Emergency & Critical Care · Acute Vertigo

HINTS to diagnose stroke. Instrumented.

The three-step bedside oculomotor examination introduced by Kattah, Talkad, Wang, Hsieh, and Newman-Toker in 2009 in Stroke - published as more sensitive than acute MRI within the first 24-48 hours of acute vestibular syndrome - built into a platform that performs the examination quantitatively, without specialist training required.

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The clinical problem the HINTS examination was built to solve.

Acute vestibular syndrome - sudden persistent vertigo, nystagmus, nausea, and unsteady gait - is among the most common neurologic presentations to the emergency department. The vast majority of cases are benign. A clinically critical minority are posterior-circulation strokes. Distinguishing benign from dangerous at the bedside is one of the highest-stakes decisions in acute care neurology.

A patient with vestibular neuritis discharged from the emergency department goes home and recovers within days. A patient with cerebellar or brainstem stroke discharged in the same condition may die, may sustain devastating disability, or may return in extremis. The published clinical literature documents that misdiagnosis of posterior-fossa stroke as benign vestibular syndrome continues to occur with clinically and medico-legally meaningful frequency.

The diagnostic challenge with acute MRI

Diffusion-weighted MRI (DWI-MRI) is the established neuroimaging modality for acute ischemic stroke detection. Within the first 24 to 48 hours of a small posterior-fossa infarction, however, DWI-MRI has a documented false-negative rate that is clinically meaningful. Posterior-fossa infarcts smaller than approximately 10 mm, and those in the pontomedullary territory, are particularly likely to be missed by early MRI.

This is the gap the HINTS examination addresses. Bedside oculomotor examination - performed correctly - can identify posterior-circulation stroke that early MRI may not yet detect.

The Kattah/Newman-Toker 2009 paper.

Kattah, Talkad, Wang, Hsieh, and Newman-Toker at Johns Hopkins published in 2009 in Stroke the paper that introduced the HINTS examination - the three-step bedside oculomotor protocol that has reshaped how the acute vestibular syndrome is evaluated in evidence-based emergency neurology.

Kattah JC, Talkad AV, Wang DZ, Hsieh YH, Newman-Toker DE. HINTS to diagnose stroke in the acute vestibular syndrome: three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging. Stroke. 2009;40(11):3504–3510.

PMID 19762709

The central finding: in patients with acute vestibular syndrome, the HINTS examination performed by a trained examiner identified posterior-circulation stroke with sensitivity exceeding that of acute diffusion-weighted MRI within the first 24 to 48 hours of symptom onset. The paper title is itself definitional of the central observation. The HINTS line of work has been extended through subsequent publications in the years since.

Saber Tehrani AS, Kattah JC, Mantokoudis G, Pula JH, Nair D, Blitz A, Ying S, Hanley DF, Zee DS, Newman-Toker DE. Small strokes causing severe vertigo: frequency of false-negative MRIs and nonlacunar mechanisms. Neurology. 2014;83(2):169–173.

PMID 24920847

Subsequent validation work extending the HINTS line: small strokes causing severe vertigo, the frequency with which early MRI returns false-negative results in this population, and the nonlacunar mechanisms by which small posterior-fossa infarcts may produce severe acute vestibular syndrome.

The three steps. The INFARCT mnemonic.

A patient is identified by the HINTS examination as having a central (stroke) cause if any one of the three findings is central. The INFARCT mnemonic captures the three central signs: Impulse Normal, Fast-phase Alternating, Refixation on Cover Test.

  1. HI · Head Impulse test of the vestibulo-ocular reflex. The examiner rapidly rotates the patient's head 10–20° while the patient fixates on a central target. A normal vestibulo-ocular reflex compensates and maintains fixation; an abnormal reflex produces a corrective catch-up saccade. The pattern is paradoxical: an abnormal head-impulse (catch-up saccade present) suggests a peripheral cause - vestibular neuritis. A normal head-impulse (no catch-up saccade - the "I" in INFARCT) suggests a central cause - stroke.
  2. N · Nystagmus observed in different gaze positions. Direction-changing nystagmus on horizontal gaze (right-beating on right gaze, left-beating on left gaze - the "FA" Fast-phase Alternating in INFARCT) or vertical nystagmus suggests a central cause. Direction-fixed nystagmus that remains in the same direction across gaze positions suggests a peripheral cause.
  3. TS · Test of Skew. Vertical ocular misalignment elicited by the alternating cover test - refixation on cover test, the "RCT" in INFARCT - suggests a central cause indicating brainstem involvement. Absence of skew is consistent with a peripheral cause.

