**Patient Analysis**

**Patient Information:**  
- Name: Mr Patient  
- Age: 13 years  
- Gender: Male  
- Medical History: Not specified (non-contributory)

**Current Symptom:**  
- Headache

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### 1. Potential Differential Diagnoses

Given the limited information (isolated headache in a 13-year-old male), the following are common and important causes to consider:

- **Primary Headache Disorders:**
  - Migraine (with or without aura)
  - Tension-type headache
  - Cluster headache (less common in this age group)

- **Secondary Headache Causes:**
  - Viral or bacterial infection (e.g., sinusitis, upper respiratory tract infection, meningitis)
  - Medication overuse headache
  - Head trauma/concussion
  - Vision problems (e.g., refractive errors)
  - Dehydration
  - Intracranial pathology (e.g., tumor, hydrocephalus, idiopathic intracranial hypertension)
  - Hypertension

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### 2. Recommended Diagnostic Tests

**Initial evaluation should be guided by clinical history and physical examination.**  
If red flags or concerning features are present, consider:

- **Basic Investigations:**
  - Vital signs (including blood pressure)
  - Neurological examination
  - Fundoscopic examination (for papilledema)
  - Visual acuity assessment

- **If indicated by history/exam:**
  - CBC, CRP/ESR (if infection or inflammation suspected)
  - Urinalysis (if systemic symptoms)
  - Brain imaging (CT/MRI) if red flags present (see below)
  - Lumbar puncture (if meningitis or increased intracranial pressure suspected)

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### 3. Urgency Level

- **Low to Medium** (based on current information)
  - **If no red flags** or abnormal findings on history/exam, outpatient evaluation is appropriate.
  - **If red flags present** (see below), urgency increases to **High**—immediate evaluation required.

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### 4. Key Observations and Clinical Notes

- **History is critical:** Onset, duration, character, location, associated symptoms (nausea, vomiting, visual changes, photophobia, phonophobia, fever, neck stiffness, recent trauma, etc.).
- **Physical exam:** Complete neurological and general examination.
- **Family history:** Migraine or other headache disorders.
- **Medication and substance use:** Caffeine, over-the-counter medications, recent changes.
- **Psychosocial factors:** Stress, sleep patterns, school performance.

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### 5. Red Flags to Watch For

Immediate evaluation is warranted if any of the following are present:

- Sudden, severe ("thunderclap") headache
- Headache with fever, neck stiffness, photophobia (meningitis/encephalitis)
- Headache with altered mental status, seizures, or focal neurological deficits
- Headache that wakes the patient from sleep or is worse in the morning
- Headache with vomiting (especially projectile)
- Recent head trauma
- Visual changes (blurred vision, double vision, vision loss)
- Papilledema on exam
- Immunocompromised status or known malignancy

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### 6. Confidence Level

- **Low**
  - Due to the extremely limited clinical information provided (only "headache" as a symptom and no relevant medical history), the confidence in this analysis is low. A thorough clinical history and examination are essential for accurate diagnosis and management.

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**Summary:**  
The differential for headache in a 13-year-old is broad, ranging from benign primary headache disorders to serious secondary causes. Careful assessment for red flags is crucial. If any concerning features are present, urgent evaluation is required. Otherwise, outpatient workup and management may be appropriate. Further history and examination findings are needed for a definitive assessment.

**Recommendation:**  
Advise prompt in-person evaluation by a healthcare professional for a detailed history, examination, and appropriate investigations.