Resources

Glossary

The working vocabulary of positional vertigo. Inline dotted terms throughout the chapter link here.

Activities-specific Balance Confidence (ABC) Scale: A self-report scale of confidence in performing daily activities without losing balance — captures the psychological dimension of fall risk.
Adaptation: A rehabilitation mechanism that recalibrates the VOR using retinal slip as an error signal, restoring gaze stability during head movement.
Berg Balance Scale (BBS): A 14-task performance scale of static and dynamic balance, predictive of falls and responsive to rehabilitation progress.
Bilateral vestibular hypofunction (BVH): Reduced or absent function in both vestibular systems, causing oscillopsia and high fall risk. VRT relies on substitution and safety, not VOR recovery.
Cognitive behavioural therapy (CBT): A psychotherapy addressing maladaptive thoughts and avoidance behaviour, used adjunctively when dizziness is accompanied by anxiety — especially in PPPD.
Computerised Dynamic Posturography (CDP): Force-platform testing that quantifies postural sway under varied sensory conditions; its Sensory Organization Test isolates vestibular, visual and proprioceptive contributions.
Dizziness Handicap Inventory (DHI): A validated 25-item questionnaire quantifying the physical, functional and emotional impact of dizziness; sensitive to change and used to track VRT progress.
Dynamic Visual Acuity (DVA): A test of the ability to maintain clear vision during head movement; a drop in acuity with motion signals a VOR deficit.
Functional Gait Assessment (FGA): A performance measure of gait under challenge (head turns, obstacles, narrow base), assessing dynamic stability and fall risk.
Gaze stabilisation exercises: Exercises that train the eyes to stay fixed on a target during head motion (e.g. X1 and X2 viewing), recalibrating the VOR.
Habituation: Reduction of an abnormal symptomatic response through controlled, repeated exposure to a provocative movement or visual stimulus.
Head Impulse Test (HIT / vHIT): A bedside (or video-quantified) test of semicircular-canal VOR function; a corrective catch-up saccade after a head thrust marks hypofunction.
Home exercise programme (HEP): The structured set of VRT exercises a patient performs independently between clinic visits — typically 2–3 times daily for 10–20 minutes.
Oscillopsia: The illusory perception that the visual world bounces or moves during head motion, typically from an impaired VOR.
Persistent postural-perceptual dizziness (PPPD): A chronic functional vestibular disorder of non-spinning dizziness and unsteadiness, worsened by upright posture and visual motion. Managed with habituation, visual desensitisation and CBT.
Retinal slip: Movement of the image across the retina when the VOR fails to fully stabilise gaze. It is the error signal that drives VOR adaptation.
Sensory Organization Test (SOT): The CDP protocol that measures balance across six conditions of altered or removed visual and proprioceptive input, revealing sensory dependence.
Sensory reweighting: Central rebalancing of how heavily the brain trusts visual, vestibular and proprioceptive cues for balance — retrained by varying surface and visual conditions.
Substitution: A compensatory strategy that trains alternative sensory systems (vision, proprioception) and alternative eye movements (saccades) to replace deficient vestibular input.
Timed Up and Go (TUG): A quick mobility screen timing rise-from-chair, 3 m walk, turn and return; > 13.5 s flags elevated fall risk in older adults.
Unilateral vestibular hypofunction (UVH): Reduced vestibular function on one side (e.g. after neuritis). VRT exploits the intact side via VOR adaptation and balance retraining.
Vestibular implant: An experimental device that electrically stimulates the vestibular nerve or canals to mimic natural input, aimed at severe bilateral vestibular loss.
Vestibular Rehabilitation Therapy (VRT): A specialised, exercise-based therapy that reduces dizziness, imbalance and gaze instability by driving central compensation through adaptation, habituation and substitution.
Vestibulo-ocular reflex (VOR): The reflex that stabilises vision by generating eye movements equal and opposite to head movement. Its recalibration is the target of gaze-stabilisation exercises.
Visual Vertigo Analog Scale (VVAS): A self-report measure of dizziness provoked by visual motion; identifies visual dependence and guides visual-desensitisation exercises.
X1 viewing: A gaze-stabilisation exercise in which the head moves while the eyes fixate a stationary target, generating retinal slip to drive adaptation.
X2 viewing: A harder gaze-stabilisation exercise in which the head and the target move in opposite directions, increasing the sensorimotor demand. Introduced after X1 is mastered.