5.1 Horner’s Syndrome
Horner’s syndrome is an interruption of the sympathetic supply to the eye. It is characterized by miosis with a pupil that is slow to dilate, a mild (1–2 mm) ptosis, ipsilateral anhidrosis, and apparent enophthalmos (affected eye appears to be sunken) as a result of a combination of the ptosis and slight elevation of the inferior eyelid. The irides may be of different colors if the lesion is congenital or long standing. This three-neuron oculosympathetic pathway runs from the brain to the pupil (▶Fig. 5.1).
Fig. 5.1 Right Horner syndrome in a patient with right carotid artery dissection. The right pupil and eyelid gap are markedly narrower than on the left. (Reproduced from 12.3 Disturbances of Ocular and Pupillary Motility. In: Mattle H, Mumenthaler M, Taub E, ed. Fundamentals of Neurology: An Illustrated Guide. 2nd edition. Thieme; 2017.)
5.1.1 Causes of Horner’s syndrome
Central neurons pass from the posterior hypothalamus through the brain stem into the spinal cord, via the intermediolateral column, to synapse at the ciliospinal center of Budge at the C8–T2 level of the spinal cord.
Cerebral hemispheric lesions (e.g., hemispherectomy, massive infarction may cause an ipsilateral Horner’s syndrome)
The sympathetic and spinothalamic pathways in the brain stem lie throughout their course next to each other; therefore, Horner’s syndrome is frequently associated with contralateral pain and temperature loss.
i. Infarction (e.g., dorsolateral pontine; lateral medullary or Wallenberg’s syndrome)
ii. Demyelinating diseases (e.g., multiple sclerosis (MS))
vi. Encephalitis (e.g., herpes zoster)
These lesions usually cause loss of pain and deep tendon reflexes in the arms and frequently a bilateral Horner’s syndrome; ptosis usually draws attention to the condition.
Second-order (preganglionic) neuron
Preganglionic axons exit the cord via ventral roots to pass over the apex of the lung to enter the sympathetic cervical chain. This sympathetic chain is associated with the carotid arteries. The second-order neurons synapse at the superior cervical ganglion located at the bifurcation of the cervical carotid artery.
Trauma to the lower brachial plexus (e.g., D1 and C8 root avulsion known as Klumpke’s paralysis)
Lesions of the lower trunk of the brachial plexus (e.g., carcinoma of the lung apex extending through the apical pleura, also known as Pancoast’s tumor; metastatic disease in the axillary glands from malignant disease from the breast or elsewhere; radiation damage to the lower plexus)
Iatrogenic (e.g., surgical procedures on thyroid, larynx, pharynx, anteri- or cervical decompression, and fusion)
Neck and paravertebral masses usually lymphadenopathy (impingement upon the paravertebral sympathetic chain, e.g., thyroid tumor, lymphoma, bacterial or tuberculous abscess, tumors of the posterior mediastinum, prevertebral hematoma)
Neural sheath tumors (e.g., neurofibroma affecting the D1 nerve root)
Cervical rib syndrome (usually in young females)
Cervical disc (very rare; less than 2%)
Apical lung tumors (e.g., Pancoast’s tumors)
Aneurysms of the aorta, subclavian, or common carotid disease
Third-order (postganglionic) neuron
The third-order (postganglionic) axons leave the superior cervical ganglion to accompany the internal and external carotid arteries. Most third-order axons pass with the internal carotid artery (ICA) to reach the ipsilateral cavernous sinus and then travel with fibers of the abducens (CN VI) nerve to pass to the nasociliary branch of the trigeminal nerve and enter the orbit through the superior orbital fissure. These long ciliary nerves pass through the ciliary ganglion (without synapsing) and enter the eye in the subarachnoid space to innervate the radially oriented iris dilator muscle. Both vasomotor (flushing) and sudomotor (sweating) sympathetic fibers of the face travel with the branches of the external carotid artery.
Cluster headaches or migraine (12% of cases; postganglionic oculosympathetic palsy)
Carotid artery lesions (e.g., trauma, dissection; associated with persistent facial pain and is an indication for further evaluation)
Both the sympathetic and the parasympathetic nerves are usually damaged by these lesions leading to a semi-dilated and fixed pupil associated with other extraocular nerve palsies.
