How to manage a patient with vertigo and no nausea or vomiting, to differentiate between Acute Vestibular Syndrome (AVS) and Cerebrovascular Accident (CVA)?

Management of Vertigo without Nausea or Vomiting: Differentiating AVS from CVA

The HINTS examination is the most sensitive and specific bedside diagnostic tool for differentiating between peripheral and central causes of vertigo, with greater sensitivity than early MRI for stroke detection when performed by properly trained clinicians. 1

Understanding Acute Vestibular Syndrome (AVS) and Stroke Risk

• Acute Vestibular Syndrome (AVS) is characterized by acute onset of persistent vertigo, nystagmus, gait instability, and head-motion intolerance, with or without nausea/vomiting 2
• The absence of nausea/vomiting does not rule out serious central causes like stroke, as posterior circulation infarcts can present with isolated vertigo 2
• Although most AVS cases with normal neurological examination have benign peripheral causes (vestibular neuritis or labyrinthitis), approximately 25% may be due to cerebrovascular disease, rising to 75% in high vascular risk patients 2
• Critically, 11% of patients presenting with acute persistent vertigo but no focal neurologic symptoms/signs were found to have acute infarct on CT or MRI 2

The HINTS Examination Protocol

The HINTS examination consists of three components:

1. Head Impulse Test:

   • Assesses vestibulo-ocular reflex 1
   • Normal response (no corrective saccade) in a dizzy patient suggests central cause 1
   • Abnormal response suggests peripheral vestibular dysfunction 1

2. Nystagmus Assessment:

   • Direction-changing nystagmus in eccentric gaze suggests central cause 1, 3
   • Unidirectional horizontal nystagmus suggests peripheral cause 1

3. Test of Skew:

   • Detects vertical misalignment of the eyes 1
   • Presence of skew deviation suggests central lesion, particularly brainstem involvement 4, 3
   • Skew can identify stroke even when an abnormal head impulse test falsely suggests peripheral lesion 3

Clinical Application and Diagnostic Accuracy

• When performed by specialists, the HINTS exam has shown 100% sensitivity and 96% specificity for stroke detection 3
• The complete HINTS triad consistent with peripheral vertigo has been shown to reliably rule out abnormalities on CT/MRI 2
• HINTS examination is more sensitive than early MRI for detecting stroke (100% versus 46%), as initial MRI diffusion-weighted imaging can be falsely negative in 12% of cases within 48 hours of symptom onset 3

Imaging Recommendations

• In patients with AVS and normal neurologic examination, CT imaging has very low detection rate (<1%) of central nervous system pathology 2
• MRI with diffusion-weighted imaging is preferred over CT for suspected central causes, but may be falsely negative in the first 48 hours 3
• The American College of Radiology notes that when the HINTS examination suggests a peripheral cause, the likelihood of abnormal findings on imaging is extremely low 2, 4

Important Clinical Considerations

• The absence of nausea/vomiting in vertigo does not rule out stroke; focal neurologic symptoms/signs may be absent in one-third to two-thirds of posterior circulation strokes 2, 4
• Multiple sclerosis involving the brainstem or cerebellar peduncles is a rare cause of AVS (approximately 4% of cases) 2
• A newly described entity called Acute Vestibular Asymmetry Disorder (AVAD) can mimic vestibular neuritis but shows normal head impulse test without central lesions on imaging 5
• Vascular causes of peripheral vestibular syndrome have been reported, where small emboli may lodge in the anterior vestibular artery 6

Algorithm for Management

1. Perform complete HINTS examination
2. If HINTS suggests central cause (normal head impulse, direction-changing nystagmus, or skew deviation), obtain urgent MRI with diffusion-weighted imaging 3
3. If initial MRI is negative but clinical suspicion remains high, consider repeat MRI after 48 hours 3
4. If HINTS suggests peripheral cause and there are no other neurological signs, observation may be appropriate 2
5. Consider vascular risk factors and age in decision-making, as stroke risk increases with age and vascular risk factors 7