Classic crossed deficits from involvement of ipsilateral V, IX, X nuclei and contralateral spinothalamic tract
Partial Horner syndrome
Incomplete triad is common
Postganglionic lesions typically no anhidrosis or minimal forehead only
Only miosis and mild ptosis may be present
Awareness reduces missed diagnoses
Therapeutic Considerations
Antithrombotic evidence
CADISS trial (Cervical Artery Dissection in Stroke Study)
Randomized trial of antiplatelet versus anticoagulation in cervical artery dissection
No significant difference in stroke or death outcomes
Supports individualized choice based on clinical factors
AHA scientific statement 2021
Recommends antithrombotic therapy for 3-6 months
Anticoagulation preferred when vessel occlusion present
Antiplatelet preferred when large infarct or hemorrhagic risk
Endovascular and surgical options
Reserved for failed medical therapy or hemodynamic instability
Stenting for pseudoaneurysm or recurrent embolism on antithrombotics
Surgical repair rarely required
Natural history considerations
Carotid dissection
Recanalization in approximately 60-90% of cases by 3 months
Stroke risk highest in first 2 weeks
Pancoast tumor
Locally advanced at presentation in most cases
Five-year survival approximately 30-40% for resectable disease with multimodal therapy
Iatrogenic and post-anesthesia Horner
Self-limiting; resolves with block reversal
Document in anesthetic record for future procedures
Patient Discharge Instructions
copy discharge instructions
Discharge home instructions for Horner syndrome
Reason for droopy eyelid and small pupil
Caused by disruption of nerve supply to the eye
Underlying cause has been evaluated and treated or follow-up arranged
Medications as prescribed
Take blood thinners or antiplatelet medications exactly as directed if prescribed
Do not stop antithrombotic medications without speaking to your doctor
Warning signs to return to the emergency room immediately
Sudden weakness or numbness in face, arm, or leg
Sudden difficulty speaking or understanding speech
New or worsening vision loss
Sudden severe headache unlike any previous headache
Sudden severe neck pain or throat pain
Difficulty walking, balance problems, or sudden dizziness
Loss of consciousness or confusion
Follow-up instructions
Neurology appointment within 48-72 hours if dissection or stroke diagnosed
Bring medication list and imaging reports
Repeat vessel imaging at 3 months to assess healing
Ophthalmology appointment if eyelid drooping or pupil asymmetry persists
Primary care follow-up if no specialist arranged
Lifestyle and activity
Avoid contact sports, heavy lifting, and activities with risk of neck injury if dissection diagnosed
Until neurology or vascular surgery clears you
No driving if vision significantly affected by ptosis or double vision
Report new shoulder or arm pain to your doctor promptly if Pancoast tumor evaluation is pending
References
Guidelines and key sources
Vascular and stroke guidelines
American Heart Association and American Stroke Association guidelines for management of spontaneous cervical artery dissection
AHA scientific statement on antithrombotic treatment in cervical artery dissection 2021
CADISS trial: Cervical Artery Dissection in Stroke Study (antiplatelet vs anticoagulation)
ACR Appropriateness Criteria
ACR Appropriateness Criteria for acute onset Horner syndrome recommend CT head without contrast and CTA head and neck as first-line imaging
Emergency medicine references
Tintinalli's Emergency Medicine: Horner syndrome evaluation and management
UpToDate: Horner syndrome workup and treatment
Evidence summaries
Key studies
CADISS randomized trial: no significant difference between antiplatelet and anticoagulation in cervical artery dissection
Carotid dissection natural history: recanalization in 60-90% by 3 months; stroke risk highest in first 2 weeks
Carotid dissection presenting with headache in 65% and neck pain in 50% of cases
Apraclonidine 0.5% pharmacologic testing: sensitivity approximately 93% for confirming Horner syndrome
Coding standards
ICD-10 G90.2 Horner syndrome
ICD-10 I77.71 dissection of carotid artery
ICD-10 I63.89 other cerebral infarction (Wallenberg)
ICD-10 C34.10 malignant neoplasm of upper lobe bronchus (Pancoast)
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