What are the differential diagnoses and recommended evaluation and management for a 15‑year‑old presenting with orthostatic light‑headedness, transient visual changes, tinnitus, brain fog, and eye pain that improve when lying down?

Orthostatic Intolerance (POTS or Orthostatic Hypotension)

This 15-year-old most likely has Postural Orthostatic Tachycardia Syndrome (POTS) or orthostatic hypotension, given the constellation of orthostatic lightheadedness, visual changes, tinnitus, brain fog, and eye pain that all improve when lying down. 1

Differential Diagnosis

Most Likely: Orthostatic Intolerance Syndromes

Postural Orthostatic Tachycardia Syndrome (POTS) – Primary consideration

• Heart rate increase ≥40 bpm within 10 minutes of standing (≥40 bpm threshold for ages 12-19, not the adult 30 bpm) without significant blood pressure drop 1
• Presents with severe orthostatic intolerance: lightheadedness, palpitations, tremor, generalized weakness, blurred vision, fatigue, and brain fog 1, 2
• Predominantly affects young women and is frequently associated with recent infections, chronic fatigue syndrome, and joint hypermobility 1, 3
• Symptoms worsen in morning, after meals, with heat exposure, and after exertion 1, 4
• Tinnitus and visual disturbances (blurring, tunnel vision, loss of color) are explicitly recognized as cardinal symptoms of orthostatic syndromes 1, 3

Classical Orthostatic Hypotension – Second consideration

• Systolic BP drop ≥20 mmHg or diastolic drop ≥10 mmHg within 3 minutes of standing 1
• Symptoms develop within seconds to 3 minutes of standing 1, 3
• Same symptom profile as POTS but with documented hypotension 1, 3

Delayed Orthostatic Hypotension – Consider if symptoms develop after >3 minutes standing

• Progressive BP fall occurring after 3 minutes of standing 1, 4
• More common in elderly but can occur in adolescents with autonomic dysfunction 1

Less Likely but Must Exclude

Vasovagal Syncope (Orthostatic Variant)

• BP drop starts several minutes after standing and accelerates until syncope or recumbency 1, 3
• Typically accompanied by pallor, sweating, and nausea 1, 3
• Less likely given chronic nature and absence of syncope 1

Cardiac Arrhythmia

• Would not characteristically improve with lying down or worsen with standing 3
• Palpitations would be irregular rather than simply fast 1

Vestibular Disorders (BPPV, Vestibular Neuritis)

• BPPV provoked by head position changes relative to gravity, not standing per se 3
• Vestibular neuritis presents with acute continuous vertigo, not episodic orthostatic symptoms 3
• Visual changes would be oscillopsia (illusion of movement), not blurring or graying out 5

Posterior Circulation Insufficiency/Vertebral Artery Dissection

• Would present with additional neurologic deficits beyond orthostatic symptoms 3, 6
• Rare in this age group without trauma history 6

Functional Visual Loss

• Eye pain with visual symptoms could suggest functional overlay 7
• However, the clear postural relationship and improvement when supine strongly favor organic orthostatic pathology 1, 3

Management Plan

Immediate Assessment (First Visit)

Orthostatic Vital Signs Protocol – Critical diagnostic step

• Measure BP and HR supine after 5 minutes rest 1, 4
• Measure at 1 minute standing 1, 4
• Measure at 3 minutes standing 1, 4
• Measure at 5 minutes standing 1, 4
• Measure at 10 minutes standing – essential for POTS diagnosis, as HR increase may not peak until 10 minutes 1, 2
• Document all symptoms during the test 1, 2

Physical Examination

• Cardiovascular exam including auscultation for murmurs suggesting structural heart disease 4
• Assess for signs of heart failure or volume depletion 4
• Look for joint hypermobility (associated with POTS) 1, 3

12-Lead ECG

• Rule out cardiac conduction abnormalities 2
• Baseline before considering any pharmacologic therapy 2

Laboratory Workup

Initial Labs

• Complete blood count to evaluate for anemia or infection 2
• Comprehensive metabolic panel for electrolytes, renal function, and glucose 2
• Thyroid function tests to rule out thyroid dysfunction 2
• Iron studies (ferritin, iron, TIBC, transferrin saturation) – iron deficiency is a potential underlying cause of orthostatic intolerance 2

Non-Pharmacologic Management (First-Line)

Immediate Interventions

• Increase daily fluid intake to 2-3 liters 4, 3
• Increase salt consumption to 5-10g daily (if no contraindications) 4, 3
• Avoid prolonged standing, hot showers, large meals, and rapid postural changes 1, 3

Physical Counterpressure Maneuvers – Reduce syncope risk by ~50%

• Leg crossing with tensing of leg, abdominal, and buttock muscles 4
• Squatting during symptomatic episodes 4
• These maneuvers should be taught and practiced 4, 3

Compression Garments

• Waist-high compression stockings to reduce venous pooling 3
• More effective than knee-high stockings 3

Exercise Reconditioning

• POTS is frequently associated with deconditioning 1, 3
• Gradual exercise program starting with recumbent activities (rowing, swimming) 1

Advanced Testing (If Initial Standing Test Inconclusive)

Tilt-Table Testing

• Consider if active standing test inconclusive but symptoms strongly suggest orthostatic intolerance 2, 4
• Helps differentiate between delayed orthostatic hypotension and reflex syncope 4

24-Hour Holter Monitoring

• If symptoms suggest arrhythmia or palpitations are prominent 2, 4
• Capture episodes during symptomatic periods 2

Echocardiogram

• Consider if cardiac symptoms are prominent to rule out structural heart disease 2

Pharmacologic Management (If Non-Pharmacologic Measures Fail)

For Hypovolemic Orthostatic Hypotension

• Fludrocortisone (first-line for volume expansion) 3

For Inadequate Vasoconstriction

• Midodrine (enhances vascular tone) 3
• Caution: Monitor for supine hypertension; use cautiously in males due to urinary retention risk 3

Red Flags Requiring Immediate Emergency Referral

• Chest pain, jaw pain, or diaphoresis (rule out acute coronary syndrome) 4
• Symptoms worsen or recur despite intervention 4
• New neurologic deficits suggesting posterior circulation stroke 3, 6

Critical Pitfalls to Avoid

Don't dismiss as "just dehydration" or anxiety – Orthostatic intolerance in adolescents is a real autonomic disorder requiring systematic evaluation 2

Don't measure standing vitals for only 1-2 minutes – Delayed orthostatic hypotension and POTS may be missed; measure through 10 minutes 1, 2, 4

Don't overlook iron deficiency – Even without anemia, low ferritin can contribute to orthostatic intolerance 2

Don't forget the age-specific POTS criteria – Use ≥40 bpm HR increase for ages 12-19, not the adult ≥30 bpm threshold 1, 2

Don't ignore the eye pain – While painful eyes are less typical, they may reflect cerebral hypoperfusion or eyestrain from visual disturbances during orthostatic episodes 1, 8