What is the initial neurological specific laboratory workup for a patient presenting with dizziness?

Neurological Laboratory Workup for Dizziness

For most patients presenting with dizziness, neurological-specific laboratory testing is not routinely indicated—the diagnosis is made through targeted history, bedside examination maneuvers, and selective neuroimaging rather than blood work. 1, 2

Clinical Triage Takes Priority Over Laboratory Testing

The initial approach to dizziness focuses on categorizing the vestibular syndrome by timing and triggers rather than ordering laboratory panels 2:

• Acute Vestibular Syndrome (AVS): Persistent vertigo lasting days to weeks—highest stroke risk 3
• Triggered Episodic: Brief episodes with positional changes (typically BPPV) 1, 2
• Spontaneous Episodic: Recurrent episodes without triggers (consider Ménière's disease) 1
• Chronic Vestibular Syndrome: Persistent disequilibrium 1

When Laboratory Testing May Be Indicated

Laboratory work becomes relevant when specific systemic causes are suspected based on clinical presentation 4, 5:

Metabolic and Systemic Causes

• Orthostatic hypotension/presyncope: Check orthostatic vital signs at bedside; consider CBC, basic metabolic panel, glucose if dehydration or electrolyte disturbance suspected 1, 4
• Fluid and electrolyte disorders: Account for 17.5% of dizziness presentations in emergency settings 4
• Vasovagal syncope: Most common cause (22.3% of cases)—diagnosed clinically without laboratory testing 4

Specific Neurological Conditions Requiring Labs

• Suspected neurosyphilis: If sensory ataxia with risk factors, consider syphilis serology 1
• Autoimmune/inflammatory causes: ESR, CRP, autoimmune panels only when clinical features suggest vasculitis or inflammatory CNS disease 5

Critical Distinction: Bedside Testing vs Laboratory Testing

The most valuable "tests" for neurological causes of dizziness are performed at the bedside, not in the laboratory 3, 2:

Essential Bedside Examinations

• Dix-Hallpike maneuver: For suspected BPPV—more diagnostic than any imaging or lab 3, 2
• HINTS examination (Head Impulse, Nystagmus, Test of Skew): 100% sensitivity for stroke in AVS when performed by trained examiners 3
• Observation for spontaneous nystagmus: Central patterns (downbeating, direction-changing) indicate brainstem/cerebellar pathology 3, 2
• Gait and balance testing: Inability to stand/walk independently indicates severe vestibular or central lesion 3

Neuroimaging Over Laboratory Testing

When neurological pathology is suspected, MRI with diffusion-weighted imaging is the appropriate diagnostic test—not laboratory work 1, 3, 6:

Indications for Neuroimaging (Not Labs)

• Focal neurological deficits: Diplopia, dysarthria, facial numbness, limb weakness 3
• Abnormal HINTS examination: Normal head impulse test, direction-changing nystagmus, or skew deviation 3, 6
• New severe headache with dizziness: Mandates immediate imaging for hemorrhage, dissection, or posterior fossa pathology 3
• Sudden unilateral hearing loss with vertigo: Raises concern for AICA territory stroke 3

Imaging Yields

• CT head: Very low diagnostic yield (<1%) for isolated dizziness; sensitivity only 20-40% for causative pathology 1, 3
• MRI with DWI: Superior to CT; 4% yield in isolated dizziness, 12% when neurological findings present 1, 2

Critical Pitfalls to Avoid

• Do not order routine laboratory panels for typical peripheral vestibular disorders—the diagnostic yield is extremely low and delays appropriate bedside diagnosis 3, 2
• Do not assume laboratory testing will identify stroke risk—75-80% of posterior circulation infarctions have no focal deficits on standard examination, requiring HINTS testing and MRI instead 3
• Do not rely on patient descriptions of "spinning" vs "lightheadedness"—focus on timing, triggers, and bedside examination findings 3, 2
• Do not substitute imaging for bedside testing—Dix-Hallpike and HINTS provide more diagnostic value than imaging in most cases 3

Practical Algorithm

Step 1: Categorize by timing and triggers (AVS, triggered episodic, spontaneous episodic, chronic) 2

Step 2: Perform targeted bedside examination (Dix-Hallpike for triggered symptoms, HINTS for AVS, nystagmus assessment) 3, 2

Step 3: If bedside testing suggests peripheral cause (positive Dix-Hallpike, reassuring HINTS)—no laboratory or imaging needed 3, 2

Step 4: If red flags present (focal deficits, abnormal HINTS, severe headache, inability to walk)—proceed to MRI brain with DWI, not laboratory testing 3, 6

Step 5: Consider laboratory testing only when systemic causes suspected (orthostatic hypotension, electrolyte disturbance, infection) based on associated symptoms 4, 5