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Subjective Visual Vertical
in vertigo
Karnataka ENT Hospital and Research Centre (R)
Champions Educational and Medical Society (R)
Amogh Foundation · Chitradurga, Karnataka, India
Contents
- Introduction
- Anatomy & physiology
- Technique & technology
- Dynamic SVV
- Normal findings
- Disease signatures (summary)
- Clinical cases (15 vignettes)
- Glossary
- References
Introduction
Dr Prahlada N.B · Karnataka ENT Hospital and Research Centre · Chitradurga
The Subjective Visual Vertical (SVV) is the angle a person perceives as upright in the absence of a visual frame of reference. Healthy adults set the line within ±2° of true earth-vertical[4]. Larger tilts localise to the graviceptive pathway from utricle to cortex[2].
Anatomy & physiology
The otoliths are two saccular dilatations of the membranous labyrinth: the utricle and the saccule. The utricular macula lies in the earth-horizontal plane in the upright head. A roll-plane head tilt shears the otoconia across the hair cells of the utricular macula — this is the primary signal feeding SVV[2].
Utricular afferents travel in the superior division of the vestibular nerve to the vestibular nuclei in the pontomedullary junction. Roll-plane signals are integrated locally, then projected rostrally to the interstitial nucleus of Cajal (INC) in the rostral midbrain. The pathway decussates in the pons between these two stations. From the INC, signals reach the oculomotor nuclei (driving counter-roll and skew) and the thalamus, ultimately projecting to the parieto-insular vestibular cortex[7].
Technique & technology
Every valid SVV paradigm must remove visual cues to verticality. The bucket test[3] uses an opaque bucket with a vertical line on the inside wall; the patient looks in, the examiner rotates the bucket from a tilted start until the patient calls the line vertical. Hemispheric domes and computerised SVV systems achieve the same goal with higher precision. Static SVV is the routine paradigm; dynamic SVV (eccentric rotation, galvanic stimulation) unmasks centrally compensated asymmetries.
Dynamic SVV
Static SVV asks the patient to set a luminous line to vertical while sitting upright in a dark, silent environment. Central compensation rebalances this tonic signal over weeks, so the static SVV may normalise even when a substantial peripheral asymmetry persists. Dynamic SVV paradigms — centrifugation, off-vertical-axis rotation, and galvanic stimulation — probe the otolith system at higher frequencies and unmask these compensated asymmetries[2].
Centrifugation displaces the patient 4 cm from the rotation axis; constant-velocity rotation produces a centripetal acceleration along the inter-aural axis that stimulates one utricle selectively. Asymmetries above 5° between left-stimulus and right-stimulus settings indicate utricular asymmetry, even when static SVV is normal. The main clinical role for dynamic SVV is in chronic or compensated peripheral lesions, particularly in vestibular schwannoma surveillance.
Normal findings
| Population | Mean ± SD |
|---|---|
| Healthy adults, lab SVV | 0.0 ± 1.2° |
| Healthy adults, bucket | 0.0 ± 1.5° |
| Healthy adults >70 y | 0.0 ± 2.0° |
Upper limit of normal: ±2.0°. Borderline: ±2.0–2.5°. Abnormal: above ±2.5°. Trial-to-trial variability (SD across 10 trials) above 2° suggests cerebellar involvement even when the mean is normal[4].
Disease signatures
| Condition | Direction | Magnitude | Variability |
|---|---|---|---|
| Normal | — | 0–2° | ±1° |
| Vestibular neuritis (acute) | Ipsilesional | 5–10° | ±1° |
| Vestibular neuritis (chronic) | Often resolved | 0–3° | ±1° |
| Wallenberg | Ipsilesional | 8–15° | ±1° |
| INC lesion | Contralesional | 5–10° | ±1° |
| Ménière’s (active) | Ipsilesional | 3–6° | ±1–2° |
| Vestibular schwannoma | Ipsilesional | 1–4° | ±1° |
| SCD | Variable | Usually 0–2° | ±1° |
| BPPV | — | 0–2° | ±1° |
| Cerebellar | Variable | 0–3° | ±3–5° |
| Vestibular migraine | Variable / inconsistent | 0–4° | ±1–2° |
| PPPD | — | 0–2° | ±1° |
| Pusher (visual SVV) | — | 0–2° | ±1° |
Magnitudes are illustrative, drawn from peer-reviewed series. Real measurements vary with chronicity, dominant nerve division, age, and method.