The implementation barrier - and the platform's contribution.

The HINTS examination is not in widespread emergency-department use, despite its documented evidence base. The principal reason is that each of the three steps requires specialized training. Performance of the head-impulse maneuver, interpretation of nystagmus across gaze positions, elicitation of skew deviation - each was developed in the neuro-otology and neuro-ophthalmology specialty communities. Most emergency physicians and most general neurologists have not been trained to perform the examination correctly.

The platform addresses the implementation barrier directly. The platform's instrumented vestibulo-ocular reflex measurement - the video head-impulse test paradigm now standard in clinical vestibular practice - is the engineered version of the bedside Head Impulse test. The platform's optokinetic nystagmus, inter-saccadic interval, and fixation-stability channels capture the Nystagmus component across multiple gaze positions and discriminate direction-changing from direction-fixed patterns. The platform's vertical saccades and vergence channels capture the skew-deviation component of the Test of Skew with quantitative precision that the bedside alternating cover test cannot match.

The biomarker map

HINTS component Platform biomarker channel What the platform measures
Head Impulse Vestibulo-Ocular Reflex (gain + cancellation) VOR gain quantified across rapid head impulse delivered within the headset; catch-up saccade detection automated
Nystagmus Optokinetic Nystagmus · Inter-Saccadic Interval · Fixation Stability Nystagmus direction characterized across multiple gaze positions; direction-changing vs. direction-fixed discrimination
Test of Skew Vertical Saccades · Vergence Vertical ocular misalignment quantified to sub-degree precision; skew deviation detection automated
Adjunct localization Saccadic Latency · Saccadic Peak Velocity · Smooth Pursuit Gain Broader brainstem and cerebellar profile characterization to support localization of the central lesion

The position the platform takes.

Complement, not replace

The platform's contribution is to automate the three-step examination on a substrate that does not require fellowship-level training and does not depend on having a neuro-otologist or vascular neurologist physically available in the resuscitation bay. The platform delivers the HINTS measurement substrate quantitatively. Clinical judgment - the synthesis of the platform's output with the patient's history, risk factors, vital signs, and broader presentation - remains with the physician at the bedside. The platform is the instrument. The physician is the clinician.

Honest limits - what the platform does not yet claim.

Editorial discipline

The Kattah 2009 sensitivity result was obtained by examiners specifically trained in the HINTS technique. Demonstration that the platform's instrumented implementation reproduces the published sensitivity must come from prospective validation in emergency-department populations. That validation is the substance of the platform's Stage 5 prospective validation pathway and the basis of its planned FDA 510(k) submission with HINTS-equivalence as the predicate-comparison framing. Until that validation is complete and published, the platform's positioning is research-grade in the academic literature and pre-clearance in the regulatory sense. The platform does not claim that automated HINTS measurement has yet been demonstrated to match examiner-performed HINTS sensitivity. The platform claims that the architecture is on a credible engineering pathway to that demonstration.

The funding and academic-partnership pathway.

NIH NINDS R01 and R21 mechanisms in the acute cerebrovascular disease portfolio. BARDA emergency-readiness diagnostics. American Heart Association Grant-in-Aid. NIH NINDS Stroke Trials Network. Academic partnership with the Johns Hopkins neuro-otology and emergency-neurology community - Dr. David Newman-Toker is the principal academic voice on the HINTS examination and the natural partner for prospective validation work.

Detailed federal-funding documentation is maintained in the company's Master Funding Atlas, alongside the broader strategic portfolio.

For the emergency department, where neurologic time is shortest.

The platform's HINTS application is in active development. Academic partnership conversations and emergency-medicine community engagement are open now.

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