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For further information, see CMDT Part 24-04: Dysautonomia

Key Features

Essentials of Diagnosis

  • Postural hypotension or abnormal heart rate regulation

  • Abnormalities of sweating, intestinal motility, sexual function, or sphincter control

  • Syncope may occur

  • Symptoms occur in isolation or any combination

General Considerations

  • Primary neurodegenerative disorders with dysautonomia

    • Pure autonomic failure

    • Multisystem atrophy: constellation of parkinsonism, pyramidal signs, and cerebellar deficits

    • Parkinson disease

  • CNS lesions that may exhibit features of dysautonomias (usually postural hypotension)

    • Spinal cord transection

    • Other myelopathies above the T6 level (eg, due to tumor or syringomyelia)

    • Brainstem lesions, such as syringobulbia and posterior fossa tumors

    • Sphincter or sexual disturbances may result from cord lesions at any level

  • Peripheral causes

    • Guillain-Barré syndrome may have features of marked hypotension or hypertension or cardiac arrhythmias

    • Post-viral or paraneoplastic acute autonomic neuropathy

    • Diabetes mellitus

    • Uremia

    • Amyloidosis

    • Leprosy

    • Chagas disease

    • Hepatic porphyria

    • Botulism

    • Lambert-Eaton myasthenic syndrome

Clinical Findings

Symptoms and Signs

  • Syncope

  • Postural hypotension

  • Paroxysmal hypertension

  • Persistent tachycardia without other cause

  • Facial flushing, hypohidrosis, or hyperhidrosis

  • Vomiting, constipation, diarrhea, dysphagia, abdominal distention

  • Disturbances of micturition or defecation

  • Erectile dysfunction

  • Apneic episodes

  • Declining night vision

  • Impaired cholinergic function from botulism and the Lambert-Eaton myasthenic syndrome: constipation, urinary retention, and a sicca syndrome

Differential Diagnosis

  • Hypovolemia

  • Drugs, eg, β-blockers, calcium-channel blockers, vasodilators, diuretics

  • Situational syncope, eg, micturition, defecation, cough, swallow

  • Postural hypotension

    • Reduced cardiac output from volume depletion, aortic stenosis or cardiomyopathy, cardiac dysrhythmias, various medications

    • Endocrine disorders such as diabetes, Addison disease, hypothyroidism or hyperthyroidism, pheochromocytoma, and carcinoid syndrome


  • The neurologic examination should focus on detecting signs of parkinsonism, cerebellar dysfunction, disorders of neuromuscular transmission, and peripheral neuropathy

  • If the neurologic examination is normal,

    • Reversible, nonneurologic causes of symptoms must be considered

    • Isolated postural hypotension and syncope may relate to

      • Reduced cardiac output

      • Paroxysmal cardiac dysrhythmias

      • Volume depletion

      • Various medications

      • Endocrine and metabolic disorders, such as Addison disease, hypothyroidism or hyperthyroidism, pheochromocytoma, and carcinoid syndrome

  • For those with evidence of peripheral neuropathy,

    • Nerve conduction studies and electromyography should be done

    • Testing for HIV, amyloidosis, Sjögren syndrome, and Fabry disease is indicated

Laboratory Tests

  • Autonomic function tests

  • Patients with acute or subacute isolated dysautonomia should undergo testing for ganglionic acetylcholine receptor, anti-Hu, voltage-gated potassium channel complex, and voltage-gated calcium channel antibodies

  • Tests for vitamin B12 deficiency and diabetes

Imaging Studies

  • If there is evidence of central pathology, imaging studies will exclude a treatable structural cause

Diagnostic Procedures

  • Specialized tests include

    • Cardiovascular response to the Valsalva maneuver and deep respiration

    • Tilt-table testing

    • Thermoregulatory sweat test

    • Quantitative sudomotor axon reflex test

    • Quantitative direct and indirect axon reflex test


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