylated by the intestinal mucosa or other peripheral sites rich in monoamine oxidase (MAO), and little reaches the cerebral circulation and CNS.

Class Summary

These agents are used as alternatives to levodopa therapy in the late phase of the movement disorder. They selectively act on different subtypes of dopamine receptors throughout the brain. The mechanism through which dopaminergic agonists act is independent of the functional capacities of the striatonigral neurons and may be more effective than those of other drugs.

Bromocriptine (Parlodel, Cycloset)

Bromocriptine is a strong agonist of D2 and a partial agonist of D1 striatal dopamine receptors.

Amantadine

Amantadine may alter dopamine release or reuptake and actions at glutamate receptors.

Class Summary

These agents were widely used before levodopa was discovered.

Trihexyphenidyl

Trihexyphenidyl is an anticholinergic receptor agent affecting structures in the neostriatum.

Benztropine mesylate (Cogentin)

Benztropine mesylate is an anticholinergic receptor agent affecting structures in the neostriatum.

Class Summary

When detrusor hyperreflexia is the cause of a patient's urinary incontinence, peripherally acting anticholinergic agents (eg, oxybutynin chloride [Ditropan], tolterodine [Detrol], propantheline [Pro-Banthine]) can be applied.

Oxybutynin chloride (Ditropan XL, Gelnique, Oxytrol)

Oxybutynin chloride, a tertiary amine muscarinic receptor antagonist, is a nonspecific relaxant on smooth muscles.

Tolterodine (Detrol, Detrol LA)

Tolterodine is a competitive muscarinic receptor antagonist for overactive bladder. It differs from other anticholinergics by being selective for the urinary bladder over the salivary glands. Tolterodine has high specificity for muscarinic receptors and has minimal activity or affinity for other neurotransmitter receptors and other potential targets (eg, calcium channels).

Propantheline

Propantheline blocks the action of acetylcholine at postganglionic parasympathetic receptor sites.

Class Summary

If a special bulk-forming diet fails, lactulose occasionally is helpful. In rare cases, cisapride (Propulsid) may promote bowel movements, but this agent has been removed from the US market because of risk of cardiac rhythm disturbances.

Erythromycin (E.E.S., Ery-Tab, Erythrocin)

Erythromycin is a macrolide antibiotic that duplicates the action of motilin. By binding to and activating motilin receptors, it is responsible for migrating motor complex activity. IV administration enhances the emptying rate of liquids and solids. The effect can also be seen with oral erythromycin. The enteric-coated form may be the most tolerable. However, erythromycin's benefit as a prokinetic agent is usually marginal in MSA.

Class Summary

MSA may respond to yohimbine with BP elevation, but male erectile dysfunction only occasionally improves. Yohimbine (Yohimex, Yocon) should be given at a dose of 5.4 mg 3 times a day for the purposes of blood pressure elevation. Yohimbine has a very limited ability to improve erectile dysfunction in MSA and can dangerously elevate blood pressure when given with acetylcholinesterase inhibitors such as pyridostigmine. If adverse effects are a problem, the dose can be reduced to half a tablet 3 times a day and gradually increased to 1 tablet 3 times a day. The effect of sildenafil (Viagra) has not been determined in patients with autonomic failure. Other approaches include the use of mechanical devices, pumps, penile prostheses, or implants.

Yohimbine (Yohimex)

Yohimbine blockades alpha2 receptors in the pontomedullary region of the CNS, increasing sympathetic outflow.

Class Summary

Specific agents in this class have salt-retaining (mineralocorticoid) properties.

Fludrocortisone

Fludrocortisone has been a mainstay of pressor therapy for the last 50 years. It is a powerful mineralocorticoid that is largely devoid of a glucocorticoid effect when it is administered in low to moderate doses (0.1-0.3 mg). This agent can initially increase blood volume, which tends to normalize after the first week. Most patients gradually (over 2 wk) gain weight (usually 5-8 lb), with mild ankle edema occurring as a result of sodium retention, primarily in the extravascular compartment.

Much of the drug's benefit depends on support from tissue edema to the venous capacitance bed in the lower abdomen and extremities. With edema, the venous bed accommodates only a low volume of blood in the upright posture. The effect, in turn, improves blood return to the heart and, therefore, functional capacity. In addition to its direct effect through extravascular fluid accumulation, fludrocortisone increases alpha1-adrenoreceptor sensitivity by about 50%. During therapy, the renin-angiotensin system is suppressed (as expected).

Class Summary

These agents may reduce sympathetic outflow, which may reduce muscle tone.

Midodrine

Midodrine is a prodrug with activity as an alpha1-adrenoreceptor agonist. This agent is widely used to treat orthostatic hypotension in MSA. Midodrine acts directly on the vasculature to increase BP and avoids electrolyte abnormalities associated with fludrocortisone. However, supine hypertension is a significant problem and limits the enhancement of functional capacity in MSA. Midodrine has often caused an unpleasant sensation in the scalp (due to piloerection).

Class Summary

These agents augment coronary and cerebral blood flow. Agents such as ephedrine have been used in patients with MSA and share with midodrine the possible complication of excessive supine hypertension. The advantage of these short-acting vasopressors is that they can be given during the day if the patient does not lie down for 3-4 hours after taking them. A late-afternoon dose should be avoided if possible.

Droxidopa (Northera)

Droxidopa is an oral norepinephrine precursor that is directly metabolized to norepinephrine by dopa-decarboxylase which is extensively distributed throughout the body. Peak droxidopa plasma concentrations are associated with increases in systolic and diastolic blood pressures. Droxidopa has no clinically significant effect on standing or supine heart rates in patients with autonomic failure. It is indicated for symptomatic neurogenic orthostatic hypotension (NOH) in patients with primary autonomic failure caused by diseases and conditions (eg, Parkinson disease, multiple system atrophy, and pure autonomic failure, dopamine beta-hydroxylase deficiency, and nondiabetic autonomic neuropathy).

Ephedrine

Ephedrine is a sympathomimetic amine. It is an alpha- and a beta-adrenergic agonist and a peripheral vasoconstrictor.

Class Summary

These agents correct anemia associated with MSA.

Epoetin alfa (Epogen, Procrit)

This is a recombinant EPO that has been shown to increase the functional capacity of patients with MSA, particularly those with characteristic mild anemia. Up to 38% of patients with severe autonomic failure have anemia. A lack of sympathetic stimulation may lead to decreased EPO production and anemia. Sympathetic impairment and low plasma norepinephrine levels are correlated with the severity of anemia.

Even low doses (25-50 U/kg SC 3 times weekly) of epoetin alfa have successfully corrected anemia and improved upright BP. The drug's biologic activity mimics that of human urinary EPO, which stimulates the division and differentiation of committed erythroid progenitor cells and induces the release of reticulocytes from bone marrow into the bloodstream.

Class Summary

These agents have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclo-oxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions.

Indomethacin (Indocin)

Indomethacin inhibits vasodilator prostaglandin synthesis.

Class Summary

These agents prevent histamine response in sensory nerve endings and blood vessels. They are more effective in preventing histamine response than in reversing it.

Diphenhydramine (Benadryl, Diphenhist)

Diphenhydramine is a first-generation antihistamine with anticholinergic effects that binds to H1 receptors in the CNS and body. It competitively blocks histamine from binding to H1 receptors.

Diphenhydramine affects structures in the neostriatum. It has significant antimuscarinic activity and penetrates the CNS, giving the drug a pronounced tendency to induce sedation. Approximately half of patients treated with conventional doses have some somnolence.