Horner's Syndrome

Synonym: Bernard-Horner syndrome (commonly used in France)¹

This is a rare condition that results from disruption of the sympathetic nerves supplying the eye. There is the triad of:

• Partial ptosis (upper eyelid drooping)
• Miosis (pupillary constriction)
• Hemifacial anhidrosis (absence of sweating)¹

• First-order sympathetic fibres originate in the hypothalamus and descend through the brainstem to level C8-T2 of the spinal cord where they synapse on pre-ganglionic sympathetic nerve fibres.
• Second-order fibres leave the cord at level T1 and ascend in the sympathetic chain over the apex of the lung to synapse in the superior cervical ganglion at the level of the bifurcation of the common carotid artery (C3-4).
• Third-order (post-ganglionic) fibres pass alongside the internal carotid artery, sending branches to the blood vessels and sweat glands of the face, and pass via the cavernous sinus to enter the eye via the superior orbital fissure. They pass via the long ciliary nerves to supply the iris dilator and the Müller muscle.

Symptoms¹

• Inability to fully open eye on affected side.
• Loss of sweating on affected side.
• Facial flushing (if pre-ganglionic lesion).
• Orbital pain/headache (if post-ganglionic lesion).
• There may be other symptoms depending on the underlying cause (see below), e.g. head, neck or facial pain on affected side if associated with carotid artery dissection.

Signs^1,2

• Constricted pupil on affected side:
  • Shine a torch in the eye to make the pupil constrict.
  • Remove the torch and watch the pupil dilate.
  • Do the same on the other side and compare the response.
  • The affected pupil lags behind the other in dilation as it lacks sympathetic tone.³
• Ipsilateral dry skin on face due to loss of sweating:
  • Take both index fingers and place then together in the middle of the forehead. Then run them laterally over the forehead to just lateral to the eyebrows.
  • On the affected side there may be more friction as the skin is drier because there is no sweating on that side.
  • A lesion in the common carotid artery area causes loss of sweating that involves the entire side of the face.
  • Lesions distal to the carotid bifurcation produce lack of sweating on the medial aspect of the forehead and the side of the nose.⁴
• Ipsilateral partial ptosis (drooping of upper eyelid) with possible paradoxical contralateral eyelid retraction.
• There may be apparent mild enophthalmos due to the sagging lid.
• There is increased amplitude of accommodation.
• Heterochromia irides may occur with congenital Horner's syndrome.⁵ The iris on the affected side remains blue whilst the other changes to brown. Pigmentation of the iris is under sympathetic control and is usually complete by the age of 2.
• Examine for the presence of lymphadenopathy (see below).
• Other signs depend on underlying cause (see below).

• Horner's syndrome associated with pain needs investigation. If there is arm, shoulder or hand pain think of Pancoast's syndrome. If pain is in the face or neck, think of carotid dissection. Pain and transient visual loss may be due to carotid dissection.⁶
• Unless there is a known aetiology such as birth trauma, all children with acquired Horner's syndrome require thorough investigation as there is frequently serious underlying disease including neuroblastoma, trauma, rhabdomyosarcoma and brainstem vascular malformation.^7,8
• A rare congenital form of Horner's syndrome is described.⁵ It may present as an autosomal dominant or as a spontaneous mutation.
• Pre-ganglionic lesions are less common but more likely to be malignant.

• The differential diagnosis of Ptosis is discussed in a dedicated article.
• Pupillary Abnormalities are also discussed in a dedicated article.
• Also consider unilateral use of miotic drugs.

Investigations will be guided by suspected aetiology. For example:

• Chest X-ray may show an apical carcinoma of the lung.
• CT/MRI may be useful to identify a cerebrovascular accident.
• Angiography/carotid ultrasound may demonstrate dissection of the carotid artery.

Pharmacological testing²

Pharmacological testing can help to confirm the diagnosis and identify if the lesion is pre-ganglionic or post-ganglionic.

• Cocaine eye drops will normally cause dilatation of the pupil but there is no response in Horner's syndrome. It inhibits the re-uptake of noradrenaline but this requires an intact sympathetic system. It confirms the diagnosis but does not localise the lesion.
• Apraclonidine is an alternative to cocaine. They have little effect on a normal pupil but cause dilation of a pupil affected by Horner's syndrome.
• Hydroxyamphetamine 1% drops can also be instilled to both eyes but wait at least 48 hours after performing the cocaine test. The drops stimulate the release of norepinephrine from postganglionic nerves and cause dilation of the pupil (similar to that in the unaffected eye) if these nerves are intact. Hence, a first or second-order nerve lesion will result in dilation but no dilation occurs with third-order (postganglionic) lesions.

Horner's syndrome is a physical sign. Management involves diagnosis of the underlying condition and treatment as appropriate.

Johann Friedrich Horner was a Swiss ophthalmologist born in 1831. He was made Professor of Ophthalmology in Zurich in 1873. He described the syndrome that bears his name in 1869.¹⁰ In France it it called Bernard-Horner syndrome, adding the name of Claude Bernard. Horner died in Zurich in 1886. His other achievements included the observation that red-green colour blindness is transferred to males through the female line.