What is the approach to assessing headache in a pregnant patient, including history, examination, and investigation?

Approach to Assessment of Headache in Pregnancy

History Taking

Begin by identifying "red flag" features that mandate urgent evaluation, as pregnant women face unique risks for life-threatening secondary headaches including cerebral venous thrombosis, stroke, preeclampsia/eclampsia, and reversible cerebral vasoconstriction syndrome. 1, 2

Critical Red Flags Requiring Immediate Investigation

• Sudden onset "thunderclap" headache (peaking within seconds to minutes) suggesting subarachnoid hemorrhage or RCVS 3, 2
• New headache after 20 weeks gestation with hypertension, visual changes, or proteinuria indicating preeclampsia/eclampsia 1, 2
• Headache worsened by Valsalva maneuver (coughing, straining, bending) suggesting increased intracranial pressure 3, 1
• Headache awakening patient from sleep which may indicate serious secondary pathology 3, 1
• Progressive worsening over days to weeks suggesting evolving mass lesion or venous thrombosis 3, 2
• Fever or signs of infection requiring urgent evaluation for meningitis/encephalitis 3, 1
• Focal neurological symptoms including motor weakness, visual field defects, or altered consciousness 1, 2
• Late pregnancy or peripartum timing when cerebrovascular complications peak 4, 2

Essential History Components for Primary Headache Diagnosis

• Headache duration: Migraine lasts 4-72 hours; tension-type is variable; cluster headache lasts 15-180 minutes 5, 6
• Location: Unilateral location suggests migraine; bilateral suggests tension-type 5
• Character: Throbbing/pulsating favors migraine; pressing/tightening suggests tension-type 5
• Intensity: Moderate-to-severe intensity with worsening on routine activity indicates migraine 5
• Associated symptoms: Nausea/vomiting, photophobia, and phonophobia strongly suggest migraine 5
• Previous headache history: Long history of similar headaches without pattern change suggests benign primary headache 3
• Medication use: Analgesic use >10 days per month indicates medication overuse headache 3
• Timing in pregnancy: Migraine often remits during pregnancy, especially after first trimester; new-onset or worsening headache warrants investigation 5

Pregnancy-Specific Risk Assessment

• Gestational age: Late pregnancy and peripartum period carry highest risk for cerebrovascular complications 4, 2
• Blood pressure measurements: Essential to screen for preeclampsia 1, 2
• Proteinuria assessment: Required when preeclampsia suspected 1, 2
• Hypercoagulability awareness: Pregnancy increases risk of cerebral venous thrombosis and arterial dissection 1, 7

Physical and Neurological Examination

A thorough neurological examination is mandatory to identify abnormalities requiring urgent neuroimaging. 5, 1

Key Examination Components

• Vital signs: Blood pressure elevation suggests preeclampsia; fever indicates infection 1, 2
• Fundoscopic examination: Papilledema indicates increased intracranial pressure; retinal hemorrhages suggest preeclampsia 1, 2
• Cranial nerve examination: Focal deficits suggest structural lesion or stroke 1, 2
• Motor and sensory examination: Weakness or sensory loss indicates focal pathology 1, 2
• Coordination and gait testing: Ataxia suggests posterior fossa lesion or PRES 1, 2
• Meningeal signs: Neck stiffness suggests meningitis or subarachnoid hemorrhage 1, 2
• Mental status assessment: Altered consciousness mandates urgent investigation 1, 2

Investigation Strategy

When Neuroimaging is Indicated

MRI without contrast is the preferred imaging modality in pregnancy to minimize radiation exposure to the fetus. 1, 4

Absolute Indications for Urgent Neuroimaging

• Any abnormal neurological examination findings 3, 1
• Red flag symptoms including thunderclap onset, progressive worsening, or focal neurological symptoms 3, 1
• New headache after age 50 (if applicable) 3
• Atypical headache pattern not fitting primary headache criteria 3, 1
• Late pregnancy or peripartum presentation with severe headache 4, 2

Imaging Modality Selection

• MRI brain without contrast: First-line imaging to avoid radiation exposure 1, 4
• MR angiography and venography: When vascular pathology (stroke, dissection, venous thrombosis, RCVS) suspected 2, 4
• CT head without contrast: Only if MRI unavailable and urgent imaging required; use lowest radiation dose 1
• Contrast agents: Avoid unless absolutely necessary; gadolinium crosses placenta and iodinated contrast has theoretical thyroid risks 1, 4

Additional Investigations When Indicated

• Lumbar puncture: Required when subarachnoid hemorrhage suspected with negative imaging, or for meningitis/encephalitis evaluation 2
• Laboratory studies: Complete blood count, comprehensive metabolic panel, coagulation studies when vascular pathology suspected 2
• Urinalysis and urine protein: Essential when preeclampsia considered 1, 2
• Electroencephalography: Only if seizure disorder suspected 5
• Ultrasound of head and neck vessels: Alternative to MRA when MRI contraindicated 2

When Imaging is NOT Required

• Normal neurological examination with features consistent with primary headache (migraine or tension-type) 3
• Long history of similar headaches without change in pattern 3
• First or second trimester presentation with typical migraine features and normal examination 7, 8

Common Pitfalls to Avoid

• Do not dismiss new or worsening headache in late pregnancy as "just migraine" without excluding preeclampsia, RCVS, or venous thrombosis 2, 4
• Do not delay imaging when red flags present due to radiation concerns; untreated serious pathology poses far greater fetal risk than MRI 1, 4
• Do not assume primary headache diagnosis without thorough neurological examination 1, 2
• Maintain high suspicion for carbon monoxide toxicity in appropriate exposure contexts 1
• Recognize that primary headaches can begin de novo in pregnancy, especially first trimester, but secondary causes must be excluded first 4, 8