What labs should be ordered for an ER patient presenting with vertigo?

Laboratory Testing for ER Patients Presenting with Vertigo

For patients presenting to the emergency room with vertigo, routine laboratory testing is generally not indicated unless there are specific clinical findings or risk factors suggesting an underlying metabolic or systemic cause.

Initial Assessment and Categorization

The approach to vertigo in the emergency department should focus on categorizing the presentation based on timing and triggers rather than ordering routine labs:

• Acute Vestibular Syndrome (AVS): Continuous dizziness lasting days to weeks with nausea, vomiting, head motion intolerance
• Triggered Episodic Vestibular Syndrome: Brief episodes triggered by specific actions (e.g., BPPV)
• Spontaneous Episodic Vestibular Syndrome: Episodes not triggered by specific actions
• Chronic Vestibular Syndrome: Dizziness lasting weeks to months

Laboratory Testing Recommendations

When Labs Are NOT Indicated:

• Typical BPPV with positive Dix-Hallpike test
• Isolated vertigo with normal neurological examination and HINTS examination consistent with peripheral vertigo
• Patients who have returned to baseline normal neurologic status

When Labs ARE Indicated:

• Glucose testing: When hypoglycemia is suspected based on history or risk factors 1
• Electrolytes (particularly sodium): When hyponatremia is suspected, especially in patients with psychogenic water ingestion or on diuretics 1
• Pregnancy test: For women of childbearing age, as pregnancy may affect testing, disposition, and treatment options 1
• Additional labs: For patients with known medical disorders such as renal insufficiency or malnutrition 1

Critical Physical Examination Components

The HINTS examination is more valuable than laboratory testing for distinguishing between benign peripheral causes and potentially life-threatening central causes of vertigo:

• Head Impulse test: Abnormal in peripheral causes, normal in central causes
• Nystagmus: Direction-changing in central causes, unidirectional in peripheral causes
• Test of Skew: Present in central causes, absent in peripheral causes
• Hearing assessment (HINTS+): Adds hearing assessment to increase sensitivity to 99% 2

Imaging Considerations

• MRI head: Indicated for AVS with abnormal HINTS exam or neurological deficits, or high vascular risk patients with AVS even with normal exam 1
• CT head: Less sensitive than MRI, especially for posterior fossa lesions, with low yield (<1%) in isolated dizziness without neurological deficits 1

Important Caveats

• Posterior circulation stroke can present with isolated vertigo in up to 25% of cases, with prevalence increasing to 75% in high vascular risk cohorts 2
• Laboratory testing is of very low yield in patients with a new-onset vertigo who have returned to baseline 1
• The HINTS examination, when performed by neurologists, has a sensitivity of 96.7% and specificity of 94.8% for detecting central causes, but is less accurate when performed by emergency physicians without specialized training 3, 4

Remember that the history and physical examination will predict the majority of patients who will have laboratory abnormalities, making routine lab testing unnecessary in most cases of isolated vertigo 1.