Clinical cases
Case 01 — Sudden vertigo in a 42-year-old man
Vignette. A 42-year-old previously healthy man presents to the emergency department with 36 hours of continuous vertigo, nausea, and unsteadiness. He had a viral upper respiratory infection two weeks ago. On examination he has spontaneous left-beating horizontal-torsional nystagmus, a positive head impulse test to the right, no skew, no hearing loss. Bucket SVV reads +7.5° (tilted to the patient's right) with low trial-to-trial variability.
SVV. +7.5° ± 1.2° — Large ipsilesional tilt, low variability.
Question. What is the most likely diagnosis?
Answer. Right vestibular neuritis
Teaching point. A clean peripheral pattern: ipsilesional SVV tilt + positive HIT + no central signs = peripheral vestibular lesion. The Bárány Society criteria recognise this constellation as acute unilateral vestibulopathy / vestibular neuritis.
Case 02 — Vertigo with hoarseness in a 67-year-old smoker
Vignette. A 67-year-old hypertensive smoker presents with sudden onset vertigo, dysphagia, and hoarseness for 6 hours. Examination shows left Horner's syndrome, left palatal weakness, decreased pain and temperature on the left face and right body, and a wide-based gait with falls to the left. Head impulse test is normal. Bucket SVV reads −11° (tilted to the patient's left) with a complete ocular tilt reaction.
SVV. -11.0° ± 1.4° — Large ipsilesional tilt with complete OTR, normal HIT.
Question. Where is the lesion?
Answer. Left lateral medulla
Teaching point. A grossly tilted SVV with a normal HIT in an acutely vertiginous patient is a posterior-circulation stroke until proven otherwise. The decussation rule places the lesion below the pontomesencephalic junction; the cranial nerve findings localise it to the lateral medulla.
Case 03 — Diplopia and head tilt after a small midbrain bleed
Vignette. A 58-year-old woman on warfarin presents with sudden-onset vertical diplopia and a persistent leftward head tilt. Examination shows skew deviation (right eye hypotropic), conjugate ocular counter-roll to the left, and a left head tilt. Saccades and pursuit are otherwise intact. Bucket SVV is −9° (tilted left). MRI shows a small haemorrhage in the right rostral midbrain.
SVV. -9.0° ± 1.4° — Contraversive tilt — away from the right-sided lesion.
Question. Which structure is most likely involved?
Answer. Right interstitial nucleus of Cajal (INC)
Teaching point. The decussation is the single most useful localising fact in roll-plane vestibular signs. Lesions below it tilt the SVV toward the lesion; lesions above it tilt the SVV away.
Case 04 — Imbalance with normal HIT in a 71-year-old
Vignette. A 71-year-old man with breast cancer (treated five years ago) presents with progressive unsteadiness over three months. He has gaze-evoked nystagmus in all directions, impaired smooth pursuit, and a wide-based gait. Head impulse test is normal. Bucket SVV mean is −1.5°. Standard deviation across 10 trials is 4.2°.
SVV. -1.5° ± 4.2° — Mean within normal limits, SD grossly elevated.
Question. What does the SVV pattern suggest?
Answer. Cerebellar dysfunction
Teaching point. Report the SD or IQR alongside the mean. A cerebellar SVV looks normal until you notice the spread. In this patient the picture suggests paraneoplastic cerebellar degeneration; the SVV variability is the quantitative bedside marker.
Case 05 — Autophony and a near-normal SVV
Vignette. A 39-year-old singer reports hearing her own voice and footsteps inside her head, brief vertigo when she strains, and a low-frequency conductive hearing loss with intact reflexes on the right. Bucket SVV is +1.0°. oVEMP amplitudes are augmented on the right with thresholds lowered by 15 dB.
SVV. +1.0° ± 1.1° — Within normal limits.
