Overview
Pure autonomic failure (PAF) is a neurodegenerative disorder characterized by isolated autonomic dysfunction without extrapyramidal or cerebellar symptoms, leading to symptoms such as orthostatic hypotension, urinary incontinence, and impaired sweating.Diagnosis
Key Diagnostic Criteria:
- Orthostatic hypotension unresponsive to fluid or salt loading 3.
- Absence of parkinsonian or cerebellar signs 1.
Recommended Tests:
- Upright tilt table test to assess vasopressin response (increased vasopressin indicates normal baroreceptor function, differentiating PAF from MSA) 1.
- Sweat test using intradermal methacholine to evaluate sudomotor function (both PAF and MSA show reduced sweat production) 2.
Grading:
- Clinical criteria and autonomic function tests help differentiate from other autonomic neuropathies like MSA 12.Management
First-Line Treatments:
- Non-pharmacological interventions: increased salt and fluid intake, compression garments, and elevating the head of the bed 3.
Pharmacological Treatments:
- Fludrocortisone for sodium retention and volume expansion 3.
- Midodrine for vasoconstriction to manage hypotension 3.
- Pyridostigmine may be considered for its effects on sweat and salivary gland function, though evidence is limited 2.Special Populations
Elderly:
- Increased susceptibility to orthostatic hypotension; careful monitoring and management of fluid and salt intake are crucial 3.
Comorbidities:
- Management of comorbidities like cardiovascular disease requires careful consideration of hypotensive medications and orthostatic symptoms 3.Key Recommendations
Use upright tilt table testing to differentiate PAF from MSA by assessing vasopressin response during hypotension 1 (Evidence: Strong).
Employ intradermal methacholine sweat testing to evaluate sudomotor function, noting reduced sweat production in both PAF and MSA 2 (Evidence: Moderate).
Implement non-pharmacological measures such as increased salt and fluid intake for managing orthostatic hypotension in PAF patients 3 (Evidence: Moderate).References
1 Kaufmann H, Oribe E, Miller M, Knott P, Wiltshire-Clement M, Yahr MD. Hypotension-induced vasopressin release distinguishes between pure autonomic failure and multiple system atrophy with autonomic failure. Neurology 1992. link
2 Baser SM, Meer J, Polinsky RJ, Hallett M. Sudomotor function in autonomic failure. Neurology 1991. link
3 Wilcox CS, Puritz R, Lightman SL, Bannister R, Aminoff MJ. Plasma volume regulation in patients with progressive autonomic failure during changes in salt intake or posture. The Journal of laboratory and clinical medicine 1984. link