Autonomic function testing

Abstract Autonomic function tests are essential tools in clinical neurophysiology, used to objectively assess the integrity and performance of the autonomic nervous system. This chapter covers the three principal domains of autonomic testing: sympathetic cardiovascular (adrenergic) function, sympathetic sudomotor (cholinergic) function and parasympathetic (cardiovagal) function. Sympathetic adrenergic testing includes the tilt-table test and blood pressure response to the Valsalva manoeuvre, evaluating vasomotor control and orthostatic tolerance. Sudomotor testing assesses postganglionic cholinergic pathways using the quantitative sudomotor axon reflex test (QSART) and the sympathetic skin response (SSR). Parasympathetic cardiovagal function is evaluated through heart rate variability during sinusoidal deep breathing, heart rate response to Valsalva manoeuvre and the 30:15 ratio following active standing. The chapter reviews relevant autonomic anatomy and provides step-by-step protocols for test setup and execution, with attention to patient preparation, environmental factors and artefact minimisation. Standard reference values and interpretation criteria are provided to aid in clinical decision-making and reporting.