Acute Vestibular Syndrome vs Stroke
Acute vestibular syndrome (AVS): Acute dizziness with N/V, unsteady gait, nystagmus, intolerance to head motion, and lasts ≥24 hrs; no focal neuro signs (hemiparesis, hemisensory loss, gaze palsy)
- Most common causes: Vestibular neuritis (labyrinthitis) and vertebrobasilar CVA
- Central causes: Vertebrobasilar CVA (83%), multiple sclerosis (11%), other (6%)
- Over 50% of vertebrobasilar CVA’s have no focal neuro deficit
- Excludes benign positional vertigo and Meniere’s (< 24 hrs of continuous sx)
Which bedside tests can help differentiate peripheral from central causes of AVS?
- Differentiating type of dizziness (vertigo, presyncope, unsteadiness)
- Onset of dizziness (sudden vs gradual)
- Provocative head movement (eg. Hallpike-Dix)
- Proportionality of sx such as severity of dizziness, vomiting, gait impairment (eg. severe gait impairment with mild dizziness does not mean central cause)
- Hearing loss
- Patterns and vectors of nystagmus
- Noncontrast head CT has sensitivity of only 16% for acute ischemic CVA
- Multiple prodromal episodes of dizziness – Predictive of central cause (CVA)
- Headache or neck pain – Predictive of central cause (CVA, vertebral artery dissection) with positive LR = 3.2. Absence of pain not as predictive.
- Any neurologic signs, esp. truncal ataxia (unable sit upright with arms crossed) and severe gait instability – Strongly predictive of central cause
- Horizontal head impulse test (vestibular-ocular reflex) – If normal, predictive of central cause (positive LR 18.4, negative LR 0.16)
- Gaze-evoked nystagmus (right-beating nystagmus on right gaze and left-beating nystagmus on left gaze) = dysfunction of gaze-holding structures in brainstem and cerebellum – If abnormal, predictive of central cause (specificity 92%, sens 38%)
- Vertical ocular misalignment on alternate cover test – If abnormal skew deviation, predictive of central cause (specificity 98%, sens 30%)
- Diffusion-weighted MRI is good but not perfect - Sensitivity 83% for ischemic CVA
- Head Impulse test
- Gaze-evoked Nystagmus
- Test of Skew
Abnormal findings summarized using INFARCTs acronym:
- Impulse Normal
- Fast-phase Alternating
- Refixation on Cover Test
If any 1 of 3 abnormal, sensitivity 100% and specificity 96% for central cause
HINTS test seems just as good as diffusion-weighted MRI to r/o CVA in AVS.
- Tarnutzer AA et al. CMAJ. 2011; 183(9): E571-592.
- Kattah et al, Stroke, 2009