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Horner’s Syndrome

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Overview

Horner’s syndrome (HS) describes the signs and symptoms seen due to damage to the sympathetic trunk (paired nerve fibres that run from the base of the skull to the coccyx and form part of the sympathetic nervous system). Therefore, it describes reduced sympathetic activity.

HS is characterised by a classic triad of:

The signs and symptoms are seen on the ipsilateral side of the lesion.

Pathophysiology

As a reminder, in the sympathetic nervous system, nerves from the central nervous system (CNS) synapse with a cluster of cell bodies known as a ganglion. These nerves are known as preganglionic nerves. Nerve fibres then emerge from the ganglion and synapse at an effector organ. These are postganglionic fibres.

These can also be described as:

  • First-order sympathetic fibres – emerge from the CNS:
    • Originate in the hypothalamus and synapse with preganglionic nerve fibres
  • Second-order sympathetic fibres – preganglionic fibres:
    • Leave the spinal cord at T1 and ascend over the lung apex and synapse with the superior cervical ganglion at C3-C4
  • Third-order sympathetic fibres – postganglionic fibres:
    • Are close to the internal carotid artery. They pass through the cavernous sinus to enter the eye via the superior orbital fissure.

Since HS describes lesions to the sympathetic trunk, the underlying cause may be in the CNS, preganglionic nerves, or postganglionic nerves.

Presentation

HS is characterised by a classic triad of:

  • Ptosis (partial) – upper eyelid drooping which can cause an apparent enophthalmos
  • Miosis – pupillary constriction
  • Anhidrosis (hemifacial) – absence of sweating

Localisation and Causes

Anhidrosis can be used to distinguish between the causes and localise where the pathology is:

  • Central (CNS) lesions (first order neurone disorder) – anhidrosis of face, arm, and trunk:
  • Preganglionic lesions (second order neurone disorder) – anhidrosis of face only:
    • Pancoast’s tumour
    • Thyroidectomy
    • Trauma
    • Cervical rib
  • Postganglionic lesions (third order neurone disorder) – no anhidrosis:

Investigations

Investigations are guided by the suspected underlying cause:

  • Chest x-ray:
    • If Pancoast’s tumour or another lung tumour is suspected
  • Cocaine or apraclonidine eye drops:
    • Normally causes pupil dilation as it inhibits noradrenaline reuptake but this does not occur in HS

Management

Overview

The management of HS involves managing its underlying cause.

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