The core signs, animated. Read the eyes.

Posterior-canal BPPV — the commonest positional vertigo.

Provoked by the Dix-Hallpike after a short latency: up-beating with a torsional component toward the down ear, building then fading inside a minute, and weaker on each repeat. Treated with the Epley, not referred.

Horizontal-canal BPPV — direction-changing on the roll test.

Purely horizontal nystagmus that reverses direction as the head is rolled to each side while supine. The common geotropic form beats toward the ground in both positions. Treated with a barbecue-roll or Gufoni maneuver, not the Epley.

Horizontal-canal BPPV — beats away from the ground (cupula variant).

Direction-changing horizontal nystagmus on the roll test that beats away from the ground (apogeotropic), the less common cupula-bound variant. Still peripheral — treated with Gufoni or roll maneuvers.

Vestibular neuritis — one direction, suppressed by fixation.

Spontaneous horizontal nystagmus that beats the same direction in every gaze position and gets stronger without visual fixation. With an abnormal head impulse and no skew, it points to peripheral neuritis.

A central red flag — think cerebellar.

Pure downbeat nystagmus with no torsion, no latency, persistent and non-fatigable, not suppressed by fixation. Do not treat as BPPV — refer for a central work-up (e.g. cerebellar or craniocervical-junction cause).

The fast phase reverses with gaze — central until proven otherwise.

As the eyes move, the fast phase changes direction (right-beating on right gaze, left-beating on left gaze). In acute continuous vertigo this is a central sign — part of the dangerous HINTS pattern.

Abnormal VOR — reassuringly peripheral in continuous vertigo.

On a rapid head thrust the eyes are dragged off the target, then a corrective (catch-up) saccade brings them back. In acute vestibular syndrome this ABNORMAL result points to a peripheral cause (neuritis), not central.

A normal impulse in continuous vertigo is the danger sign.

The eyes stay locked on the target through the thrust, with no catch-up saccade. Reassuring in a well patient — but in someone with acute continuous vertigo who cannot walk, a NORMAL impulse is the worrying, central sign.

Vertical misalignment — specific for central.

On the alternate-cover test the just-uncovered eye makes a small vertical refixation. Skew is the least sensitive but most specific of the three HINTS signs — when present in acute continuous vertigo, refer.

The mirror image of downbeat — same red flag.

Pure up-beating nystagmus in primary gaze, no torsion, spontaneous rather than positionally provoked. Like downbeat, this localises to the brainstem or cerebellum (pontomesencephalic or medullary) and is central on its own in acute vertigo — never treat it as BPPV.

Rotary beating with no horizontal or vertical component — central.

The fast phase is purely rotary — the iris markings turn, but the eye does not drift horizontally or vertically. Isolated torsional nystagmus is a brainstem sign; it can be the ONLY abnormal finding in an otherwise reassuring-looking exam, so look for it deliberately.

Real peripheral neuritis is rarely purely horizontal.

Unidirectional, but with both a horizontal and a torsional component together — the more realistic texture of vestibular neuritis (the labyrinth's canals are rarely damaged in perfect isolation). Still peripheral: with an abnormal head impulse and no skew, treat as neuritis, not as something more exotic.

The reassuring baseline — know what quiet looks like.

The eyes sit still with no beating at rest, in gaze, or after a positional maneuver. A negative positional test does not exclude BPPV — with a suggestive history, the guideline's answer is to repeat the test on another occasion (Bhattacharyya 2017). And a symptomatic patient with no nystagmus is outside the syndrome HINTS was validated in (Kattah 2009): the battery is not interpretable here, and continuous symptoms without nystagmus still warrant a careful general neurological exam and escalation on any other red flag.

The reassuring result — no vertical refixation either way.

Covering and uncovering each eye in turn produces no vertical correction — the eyes stay level. Absence of skew is reassuring but, on its own, the least powerful of the three HINTS signs: it never overrides an abnormal impulse or dangerous nystagmus finding elsewhere in the exam.

Peripheral nystagmus grows toward the fast phase but never reverses.

A unidirectional vestibular nystagmus is strongest looking toward the fast phase and weakest looking away, and it keeps the same direction across gaze. That intensity gradient is peripheral. A fast phase that switches direction with gaze is gaze-evoked and central instead.

A transient nystagmus released by vigorous head-shaking.

After about twenty seconds of brisk horizontal head-shaking, a stored vestibular imbalance can release a short-lived nystagmus. A horizontal beat toward the stronger ear fits a peripheral loss; a cross-coupled response, such as a vertical beat after horizontal shaking, suggests a central lesion. It is a provoking test, not a localiser on its own.

An abnormal impulse hidden inside the head thrust.

The catch-up saccade lands while the head is still moving, masked in the blur of the thrust rather than clearly after it. It is easy to miss with the naked eye and is why the video head-impulse test was developed to time it. It is still an ABNORMAL, peripheral result - a 'normal-looking' impulse deserves a second look before you trust it.

Catch-up saccades on thrusts to both sides.

When the head impulse is abnormal testing to either side, a single peripheral lesion cannot explain it. It points to bilateral vestibular loss, for example after ototoxic drugs, which gives oscillopsia and imbalance worse in the dark (Barany Society criteria). With acute vertigo and NEW unilateral hearing loss, an abnormal impulse on that same side does not secure a peripheral cause — AICA-territory stroke infarcts the inner ear and brainstem together and can mimic labyrinthitis (Lee 2009, Stroke); see HINTS-plus. The animation shows one side for clarity; in the patient with bilateral loss the catch-up saccade appears on thrusts to either direction.

Skew, head tilt, and ocular counter-roll, all toward one side.

A lesion of the graviceptive pathway tilts the eyes and head together: a vertical skew on the cover test, a head tilt toward the lower eye, and conjugate ocular torsion (counter-roll). A lower-brainstem or peripheral lesion tilts toward the lesion side; a midbrain lesion tilts away. The vertical skew is the component the HINTS cover test picks up.