How should I perform a bedside examination of nystagmus?

How to Examine Nystagmus at the Bedside

To examine nystagmus at the bedside, perform the Dix-Hallpike maneuver for posterior canal involvement and the supine roll test for lateral canal involvement, carefully observing for characteristic eye movements including direction, latency, duration, and response to visual fixation. 1

Essential Examination Components

Primary Observation Techniques

Direct observation of spontaneous nystagmus should be performed first with the patient's eyes open in primary gaze position, noting any involuntary rhythmic eye movements. 1 The examiner should specifically assess:

• Direction of nystagmus: Identify whether the fast phase beats horizontally, vertically, or has a torsional (rotatory) component 1
• Effect of gaze position: Observe the patient looking straight ahead, then in eccentric gaze positions (left, right, up, down) 2
• Visual fixation effect: Peripheral nystagmus should increase when visual fixation is removed 3

The Dix-Hallpike Maneuver (Posterior Canal Testing)

This is the gold standard test for posterior canal BPPV and must be performed systematically: 1

1. Starting position: Seat the patient upright on the examination table with legs extended 1
2. Head rotation: Turn the patient's head 45° to the right (to test the right ear) to align the posterior semicircular canal with the sagittal plane 1
3. Rapid positioning: Quickly move the patient from sitting to supine with the head hanging 20° below horizontal, maintaining the 45° rotation 1
4. Observe for characteristic findings: 1
   • Latency period: 5-20 seconds (rarely up to 60 seconds) between positioning and nystagmus onset 1
   • Nystagmus pattern: Torsional (rotatory) and upbeating (toward the forehead) nystagmus 1
   • Duration: Symptoms and nystagmus resolve within 60 seconds from onset 1
   • Crescendo-decrescendo pattern: Nystagmus begins gently, increases in intensity, then declines 1
5. Return to upright: After resolution, slowly return patient to sitting; reversal of nystagmus direction may occur 1
6. Repeat on opposite side: Turn head 45° to the left and repeat the maneuver 1

The Supine Roll Test (Lateral Canal Testing)

This test identifies lateral semicircular canal BPPV, which would be missed by Dix-Hallpike testing alone: 1

1. Position patient supine: Lay the patient flat facing upward 1
2. Rapid head rotation: Quickly turn the head 90° to one side, then return to center, then 90° to the opposite side 1
3. Observe nystagmus pattern: 1
   • Geotropic nystagmus (beating toward the ground): The side with strongest nystagmus is the affected ear 1
   • Apogeotropic nystagmus (beating away from the ground): The side opposite the strongest nystagmus is the affected ear 1
   • Direction-changing: Nystagmus changes direction with head position 1

Advanced Bedside Techniques

Removing Visual Fixation (Penlight-Cover Test)

To unmask peripheral nystagmus that may be suppressed by visual fixation: 3

• Shine a penlight in one eye while intermittently occluding the other eye 3
• Peripheral vestibular nystagmus should increase in intensity (slow-phase velocity increases approximately 42%) when fixation is blocked 3
• This is a low-cost alternative to Frenzel goggles for disrupting visual fixation 3

The HINTS Examination (For Acute Vestibular Syndrome)

When differentiating peripheral from central causes in acutely dizzy patients, perform this three-step examination: 4

1. Head Impulse Test: Assess vestibulo-ocular reflex function 4
2. Nystagmus observation: Check for direction-changing nystagmus in eccentric gaze 4
3. Test of Skew: Use prism cross-cover test to detect vertical ocular misalignment 4

This bedside examination is more sensitive (100%) for stroke than early MRI in acute vestibular syndrome. 4

Critical Nystagmus Characteristics to Document

Pattern Recognition

Document these specific attributes: 2

• Trajectory: Horizontal, vertical, torsional, or mixed 2
• Conjugacy: Whether both eyes move together 2
• Velocity and waveform: Jerk (fast and slow phases) versus pendular (only slow phases) 2
• Amplitude and frequency: Size and rate of oscillations 2
• Temporal profile: Constant, paroxysmal, or triggered 2

Red Flags for Central Causes

These nystagmus patterns are highly predictive of central (stroke/CNS) pathology: 5

• Pure vertical nystagmus in primary gaze 5
• Pure torsional nystagmus without horizontal component 5
• Downbeat nystagmus 5
• Apogeotropic horizontal positional nystagmus that is treatment-refractory 5
• Direction-changing nystagmus in eccentric gaze 4
• Skew deviation (vertical misalignment), which predicts brainstem involvement in 30% of cases 4

Common Pitfalls to Avoid

Do not repeat the Dix-Hallpike maneuver multiple times to demonstrate fatigability, as this unnecessarily subjects patients to repeated vertigo and may interfere with immediate treatment. 1 Fatigability is not required for diagnosis. 1

Do not assume normal imaging rules out pathology: Early MRI diffusion-weighted imaging can be falsely negative in 12% of stroke cases within 48 hours of symptom onset, making bedside examination critical. 4

Recognize that skew deviation can identify stroke even when an abnormal head impulse test falsely suggests a peripheral lesion, particularly in lateral pontine strokes. 4