Glossary of VNS and nervous system terms

An adverse event is an unfavourable occurrence recorded during a study, without automatically establishing causation.

The auricular branch of the vagus nerve is a sensory branch that contributes to the innervation of parts of the external ear.

Auricular vagus nerve stimulation is a broad term for stimulation approaches that use the outer ear as the access location for vagus-related pathways.

The autonomic nervous system is the part of the nervous system that helps regulate internal functions such as circulation, digestion, temperature, and adaptation to changing demands.

The cavum conchae is the lower, larger part of the conchal bowl of the outer ear, below the crus of the helix and near the ear-canal entrance.

Certainty of evidence describes confidence that the true effect is close to the reported estimate.

Cervical non-invasive vagus nerve stimulation applies external electrical stimulation at the neck with the intention of influencing cervical vagal pathways without surgery.

A contraindication identifies a situation in which a device or intervention should not be used.

The cymba conchae is the upper, smaller part of the conchal bowl of the outer ear, above the crus of the helix.

Duty cycle describes how much of a repeating on/off cycle contains active stimulation.

The earlobe is the soft, lower part of the outer ear and is composed mainly of skin, connective tissue, and fat rather than cartilage.

An electrode is the conductive interface through which an electrical stimulator delivers current to the body.

Heart rate variability is the variation in time intervals between consecutive heartbeats, usually measured from normal-to-normal cardiac intervals.

Implanted vagus nerve stimulation uses a surgically placed electrode and implanted pulse generator to deliver programmed stimulation to the cervical vagus nerve.

Intended use defines the product's purpose and the conditions and users for which that purpose is communicated.

A meta-analysis statistically combines compatible results from multiple studies.

Non-invasive vagus nerve stimulation refers to external stimulation methods that do not require a surgically implanted electrode or pulse generator.

The parasympathetic nervous system is a major autonomic division that supports functions associated with maintenance, digestion, recovery, and energy conservation.

A precaution identifies circumstances that require added care or assessment rather than automatically prohibiting use.

Pulse width is the duration of an individual electrical pulse or pulse phase, commonly expressed in microseconds.

An RCT uses random allocation to compare outcomes between intervention groups.

A serious adverse event meets defined outcome-based seriousness criteria; seriousness is not the same as symptom intensity.

Session duration is the total elapsed time assigned to one stimulation session.

Sham stimulation is a comparison condition intended to resemble active stimulation without matching the full active protocol.

Stimulation frequency is the number of pulses or repeated stimulation cycles delivered per second, usually expressed in hertz.

Stimulation intensity describes the magnitude of the electrical output used during stimulation, often reported as current amplitude or relative to a sensory or discomfort threshold.

The stimulation site is the anatomical location where an electrode or device contact delivers electrical stimulation.

The sympathetic nervous system is a major division of the autonomic nervous system that helps mobilise resources and coordinate responses to changing demands.

A systematic review uses explicit methods to find, appraise, and synthesise a defined body of evidence.

Target engagement asks whether an intervention measurably affected the target its mechanism predicts.

Tolerability describes how acceptable or manageable an intervention is under the conditions studied, including whether participants can continue it without unacceptable burden.

The tragus is the small cartilaginous projection in front of the opening of the external ear canal.

Transcutaneous auricular vagus nerve stimulation is an ear-based form of tVNS delivered through the skin at selected regions of the outer ear.

Transcutaneous vagus nerve stimulation means stimulation delivered through the skin with the intention of influencing vagal pathways.

Vagal tone is an imprecise umbrella term used to describe aspects of ongoing vagal influence, especially on cardiac regulation.

The vagus nerve is the tenth cranial nerve and a major two-way communication pathway between the brainstem and organs in the chest and abdomen.

Vagus nerve stimulation is the deliberate use of electrical stimulation intended to influence vagal pathways.

A waveform is the time-varying shape and polarity pattern of the electrical output delivered by a stimulator.