Horner’s Syndrome

Neuroanatomy of the oculo-sympathetic pathway

• First-order neurons arise in the posterolateral hypothalamus
• They descend ipsilaterally through the midbrain and pons, terminating in the interomedio-lateral cell columns of the spinal cord at the levels of C8 – T2
• Second-order neurons exit the cord at T1 and ascend via the cervical sympathetic chain
  • The sympathetic chain is near the subclavian artery and pulmonary apex
• Second-order neurons synapse in the superior cervical ganglion, which is at the level of the bifurcation of the common carotid into the internal and external carotid arteries
• Third-order neurons ascend along the internal carotid artery, through the carotid canal and cavernous sinus, entering the orbit via the superior orbital fissure

Clinical findings

• Partial ptosis due to paralysis of the superior tarsal (Muller) muscle
  • Overcome by voluntary upgaze
  • Paralysis of the lower Muller muscles will also cause elevation of the lower lid
  • Not fatigable
  • The normal pupil should be completely unobscured by the upper eyelid
• Miosis (pupillary constriction) due to paralysis of the long ciliary nerve and unopposed parasympathetic pupil constrictor activity
  • Pupil will constrict normally to light, but subsequent dilation is sluggish
• Anhidrosis in first and second-order (pre-ganglionic) lesions
  • In first-order Horner’s, anhidrosis will affect the face, upper arms and trunk
  • In second-order Horner’s, only the face will be affected
  • Third-order Horner’s does not result in anhidrosis because the level of the lesion is after the sympathetic supply to the apocrine glands
• Face
  • Ipsilateral trigeminal sensory loss with ipsilateral cerebellar and cranial nerve signs, contralateral cortical loss in the limbs (Wallenberg’s syndrome)
  • Visual fields (pituitary tumour)
  • Eye movements (cavernous sinus thrombosis)
• Neck
  • Scars (central line insertion, trauma, previous neck surgery)
  • Aneurysms
  • Masses (tumours, lymphadenopathy, goitre)
• Upper limbs
  • Nicotine staining
  • Clubbing, wasting of interossei, sensory loss over C8 – T1 (Pancoast’s syndrome)
  • Dissociated sensory loss (pain and temperature with preserved vibration), lower motor neuron pattern of weakness, fasciculations (syringomyelia)
• Chest
  • Cervical rib
  • Scars of previous thoracic surgery
  • Apical lung mass (Pancoast’s tumour)

Differential diagnosis

• First-order
  • Arnold-Chiari malformation
  • Pituitary tumour
  • Wallenberg (lateral medullary) syndrome
  • Hypothalamic stroke
  • High cervical myelopathy
  • Syringomyelia
• Second-order
  • Pancoast’s tumour
  • Subclavian artery dissection / aneurysm
  • Thyroid masses
  • Cervical rib
  • Aortic aneurysm / dissection
  • Neck surgery
  • Central venous catheterization
  • Shoulder dystocia at birth (trauma to brachial plexus)
  • Lymphadenopathy
• Third-order
  • Internal carotid artery dissection
  • Cluster headache
  • Cavernous sinus thrombosis

Investigations

• Confirmatory test (apraclonidine test); can also use 1:1000 adrenaline eye drops
  • Apraclonidine is a weak alpha-1 and strong alpha-2 agonist
  • Due to hypersensitivity of the denervated pupil dilator and Muller muscles
  • Apraclonidine application hence results in reversal of miosis and lid elevation
  • Little or no response in normal eye
  • False negatives: acute Horner’s when alpha-2 receptors have yet to be up-regulated
• Cocaine test: cocaine inhibits noradrenaline re-uptake. In normal eye, pupil will dilate. There will be no reaction in the affected eye due to sympathetic denervation.
• First-order:
  • MRI brain (structural lesions, stroke)
  • MRI cervical spine (syrinx, cervical myelopathy)
• Second-order:
  • Chest radiograph (apical lung tumour)
  • Angiogram for large artery aneurysm / dissection
• Third-order:
  • CT venogram (cavernous sinus thrombosis)

Summary

This patient has Horner’s syndrome. There is a partial ptosis which is overcome by upgaze. There is miosis and delayed pupil dilation following constriction to light. In addition, there is anhidrosis of the face, with sparing of the arms and trunk. This suggests a second-order Horner’s syndrome.

There was no palpable cervical rib or scars to suggest previous neck surgery. On examination of the upper limbs, there is clubbing, wasting of the dorsal interossei and a sensory loss over C8/T1, suggesting the presence of a Pancoast’s tumour. There were no palpable expansile masses to suggest an aneurysm.

In summary, this patient has a second-order Horner’s syndrome secondary to a Pancoast’s tumour.