Horner’s syndrome

DEFINITION / OVERVIEW AND ETIOLOGY

Any lesion along the oculosympathetic pathway can cause Horner’s syndrome. There are three parts or orders to the oculosympathetic pathway. First-order sympathetic fibers arise from the hypothalamus and descend uncrossed through the brainstem and terminate/synapse in the spinal cord at the level of C8–T2. Second-order sympathetic fibers exit the spinal cord at the level of T1 and enter the sympathetic cervical chain, where they arch over the pulmonary apex and the subclavian artery and then ascend the common carotid artery to synapse in the superior cervical ganglion at the bifurcation of the carotid artery. Third-order fibers exit the superior cervical ganglion and ascend along the internal carotid artery, traveling into the cavernous sinus, and entering the orbit to innervate the iris dilator and Muller muscle, the eyelid retractor muscles.

First-order neuron lesions include Arnold–Chiari malformation, meningitis, cerebral vascular accident involving the brainstem, and demyelinating disorders. Second-order neuron lesions include tumor at the apex of the lung, brachial plexus injury from birth trauma, central venous catheterization, trauma or surgical injury (radical neck dissection, thyroid surgery, carotid angiography, cardiac surgery), chest tubes, lymphadenopathy,

270

270 Right Horner’s syndrome with slight ptosis,enophthalmos,pupillary constriction and decreased sweating.(From Strobel S et al. Paediatrics and Child Health –The Great Ormond Street Colour Handbook,Manson Publishing.)

lesions of the middle ear (acute otitis media), and neuroblastoma. Third-order lesions include internal carotid artery dissection, idiopathic inflammation of the orbit, carotid-cavernous fistula, herpes zoster, and migraine headaches.

CLINICAL PRESENTATION

When the sympathetic innervation to the eye is interrupted the retractor muscles of the eyelids are weakened, allowing the upper lid to droop and the lower lid to rise (this is called ptosis of the upper and lower lids) (270). The dilator muscle of the iris is weakened, allowing the pupil to become smaller. Vasomotor and sudomotor control of parts of the face may be impaired. This combination of ptosis, pupil miosis, and anhidrosis is called Horner’s syndrome. If the Horner’s syndrome is congenital it may cause a lighter colored iris on the involved side.

DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS

The diagnosis can be made clinically with this constellation of features: mild (1–2 mm) ptosis of the upper and lower lids, smaller pupil on the involved side which responds well to light, with the pupil asymmetry between the two eyes greater in darkness than in light, and a pupil that dilates more slowly when the lights are extinguished (dilation lag). Depending on the location of the lesion on the sympathetic chain there may be loss of sweating and redness on the involved side of the face with exertion. A lighter colored iris supports the diagnosis of a congenital Horner’s syndrome.

The diagnosis of Horner’s syndrome can be further substantiated by pharmacologic testing with 4–10% cocaine solution. Cocaine blocks the reuptake of norepinephrine into the sympathetic nerve endings. In the normal eye the cocaine causes dilation of the pupil. However, if there is any lesion on the sympathetic chain an insufficient quantity of norepinephrine will accumulate and the involved pupil will not dilate as well as the normal one. Hydroxyamphetamine drops can be used to distinguish between first-/second- order neuron involvement and third-order neuron involvement.6, 7

The differential diagnosis would include physiologic anisocoria (natural variation in pupil size, not pathologic). Cranial third nerve palsy causes ptosis but also should display motility

disturbances, and the pupil should be large and nonreactive if the third nerve palsy involves the pupil. Iris sphincter muscle damage from trauma or intraocular inflammation can lead to a smaller pupil. Use of certain iris sphincter constricting eyedrops could lead to a smaller pupil.

MANAGEMENT/TREATMENT

As noted above it may be necessary to test with cocaine drops to confirm the diagnosis of Horner’s syndrome. If the etiology is known, such as chest surgery, chest tubes, neck surgery, central venous catheterization, brachial plexus injury, or brainstem lesions on MRI, then no further work-up is indicated. If the etiology is unknown a work-up is indicated regardless of whether the onset of the Horner’s syndrome is congenital or acquired. Work-up should include MRI of brain and orbits, neck, and upper chest to the level of the aortic arch. This ensures complete imaging of the oculosympathetic pathway. Many cases have no obvious etiology. The ptosis can be corrected with surgery but it is usually quite mild and not problematic. Mild dilating drops can enlarge the pupil but typically are not used by these patients. The vision in the involved eye is normal.

Congenital ocular motor apraxia

DEFINITION/OVERVIEW AND ETIOLOGY

Congenital ocular motor apraxia is characterized by impaired ability to generate quick (typically horizontal) eye movements on command. The eye movements can be elicited with horizontal head movements but not volitionally.8 CNS abnormalities have been noted which include bilateral lesions of the frontoparietal cortex, agenesis of the corpus callosum, hydrocephalus, and cerebellar abnormalities. Frequently neuroimaging is normal.

