What labs are recommended for a teenager presenting with facial twitching?

Laboratory Evaluation for Facial Twitching in Teenagers

For a teenager presenting with facial twitching, a focused laboratory workup should include complete blood count, electrolytes, calcium, magnesium, glucose/HbA1c, and Lyme disease serology in endemic areas. The approach to laboratory testing should be guided by clinical presentation rather than routine panels.

Initial Assessment Considerations

When evaluating facial twitching in a teenager, consider these key differential diagnoses:

• Bell's palsy
• Hemifacial spasm
• Seizure disorders
• Tic disorders
• RASopathies (e.g., cardio-facio-cutaneous syndrome)
• Myasthenia gravis
• Conversion disorder

Recommended Laboratory Testing

First-Line Tests:

• Complete blood count
• Basic metabolic panel (electrolytes, BUN, creatinine)
• Calcium and magnesium levels
• Random glucose or HbA1c
• Lyme disease serology (in endemic areas) 1

Second-Line Tests (Based on Clinical Suspicion):

• Thyroid function tests
• Antinuclear antibody (ANA)
• Anti-acetylcholine receptor antibodies (if myasthenia gravis suspected) 1
• Drug/toxicology screen (if substance use suspected)

When to Consider Neuroimaging

Brain MRI should be considered when:

• Facial twitching is persistent (>3 months)
• Associated with other neurological symptoms
• Asymmetric or progressive symptoms
• Atypical presentation (e.g., isolated branches of facial nerve involvement) 2

Special Considerations

Lyme Disease Testing

In endemic areas, Lyme disease testing is particularly important as it can cause facial nerve palsy in up to 25% of cases. The recommended approach is a two-step process:

1. Initial screening with ELISA or IFA
2. If positive/borderline, confirm with Western blot 1

Myasthenia Gravis

If variable facial weakness with fatigue is present:

• Consider anti-acetylcholine receptor antibodies
• Anti-MuSK antibodies (if seronegative)
• Single-fiber electromyography (considered gold standard) 1

Bell's Palsy vs. Other Causes

While Bell's palsy typically doesn't require extensive laboratory testing, atypical presentations warrant investigation:

• Bilateral involvement
• Slow progression
• Associated symptoms (headache, other neurological findings)
• Failure to improve within 3 months 3

Common Pitfalls to Avoid

1. Overreliance on laboratory testing: History and physical examination remain the cornerstone of diagnosis for facial twitching.

2. Missing Lyme disease: In endemic areas, failure to test for Lyme disease can lead to missed treatment opportunities.

3. Overlooking metabolic causes: Electrolyte abnormalities (particularly calcium and magnesium) can cause facial twitching and are easily treatable.

4. Assuming Bell's palsy without proper evaluation: Bell's palsy is a diagnosis of exclusion after other causes have been ruled out 1.

5. Delaying treatment: If Bell's palsy is suspected, treatment with oral steroids should begin within 72 hours of symptom onset, even while diagnostic workup continues 3.

Remember that facial twitching in teenagers can have various etiologies, and laboratory testing should be targeted based on clinical presentation rather than ordered as a standard panel for all patients.