Unilateral Headache When Standing Up
The most likely diagnosis is spontaneous intracranial hypotension (SIH), which should be your primary consideration when a patient presents with a one-sided headache that develops upon standing. 1
Primary Diagnosis: Spontaneous Intracranial Hypotension
SIH presents with orthostatic headache that can be unilateral or bilateral and follows a characteristic pattern 1:
- Absent or only mild (1-3/10 severity) upon waking or after prolonged lying flat 1
- Onset occurs within 2 hours of becoming upright 1
- Improves by >50% within 2 hours of lying flat 1
- Timing of onset and offset is consistent 1
The headache may also present as an "end of the day" or "second half of the day" pattern with improvement when lying flat 1. While the guideline doesn't specifically emphasize unilaterality, SIH can present with one-sided pain and should be strongly suspected when the orthostatic pattern is present.
Associated Symptoms That Increase Suspicion
Look for accompanying features that strengthen the diagnosis of SIH 1:
- Neck pain or stiffness
- Nausea and vomiting
- Hearing changes (muffled hearing, tinnitus)
- Visual disturbances
- Dizziness
Critical Differential Diagnoses to Exclude
Orthostatic Hypotension
This autonomic disorder causes similar positional symptoms but is distinguished by 1:
- Documented blood pressure drop: ≥20 mmHg systolic or ≥10 mmHg diastolic upon standing 1
- Confirmed through formal standing tests with hemodynamic monitoring 1
- Associated symptoms include dizziness, lightheadedness, visual disturbances, and weakness 1
The timing varies by subtype 1:
- Initial OH: 0-15 seconds after standing 1
- Classical OH: 30 seconds to 3 minutes 1
- Delayed OH: >3 minutes 1
Postural Tachycardia Syndrome (PoTS)
Distinguished by 1:
- Heart rate increase >30 bpm within 10 minutes of standing (>40 bpm in ages 12-19) 1
- Symptoms of orthostatic intolerance (lightheadedness, palpitations, tremor, weakness, blurred vision, fatigue) 1
- Syncope is rare in PoTS 1
- Requires formal standing test documentation 1
Cervicogenic Headache
Differentiated by 1:
- Provoked by cervical movement rather than posture 1
- Reduced cervical range of motion 1
- Associated myofascial tenderness 1
- Presence of cervical pathology 1
Migraine
Distinguished by 1:
- Provoked by movement rather than posture 1
- Migrainous features: throbbing quality, photophobia, phonophobia, nausea 1
- History of similar episodes with typical migraine biology 1
Diagnostic Workup Algorithm
Step 1: Detailed History
Document the precise orthostatic pattern 1:
- Severity when lying flat vs. standing
- Time to onset after standing
- Time to improvement after lying flat
- Consistency of this pattern
- Associated symptoms listed above
Step 2: Physical Examination
- Vital signs including orthostatic blood pressure and heart rate measurements 1
- Complete neurological examination 2
- Fundoscopy to assess for papilledema 2
- Cervical spine range of motion and palpation 1
Step 3: Formal Standing Test
If orthostatic hypotension or PoTS is suspected 1:
- Measure blood pressure and heart rate supine after 5 minutes rest
- Repeat measurements at 1,3,5, and 10 minutes of standing
- Document symptoms at each time point
Step 4: Neuroimaging
If SIH is suspected based on orthostatic headache pattern 1:
- Brain MRI with and without contrast is the initial imaging modality
- Look for characteristic findings: brain sagging, pachymeningeal enhancement, subdural fluid collections
- Spinal imaging may be needed to identify CSF leak location
Step 5: Specialist Referral
Refer to neurology within 2-4 weeks if the patient can care for themselves 1. Refer within 48 hours if they cannot care for themselves but have help, or emergency admission if they cannot care for themselves and lack help 1.
Common Pitfalls to Avoid
Do not assume all positional headaches are benign tension-type or migraine 2. The orthostatic pattern is a red flag requiring specific evaluation 1.
Do not miss SIH because the orthostatic component may not always be obvious initially 2. Specifically ask about headache severity when lying flat versus standing 1.
A negative standing test does not exclude PoTS if clinical suspicion is high—consider additional autonomic testing 1.
Do not confuse movement-provoked headache (migraine) with posture-provoked headache (SIH or orthostatic hypotension) 1. This distinction is critical for accurate diagnosis.
In patients over 50 with new-onset headache, maintain high suspicion for secondary causes 2, 3 including temporal arteritis, which can present with unilateral headache but typically has additional features like jaw claudication and elevated inflammatory markers 4.