What is Horner’s Syndrome?
Neuroanatomy of Horner’s Syndrome
- Preganglionic fibers originate in the hypothalamus and descend through the brainstem to the C8-T2 region of the spinal cord (also known as the Ciliospinal Center of Budge) (1-3)
- Currently a first order neuron prior to any synapse
- These fibers then synapse in the Ciliospinal Center of Budge (1,2)
- This is the first synapse in the pathway which results in a second order neuron
- The now second order preganglionic fibers exit the spinal cord and travel over the apex of the lung. They join the cervical sympathetic chain of ganglia in the neck region (1,2).
- The fibers then ascend and go on to synapse in the superior cervical ganglion (located near the mandible and where the common carotid artery bifurcates)(1,2).
- This is the second synapse in the pathway, so the fibers exit as a postganglionic third order neuron.
- The third order postganglionic fibers leave the superior cervical ganglion to form a plexus with the internal carotid artery (ICA). The plexus enters the skull via the carotid canal and travels through the cavernous sinus (1,2).
- Note that the pupillomotor fibers and fibers that innervate sweat glands of the medial forehead travel via the internal carotid with the third order sympathetics. The fibers that supply the sweat glands of the rest of the face as well as the vasomotor and sudomotor fibers travel via the external carotid arteries to branch off more proximally (1,3).
- Once within the ocular orbit, the sympathetic fibers may take one of several courses:
- Travel with the superior division of Cranial Nerve 3 (CN III) to innervate the upper eyelid via Mueller’s muscle (4,5)
- Travel with the nasociliary branch of CN V1(ophthalmic branch of the trigeminal nerve) and follow one of its expansions (1,2,5):
- The Long Posterior Ciliary Nerves (LPCN): The LPCNs carry the sympathetic fibers to innervate the iris dilator muscle. (Note the LPCNs themselves provide sensory innervation to cornea, iris, and ciliary muscle) (1,5)
- The Short Posterior Ciliary Nerves (SPCN): The sympathetic fibers may exit with SPCNs after leaving the ciliary ganglion and go on to innervate the conjunctival and choroidal blood vessels. (Note the SPCNs themselves are a branch of the inferior division of CN III and innervate the ciliary and iris sphincter muscles via parasympathetic innervation) (1,5)
- Travel with the vidian nerve to innervate the blood vessels of the lacrimal nerve (5).
Time to play NAME THAT LESION!
First Order Neuron Lesion
Examples of first order lesions include but are not limited to: Intracranial tumors, spinal cord tumors, hemorrhage of the hypothalamus, cerebral vascular accidents, demyelination (such as Multiple Sclerosis), Arnold-Chiari malformation, inflammatory or infectious myelitis, lateral medullary syndrome, encephalitis, syringomyelia, vessel infarction, neoplasms, or trauma to the head or spine (1,2).
Second Order Neuron Lesion
Examples of second order lesions include but are not limited to: a subclavian artery aneurysm, Pancoast’s syndrome (most commonly from non-small cell lung carcinoma), metastasis of malignant tumors, thyroid malignancies, trauma to spinal cord or ribs, neck hematoma, or iatrogenic causes (surgical procedures in the spinal cord, neck, or thorax). Many preganglionic Horner’s syndromes also have no identifiable cause (1,2).
Third Order Neuron Lesion
Examples of lesions include but are not limited to: Artery dissection or aneurysm, thrombosis, tumors at base of skull, neck, or pituitary, surgical procedures (such as a stent), acute thrombosis, trauma, ectatic jugular veins, malignant tumors or metastasis, and migraine or cluster headaches (1,2).
Diagnosing Horner’s Syndrome
- Any form of cocaine should not be used for patients who have pre-existing heart conditions, hypertension, or epilepsy. The drug can induce tachycardia, seizures, restlessness, anxiety, myocardial infarction, and stroke (6).
- Apraclonidine can cause a reduction in intraocular pressure and is contraindicated in patients taking MAO inhibitors (7).
- Phenylephrine and hydroxyamphetamine should not be used in patients with heart or thyroid conditions (8,9).
- Step One: Confirm the presence of Horner’s with one of these two drugs:
- Cocaine ophthalmic drops (poor/no dilation in Horner’s pupil)
- Apraclonidine Ophthalmic drops (dilation of Horner’s pupil)
- Step Two: Localize the lesion (pre- or postganglionic)
- Phenylephrine (No dilation in preganglionic Horner’s; pupil dilation in postganglionic Horner’s)
- Hydroxyamphetamine (Pupil dilation in preganglionic Horner’s; no dilation in postganglionic Horner’s)
Treatment and management
Clinical Pearls and Takeaways in Horner’s Syndrome Management
- Take a thorough history and perform a careful clinical examination
- Remember, Horner’s syndrome anisocoria is more evident in dim illumination
- Ask about surgeries, trauma, and long standing medical conditions
- An acute onset painful Horner’s is a medical emergency. Refer these patients immediately!
- Topical solutions can help us determine the presence of and localize Horner’s lesions
- Be aware of the side effects and contraindications of any medication you use in your exam room
- Always consider differential diagnosis when you suspect Horner’s Syndrome
- Optometrists often have the opportunity to first diagnose Horner’s Syndrome due to the presentation of ocular symptoms. You may be crucial in ensuring the patient gets appropriate and timely treatment
- Horner’s Syndrome is a condition is best managed by the collaboration of an interdisciplinary medical team
- Khan, Z, et al. “Horner Syndrome” Treasure Island (FL): StatPearls Publishing; PMID: 29763176. 2020 Feb.
- Kanagalingam, S, et al. "Horner Syndrome: Clinical Perspectives." Eye Brain. 2015;7:35-46. doi: 10.2147/EB.S63633.
- Zwueste, DM, et al. “A Review of Horner’s Syndrome in Small Animals.” Can Vet J. 60(1): 81-88(2019).
- Park, JM, et al. “Microscopic Characteristics of the Inferior Tarsal Muscle and Its Surroundings in Korean.” Int J Ophthalmol. 6(2): 126-130(2013). doi: 10.3980/j.issn.2222-3959.2013.02.03.
- Cheatham, KM, et al. Part One Applied Science Review Guide Part 1. 7th Ed. KMK Educational Services LLC; (1): 161-163(2014).
- Richards, JR, et al. “Cocaine” Treasure Island (FL): StatPearls Publishing; 2020 Feb.
- Morales J, Brown SM, Abdul-Rahim AS, Crosson CE. Ocular Effects of Apraclonidine in Horner Syndrome.Arch Ophthalmol. 2000;118(7):951–954. doi:10-1001/pubs.Ophthalmol.-ISSN-0003-9950-118-7-ecs90240
- Richards, E, et al. “Phenylephrine” Treasure Island (FL): StatPearls Publishing; 2019 Oct.
- LL Simpson. “Blood Pressure and Heart Rate Response Evoked by P-Hydroxyamphetamine and by P-Hydroxynorephedrine II. A Quantitative Assessment of the Role of Amphetamine Metabolites in Acute Responses Evoked by D-Amphetamine.” J Pharmacol Exp Ther. 213(3): 504-8(1980).
- Falardeau, Julie. “Anisocoria.” International Ophthalmology Clinics. 59 (3): 125-139 (2019). doi: 10.1097/IIO.0000000000000276.
- Finsterer, J. “Ptosis: Causes, Presentation, and Management.” Aesth Plast Surg. 27, 193–204 (2003). https://doi.org/10.1007/s00266-003-0127-5.