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Causes of Horners Syndrome

Horner's syndrome is an interruption of the sympathetic supply to the eye, resulting in the classic triad of ptosis, miosis, and anhydrosis.

First-order neuron

Cerebral hemispheric lesions

Brain stem lesions

- Infarction

- Demyelinating diseases

- Pontine gliomas

- Syringobulbia

- Bulbar poliomyelitis

- Encephalitis

Cervical cord lesions

- Trauma

- Gliomas or ependymomas

- Syringomyelia

- Bulbar-type polio

- Amyotrophic lateral sclerosis or Lou Gehrig disease

Second-order neuron

Trauma to the lower brachial plexus

(Hypothalamus to upper thoracic cord)

E.g., hemispherectomy; massive infarction may cause ipsilateral Horner's syndrome

The sympathetic and spinothalamic pathways in the brain stem lie throughout their course next to each other. Horner's syndrome here is therefore frequently associated with contralateral pain and temperature loss

E.g., dorsolateral pontine; lateral medullary or Wallenberg's syndrome E.g., multiple sclerosis

E.g., herpes zoster

These 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

Particularly causing a central cord lesion

(Mediolateral column in the upper cord to superior cervical ganglion)

E.g., T1 and C8 root avulsion, known as Klumpke's paralysis

Lesions of the lower trunk of the brachial plexus

Iatrogenic

Neck and paravertebral masses

Neural sheath tumors Cervical rib syndrome Cervical disk

Third-order neuron

Cluster headaches

Carotid artery lesions Cavernous sinus lesions

Superior orbital fissure lesions

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 injury to the lower plexus

E.g., surgical procedures in the thyroid, larynx, pharynx, anterior cervical decompression and fusion

Impingement on the paravertebral sympathetic chain; e.g., thyroid tumor, lymphoma, bacterial or tubercular abscess, tumors of the posterior mediastinum, pre-vertebral hematoma

E.g., neurofibroma affecting the T1 nerve root Usually in young women Very rare; less than 2%

(Superior cervical ganglion via carotid tree to orbit) 12% of cases; postganglionic oculosympathetic palsy

E.g., trauma, dissection; associated with persistent facial pain, and is an indication for further evaluation

Lesions in this area usually damage both the sympathetic and the parasympathetic nerves, leading to a semi-dilated and fixed pupil, associated with other extraocular nerve palsies

Ipsilateral partial dilatation and pupillary fixation with extraocular nerve palsies

Pupillary Syndromes Argyll Robertson pupil

Loss of light reflex The pupil does not contract when a bright light is shone into the eye. Artificial light is better for testing than strong daylight. The test is best performed in a darkened room

Retained ability to ac- Strong and tonic contractions commodate

Miosis is usually present

Imperfect dilatation of pupil after instillation of atropine

Failure of ciliospinal re- When the neck is irritated or when cocaine is instilled flex into the eye, the pupil will dilate on the contralateral side

Usually bilateral

Significance: Argyll Robertson pupil is traditionally ascribed to injury to the central parasympathetic pathway in the periaqueductal area. It is a classical sign of meningovascular syphilis (e.g., neurosyphilis, tabes, and general paresis). It is also occasionally seen in epidemic brain stem encephalitis, alcoholism, pinealomas, and advanced diabetes.

Horner's Syndrome

Ptosis of varying degrees in the upper and lower eyelids

In the 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, and is known as "upside-down ptosis"

Narrowing of the palpe- Due to ptosis of the upper eyelid and slight elevation bral fissure of the lower lid: paresis of Muller's muscle

Miosis The affected pupil is slightly smaller than the con tralateral one. The resulting anisocoria is minimal in bright light, and exaggerated in darkness. Occasionally, pupillary involvement can only be demonstrated on pharmacological testing

Transient increase in accommodation

Anhidrosis

Transient vascular dilatation of face and conjunctiva

Enophthalmos

Occurs in 5%, with preganglionic lesions; sudomotor and vasoconstrictor fibers pass to the face along with branches of the external carotid artery

The conjunctiva may be slightly bloodshot due to the loss of vasoconstrictor activity

This is not an easily detected sign; it is not a feature of oculosympathetic palsy

Change in tear viscosity Iris heterochromia

In congenital Horner's syndrome, the iris on the affected side fails to become pigmented and remains a blue-gray color

Significance: Horner's syndrome results from an interruption of the sympathetic supply to the eye. The pathway has three neurons. Firstorder fibers descend from the ipsilateral hypothalamus through the brain stem and cervical cord to T1 -T2, and C8 (the 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 synapse on postganglionic sympathetic fibers. The third-order neurons travel via the internal carotid artery, 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 pupil. The sudomotor and vasoconstrictor fibers pass to the face separately, with the external carotid artery branches.

Holmes-Adie or Tonic Pupil

Widely dilated, circular pupil

Does not react to light. Pupil may react very slowly and after prolonged exposure to very bright light

Tonic accommodation

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. The cause of the condition is unknown. The dissociation between the poor or absent light reaction and the more definite response to accommodation are thought to be produced by slow inhibition of sympathetic activity, and not by any residual parasympathetic activity.

Afferent Pupillary Defect or Marcus Gunn Pupil

Shining a light into the normal eye causes brisk pupillary contraction (the affected pupil also contracts consensually). When the light is shone into the affected eye in turn, the reaction is slower and less complete, and the pupil is therefore slow to dilate again (the pupillary escape phenomenon). The reaction is best seen if the light is moved rapidly from the normal to the affected eye and vice versa, with each stimulus lasting approximately one second and two to three seconds being left in be-

tween. The affected pupil is therefore dilating when the moving light touches it.

Significance: The Marcus Gunn pupillary reaction is thought to be due to a reduction in the number of the fibers serving the light reflex on the affected side. The lesion must be prechiasmal, and almost always involves the optic nerve, often due to multiple sclerosis.

Posttraumatic Mydriasis or Iridoplegia

Irregular pupillary dilatation Poor or absent reaction to light

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. A history of trauma and findings of local periorbital or orbital injury, or both, in a conscious and mentally unaffected patient are diagnostic.

Hippus

Spontaneous, sometimes rhythmic and alternating contractions and dilations of the pupil under uniform, constant illumination. The pupils show wide excursions visible to the naked eye, gradually decreasing. This phenomenon is called hippus. Both pupils normally exhibit fine movements (known as "pupillary unrest"), particularly under high magnification. An absence of pupillary unrest suggests organic disease.

Significance: The condition is seen in normal individuals; in cases of hysteria; and is associated with incipient cataracts, multiple sclerosis, meningitis, contralateral cerebrovascular insults, and recovery from oculomotor paralysis.

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