Historical Overview
- In 1854, French physiologist Claude Bernard described a condition found in animals in which disruption of sympathetic innervation to the eye gave rise to miosis, ptosis, and anhidrosis.1
- In 1869, Swiss ophthalmologist Johann Friedrich Horner provided a more complete assessment of this condition and correctly attributed it to oculosympathetic paresis, which led to creation of the honorific term “Horner’s syndrome.”1,2
Description
- Horner’s sign, or syndrome, is actually a combination of classical clinical signs—the triad of ipsilateral ptosis, pupillary miosis, and facial anhidrosis—that occur secondary to damage or interruption of the oculosympathetic pathway.2,3
Pathophysiology
- Horner’s syndrome may develop from lesions at any point along the sympathetic pathway, and it can be either acquired or congenital. Classically, the cause of congenital Horner's syndrome has been birth trauma resulting in brachial plexus injury (Klumpke's palsy), but more aggressive etiologies, such as neuroblastoma and carotid artery thrombosis, have also been seen.4
- Potential causes of acquired Horner’s syndrome include: primary or preganglionic neuron lesions, stroke, tumor, migraine, carotid artery ischemia, brachial plexus trauma, dissecting carotid aneurysm, middle cranial fossa neoplasm, and iatrogenic injury.
- The long anatomical pathway of the oculosympathetic chain makes it vulnerable to many pathological processes.
- In most cases, the cause of isolated Horner’s syndrome is benign or from a previously identified cause, such as surgery, but it’s important to also consider the possibility of carotid dissection and neoplasm.3
Instructions
- Obtain an accurate and complete patient history, including prior trauma, sensory loss, and pain in the face, neck, shoulders, or arms. Also ask if the patient has recently undergone an interventional procedure that has the potential to cause relevant neurologic damage.
- Measure the pupillary diameter in dim and bright light and the reactivity of the pupils to light and accommodation.
- Examine for dilation lag of the pupil immediately after dimming the lights.
- Examine the upper lids for ptosis and the lower lids for upside-down ptosis.
- Observe for extraocular movements.
- Perform a biomicroscopic examination of the pupillary margin and iris structure and color.
- Perform a visual field testing and test of facial sensation.
- Observe for the presence of nystagmus, facial swelling, lymphadenopathy, or vesicular eruptions.5
Related Signs and Tests3,4
- The “harlequin” sign: asymmetric facial flushing
- Pharmacological testing
- 4% cocaine drops
- Apraclonidine
- Hydroxyamphetamine
- Pholedrine
- Carotid Doppler ultrasound
- Chest X-ray
- Cervical spine X-ray
- MRI
Diagnostic Performance Characteristics
- A diagnosis of Horner’s syndrome should be considered in any patient with anisocoria associated with what appears to be normal pupillary constriction to light in both the larger and smaller pupil. The presence of dilation lag of the smaller pupil, when present, is also helpful in making the diagnosis.
- Patients in whom Horner’s syndrome is suspected should be evaluated for evidence of cranial nerve dysfunction, particularly an ipsilateral abducens nerve paresis that may indicate a lesion of the cavernous sinus or, in very rare cases, of the brain stem.1