How can vestibular, disequilibrium, central, and peripheral neurological diseases be differentiated by bedside neurological examination?

Differentiating Vestibular, Disequilibrium, Central and Peripheral Neurological Disease Through Bedside Examination

The key to differentiating central from peripheral vestibular disease at the bedside is nystagmus pattern analysis: central lesions produce downbeating nystagmus without torsional component, direction-changing nystagmus without head position changes, gaze-evoked nystagmus, or direction-switching nystagmus (beating right with right gaze, left with left gaze), while peripheral lesions produce horizontal-torsional nystagmus that fatigues and is suppressed by visual fixation 1.

Critical Nystagmus Patterns for Central vs. Peripheral Differentiation

Central Vestibular Signs (Red Flags)

• Downbeating nystagmus on Dix-Hallpike maneuver, particularly without torsional component and not modified by positional changes 1
• Direction-changing nystagmus occurring without head position changes (periodic alternating nystagmus) 1
• Gaze-evoked nystagmus that does not fatigue and is not suppressed by visual fixation 2
• Direction-switching nystagmus (beats right with right gaze, left with left gaze) 1
• Baseline nystagmus without provocative maneuvers (though this can also indicate vestibular neuritis) 1

Peripheral Vestibular Signs

• Horizontal-torsional nystagmus that fatigues with repeated testing
• Nystagmus suppressed by visual fixation
• Positive head impulse test (corrective saccade when head is rapidly turned)

Associated Neurological Findings

Central Lesions (Brainstem/Cerebellar Stroke)

Physical examination reveals posterior circulation findings 1:

• Dysarthria (speech difficulty)
• Dysmetria (limb incoordination on finger-to-nose testing)
• Dysphagia (swallowing difficulty)
• Sensory or motor loss
• Horner's syndrome (ptosis, miosis, anhidrosis)
• Skew deviation (40% sensitive but highly specific for central lesions) 3
• Severe postural instability disproportionate to nystagmus 2

Peripheral Lesions

• Isolated vestibular symptoms without other neurological deficits
• Normal limb coordination
• No cranial nerve deficits beyond CN VIII
• Hearing loss, tinnitus, or aural fullness may accompany vertigo 1

Algorithmic Approach to Bedside Examination

Step 1: Assess Nystagmus Pattern

1. Observe spontaneous nystagmus without head movement

   • Present without provocation → Consider vestibular neuritis OR central lesion
   • Absent → Proceed to provocative testing

2. Perform Dix-Hallpike maneuver

   • Upbeating-torsional nystagmus that fatigues → BPPV (peripheral)
   • Downbeating without torsion, non-fatiguing → Central lesion 1

3. Test gaze-evoked nystagmus

   • Direction-switching with gaze direction → Central 1
   • Suppressed by visual fixation → Peripheral

Step 2: Head Impulse Test

• Corrective saccade (positive test) → Peripheral vestibular loss
• Normal smooth pursuit of target → Central lesion more likely

Step 3: Test for Skew Deviation

• Vertical misalignment on alternate cover test → 40% sensitive but highly specific for central lesion 3

Step 4: Complete Neurological Examination

• Assess for dysarthria, dysmetria, dysphagia → Central
• Check for sensory/motor deficits → Central
• Evaluate gait and coordination → Severe instability suggests central 2

Critical Pitfalls to Avoid

10% of cerebellar strokes present identically to peripheral vestibular disorders 1. The onset is typically more sudden than vestibular neuritis, but isolated vestibular symptoms without other neurological findings can occur in up to 75% of posterior circulation strokes 4.

Multivariate assessment increases accuracy: Using isolated signs alone is unreliable, but combining multiple findings (head impulse test, nystagmus pattern, skew deviation) increases sensitivity and specificity to 92% 3.

Failure to respond to conservative management (canalith repositioning or vestibular rehabilitation) should raise concern for misdiagnosis and possible central pathology 1.

Disequilibrium vs. True Vertigo

True vertigo (spinning sensation) indicates vestibular system involvement—either peripheral or central 5. Disequilibrium (imbalance without spinning) suggests:

• Bilateral vestibular loss
• Cerebellar dysfunction
• Proprioceptive deficits
• Multisensory imbalance

Patients must clearly describe rotational spinning for vestibular diagnosis. Vague "dizziness" or lightheadedness suggests non-vestibular causes (cardiovascular, metabolic, psychiatric) 5.

Time Course Considerations

• Seconds: BPPV (peripheral)
• Minutes to hours: Vestibular migraine, TIA (can be central or peripheral)
• Hours to days: Meniere's disease (peripheral), vestibular migraine
• Days to weeks: Vestibular neuritis (peripheral), stroke (central)

Associated symptoms matter: Hearing loss, tinnitus, and aural fullness strongly suggest peripheral pathology 1, 5. Migraine features (photophobia, phonophobia, visual aura) suggest vestibular migraine 1.