Abstract

The Autonomic Nervous System (ANS) regulates numerous involuntary bodily functions, including cardiovascular control, digestion, and thermoregulation. Disruptions in ANS function are associated with a diverse array of neurological and systemic disorders. Traditional autonomic testing methods, such as the Valsalva manoeuvre and orthostatic tests, primarily focus on cardiovascular reflexes, offering valuable yet indirect insights into autonomic pathways. However, technological advancements have led to the emergence of modern methods like heart rate variability (HRV) analysis, microneurography, and quantitative sudomotor axon reflex testing (QSART), which provide more precise assessments of both sympathetic and parasympathetic function. Despite their potential, the integration of these contemporary methods into routine clinical practice remains limited due to their complexity and resource requirements. This review aims to provide a comprehensive overview of classical and modern ANS testing methods, emphasising their clinical relevance in daily practice to enhance patient-care. Aims and Methods of ANS Testing: Autonomic nervous system (ANS) testing is essential for evaluating the severity and distribution of autonomic dysfunction, diagnosing conditions such as autonomic neuropathy and orthostatic intolerance, and monitoring disease progression or treatment efficacy. Most tests assess cardiovascular reflexes in response to various stimuli, activating sympathetic or parasympathetic outflow. Classical methods, including the Ewing Battery, Head-Up Tilt (HUT) test, and Deep Breathing Test, remain clinically significant, especially in settings lacking advanced technology. Contemporary methods have revolutionised ANS testing, with HRV analysis providing in-depth insights into autonomic control over heart rate, while Microneurography and QSART assess sympathetic nerve activity and sudomotor function, respectively. Conclusion: The evolution of autonomic function testing, from simple measures to advanced techniques, enhances our understanding of ANS regulation. Classical methods remain invaluable, yet newer technologies like HRV analysis and QSART offer detailed evaluations for complex autonomic conditions. Broad clinical integration of these contemporary methods alongside traditional approaches is essential for improving patient care.

• 1.   Spalding JMK. Disorders of the autonomic nervous system. J Neurol Neurosurg Psychiatry. 1966; 35:276-91.
• 2.   Freeman R, Wieling W, Axelrod FB, Benditt DG, Benarroch E, Biaggioni I, et al. Autonomic nervous system testing: a review of the literature and current clinical applications. Neurology. 2013; 80(1):1-13.
• 3.   Benarroch EE. The autonomic nervous system: basic anatomy and physiology. Continuum (Minneap Minn). 2013; 19(1):19-39.
• 4.   Zygmunt A, Stanczyk J. Methods of evaluation of autonomic nervous system function. Arch Med Sci. 2010 Feb; 6(1):11-8. DOI: 10.5114/aoms.2010.13500.
• 5.   Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Front Public Health. 2017;5:258.
• 6.   Lombardi F. Clinical utility of heart rate variability: perspectives from the European Society of Cardiology Task Force. Card Electrophysiol Rev. 2002; 6(3):245-9.
• 7.   Malik M. Heart rate variability: standards of measurement, physiological interpretation, and clinical use. Circulation. 1996;93(5):1043-65.
• 8.   Ewing DJ, Clarke BF. “Diagnosis and management of diabetic autonomic neuropathy.” Br Med J. 1982; 285(6346):916-918.
• 9.   Low PA, Tomalia VA. “Clinical autonomic testing: then and now.” Clin Auton Res. 2015; 25(2):85-89.
• 10.   Freeman R. “Autonomic peripheral neuropathy.” Lancet. 2005; 365(9466):1259-1270.
• 11.   Malliani A, Pagani M, Lombardi F. “Cardiovascular neural regulation explored in the frequency domain.” Circulation. 1991; 84(2):482-492.
• 12.   Ewing DJ, Hume L, Campbell IW, Murray A, Neilson JM, Clarke BF. “Autonomic mechanisms in the initial heart rate response to standing.” J Appl Physiol Respir Environ Exerc Physiol. 1980; 49(5):809-814.
• 13.   Valsalva AM. De aure humana tractatus. Utrecht: Traj ad Rhenum; 1707.
• 14.   Johnson RH, Lee GDJ, Oppenheimer DR, Spalding JMK. Autonomic function in cerebrovascular accidents. Lancet. 1966; 1(731):276-80.
• 15.   Varshney VP, Bedi M.Ghai’s textbook of practical Physiology, 10th Edition, 2023;2.29;186-91

Data Sharing Statement

Funding