What is the diagnosis and management of Horner syndrome?

Horner Syndrome: Diagnosis and Management

Clinical Presentation and Recognition

Horner syndrome presents with the classic triad of ptosis, miosis, and anhidrosis, and the most critical diagnostic imperative is to urgently rule out carotid or vertebral artery dissection, particularly in patients presenting with ipsilateral head or neck pain. 1, 2

Key Clinical Features to Identify

• Anisocoria greater than 1 mm should immediately raise suspicion during pupillary examination 2
• Ipsilateral head or neck pain accompanying Horner syndrome is the hallmark warning sign of arterial dissection, occurring in 50-95% of cases before cerebral or retinal ischemia develops 1, 3
• The classic triad of traumatic mechanism, ipsilateral Horner syndrome, and contralateral hemiparesis mandates immediate vascular imaging for carotid dissection 2, 3

Pattern of Anhidrosis Localizes the Lesion

• Hemifacial anhidrosis indicates central (first-order) or preganglionic (second-order) lesions 3
• Minimal or absent anhidrosis suggests postganglionic (third-order) lesions, most commonly carotid dissection 3

Comprehensive Neurological Examination

Essential Examination Components

• Assess for additional cranial nerve palsies (III, IV, VI) which may indicate cavernous sinus pathology 2
• Check for nystagmus or hearing loss to evaluate for vestibular involvement 2
• Perform fundus examination to detect papilledema or optic atrophy 1, 2
• Evaluate for motor or sensory changes, ataxia, vertigo, dizziness, or nausea which may indicate brainstem pathology 1, 2, 3

Diagnostic Imaging: The Critical First Step

CT angiography (CTA) of the head and neck with IV contrast is the preferred initial imaging modality with 100% sensitivity for detecting arterial dissection. 2

Imaging Protocol Requirements

• Imaging must include the entire course from the aortic arch through the carotid and vertebral arteries to the circle of Willis 2
• MRA is an acceptable alternative to CTA for diagnosis of cervical artery dissection 1
• Routine CT head imaging is insufficient and may miss the underlying vascular pathology 4
• Carotid duplex ultrasonography may identify a dissection flap and differential flow in true and false lumens, but CTA or MRA is increasingly used to establish the diagnosis 1

Critical Diagnostic Pitfall

Carotid artery dissection must be ruled out urgently in patients presenting with the classic triad, as 50-95% develop cerebral or retinal ischemia. 2, 3 This is particularly critical in younger patients under 45 years, as vertebral artery dissection accounts for 10-15% of ischemic strokes in this age group 2

Pharmacological Confirmation

Apraclonidine 0.5% testing confirms the diagnosis of Horner syndrome and should be performed when the clinical diagnosis is uncertain 5, 6

Etiologies by Anatomical Location

Postganglionic (Third-Order) Lesions - Most Common

• Carotid artery dissection is the most common postganglionic cause, accounting for approximately 2% of all ischemic strokes and up to 15% in younger patients 1, 3
• Dissection results from an intimal tear initiating an intramural hematoma that disrupts sympathetic fibers traveling along the carotid artery 1, 3
• Associated conditions include fibromuscular dysplasia (15% association), connective tissue disorders, bicuspid aortic valve (1-5% incidence), penetrating trauma, and sudden/excessive neck movement 1, 3

Preganglionic (Second-Order) Lesions

• Thoracic pathology including Pancoast tumors, mediastinal masses, or thoracic trauma affecting the sympathetic chain at T1-T2 3
• Neck and chest surgical procedures are a common iatrogenic cause 5

Central (First-Order) Lesions

• Brainstem pathology causing Horner syndrome accompanied by other neurological deficits including motor/sensory changes, ataxia, vertigo, or nausea 1, 3

Management of Carotid Dissection

Antithrombotic treatment with either anticoagulation (heparin, low-molecular-weight heparin, or warfarin) or antiplatelet therapy (aspirin, clopidogrel, or extended-release dipyridamole plus aspirin) for at least 3-6 months is reasonable for patients with extracranial carotid or vertebral arterial dissection associated with ischemic stroke or TIA. 1

Treatment Approach

• Conservative management with anticoagulation is the usual approach, with generally favorable prognosis 1
• No randomized trials have compared anticoagulant and antiplatelet therapy with one another or with placebo 1
• Once symptoms resolve, antiplatelet therapy may replace anticoagulation 1
• Dual antiplatelet therapy has been reported with complete resolution of dissection on follow-up imaging 4

When to Consider Intervention

Carotid angioplasty and stenting might be considered when ischemic neurological symptoms have not responded to antithrombotic therapy after acute carotid dissection 1

Management of Fibromuscular Dysplasia

Revascularization is not recommended for patients with asymptomatic FMD of a carotid artery, regardless of the severity of stenosis. 1

Recommended Management for FMD

• Administration of platelet-inhibitor medication is beneficial in patients with FMD of the carotid arteries to prevent thromboembolism 1
• Annual noninvasive imaging of the carotid arteries is reasonable initially to detect changes in extent or severity of disease, with less frequent studies once stability is confirmed 1
• Carotid angioplasty with or without stenting is reasonable for patients with retinal or hemispheric cerebral ischemic symptoms related to FMD of the ipsilateral carotid artery 1

Specialist Referral

Immediate vascular neurology or neurosurgery consultation is required if arterial dissection is identified. 2

• Neuro-ophthalmology consultation is important for diagnosis confirmation and management 2
• Diagnosis and management requires the training and clinical judgment of an experienced ophthalmologist and in some cases a neuro-ophthalmologist 1

Critical Clinical Pearls

• When a cause for Horner syndrome is identified, it is usually known before Horner syndrome is discovered, making it an afterthought in most cases 5
• However, in an important minority of cases involving carotid dissection or tumor, the identification of Horner syndrome is critical to discovering these conditions 5
• Idiopathic Horner syndrome is a diagnosis of exclusion only after comprehensive workup, as life-threatening causes like carotid dissection must be ruled out urgently 3
• Among pharmacologically-confirmed cases, procedures in the neck, chest, skull base, and paraspinal region account for most identified causes, with cervical carotid dissection the next most common 5