• 12 SECTION Disorders Pupil

Horner Syndrome

Key Facts

•Miosis and ipsilateral ptosis

•Caused by sympathetic denervation

•Lesion may lie within the first (central), second (preganglionic), or third (postganglionic) segment of oculosympathetic pathway

•Causes of postganglionic Horner syndrome:

•cervical carotid dissection

•surgery, trauma, or mass in neck

•cavernous sinus lesion

•cluster headache

•idiopathic

•Causes of preganglionic Horner syndrome in children:

•birth injury

•neuroblastoma

•Causes of preganglionic Horner syndrome in adults:

•surgery, trauma, or mass in paraspinal, neck, or apical lung regions

•Causes of central Horner syndrome:

•dorsolateral medullary infarction (Wallenberg syndrome)

•cervicothoracic cord syrinx, trauma, or tumor

Clinical Findings

•Anisocoria in dim light with normal pupil constriction to bright light

•Ptosis ipsilateral to smaller pupil

•Anisocoria rarely >2 mm

•Dilation lag of affected pupil

•Ptosis, never >3 mm, need not be present

•Ipsilateral elevation of lower lid (upside down ptosis) sometimes

•Ipsilateral conjunctival injection sometimes

•Ipsilateral facial anhydrosis (central or preganglionic lesions)

Ancillary Testing

•30 min after instillation of cocaine 10%, residual anisocoria should be >1 mm

•Apraclonidine 0.5% should eliminate anisocoria or cause reversal of anisocoria (small pupil becomes larger pupil)

•MRI or magnetic resonance angiography should extend from skull vertex to midthoracic region regardless of results of topical pharmacologic pupil tests

• use dedicated ‘carotid dissection’ protocol if Horner syndrome is acute

Differential Diagnosis

•Ptosis from trauma, senescence, or myasthenia gravis

•Miosis from physiologic anisocoria or iris pathology

A

B

C

Fig. 12.10 Right Horner syndrome. (A) In dim illumination, left pupil is larger than right pupil. (B) In brightness, both pupils constrict normally. (C) After instillation of 10% cocaine, right pupil dilates less than left pupil.

A B

Fig. 12.11 Right internal carotid artery dissection.

(A) Precontrast axial T1 shows a white crescent around the right internal carotid artery at a high cervical level, indicating a blood clot dissected within the vessel wall (arrow). (B) Maximum intensity projection magnetic resonance angiography of the neck vessels shows that the lumen of the right internal carotid artery lumen is narrowed (arrowheads) compared with the normal caliber left carotid artery (arrow).

Syndrome Horner