Question. How does the SVV finding fit the diagnosis?
Answer. It is consistent with right superior canal dehiscence
Teaching point. A normal SVV in the presence of augmented oVEMP and conductive hyperacusis is diagnostic. SVV's value here is in confirming utricular preservation, which both supports the diagnosis and informs counselling about potential post-surgical changes.
Case 06 — Fluctuating hearing and vertigo over 18 months
Vignette. A 51-year-old woman has had four episodes of vertigo over 18 months, each lasting 4–6 hours with associated left aural fullness and worsening of her low-frequency hearing loss. Between attacks she is symptom-free. Bucket SVV values across four visits: −3.5° (during attack), −2° (1 week later), −0.5° (1 month later), −3° (during the next attack two months later).
SVV. -3.5° ± 1.0° — Fluctuating ipsilesional tilt — larger during attacks, normalising between.
Question. What does the longitudinal SVV pattern tell you?
Answer. Left utricular involvement that fluctuates with disease activity — consistent with Ménière's
Teaching point. Serial SVV is a quantitative way to monitor utricular involvement in Ménière's disease. A consistent ipsilesional direction across multiple visits, with magnitude tracking disease activity, supports the diagnosis and identifies the side.
Case 07 — Vertigo with a normal HIT and a normal SVV
Vignette. A 34-year-old woman presents with two days of severe vertigo and nausea. Examination shows down-beating torsional nystagmus that does not change direction with gaze. Horizontal head impulse test is normal in both directions. Hearing is normal. Bucket SVV is +0.5°. cVEMP is absent on the left; oVEMP is preserved bilaterally. Caloric responses are symmetric.
SVV. +0.5° ± 1.1° — Within normal limits — utricular function preserved.
Question. What is the most likely diagnosis?
Answer. Left inferior-division vestibular neuritis
Teaching point. Normal SVV does not exclude vestibular neuritis — it excludes superior-division involvement. The clean dissociation between SVV (utricle) and cVEMP (saccule) lets you partition the neuritis by nerve division. This is why both SVV and VEMP belong in the same work-up.
Case 08 — Asymmetric hearing loss with mild imbalance over two years
Vignette. A 56-year-old engineer presents with two years of progressively worsening right-sided hearing loss and word discrimination out of proportion to his pure-tone audiogram. He reports mild imbalance with quick head movements but no rotational vertigo. Examination is unremarkable except for the audiogram. Bucket SVV is +1.5° (right) with a normal SD. Caloric testing shows a 65% right-sided weakness. Dynamic SVV (eccentric chair rotation) on the affected side produces a +5° tilt.
SVV. +1.5° ± 1.1° — Near-normal static SVV; dynamic SVV unmasks a 5° asymmetry.
Question. Why is the static SVV near-normal despite a 65% caloric weakness?
Answer. Slow tumour growth has permitted central compensation of the static asymmetry
Teaching point. Use dynamic SVV in suspected vestibular schwannoma. A normal static SVV in a patient with audiometric asymmetry does not exclude a sizeable tumour — the compensation hides it. MRI of the internal auditory canal remains the diagnostic test.
Case 09 — Episodic vertigo, headache, and a wandering SVV
Vignette. A 28-year-old woman with a history of migraine without aura presents with three discrete episodes of vertigo over the last year, each lasting 2–4 hours, accompanied by photophobia and a unilateral pulsating headache. Bucket SVV across the three attacks: episode 1 was +3.5°, episode 2 was −2.0°, episode 3 was +0.5°. Between attacks SVV normalises completely. Audiogram and caloric testing are normal. MRI is normal.
SVV. +3.5° ± 1.2° — Variable SVV tilt that changes direction across attacks.
Question. Which finding most supports vestibular migraine over Ménière's disease?
Answer. The direction of SVV tilt changes between episodes
Teaching point. Serial SVV tracking across attacks is the most informative use of the test in episodic vertigo. Consistent ipsilesional direction → Ménière's. Variable direction → vestibular migraine.
