04/12/2025
The HINTS Exam
Cerebellar stroke can present similarly to peripheral vestibular disorders, making early diagnosis challenging. The HINTS exam is a bedside oculomotor assessment designed to differentiate central causes such as cerebellar stroke from peripheral vestibular neuritis in patients with acute vestibular syndrome.
The HINTS Exam: Components and Interpretation
1. Head Impulse Test
• Technique: Rapid, small-amplitude, unpredictable head thrusts while the patient fixates on the examiner’s nose.
• Peripheral Finding: An abnormal test with a corrective catch-up saccade when the head is turned toward the lesioned side, indicating a deficit in the peripheral vestibular system.
• Central Finding: A normal test with no corrective saccade, suggesting preserved vestibulo-ocular reflex function despite severe vertigo, which is concerning for a central lesion such as a cerebellar or brainstem stroke.
2. Nystagmus
• Technique: Observe nystagmus in primary gaze and with lateral gaze.
• Peripheral Finding: Unidirectional horizontal nystagmus that does not change direction with gaze, typically with the fast phase beating away from the lesion.
• Central Finding: Direction-changing nystagmus (such as right-beating on right gaze and left-beating on left gaze) or vertical or pure torsional nystagmus. These patterns point toward a central cause involving cerebellar or brainstem pathways.
3. Test of Skew
• Technique: Alternate cover or cover-uncover test to detect vertical ocular misalignment.
• Peripheral Finding: No vertical skew deviation.
• Central Finding: Presence of skew deviation with vertical realignment of the eye when uncovered, reflecting disruption of the central otolithic pathways.
The HINTS Rule: INFARCT
• I: Impulse (Head Impulse test) Normal
• N: Nystagmus direction-changing
• F: Fast-phase alternating
• A: Alternating cover test shows skew deviation
Any central sign raises concern for a central cause such as posterior circulation stroke.
Limitations and Important Considerations
• The exam is validated only for patients with continuous acute vestibular syndrome; it should not be applied to brief, positional, or episodic vertigo.
• Accurate performance requires adequate examiner skill, particularly in generating rapid and unpredictable head thrusts for the head impulse test.
• Small cerebellar strokes, particularly those without brainstem involvement, can occasionally produce a false peripheral pattern, including an abnormal head impulse test.
• Severe gait or truncal ataxia, even in the presence of a peripheral-pattern HINTS result, should prompt concern for cerebellar stroke.
• Early MRI of the posterior fossa may be falsely negative; thus, HINTS should be integrated with overall clinical impression rather than used in isolation.
