Clinical Features and Management of Autonomic Neuropathy
Introduction to Autonomic Neuropathy
- Autonomic neuropathy presents with a diverse range of clinical manifestations affecting multiple organ systems, primarily involving cardiovascular, gastrointestinal, urogenital, and sudomotor functions, as noted by the American Diabetes Association 1
Cardiovascular Manifestations
- Resting tachycardia (>100 bpm) is often an early sign of cardiovascular autonomic neuropathy (CAN) 2
- Orthostatic hypotension (a fall in systolic or diastolic blood pressure by >20 mmHg or >10 mmHg, respectively, upon standing without appropriate heart rate increase) is a hallmark feature of advanced CAN 2
- Decreased heart rate variability with deep breathing is often the earliest detectable abnormality in CAN, even before symptoms appear, according to the American Heart Association 3
- QT interval prolongation, which increases risk of arrhythmias, is a concern in patients with CAN 2
- Silent myocardial ischemia due to impaired pain perception is a risk in patients with autonomic neuropathy 2
Gastrointestinal and Urogenital Manifestations
- Postprandial hypotension occurring after meals is a manifestation of autonomic neuropathy 2
- Erectile dysfunction in males is a common early manifestation of autonomic neuropathy, as reported by the American Urological Association 4
- Female sexual dysfunction including decreased sexual desire, increased pain during intercourse, decreased arousal, and inadequate lubrication is associated with autonomic neuropathy, according to the American College of Obstetricians and Gynecologists 1
- Bladder dysfunction presenting as urinary incontinence, nocturia, frequent urination, urination urgency, and weak urinary stream is a symptom of autonomic neuropathy 1
Peripheral Vascular and Clinical Progression
- Increased peripheral blood flow resulting in warm skin is a manifestation of autonomic neuropathy 2
- Early/possible CAN: One abnormal cardiovagal test result, as defined by the American Diabetes Association 3
- Definite/confirmed CAN: At least two abnormal cardiovagal test results, according to the American Heart Association 3
- Severe/advanced CAN: Presence of orthostatic hypotension in addition to abnormal heart rate test results, as noted by the American Autonomic Society 3
Diagnostic Considerations and Risk Factors
- Assessment for autonomic neuropathy should include cardiovascular autonomic reflex tests (CARTs), as recommended by the American Diabetes Association 5
- Age and diabetes duration are major risk factors, with prevalence increasing up to 65% in long-standing diabetes, according to the American Diabetes Association 3
- Glycemic control is a key risk factor, particularly in type 1 diabetes, as reported by the American Diabetes Association 3
Treatment Approach and Clinical Implications
- Gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and sodium channel blockers are recommended as initial pharmacologic treatments for neuropathic pain in diabetic autonomic neuropathy, as suggested by the American Diabetes Association 1
- Optimization of glucose control to prevent or delay neuropathy development in type 1 diabetes and slow progression in type 2 diabetes, as recommended by the American Diabetes Association 1
- Management of bladder dysfunction with scheduled voiding and anticholinergic medications when appropriate, according to the American Urological Association 1
- CAN is a risk marker of mortality and cardiovascular morbidity, as noted by the American Heart Association 3
- Patients with autonomic neuropathy require careful perioperative management due to increased risk of hemodynamic instability, as reported by the American Society of Anesthesiologists 2
Autonomic Neuropathy Phenotypes and Diagnostic Considerations
Clinical Manifestations
- Autonomic symptoms often appear alongside sensory and motor deficits in generalized polyneuropathy, particularly in diabetic neuropathy, with common manifestations including cardiovascular symptoms and gastrointestinal dysfunction, according to the American Diabetes Association 6
- Common manifestations of autonomic neuropathy include cardiovascular symptoms, gastrointestinal dysfunction, and urogenital problems, as reported by the American Diabetes Association 7, 8
Diagnostic Recommendations
- Symptoms and signs of autonomic neuropathy should be assessed in patients with microvascular complications, particularly kidney disease and diabetic peripheral neuropathy, as recommended by the American Diabetes Association 6, 9
- Screening for autonomic neuropathy should include asking about orthostatic dizziness, syncope, or dry cracked skin in the extremities, according to the American Diabetes Association 6
Treatment and Management
- Recognition and treatment of autonomic neuropathy may improve symptoms, reduce sequelae, and improve quality of life, as stated by the American Diabetes Association 9
- Treatment of autonomic neuropathy focuses on optimizing glucose control in diabetic patients to prevent or delay the development of neuropathy, as recommended by the American Diabetes Association 6, 7
Autonomic Neuropathy as a Type of Polyneuropathy
Relationship Between Autonomic Neuropathy and Polyneuropathy
- Autonomic neuropathy occurs in several distinct phenotypes in relation to polyneuropathy, including as one component of a generalized polyneuropathy, as a distinct autonomic neuropathy phenotype, and as part of distal small fiber sensory polyneuropathy 10
- In distal symmetric polyneuropathy with autonomic involvement, the most common clinical findings are abnormalities of sweating and circulatory instability in the feet 10
Important Clinical Distinctions
- In some autonomic neuropathies, autonomic fibers can be affected in isolation and their involvement may precede somatic fiber involvement 10, 11
Diagnostic Considerations
- Autonomic testing may be considered in the evaluation of patients with polyneuropathy to document autonomic nervous system dysfunction (Level B evidence) 11
- A battery of validated autonomic tests is recommended to achieve the highest diagnostic accuracy (Level B evidence) 11
- Heart rate variability testing is a simple and reliable test of cardiovagal function that detects the presence of diabetic polyneuropathy with nearly the same sensitivity as nerve conduction studies 10
Diagnostic Testing for Dysautonomia and Small Fiber Neuropathy
Indications for Diagnostic Testing
- Electromyography (EMG) and autonomic testing (Sudoscan) are medically necessary for patients with dysautonomia, idiopathic intracranial hypertension, migraines, and small fiber neuropathy, as seen in a 32-year-old female patient 12
- Sudomotor dysfunction testing is particularly valuable in documenting small fiber neuropathy in the skin, as sweat glands are mediated by small fiber nerves 13