Case 10 — Persistent dizziness six months after vestibular neuritis
Vignette. A 45-year-old man had an episode of vestibular neuritis six months ago. He recovered the rotational vertigo within three weeks. However, he reports persistent non-spinning dizziness, unsteadiness when walking in supermarkets and crowds, and visual motion sensitivity. Bedside neuro-otological examination is normal. Bucket SVV is −0.5° with a normal SD. Caloric testing shows full recovery on the previously affected side.
SVV. -0.5° ± 1.0° — Normal — consistent with PPPD.
Question. What is the most likely diagnosis?
Answer. Persistent postural-perceptual dizziness (PPPD)
Teaching point. Normal SVV is part of the PPPD picture, not against it. The disorder is functional rather than structural: vestibular testing must be normal (or stable from a prior event) for the diagnosis to apply. SVV here helps reassure the patient that their graviceptive system is intact.
Case 11 — Stroke patient who resists being made upright
Vignette. A 72-year-old man is 5 days into rehabilitation after a right hemispheric ischaemic stroke. He has a left hemiparesis and left hemispatial neglect. When seated, his trunk lists 15° to the left, and he pushes hard against the therapist's attempts to correct it, insisting he is upright. Bedside bucket SVV (visual vertical) is +0.5°. When passively tilted in a chair with eyes closed and asked to indicate when he is upright, he consistently calls upright at a position 13° tilted to the left.
SVV. +0.5° ± 1.2° — Visual SVV near-normal; postural vertical grossly tilted.
Question. Which condition does this dissociation indicate?
Answer. Pusher syndrome (contraversive pushing)
Teaching point. Test both visual and postural verticals when a stroke patient resists being made upright. Pusher syndrome is a major obstacle to rehabilitation, and recognising it changes the therapy approach (visual feedback rather than standard balance training).
Case 12 — Oscillopsia and unsteadiness after months of IV gentamicin
Vignette. A 64-year-old man with a history of methicillin-resistant Staphylococcus aureus endocarditis received six weeks of intravenous gentamicin. He now reports oscillopsia while walking and inability to see signs while in a moving car. Examination: positive bilateral horizontal head impulse tests with corrective saccades. No nystagmus. Bucket SVV is 0.0° with a normal SD. Dynamic visual acuity drops by 5 lines with head motion. Caloric responses are bilaterally absent.
SVV. +0.0° ± 1.1° — Symmetrically absent — and so the SVV is normal.
Question. Why is the SVV normal despite complete vestibular failure?
Answer. Bilateral symmetric vestibular loss produces no asymmetry signal
Teaching point. A normal SVV does not mean a normal vestibular system. Bilateral symmetric failure produces a normal SVV because the test depends on asymmetry between the two sides. Use the HIT, caloric test, and dynamic visual acuity to detect bilateral vestibulopathy — SVV is the wrong tool.
Case 13 — Brief spinning sensation when turning over in bed
Vignette. A 56-year-old woman reports brief episodes of spinning lasting about 20 seconds, triggered by turning over in bed and by looking up at a high shelf. Between episodes she is well. Examination is unremarkable. Dix-Hallpike test on the right reproduces an upbeating-torsional nystagmus that fatigues with repetition. Bucket SVV is +0.5° with a normal SD. Audiogram is normal.
SVV. +0.5° ± 1.1° — Within normal limits.
Question. What does the normal SVV tell you?
Answer. It is consistent with right posterior canal BPPV
Teaching point. Normal SVV in suspected BPPV is reassuring and supportive of the diagnosis. A grossly tilted SVV in a patient labelled BPPV should prompt a search for additional vestibular pathology — coexisting neuritis is well described.
Case 14 — Continuous vertigo for two days with no hearing loss
Vignette. A 38-year-old man presents with two days of continuous spinning vertigo, severe nausea, and inability to walk without support. He had a cold the week before. Examination shows spontaneous left-beating horizontal nystagmus, a positive head impulse test to the right, no skew deviation, and normal hearing on both sides. Bucket SVV is +6° (tilted to his right) with low variability.
SVV. +6.0° ± 1.2° — Moderate ipsilesional tilt — classical peripheral pattern.
Question. Which feature most supports a peripheral rather than central cause?
