In a multiple sclerosis patient with vertigo, when and how should I perform the head‑impulse test (h‑HIT), and what do normal versus abnormal results indicate?

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Head-Impulse Test (h-HIT) in Multiple Sclerosis with Vertigo

Direct Answer

In an MS patient with acute, continuous vertigo and spontaneous nystagmus at rest, perform the horizontal head impulse test (h-HIT) as part of the HINTS examination to distinguish central (MS-related) from peripheral vestibular causes—a normal h-HIT strongly suggests central pathology including MS demyelination, while an abnormal h-HIT indicates peripheral vestibulopathy.

When to Perform h-HIT

The h-HIT should only be performed when specific criteria are met 1:

  • Patient has continuous dizziness (not episodic or positional)
  • Spontaneous nystagmus is present at rest (visible without head movement)
  • Patient presents with acute vestibular syndrome (AVS): vertigo, nausea/vomiting, gait instability, nystagmus, and head-motion intolerance 2

Critical pitfall: Do not perform h-HIT on patients without nystagmus at rest—this leads to misdiagnosis and inappropriate interpretation 1.

How to Perform h-HIT

Apply rapid, unpredictable, small-amplitude (10-20 degrees) horizontal head rotations while the patient fixates on your nose. Observe for:

  • Corrective saccades (catch-up eye movements after head rotation stops)
  • Ability to maintain visual fixation during head movement

Video head impulse testing (vHIT) provides quantitative VOR gain measurements, with a cutoff of 0.7 being highly reliable for distinguishing central from peripheral causes 3.

Interpretation in MS Patients

Normal h-HIT (No corrective saccades, VOR gain >0.7)

  • Strongly suggests central pathology including MS demyelination 4
  • MS accounts for approximately 4% of AVS cases 2, 5
  • MS-related AVS lesions can occur in varied locations: medulla, cerebellar peduncles, pontine tegmentum, midbrain—not just the 8th nerve fascicle 5
  • Nearly all MS patients with AVS have additional central oculomotor signs on examination 2, 5
  • In some MS cases, a normal h-HIT may be the only central sign distinguishing it from vestibular neuritis 5

Abnormal h-HIT (Corrective saccades present, VOR gain <0.7)

  • Typically indicates peripheral vestibulopathy (vestibular neuritis/labyrinthitis)
  • However, 9% of stroke patients can have abnormal h-HIT (vestibulocerebellar, pontocerebellar, or pontocerebello-labyrinthine strokes) 4
  • MS patients can show canal-selective VOR gain reductions and asymmetry even with mild disability 6

Critical Context for MS Patients

MS-specific considerations:

  • MS patients with relapsing-remitting disease show lower VOR gains in multiple canals (right anterior/posterior, left posterior, left lateral) and higher asymmetry across canal planes compared to controls 6
  • The presence of cerebellar lesions on MRI does not necessarily correlate with h-HIT abnormalities 6
  • Functional head impulse testing shows negative correlation between vestibular symptom severity and test performance in MS patients 7

Integration with HINTS Examination

The h-HIT is one component of the complete HINTS triad 2:

  1. Head Impulse Test: Normal = central
  2. Nystagmus direction: Bidirectional or vertical = central; unidirectional horizontal = peripheral
  3. Test of Skew: Present = central

When performed by specially trained practitioners, HINTS has 100% sensitivity for detecting stroke (superior to early MRI at 46%) 2. However, non-expert performance shows mixed results 2.

Imaging Decisions

  • If complete HINTS examination suggests peripheral vertigo in a patient without known MS, imaging may not be required 2
  • If h-HIT is normal (suggesting central cause) in an MS patient, proceed with MRI brain without and with contrast to evaluate for new demyelinating lesions 2
  • MS patients with AVS and normal h-HIT should receive MRI even without other focal neurologic deficits, as 75-80% of AVS from central causes lack obvious focal deficits 2

Management Implications

MS patients with AVS from demyelinating lesions typically improve with steroid therapy 5. Early identification through proper h-HIT interpretation enables timely treatment initiation.

References

2
Guideline

acr appropriateness criteria® dizziness and ataxia: 2023 update.

Journal of the American College of Radiology, 2024

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.