Feline Horner’s Syndrome: Vet Guide 2025 🐱👁️‍🩺

Hello compassionate cat lovers! I’m Dr Duncan Houston BVSc 🩺. Horner’s syndrome in cats is a striking—but often benign—condition caused by damage to the sympathetic nerve supply to one eye. It leads to a distinctive combination of signs: drooping eyelid, constricted pupil, sunken appearance, and a raised third eyelid. Though not painful, it can signal serious underlying issues. This 2025 guide explores causes, diagnosis, treatment, prognosis, and what you can do at home to support your feline friend 😊.

🔍 What Is Horner’s Syndrome?

Horner’s syndrome is a neurological symptom complex resulting from disruption of the sympathetic pathway supplying the eye and periocular area. When these nerves fail, the parasympathetic system dominates, causing characteristic changes in eyelid and pupil function :contentReference[oaicite:3]{index=3}.

👁️ Classic Signs & Symptoms

Horner’s syndrome is identifiable by a set of four hallmark signs, often affecting one side:

• Miosis – constricted pupil even in dim light :contentReference[oaicite:4]{index=4};
• Ptosis – subtle drooping of the upper eyelid :contentReference[oaicite:5]{index=5};
• Enophthalmos – sunken eye appearance due to loss of sympathetic tone :contentReference[oaicite:6]{index=6};
• Third eyelid protrusion – the nictitating membrane lifts over the eye :contentReference[oaicite:7]{index=7}.

Other subtle signs may include facial redness from dilated blood vessels :contentReference[oaicite:8]{index=8}.

📚 Understanding the Nerve Pathway

The sympathetic pathway consists of three neurons:

1. First-order (central) – from the hypothalamus down the spinal cord;
2. Second-order (preganglionic) – exits the spine in the chest, travels up the neck;
3. Third-order (postganglionic) – from the cranial cervical ganglion through the middle ear to the eye :contentReference[oaicite:9]{index=9}.

⚠️ Causes & Risk Factors

In cats, Horner’s often correlates with identifiable causes:

• Trauma – car accidents, high-rise falls, neck/chest injury :contentReference[oaicite:10]{index=10};
• Otitis media/interna – ear infections affecting sympathetic nerves :contentReference[oaicite:11]{index=11};
• Retrobulbar disease – abscesses, tumors behind the eye :contentReference[oaicite:12]{index=12};
• Chest lesions – masses or trauma impacting second-order neurons :contentReference[oaicite:13]{index=13};
• Central lesions – brainstem injury, spinal disease, stroke;
• Idiopathic – idiopathic cases are rare in cats (<1%) compared to dogs :contentReference[oaicite:14]{index=14}.

🔬 How It’s Diagnosed

• History & Physical Exam – including ear exam, checking for trauma or masses :contentReference[oaicite:15]{index=15};
• Pharmacologic Testing – phenylephrine drop test helps localize lesion within the nerve pathway :contentReference[oaicite:16]{index=16};
• Diagnostic Imaging – X-rays of chest/neck/head; CT/MRI to detect masses or nerve damage :contentReference[oaicite:17]{index=17};
• Neurologic & Otoscopic Exam – identifies ear issues or neurological deficits :contentReference[oaicite:18]{index=18}.

🛠️ Treatment Strategies

1. Manage the Underlying Cause

• Ears: treat otitis with systemic antibiotics ± surgery (TECA‑BO) :contentReference[oaicite:19]{index=19};
• Trauma/abscesses: may require surgery, abscess drainage;
• Chest tumors: may require oncologic treatment;
• Central lesions: neurosurgical or supportive care depending on diagnosis.

2. Symptomatic Support

• Eye lubricants to prevent dryness and exposure keratitis;
• Phenylephrine drops may hasten resolution in postganglionic cases :contentReference[oaicite:20]{index=20};
• Pain management if underlying disease is painful.

📈 Prognosis & Recovery

• Postganglionic causes (ear or local injury) have a good prognosis; may resolve within 2–6 weeks :contentReference[oaicite:21]{index=21};
• Preganglionic or central lesions often have a guarded prognosis;
• Idiopathic cases are very uncommon in cats;
• Condition itself is not painful or vision-threatening—but underlying diseases may be serious.

🏡 Home Monitoring & Care

• Observe and log eyelid position, pupil size, eye sunkenness via **Ask A Vet app** 📱;
• Monitor appetite, grooming, behavior for signs of systemic illness;
• Administer any medications as prescribed—especially eye drops or antibiotics;
• Keep ears clean and dry in cases of otitis;
• Plan follow-up visits and imaging per vet’s advice.

📝 Key Takeaways

• Horner’s syndrome is a visible sign of sympathetic nerve dysfunction—miosis, ptosis, enophthalmos, and third eyelid protrusion;
• It's not painful, but may signal deeper health concerns;
• Identifying the lesion’s location guides prognosis and treatment;
• Treating the cause—ear infections, trauma, tumors—is the focus;
• Supportive care at home helps comfort and recovery.

📞 When to Contact Ask A Vet

If you notice droopy eyelids, a constricted pupil, sunken eye, or raised third eyelid—especially following trauma, ear illness, or unusual behavior—use the **Ask A Vet app** 💬 promptly for guided care and vet referral.

✨ Final Thoughts

While Horner’s syndrome can look worrying, it's often reversible—especially with prompt diagnosis and treatment. Your attention to eye changes and willingness to seek care makes a huge difference in helping your cat recover and thrive. You’re your cat's eyes in catching what they can’t tell you ❤️🐾.