Horner's Syndrome - Signs and Symptoms

Signs and Symptoms

Signs that are found in patients on the affected side of the face include

• partial ptosis (drooping of the upper eyelid from loss of sympathetic innervation to the superior tarsal muscle, also known as Müller's muscle)
• upside-down ptosis (slight elevation of the lower lid)
• anhidrosis (decreased sweating on the affected side of the face)
• miosis (small pupils)
• enophthalmos (the impression that the eye is sunk in)
• loss of ciliospinal reflex
• bloodshot conjunctiva, depending on the site of lesion.

Sometimes there is flushing on the affected side of the face due to dilation of blood vessels under the skin. The pupil's light reflex is maintained as this is controlled via the parasympathetic nervous system.

In children, Horner's syndrome sometimes leads to heterochromia: a difference in eye color between the two eyes. This happens because a lack of sympathetic stimulation in childhood interferes with melanin pigmentation of the melanocytes in the superficial stroma of the iris.

In veterinary medicine, signs can include partial closure of the third eyelid, or nictitating membrane.