Answer. Ipsilesional SVV tilt combined with a positive head impulse test on the same side
Teaching point. The HINTS-plus pattern works because central and peripheral findings dissociate. SVV adds a graviceptive measurement to the canal-based head impulse test. Peripheral lesion = both findings on the same side, both consistent. A discrepancy — especially a normal HIT with a large SVV tilt — is the warning sign for a central cause.
Case 15 — Bouncing vision while walking after IV antibiotics
Vignette. A 60-year-old man finished a 4-week course of intravenous gentamicin two months ago for endocarditis. He now reports that signs at the railway station 'bounce' as he walks, and he cannot read his phone in a moving car. He has no rotational vertigo. Examination: head impulse test is positive in both directions with bilateral corrective saccades. Bucket SVV is 0.0° with a normal SD. Caloric responses are bilaterally absent.
SVV. +0.0° ± 1.0° — Symmetrically absent input gives a normal SVV.
Question. Why is the SVV normal in a patient with profound vestibular failure?
Answer. SVV depends on the difference between right and left graviceptive inputs
Teaching point. A normal SVV does not rule out vestibular pathology. Bilateral symmetric vestibulopathy is the classic example: a profoundly impaired patient with a normal SVV. The diagnosis depends on the HIT and dynamic visual acuity, not SVV.
Glossary
- Subjective Visual Vertical (SVV)
- The angle a person perceives as upright when adjusting a luminous line in an otherwise dark environment. Reflects central integration of otolith (graviceptive) input, ocular counter-roll, and visual cues. Normal range in healthy adults is roughly ±2° from true earth-vertical.
- Subjective Visual Horizontal (SVH)
- Same paradigm as SVV but with the perceived horizontal axis. Test–retest reliability and disease sensitivity are comparable to SVV; the two are typically orthogonal and used interchangeably in most labs.
- Utricle
- Horizontally-oriented otolith organ that senses linear acceleration in the earth-horizontal plane and head tilt in the roll plane. The dominant graviceptor in upright stance; SVV tilt after unilateral vestibular loss is largely a utricular signal.
- Saccule
- Vertically-oriented otolith organ sensing vertical linear acceleration (e.g., gravity along the long axis of the body). Primary afferent target for cVEMP. Contributes less to SVV than the utricle.
- Ocular Tilt Reaction (OTR)
- Triad of head tilt, skew deviation, and ocular counter-roll, all toward the same side. Indicates a lesion of the graviceptive pathway from the utricle to the interstitial nucleus of Cajal. SVV tilts toward the lower (hypotropic) eye in peripheral and pontomedullary lesions; tilts to the contralesional side in pontomesencephalic lesions above the decussation.
- Skew deviation
- Vertical misalignment of the eyes arising from imbalance of otolith input. One eye is hypertropic, the other hypotropic. Part of the ocular tilt reaction.
- Interstitial nucleus of Cajal (INC)
- Midbrain integrator for vertical and torsional eye position, located in the rostral midbrain near the rostral interstitial nucleus of the medial longitudinal fasciculus. Lesions cause contraversive OTR and SVV tilt.
- Graviception
- The neural sense of gravity. Combines otolith afferents, somatosensory cues (truncal graviceptors), and visual cues; integrated in the brainstem, cerebellum, thalamus, and parieto-insular vestibular cortex.
- Bucket test
- Low-cost SVV paradigm: the patient looks into a bucket with a vertical line drawn inside the rim, eliminating external visual cues. The examiner rotates the bucket from a tilted starting position until the patient calls the line vertical. Validated against laboratory SVV with ~1° agreement.
- Vestibular Evoked Myogenic Potential (VEMP)
- Short-latency myogenic reflex to high-intensity sound or vibration; cVEMP probes saccule→inferior vestibular nerve→SCM, oVEMP probes utricle→superior vestibular nerve→inferior oblique. Companion test to SVV for otolith function.
- Wallenberg syndrome
- Lateral medullary stroke producing ipsiversive OTR and ipsilesional SVV tilt (often large, 5–15°). Classic localiser for vestibular nuclei involvement.
References
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