Glossary

Nystagmus beating toward the upper ear (toward the ceiling) on supine roll testing. In lateral canal BPPV, apogeotropic nystagmus suggests cupulolithiasis or a variant. The affected ear is the side where the response is LESS intense (reverse of geotropic).

A side-to-side audiometric difference suggesting a retro-cochlear lesion. The classical screening criterion is >15 dB asymmetry at 3 or more contiguous frequencies. In a dizzy patient, asymmetric hearing loss raises suspicion of vestibular schwannoma and warrants MRI with IAM protocol.

Symptoms localising to the brainstem or posterior circulation: dizziness (with other features), diplopia, dysarthria, dysphagia, drop attacks, and perioral or limb numbness. Reproducible brainstem symptoms on sustained head rotation are the hallmark of RVAS and warrant urgent vascular workup.

The pathological state in which free-floating otoconia move within the lumen of a semicircular canal under gravity, producing brief positional vertigo (BPPV). Distinct from cupulolithiasis, where otoconia adhere to the cupula. Canalithiasis produces fatigable, latent nystagmus; cupulolithiasis is non-fatiguing.

An adaptive process by which the brain shifts its sensory weighting when one input becomes unreliable. In chronic cervicogenic patients, prolonged altered cervical input leads to over-reliance on vision — producing the supermarket, scrolling, and crowd-environment symptoms of Route 4. Requires retraining rather than further manual therapy.

A complementary reflex to the VOR that uses neck-derived (rather than labyrinthine) input to stabilise gaze during head-on-trunk and trunk-on-head movements. Normally subordinate to the VOR but can be up-regulated in vestibular hypofunction.

Otoconia adherent to the cupula of a semicircular canal, producing sustained positional vertigo and non-fatiguing apogeotropic nystagmus in the lateral canal variant. Less common than canalithiasis and often more resistant to repositioning.

Nystagmus beating toward the lower ear (toward the earth) on supine roll testing. In lateral canal BPPV, geotropic nystagmus indicates canalithiasis. The affected ear is the side where the response is more intense.

A treatment approach using graded, repeated provocation of dizziness-triggering positions to desensitise the central response over time. Useful for some forms of motion-provoked dizziness and as a second-line BPPV strategy. CONTRAINDICATED in RVAS, where habituation may worsen the underlying vascular event.

A quantitative measure of side-to-side VEMP amplitude difference, calculated by the Jongkees formula: 100 × |L − R| / (L + R). IAR > 35% is generally considered abnormal and suggests asymmetric saccular or inferior vestibular nerve function.

The sense of self-position and movement of body parts in space, derived primarily from muscle spindles, Golgi tendon organs, and joint receptors. Cervical proprioception is dominated by the deep suboccipital muscles and is the foundation of the proprioceptive cervicogenic mechanism (Route 1).

The integrated process by which sensory information (proprioceptive, vestibular, visual) is processed centrally to produce coordinated motor output for posture and gaze. Cervical sensorimotor retraining — addressing JPE, oculomotor control, balance, and movement sense — is a Level-2-evidence cornerstone of Route 1 management (Sremakaew 2023).

The reflex that stabilises gaze during head movement by driving the eyes in the opposite direction at equal velocity (VOR gain ≈ 1.0). Tested clinically by the head impulse test (bedside) or video head impulse test (instrumented). Reduced gain indicates peripheral vestibular hypofunction.

Projections from the vestibular nuclei to brainstem autonomic centres (rostral ventrolateral medulla, nucleus of the solitary tract) that mediate the autonomic accompaniments of vestibular signals — nausea, pallor, sweating, palpitations. Drives the Route 2 cervicogenic presentation, where autonomic features dominate.