In a 29-year-old construction worker presenting with a 24‑hour severe unilateral temporal headache, a left axillary herpes zoster rash, and bilateral pinpoint pupils (miosis), what is the differential diagnosis and appropriate acute management for his headache?

Differential Diagnosis and Acute Headache Management

Critical Assessment: This is a Medical Emergency

This patient requires immediate neuroimaging and urgent evaluation for life-threatening secondary causes of headache, particularly given the bilateral pinpoint pupils which suggest either opioid toxicity or brainstem involvement. 1

Differential Diagnosis

Primary Concerns (Red Flags Present):

1. Herpes Zoster with CNS Complications

• Herpes zoster meningoencephalitis – The combination of severe temporal headache, zoster rash, and bilateral miosis (pinpoint pupils) raises concern for viral spread to the brainstem/trigeminal nuclei 2, 3
• VZV can cause direct brainstem involvement affecting the trigeminal tract and nuclei, which can present with severe headache preceding or accompanying the rash by 24-72 hours 1, 4
• Bilateral pupillary involvement suggests either bilateral cranial nerve involvement or brainstem pathology 2, 5

2. Opioid Toxicity

• Construction worker with bilateral pinpoint pupils and severe headache – This occupational context combined with bilateral miosis is highly suspicious for opioid exposure/overdose [@general medical knowledge@]
• Fentanyl or other opioid exposure is common in construction settings and can present with severe headache, altered mental status, and characteristic bilateral pinpoint pupils [@general medical knowledge@]

3. Subarachnoid Hemorrhage (SAH)

• Severe temporal headache of acute onset (24 hours) is a classic red flag for SAH 1
• "Thunderclap" quality headache requires immediate exclusion of SAH 1

4. Herpes Zoster Vasculitis

• VZV can cause cerebral vasculitis mimicking giant cell arteritis, presenting with severe temporal headache and CNS involvement 6

Secondary Considerations:

5. Acute Herpes Zoster Ophthalmicus with Ophthalmoplegia

• Complete oculomotor nerve involvement can occur with HZ ophthalmicus and present with pupillary abnormalities, though typically unilateral 5

6. Meningitis

• Fever, severe headache, and altered mental status would support this, though not explicitly mentioned 1

Immediate Management Algorithm

Step 1: Stabilize and Assess for Opioid Toxicity

• Check respiratory rate, oxygen saturation, and level of consciousness immediately [@general medical knowledge@]
• If respiratory depression present (RR <12, altered consciousness): Administer naloxone 0.4-2 mg IV/IM/intranasal immediately [@general medical knowledge@]
• Secure airway if needed 1

Step 2: Urgent Neuroimaging

• Non-contrast CT head immediately to exclude SAH, intracranial hemorrhage, or mass effect 1
• If CT negative but high suspicion for SAH: Lumbar puncture for xanthochromia (ideally after 12 hours from headache onset, but clinical urgency may necessitate earlier) 1
• MRI brain with contrast if CT negative – to evaluate for brainstem/trigeminal tract involvement by VZV, encephalitis, or vasculitis 1, 2

Step 3: Antiviral Therapy (Do Not Delay)

• Start IV acyclovir immediately while awaiting imaging results given confirmed zoster rash and severe headache suggesting possible CNS involvement 1
• Dosing: Acyclovir 10-15 mg/kg IV every 8 hours (adjust for renal function) 1
• High-dose IV acyclovir is the treatment of choice for VZV infections with suspected CNS involvement in any patient 1

Step 4: Acute Headache Management

For severe headache relief while diagnostic workup proceeds:

• Avoid opioids given bilateral miosis and unclear etiology [@general medical knowledge@]
• IV ketorolac 30 mg (if no contraindications: renal impairment, GI bleeding risk) 1
• IV prochlorperazine 10 mg or metoclopramide 10 mg for nausea and headache relief 1
• IV dexamethasone 10-24 mg may reduce inflammation if VZV meningoencephalitis suspected [@general medical knowledge@]
• IV fluids for hydration [@general medical knowledge@]

Step 5: Additional Diagnostic Studies

• Lumbar puncture if imaging shows no contraindication and meningoencephalitis suspected: CSF analysis including VZV PCR, cell count, protein, glucose 1, 3
• Urine drug screen to evaluate for opioid or other substance exposure [@general medical knowledge@]
• Blood cultures if febrile [@general medical knowledge@]

Critical Pitfalls to Avoid

1. Do not attribute bilateral pinpoint pupils solely to herpes zoster – This is atypical and demands evaluation for opioid toxicity or brainstem pathology 2, 5

2. Do not delay antiviral therapy – VZV encephalitis has significant morbidity/mortality; IV acyclovir should be started empirically if CNS involvement suspected 1, 3

3. Do not use oral antivirals – This patient requires IV acyclovir given severe presentation and possible CNS involvement 1

4. Do not miss SAH – Severe acute temporal headache is SAH until proven otherwise 1

5. Do not give opioids for pain control until opioid toxicity is excluded [@general medical knowledge@]

6. Do not assume unilateral zoster means unilateral disease – VZV can cause bilateral CNS manifestations despite unilateral rash 2, 6