Horner’s Syndrome

The patients in these two photos show the classical signs of Horner’s syndrome. In the first photo (Figure 1), there is left-sided partial ptosis, miosis and anhidrosis. Whilst in the second photo (Figure 2), there is right-sided ptosis and miosis.

Horner’s syndrome is caused by a lesion affecting the sympathetic pathway. This pathway starts as the 1st order sympathetic neuron which originates from the hypothalamus, travelling along as sympathetic fibres in the brainstem and terminates at the C8-T1 level of the spinal cord. The first-order neurons then branch with second order neurons (pre-ganglionic tract), which travels a long intra-thoracic course from the C8-T1 level of the spinal cord to the superior cervical ganglion at the level of C2. Finally, the cervical sympathetic pathway continues as third order neurons (post-ganglionic tract) which travels from the cervical ganglion at the level of C2, along the carotid artery, through the superior orbital fissures, cavernous sinus, orbital apex and finally terminates by supplying the levator palpebrae superioris muscle, superior tarsal muscle and the pupillary dilator muscles. Branches from the 3rd order sympathetic neurons also supply the sweat glands and blood vessels of the face. As the function of the levator palpebrae superioris and superior tarsal muscles include raising the upper eyelid, and the pupillary dilator muscles is involved in dilation of the pupil, patients with Horner’s syndrome may therefore present with partial ptosis and miosis.

Any lesion affecting the 1st, 2nd and 3rd order cervical sympathetic neurons may result in Horner’s syndrome and common causes would include: 1) brainstem stroke causing lateral medullary syndrome, 2) Pancoast’s tumour affecting the lung apex, 3) thoracic aortic aneurysm, 4) carotid artery dissection, 5) cavernous sinus pathologies and 6) local eye pathologies.