Superior orbital fissure lesions (ipsilateral partial dilatation and pupillary fixation with extraocular nerve palsies)
Mahoney NR, Liu GT, Menacker SJ, et al. Pediatric Horner’s syndrome: Etiologies and role of Imaging and Urine studies to detect neuroblastoma and other responsible mass lesions. Am J Pathol 2006;142(4):651–659
Asch AJ. Turner’s syndrome occurring with Horner’s syndrome. Seen with coarctation of the aorta and aortic aneurysm Am J Dis Child 1999;133(8):827–830
Schievink WI. Spontaneous dissection of the carotid and vertebral arteries. N Engl J Med 2001;344(12):898–906
5.2 Abnormal Pupils
This refers to unequal pupils. This is physiological in about 20% of people. However, if this is a new complaint, the steps to the underlying diagnosis lie in determining which of the pupils is abnormal and then look for associated signs. The first step is to compare the pupils in light and dim conditions.
If there is a poor reaction to light in one eye and the anisocoria is more evident in a well-lit room, then the affected pupil is abnormally large.
If there is a good reaction to light in both eyes but a poor dilation in the dark (i.e., the anisocoria is enhanced), then the affected pupil is abnormally small.
There is poor constriction in a well-lit room.
Drugs (i.e., antipsychotic agents, atropine, cocaine, adrenaline)
Pharmacological dilation (i.e., dilating drops)
Serotonin syndrome (a toxic reaction to serotonin)
There is poor dilation in a dim light.
Drugs (i.e., Heroin, fentanyl, Codeine, tramadol and other narcotics)
1Drugs are by no means the single factor of pupil change, but depending on the type of drug involved they can cause pupils to constrict, dilate, or show a lack of reactivity. Drugs are often the first suspect in any pupil change where there has been no trauma and no history of an existing illness.
Uveitis with synechiae (adhesions)
Pancoast tumor (carcinoma of the lung apex)
Leukocoria: This refers to a white pupil and may be due to a number of conditions.
Congenital cataracts (must exclude the possibility of a retinoblastoma)
Persistent fetal vasculature syndrome
A pupil should be round. Any deviation from this suggests abnormalities.
Congenital iris defects (e.g., colobomata)
A fixed oval pupil in association with severe pain, a red eye, a cloudy cornea and systemic malaise.
Light reflex test: Abnormalities arise as a result of severe optic nerve damage (e.g., transection). The patient will be blind in the affected eye; neither pupil reacts when the affected side is stimulated, but both pupils react normally when the fellow eye is stimulated.
Swinging flashing test: When the pupil exhibits a relative afferent pupillary defect (RAPD), it is known as a Marcus Gunn pupil. It suggests optic nerve disease, central retinal artery or vein occlusions. A mild RAPD may also occur in amblyopia, with vitreous hemorrhage, retinal detachment, or advanced macular degeneration.
Near-reflex test: There are several causes of light-near dissociation that can be grouped according to whether the problem is unilateral or bilateral.
5.3 Pupillary Syndromes
5.3.1 Argyll Robertson pupil
The pupil does not contract when the eye is exposed to bright light. Artificial light is better for testing than strong daylight. Best performed in a darkened room.
Retention of power of accommodation
Strong and tonic contractions to near effort
Imperfect dilatation of pupil after instillation of atropine
When the neck is irritated or when cocaine is instilled into the eye the pupil will dilate on the contralateral side.
5.3.2 Horner’s syndrome
Ptosis of variable degree of the upper and lower eyelid
In its worst form, the lid may reach to the edge of the pupil, whereas in mild cases the ptosis is barely detectable; isolated ptosis of the lower lid may occur, known as “upside-down ptosis.”
Narrowing of the palpebral fissure
This happens due to ptosis of the upper eyelid and slight elevation of the lower lid: paresis of Müller’s muscle
The affected pupil is slightly smaller than its fellow; the resultant anisocoria is minimal in a bright light and exaggerated in darkness. Occasionally, pupillary involvement can only be demonstrated on pharmacological testing.
Transient increase in accommodation
Occurs in 5% patients, with preganglionic lesions; sudomotor and vasoconstrictor fibers to face travel with branches of the external carotid artery.
Transient vascular dilatation of face and conjunctiva
The conjunctiva may be slightly bloodshot due to the loss of vasoconstrictor activity.
This sign is not easily detected; it is not a feature of oculosympathetic palsy.
