What labs should be ordered for an adult patient with a history of neurological symptoms, presenting with tongue numbness, migraines with aura, and headaches?

Laboratory Testing for Tongue Numbness, Migraines with Aura, and Headaches

In patients presenting with tongue numbness, migraines with aura, and headaches, routine laboratory testing is generally not indicated if the neurological examination is normal and the clinical presentation is consistent with typical migraine with aura. 1

When Laboratory Testing Is NOT Required

The diagnosis of migraine with aura is primarily clinical, based on medical history rather than laboratory or imaging studies. 1 Specifically:

• Typical migraine with aura (including sensory symptoms like tongue numbness that spread gradually over ≥5 minutes, last 5-60 minutes, and are followed by headache within 60 minutes) does not require laboratory workup if the neurological examination is normal 1, 2
• The prevalence of significant abnormalities in migraine patients with normal neurological examination is only 0.2%, similar to asymptomatic volunteers (0.4%) 2
• Medical history remains the mainstay of diagnosis, requiring documentation of: age at onset, duration and frequency of episodes, pain characteristics, accompanying symptoms (photophobia, phonophobia, nausea/vomiting), and detailed aura symptom characteristics 1

When Laboratory Testing SHOULD Be Considered

Laboratory studies become relevant when red flag features suggest secondary causes rather than primary migraine:

Critical Red Flags Requiring Workup:

• New-onset headache in patients over age 50: Consider ESR/CRP to evaluate for temporal arteritis 2
• Unexplained fever with headache: May indicate meningitis; consider CBC, inflammatory markers, and potentially lumbar puncture 2
• Weight loss associated with headache: Suggests possible malignancy; consider CBC, comprehensive metabolic panel, inflammatory markers 2
• Abnormal neurological examination findings: Significantly increases likelihood of intracranial pathology requiring comprehensive evaluation 2, 3

Specific Laboratory Considerations:

• ESR and CRP: Essential if temporal arteritis is suspected (age >50, new-onset headache, jaw claudication, vision changes) 2
• Complete blood count: Indicated with fever, weight loss, or systemic symptoms 2
• Comprehensive metabolic panel: Consider if altered consciousness, personality changes, or systemic illness present 2
• Thyroid function tests: May be considered if headache pattern changes coincide with other thyroid-related symptoms (though not specifically mentioned in guidelines, this is standard clinical practice)

Neuroimaging vs. Laboratory Testing

Neuroimaging takes priority over laboratory testing when evaluating concerning headache presentations. 2, 3 Specific indications include:

• Headache awakening patient from sleep (suggests increased intracranial pressure) 2, 4, 3
• Headache worsened by Valsalva maneuver 2, 3
• Progressive headache worsening over time 2, 4
• Thunderclap or "worst headache of life" 2, 4
• Any unexplained abnormal neurological examination finding 2, 3
• Marked change in previously stable headache pattern 2

MRI with and without contrast is the preferred imaging modality due to higher resolution and absence of radiation exposure, except when acute hemorrhage is suspected (use CT without contrast). 2, 4

Critical Clinical Pitfalls to Avoid

• Do not order routine labs in patients with typical migraine features and normal neurological examination, as this leads to unnecessary testing without changing management 2
• Do not dismiss tongue numbness as atypical if it follows the typical aura pattern (gradual spread over ≥5 minutes, duration 5-60 minutes, unilateral, followed by headache) 1, 5
• Do not confuse sensory aura symptoms with red flags when they meet ICHD-3 criteria for typical aura 1, 4
• Do not overlook brainstem aura features: If tongue numbness is accompanied by dysarthria, vertigo, tinnitus, diplopia, or ataxia, this suggests migraine with brainstem aura and warrants MRI to exclude posterior circulation pathology 6
• Recognize that false positive findings are more likely than true positives when pre-test probability is low, potentially leading to unnecessary anxiety and further invasive procedures 2

Algorithmic Approach

1. Obtain detailed history: Document aura characteristics (onset, spread, duration, unilaterality, positive features), headache features, and family history 1, 3
2. Perform thorough neurological examination 1
3. If examination is normal AND symptoms meet ICHD-3 criteria for typical migraine with aura: No laboratory testing or imaging required 1, 2
4. If red flags present (age >50 with new-onset, fever, weight loss, abnormal exam, progressive worsening, sleep-related, Valsalva-worsened): Order targeted labs based on specific concern AND neuroimaging 2, 3
5. If brainstem features present (dysarthria, vertigo, diplopia with tongue numbness): MRI brain without contrast is recommended 6