Distinct Phenotypes of Autonomic Neuropathy
Yes, autonomic neuropathy occurs in three distinct phenotypes: as a component of generalized polyneuropathy, as a distinct autonomic neuropathy, and as part of small fiber sensory polyneuropathy. 1, 2
Autonomic Neuropathy as a Component of Generalized Polyneuropathy
- Autonomic symptoms often appear alongside sensory and motor deficits in generalized polyneuropathy, particularly in diabetic neuropathy 3
- Common manifestations include cardiovascular symptoms (orthostatic hypotension, resting tachycardia), gastrointestinal dysfunction (gastroparesis, constipation, diarrhea), and urogenital problems (erectile dysfunction, neurogenic bladder) 3
- In distal symmetric polyneuropathy with autonomic involvement, the most common clinical findings are abnormalities of sweating and circulatory instability in the feet 2
Distinct Autonomic Neuropathy
- Autonomic fibers can be affected in isolation, with autonomic involvement sometimes preceding somatic fiber involvement 2
- Autoimmune autonomic ganglionopathy is a pure autonomic neuropathy that typically affects both cholinergic and adrenergic functions 4
- Acute autonomic neuropathy can occur following infections, with profound autonomic failure as the primary presentation 5
- Autonomic testing reveals specific patterns of dysfunction affecting cardiovascular, sudomotor, and other autonomic domains 6
Autonomic Neuropathy as Part of Small Fiber Sensory Polyneuropathy
- Small fiber polyneuropathy presents with prominent pain and autonomic symptoms with minimal or absent motor findings 7
- Characterized by burning pain affecting the feet along with autonomic dysfunction 1
- Skin biopsy with intraepidermal nerve fiber density measurement is valuable for diagnosing this phenotype 1, 7
- Heart rate variability testing can detect autonomic dysfunction with nearly the same sensitivity as nerve conduction studies 2
Diagnostic Considerations
- A battery of validated autonomic tests rather than a single test is recommended to achieve the highest diagnostic accuracy 1, 2
- Autonomic testing should include heart rate variability, orthostatic blood pressure measurements, and sudomotor function tests 2
- Symptoms and signs of autonomic neuropathy should be assessed in patients with microvascular complications, particularly kidney disease and diabetic peripheral neuropathy 3
- Screening should include asking about orthostatic dizziness, syncope, or dry cracked skin in the extremities 3
Clinical Implications
- Recognition and treatment of autonomic neuropathy may improve symptoms, reduce sequelae, and improve quality of life 3
- Treatment focuses on optimizing glucose control in diabetic patients to prevent or delay the development of neuropathy 3
- For immune-mediated forms like autoimmune autonomic ganglionopathy, immunomodulatory treatments may be effective 4
- Although recovery of sensory impairment is often poor, autonomic dysfunction may improve to some degree within several months in acute forms 5