Test of Skew & HINTS

Cover one of the patient's eyes, then quickly swap which eye is covered. Watch the uncovered eye each time. A vertical refixation movement on uncovering means the eyes were vertically misaligned — that's skew deviation, and in acute vertigo it points to a brainstem or cerebellar lesion.

Skew arises from imbalance in the central otolith-ocular (graviceptive) pathway. It is rare in isolated peripheral vestibular disease and so is highly specific for a central lesion when present in AVS.1 Patient fixates a distant target, examiner alternately covers each eye, watches for a vertical refixation saccade. The hypotropic (lower) eye lies on the lesion side.

Skew is the "S" of HINTS. It can be subtle — alternate cover testing must be deliberate and unhurried. Maddox-rod or double-Maddox-rod quantifies the misalignment and any associated ocular torsion. Persistent skew with vertigo always warrants imaging.

Combine the three steps: Head Impulse, then Nystagmus direction on lateral gaze, then Test of Skew. If ANY of the three has a "central" pattern — normal HIT in a patient with active nystagmus, direction-changing nystagmus, or skew on cover — treat it as stroke until imaging and time say otherwise.

Acute vestibular syndrome— sudden, continuous vertigo > 24 h with spontaneous nystagmus and gait imbalance — is the only setting in which HINTS applies. About a quarter of AVS is stroke,4,6 and ~10–20% of small posterior-fossa infarcts are missed by early DWI-MRI in the first 24–48 h.5 In that window the HINTS triad outperforms imaging when performed by a trained clinician.1 HINTS-plus adds a bedside hearing screen — sudden hearing loss with a central pattern raises suspicion for AICA- territory stroke.2,3

Pitfalls: HINTS does not apply to episodic vertigo, to chronic dizziness, or to patients whose nystagmus has resolved. Operator skill is decisive — in untrained hands the published sensitivities collapse. Video-oculography support, where available, raises both accuracy and confidence.