In congenital Horner’s syndrome, the iris on the affected side fails to become pigmented and remains a blue-grey color.
Significance
Horner’s syndrome results from an interruption of the sympathetic supply to the eye. The pathway has three neurons. First-order fibers descend from the ipsilateral hypothalamus through the brain stem and cervical cord to T1–T2, and C8 (ciliospinal center of Budge). They synapse on ipsilateral preganglionic sympathetic fibers, exit the cord through the first and second anterior dorsal roots, ascend in the cervical sympathetic chain as second-order neurons to the superior cervical ganglion, and then they synapse on postganglionic sympathetic fibers. The third-order neurons travel via the ICA, pass to the Gasserian ganglion and through the first division of the trigeminal nerve to the orbit and innervate the radial smooth muscle of the iris pupil. The sudomotor and vasoconstrictor fibers travel to face separately with the external carotid artery branches. (See “Causes of Horner’s syndrome.”)
5.3.3 Holmes–Adie or “tonic” pupil
Widely dilated, circular pupil
Pupil may react very slowly, i.e., after prolonged exposure to very bright light.
Strong and tonic contraction to near effort
Usually unilateral (80%) and more frequently found in females.
Often associated with loss of knee tendon reflexes and impairment of sweating.
Significance
The Holmes–Adie or tonic pupil is due to the degeneration of the nerve cells in the ciliary ganglion (▶Fig. 5.2). The cause of this condition is not known but it often occurs after a viral illness (e.g., herpes zoster ophthalmicus).
The dissociation between the poor or absent light reaction and of the more definite response to accommodation are thought to be produced by slow inhibition of the sympathetic and not by any residual parasympathetic activity. Diagnosis is confirmed by the pupil’s hypersensitivity to weak miotic drops (e.g., 0.05–0.125% pilocarpine) which cause the abnormal pupil to contract vigorously and the normal pupil minimally.
5.3.4 Afferent pupillary defect or Marcus Gunn pupil
The normal eye has a brisk pupillary constriction when exposed to light (the affected eye will also constrict consensually). When a light is shone into the normal eye it will cause a brisk pupillary constriction; the affected eye will also constrict consensually. When the light in turn is shone into the affected eye, the reaction is slower, less complete, and so brief that the pupil is slow to dilate again (the pupillary escape phenomena) (▶Fig. 5.3). The reaction is best seen when:
The light is moved rapidly from the normal to the affected eye and vice versa,
Each stimulus lasting approximately 1 second with 2–3 seconds in between. The affected pupil will thus be dilating when the swinging light hits it.
5.3.5 Posttraumatic mydriasis or iridoplegia
Significance
Disruption of the fine short ciliary nerve filaments in the sclera by blunt trauma results in a usually transient paralysis of the iris causing an irregularly dilated pupil with impairment of the light reaction. History of trauma and findings of local periorbital/orbital injuries in a conscious and mentally intact patient are diagnostic.
5.3.6 Hippus
Spontaneous, partially rhythmic and alternate contractions and dilatations of the pupil under uniform, constant illumination. The pupils present wide excursions visible to the naked eye, gradually decreasing. This phenomenon is called hippus. Pupils normally exhibit fine movements, i.e., pupillary unrest, particularly under high magnification. Absence of pupillary unrest is indicative of organic disease.
5.3.7 Unilateral pupillary dilatation (mydriasis)
Local mydriatic and cycloplegic drug agents
Migraine (cluster headaches often lead to miosis with Horner′s syndrome)
A large pupil nonreacting to initially to accommodation and to light or convergence, develops suddenly several days after an infection or trauma.
When the neck is irritated or when cocaine is instilled into the eye, the pupil will dilate on the ipsilateral side.
Contralateral pupillary constriction: for example, in Horner’s syndrome
5.3.8 Bilateral pupillary dilatation (mydriasis)
See ▶Fig. 5.4.
Rostrocaudal deterioration from supratentorial masses leading to an almost irreversible cerebral damage and coma.
Anticholinergics (e.g., atropine, scopolamine, belladonna, propantheline)
Antihistamines (e.g., diphenhydramine, chlorpheniramine)
Postictal (e.g., major seizures)
Bilateral optic nerve damage and blindness
Lesions within the tectum will interfere with the decussating light reflex fibers in the periaqueductal area and result in dilated and nonreacting pupils and paralysis of the upward gaze.
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