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SYMPTOMS
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Blurry vision, lack of sweating
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SIGNS
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Mild ptosis of the upper lid (<2mm) on side of affected pupil, Mild inverse ptosis of the lower lid on side of affected pupil, Small palpebral fissure, Anisocoria that is worse in the dark (Affected pupil is more miotic), Dilation lag of the affected pupil (Need to check pupil sizes right when the lights are turned off as pupils will look equal in size after 10-15 seconds), Direct light response and near response are normal, Injection of the conjunctiva on side of affected pupil, Lower IOP on side of affected pupil, Anhidrosis
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The level of anhidrosis depends on the location of the lesion along the sympathetic pathway
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Lesion along first order neuron: Anhidrosis on half the body (on side of pupil involvement)
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Lesion along second order neuron: Anhidrosis on half the face (on side of pupil involvement)
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Lesion along third order neuron: Typically no anhidrosis but can involve the forehead on one side (on side of pupil involvement)
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Congenital Horner’s syndrome (Development before 2 years old) is also associated with iris heterochromia (on side of pupil involvement) and Harlequin sign (on side of pupil involvement)
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WORK-UP
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Pupils | EOMs | Full eye exam with dilation | Ptosis testing | Cranial nerve testing | Pharmalogic testing
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Cocaine 10% drop (Not practical anymore. Was used to confirm Horner’s syndrome): Dilates pupil that has intact sympathetic innervation (Affected pupil will fail to dilate)
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Hydroxyamphetamine 1% drop (Differentiates between a pre- and post-ganglionic Horner’s syndrome): If affected pupil fails to dilate, this is an indication of a postganglionic lesion. If the affected pupil dilates, this is an indication of a central/pre-ganglionic lesion
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Apraclonidine 0.5% or 1% drop (Used to confirm Horner’s syndrome): Dilates pupil that has denervation supersensitivity (Affected pupil will dilate) May not work until 5-8 days after the onset of Horner’s syndrome
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Phenylephrine 1% drop (Used to differentiate between a pre and post-ganglionic Horner’s syndrome): If affected pupil dilates, this is an indication of a postganglionic lesion. If the affected pupil fails to dilate, this is an indication of a central/pre-ganglionic lesions
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Need to wait more than 24 hours before putting in hydroxyamphetamine or phenylephrine if cocaine or apraclonidine was used
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TREATMENT
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If the patient presents with an acute Horner’s syndrome with no other neurological signs, ocular pain, or history of trauma or malignancy, refer patient to neurology/neuro-ophthalmologist within 6 weeks for additional testing
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If the patient presents with an acute Horner’s syndrome with other neurological signs, ocular pain, or a history of trauma or malignancy, refer patient to neurology/neuro-ophthalmologist/ER STAT (same day referral is warranted)
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If patient presents with a longstanding/stable (>1 year) Horner’s syndrome with no other neurological signs, ocular pain, or history of trauma or malignancy, refer patient to neurology/neuro-ophthalmologist on a non-urgent basis for additional testing
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Children with an acute Horner’s syndrome should be referred to a pediatrician/neurologist to rule out neuroblastoma
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FOLLOW-UP
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Follow-up depends on the underlying etiology, usually managed by a pediatrician/neurologist/neuro-ophthalmologist
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ADDITIONAL LAB | TESTS
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If suspecting a first order neuron etiology, the following should be ordered:
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MRI with and without contrast of the brain | MRI with and without contrast of the cervical and upper thoracic spinal cord
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If suspecting a second order/third order neuron etiology, the following should be ordered:
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CT angiogram that includes the circle of Willis, orbits, and goes down to T4-T5 which includes the carotid arteries and apices of the lungs | MRI of the chest
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Also if over 60 years old, the following should be ordered:
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ESR | C-reactive protein
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ETIOLOGY
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Occurs due to a lesion in the oculosympathetic pathway to the dilator muscle and Muller’s muscle
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The sympathetic pathway to the dilator muscle involves:
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First order neuron (Central): From the hypothalamus to the ciliospinal center of Budge.
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Type of lesions: Stroke or tumor of the hypothalamus, brainstem, or spinal cord
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Multiple sclerosis:
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Second order neuron (Preganglionic): From the ciliospinal center of Budge, through the brachial plexus, over the apex of the lung, to the superior cervical ganglion (near bifurcation of common carotid artery)
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Type of lesions: Subclavian artery aneurysm
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Pancoast’s tumor | Thyroid gland tumors | Neck surgery or trauma | Lung surgery or trauma
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Third order neuron (Postganglionic): From the superior cervical ganglion, along the internal carotid artery, into the cavernous sinus, to the orbit and finally the dilator muscle and Muller’s muscle
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Type of lesions: Neck surgery/trauma
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nternal carotid artery disease or surgery or trauma | Tumors or aneurysms in the cavernous sinus | Pituitary tumors | Cluster headaches
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DIFFERENTIAL DX
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Physiologic anisocoria, Adie syndrome, Argyll-Robertson pupil, Third nerve palsy
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NOTES
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The “triad” associated with Horner’s syndrome is ptosis, miosis, and anhidrosis. This classic triad can present subtly and not all three usually present at the same time.
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A painful Horner’s syndrome is commonly associated with internal carotid artery dissection
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A cranial nerve VI palsy associated with Horner’s syndrome can be due to a lesion in the cavernous sinus or brainstem
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