From the Guidelines
Positive signs for cerebellar stroke when checking eye movements in a patient with acute vertigo include direction-fixed horizontal nystagmus, gaze-evoked nystagmus, and abnormal smooth pursuit, as identified in the most recent study 1. The most important finding is a positive head impulse test (HIT), where the patient can maintain fixation during rapid head rotation, indicating central pathology rather than peripheral vestibular dysfunction. Other concerning ocular signs include:
- Skew deviation (vertical misalignment of the eyes)
- Inability to suppress nystagmus with visual fixation
- Vertical nystagmus These findings are summarized in the HINTS exam (Head Impulse, Nystagmus, Test of Skew), which has high sensitivity for detecting stroke, as noted in 1 and 1. A normal head impulse test in a patient with acute vertigo should raise suspicion for cerebellar stroke, as peripheral causes typically show a positive head impulse test where the eyes cannot maintain fixation. These ocular signs occur because cerebellar strokes affect the vestibulo-ocular pathways that coordinate eye movements, particularly those involving the inferior cerebellar artery territory, as discussed in 1 and 1. Prompt recognition of these signs is crucial as cerebellar strokes can lead to life-threatening complications from posterior fossa edema and brainstem compression. The HINTS examination, when performed by specially trained practitioners, has been shown to be even more sensitive than early MRI for the detection of infarct, as reported in 1. Therefore, it is essential to prioritize the HINTS exam in the assessment of patients with acute vertigo to promptly identify those at risk of cerebellar stroke.
From the Research
Positive Signs for Cerebellar Stroke
When assessing eye movements in a patient with acute vertigo, the following are positive signs for cerebellar stroke:
- Direction-changing nystagmus 2
- Downbeat nystagmus (DBN) 3
- Impaired horizontal and vertical pursuit 3
- Impaired VOR suppression 3
- Skew deviation, as part of the HINTS battery 4
Eye Movement Abnormalities
Abnormalities in eye movements can indicate a cerebellar stroke, including:
- Nystagmus, which can be direction-changing or downbeat 2, 3
- Abnormal head impulse test, although a normal test does not rule out cerebellar stroke 3, 5, 6
- Impaired pursuit and VOR suppression 3
Diagnostic Considerations
When diagnosing cerebellar stroke, consider the following:
- The HINTS battery (Head Impulse, Nystagmus, Skew deviation) is more sensitive than initial MRI in diagnosing stroke in patients with acute-onset vertigo 4
- A normal head impulse test does not rule out cerebellar stroke, especially in cases of posterior inferior cerebellar artery (PICA) territory infarction 5, 6
- Audiovestibular loss may herald impending infarction in the territory of anterior inferior cerebellar artery (AICA) 5, 6