Clinical Neurology · Neuro-Ophthalmology

Pupils & Horner Syndrome

Localization of Pupil Abnormalities

Common pupillary abnormalities, their clinical appearance, and the lesions or conditions that produce them.

Abnormality	Description	Causes
Marcus-Gunn pupil (afferent pupillary defect)	The affected pupil does not react to light as briskly as the unaffected pupil	Unilateral optic neuropathies, chiasmal and optic tract lesions
Horner syndrome	Miosis, with an increase in anisocoria in the dark – ptosis of the upper and lower lids, variable anhidrosis – slow pupillary redilation in the dark	Acquired (see above) or congenital (there will be a heterochromic iris because of impairment of the pigmentary changes)
Adie’s tonic pupil	Dilated pupil with poor or absent response to light but preserved near response
Holmes-Adie syndrome	Triad of dilated pupil with poor or absent response to light but preserved near response, loss of deep tendon reflexes, and abnormalities of sweating	Unknown, may be viral infection of parasympathetic and dorsal root ganglia
Argyll-Robertson pupils	Pupils are small and irregular with impaired light response and intact near response	Diabetes or syphilis

Features accompanying a Horner syndrome help localize the lesion along the three-neuron oculosympathetic pathway and beyond.

Associated Symptoms	Consideration
Isolated, painful	Carotid dissection, cluster headache
Sensory level	Spinal cord
Arm numbness or weakness	Brachial plexus
Ipsilateral face and contralateral body numbness	Medulla
Sixth-nerve palsy	Cavernous sinus

The fibers of the optic tract synapse in: the primary visual pathway synapses in the LGB, the pupillomotor pathway synapses in the pretectum, and the subcortical visual pathway synapses in the superior colliculus.
An afferent pupillary defect (Marcus-Gunn pupil) is seen with unilateral optic neuropathies as well as chiasmal and optic tract lesions.

Ahmed Koriesh, MD