Horner’s Syndrome

Floriana Ferranti
Ortottista ed assistente in Oftalmologia
4 minutes
It affects the face and eyes on one side of the body, causing eyelid drooping, pupil reduction, and sweating. Let’s learn more about this rare neurological disease.
Table of contents

    What is it?

    Bernard Horner syndrome also referred to as oculosympathetic paralysis, is the action of the parasympathetic system (rest and digestion) overriding the malfunctioning sympathetic system (attack and escape), the victim of an interruption in nerve signaling of the cervical sympathetic pathways from the hypothalamus to the eye.

    The sympathetic trunk has bilateral nerve emergence (the two parts of the body each have their innervation) and includes the set of nerves that emerge from the spinal cord, pass through the thorax, and, from there, travel up to the neck, face, and eye.

    What are the symptoms?

    Horner’s syndrome is characterized by the symptom triad ptosis, miosis, and anhydrosis.

    The pupil dilator muscle no longer receives innervation, vasoconstriction, and control of the sweat glands is absent due to the malfunction of the sympathetic system that regulates these mechanisms.

    The parasympathetic system prevails, so we have miosis (lack of participation of the dilator muscle), therefore:

    • the pupil dilates more slowly resulting in the absence of the direct reflex
    • peripheral vasodilatation (red and hot face on the side of the lesion)
    • peripheral anhydrosis (absence of sweating on the injured side)
    • pseudoptosis (reduced function of the smooth muscle – Müller’s muscle or superior tarsal muscle – that provides for the elevation of the eyelid.

    Other possible symptoms are enophthalmos (re-entry of the eyeball into the orbit due to slight elevation of the lower eyelid, innervated by sympathetic fibers).

    Associated with these manifestations are signs and symptoms characteristic of the causative conditions.

    What are the causes? 

    There are many causes, and it is necessary to identify them to establish treatment.

    Bernard’s syndrome can also have an idiopathic origin, i.e. without obvious reasons.

    Lesions are generally subdivided into:

    • central (first neuron of the sympathetic pathway):
      • skull base tumors (traumatic dislocation of cervical vertebrae or traumatic vertebral artery dissection)
      • neck trauma
      • syringomyelia
      • multiple sclerosis and demyelinating diseases
      • encephalitis
      • lateral medullary syndrome (or Wallenberg syndrome)
      • Chiari malformation
      • basal m (e.g. syphilis)
      • lesions of the hypothalamus or medulla oblongata
      • intrapontine hemorrhage
      • pituitary tumor
    • peripheral of preganglionic origin (second neuron of the sympathetic pathway from the spinal cord to the neck)
      • tumor of the lung (Pancoast tumor) or of the thyroid gland
      • presence of goiter, resulting in a ‘mass effect’
      • schwannoma or neuroblastoma
      • damage to one of the main blood vessels connecting to the heart (e.g. the aorta)
      • surgery to the thoracic cavity, thyroidectomy (trauma or surgical damage)
      • Klumpke’s palsy with brachial plexus involvement
      • aneurysm or dissection of the aorta
      • central vein catheterization
      • lymphadenopathy (e.g. Hodgkin’s lymphoma, leukemia, tuberculosis, or mediastinal tumors)
      • mandibular abscess
      • middle ear lesions
    • peripheral lesions of postganglionic origin (third neuron of the sympathetic pathway – from the neck to the facial skin, iris, and eyelid muscles)
      • internal carotid artery dissection with sudden pain
      • Raeder syndrome (paratrigeminal syndrome)
      • carotid cavernous fistula
      • cluster headache or migraine
      • herpes zoster (shingles)
      • tumor at the base of the skull, due to the ‘mass effect
      • infectious disease affecting the skull, such as ear infections
      • migraine
      • cavernous sinus thrombosis
      • cluster headache

    Lesion sites: hypothalamus, brainstem, cervical cord, thorax, neck, skull base, and orbit.

    Congenital or acquired?

    Horner’s syndrome can occur from birth, i.e. in the congenital form, in which the ipsilateral iris is not pigmented and remains blue-grey (Von Passow syndrome).

    It can also occur in the acquired form, which is much more common.

    Diagnosis and treatment

    To make a diagnosis, one starts with the clinical symptoms: the symptoms are associated with the cause.

    Lesions are classified in three orders:

    • first order: chemosensory deficit, dysarthria, ataxia, vertigo, and nystagmus
    • second order: previous trauma, pain in the face, neck, armpits, shoulders or arms; cough; hemoptysis; chest or neck surgery; chest intubation or central venous catheterization; neck swelling
    • third order: diplopia from plasma of the sixth nerve, numbness in the first or second division of the trigeminal nerve, and pain.

    If identifiable, the cause of Horner’s syndrome is treated; there is no treatment for primary Horner’s syndrome.


    Useful eye tests for diagnostic purposes are:

    • instillation test with cocaine and apraclonidine drops in both eyes to confirm:
      • cocaine blocks the synaptic reuptake of noradrenaline and causes dilation of the pupil in the unaffected eye
      • apraclonidine is a weak alpha-adrenergic agonist that constricts the pupil of a normal eye
      • hydroxyamphetamine to help localize the lesion
    • MRI or CT scan of the brain, cord, chest, or neck (depending on clinical suspicion) to localize the abnormality.


    Floriana Ferranti
    Ortottista ed assistente in Oftalmologia
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