Glossary

High-resolution 3D FLAIR acquired 4 hours after intravenous or 24 hours after intratympanic gadolinium. The current standard for in-vivo visualisation of endolymphatic hydrops in Ménière's disease.

Quantitative map derived from DWI. Acute ischaemic tissue shows reduced ADC; T2 shine-through can produce a bright DWI signal without true restriction, so ADC is read alongside DWI to confirm acute infarction.

CSF cistern between the pons, cerebellum and petrous bone. Site of vestibular schwannoma, meningioma, epidermoid and the classic 'ice-cream-cone' tumour configuration extending out of the IAC.

Iodinated-contrast volumetric CT of intra- and extracranial vessels. High spatial resolution makes it the modality of choice in acute settings for basilar occlusion, vertebral dissection (intimal flap, mural haematoma) and posterior-circulation stenosis.

Advanced diffusion technique that quantifies the directionality of water diffusion along white-matter tracts. Used in research to probe vestibulospinal and medial longitudinal fasciculus integrity in multiple sclerosis and chronic vestibulopathy.

MRI sequence sensitive to the random motion of water molecules. Acute cytotoxic oedema (early ischaemia) restricts diffusion and appears bright on DWI with corresponding dark ADC, allowing detection of cerebellar and brainstem infarcts within minutes of onset.

Distension of the endolymphatic compartment — the pathological substrate of Ménière's disease. Now demonstrable in vivo with delayed 3D-FLAIR after intratympanic or intravenous gadolinium.

Heavily T2-weighted thin-slice MRI sequences that produce high CSF–nerve contrast. The gold-standard read for cranial nerves in the internal auditory canal, the membranous labyrinth and the cerebellopontine angle cistern.

T2-weighted MRI sequence that nulls the cerebrospinal fluid signal, sharpening the visibility of periventricular white matter plaques (multiple sclerosis), small infarcts adjacent to CSF spaces and posterior fossa pathology.

MRI of the blood-oxygen-level-dependent (BOLD) signal during sensory, motor or cognitive tasks. In vestibular disease it maps the cortical vestibular network and its disruption in PPPD and vestibular migraine.

Paramagnetic intravenous contrast that shortens T1, brightening sites of blood–brain or blood–labyrinth barrier breakdown — vestibular schwannomas, active demyelinating plaques, suppurative labyrinthitis.

Small transcutaneous current applied behind the ears to activate the vestibular nerve — used as a stimulus in fMRI experiments to probe central vestibular processing in health and disease.

Vertigo or eye movement provoked by tragal pressure or pneumatic stimulation of the ear canal — another third-window indicator (SSCD, perilymph fistula).

Thin-section (≤0.6 mm) CT of the temporal bone optimised for the otic capsule, ossicular chain and skull base. The preferred modality for SSCD, otosclerosis, temporal bone fracture, labyrinthitis ossificans and bony involvement of cholesteatoma.

Three-step bedside battery for the acute vestibular syndrome. A normal HIT, direction-changing nystagmus or vertical skew identifies a central lesion with sensitivity exceeding early MRI DWI.

Simultaneous acquisition of metabolic (PET) and anatomical/functional (MRI) information. Promising for chronic dizziness syndromes with normal structural imaging — correlates PIVC activity with structural connectivity in one session.

Features that should trigger imaging in a vertigo presentation: focal neurology, new severe headache, vertical or direction-changing nystagmus, acute hearing loss with vertigo, vascular risk factors with sudden symptoms, failure of conservative management.

Bony canal through the petrous temporal bone carrying the facial nerve and the cochleovestibular nerve complex. The first port of call when vertigo coexists with asymmetric or sudden hearing loss.

Transtympanic injection of dilute gadolinium that diffuses into the perilymph over ~24 hours, enabling delayed-3D-FLAIR visualisation of endolymphatic hydrops without systemic contrast.

Inflammation of the membranous labyrinth, viral or bacterial. T2 may show high signal in cochlea and vestibule; post-contrast T1 reveals labyrinthine enhancement.

Ossification of the cochlea and vestibule following bacterial labyrinthitis or meningitis. HRCT shows loss of fluid signal and bony obliteration — early recognition is critical for cochlear implant planning.

Persistent perception of self-motion following prolonged passive motion (cruise, flight). PET and fMRI show altered limbic and entorhinal metabolism — evidence for central, not peripheral, dysregulation.

Recurrent vertigo, fluctuating sensorineural hearing loss, tinnitus and aural fullness, attributed to endolymphatic hydrops. Imaging is mostly used to exclude alternatives and, in research, to visualise hydrops directly.

Vascular MRI — most often time-of-flight, contrast-free. Lower spatial resolution than CTA but avoids ionising radiation and iodinated contrast; less sensitive to subtle dissection or slow flow.

Multisensory cortical region (posterior insula, parietal operculum) that integrates vestibular, visual and somatosensory input. Functional imaging shows altered PIVC activity in PPPD, vestibular migraine and MdDS.

Abnormal communication between the perilymph and middle ear, classically after barotrauma or head injury. HRCT may show pneumolabyrinth or a fracture line; direct visualisation of the fistula itself is rare.

Chronic functional vestibular disorder marked by persistent non-spinning dizziness, postural instability and visual motion hypersensitivity. Structural MRI is typically normal; fMRI and PET show altered PIVC and visuo-vestibular cortical connectivity.

Air within the membranous labyrinth — pathognomonic of a perilymphatic fistula. Identified on HRCT after head or barotrauma; direct visualisation of the fistula itself is rare.

An oblique CT reconstruction plane perpendicular to the long axis of the superior semicircular canal. Indispensable for confidently calling — or excluding — superior canal dehiscence; axial-only review over-diagnoses.

Nuclear-medicine imaging of metabolic activity using radiotracers (most commonly ¹⁸F-FDG). Used in research for chronic functional vestibular disorders (MdDS, PPPD) and clinically for skull-base and temporal-bone neoplasms.

Oblique CT reconstruction parallel to the long axis of the petrous bone and the superior canal — a complementary view to Pöschl that profiles the canal in its long axis.

A bony defect in the roof of the superior canal that creates a third mobile window — sound- or pressure-induced vertigo (Tullio, Hennebert), autophony and pseudoconductive hearing loss. HRCT in the Pöschl plane is diagnostic.

Symptom-quality–independent triage of acute dizziness by Timing, Triggers and Targeted Exam — points the clinician to the imaging modality (or no imaging) most likely to answer the clinical question.

Vertigo and oscillopsia provoked by loud sound — a clinical hallmark of a third-window lesion (most often SSCD).

Tear of the vertebral artery wall producing an intramural haematoma; classic in younger patients with vertigo plus occipital headache or neck pain after manipulation or trauma. CTA findings include intimal flap, crescent-shaped mural haematoma and tapering stenosis.

Transient ischaemia of the posterior circulation territory, often presenting as brief positional vertigo or recurrent dizziness in older adults with vascular risk factors. CTA/MRA defines the substrate (stenosis, hypoplasia, dissection).

Episodic vestibular symptoms in a patient with migraine, defined by Bárány Society criteria. Imaging is used to exclude alternatives; fMRI shows altered thalamic and cortical vestibular processing.

Benign Schwann-cell tumour arising from the vestibular nerve. Contrast-enhanced MRI is the gold standard; classic appearance is an avidly enhancing IAC mass extending into the CPA ('ice-cream cone').