CLINICAL PRESENTATION

Congenital ocular motor apraxia is characterized by an inability to generate normal voluntary horizontal saccades. The movement abnormality is noted in the first few months of life. The child may not appear to fixate and follow objects normally and can be erroneously diagnosed as being blind. Between the ages of 3 and 5 months the child will begin a characteristic head thrusting in order to move the eyes horizontally to fixate on targets. Vertical voluntary eye movements are typically normal. The head thrusts made by these patients reflect an adaptive strategy to change their eye position. In order to see an object the head will thrust toward the target and overshoot it. As the head is thrust the eyes deviate in the opposite direction and slowly come to rest on the target. Then the head slowly normalizes its position. The mechanism evoked is called the vestibulo-oculoreflex.

DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS

The diagnosis of congenital ocular motor apraxia is made clinically. Lesions of the cerebral hemispheres can cause movement abnormalities. Blindness from anterior or posterior visual pathway disease can imitate congenital ocular motor apraxia.

MANAGEMENT/TREATMENT

There is no treatment for congenital ocular motor apraxia. The head thrusts may improve in later childhood.

Myasthenia gravis

DEFINITION/OVERVIEW AND ETIOLOGY

Myasthenia gravis is a disease of abnormal neuromuscular transmission characterized by variable muscle weakness and fatigability of affected skeletal muscles, particularly the extraocular muscles and eyelids. There is a reduction in the number of acetylcholine receptors available at the muscle endplate. The nerve terminal releases an adequate amount of acetylcholine but with fewer endplates and endplate potentials produced, the end result is inefficient neuromuscular transmission and a weak muscle. The decrease in number of postsynaptic acetylcholine receptors is believed to be due to an autoimmune process whereby acetylcholine receptor antibodies are produced and block the receptors. For unknown reasons the disease affects predominantly the extraocular muscles and eyelids.

CLINICAL PRESENTATION

The hallmark feature of myasthenia gravis is variability of strength of the affected muscles. Ptosis may occur as an isolated sign or in association with extraocular muscle involvement. It is usually fleeting and fluctuating, shifting from one eye to the other. The ptosis may be bilateral and usually is asymmetric. The ptosis may be absent on awakening but appear later in the day. Involvement of the extraocular muscles, like ptosis, is extremely common in patients with myasthenia gravis. In most cases eye alignment abnormalities are associated with ptosis. All degrees of ocular motor dysfunction may occur from a single isolated muscle involvement to complete ophthalmoplegia.9

The disease may be purely ocular but in the most severe form occurs as part of a major systemic disorder with other skeletal muscles involved. Other signs and symptoms include weakness in the muscles of mastication, extensors of the neck, trunk, and limbs, dysphasia, hoarseness, dysarthria, and dyspnea. Dysphasia and dyspnea can be life-threatening. The onset of myasthenia gravis may occur at any age but is uncommon in children. A transient neonatal form, caused by the placental transfer of acetylcholine receptor antibodies from

mothers with myasthenia gravis, typically resolves quickly.

DIAGNOSIS AND DIFFERENTIAL DIAGNOSIS

The diagnosis of myasthenia gravis can be made clinically by identifying typical signs and symptoms. Roughly half of patients with ocular myasthenia will have elevated acetylcholine receptor antibodies on serologic testing. The diagnosis can also be made pharmacologically by overcoming the receptor block through the administration of acetylcholinesterase inhibitors such as edrophonium. Other office-based tests can be performed such as the sleep test or ice pack test. The sleep test is performed by having the patient take a 30-minute nap and upon awakening the ptosis or motility disturbance is reassessed. Improvement is highly suggestive of myasthenia gravis. The ice pack test is appropriate for patients with ptosis but not strabismus. An ice pack is placed on the closed eyelid for 2 minutes. If there is improvement in the ptosis on removal of the ice pack this is suggestive of myasthenia gravis.10 Repetitive nerve stimulation shows a decremental response in many patients with systemic myasthenia gravis. Single fiber electromyography is most sensitive but is not widely available.

Differential diagnoses that should be considered are: botulism, chronic progressive external ophthalmoplegia (Kearns–Sayre syndrome), Lambert–Eaton myasthenic syndrome, drug-induced myasthenic-like syndrome, and congenital myasthenic syndromes.

MANAGEMENT/ TREATMENT

Medical treatment for myasthenia gravis includes acetylcholinesterase inhibitors, corticosteroids, and other immunosuppressive agents. Thymectomy is the treatment of choice in patients with generalized myasthenia gravis with thymic enlargement. Purely ocular myasthenia gravis is usually not treated by thymectomy. The presence of a thymoma requires thymectomy.

•Introduction

•Clinical signs of childhood ocular tumors

Eyelid and conjunctiva Intraocular tumors Orbital tumors

•Diagnostic approaches

Eyelid and conjunctiva Intraocular tumors Orbital tumors

•Therapeutic approaches

Eyelid and conjunctiva Intraocular tumors Orbital tumors

•Eyelid tumors

Capillary hemangioma Facial nevus flammeus Kaposi’s sarcoma Basal cell carcinoma Melanocytic nevus Neurofibroma

Neurilemoma (schwannoma)

•Conjunctival tumors

Introduction

Choristomatous conjunctival tumors Epithelial conjunctival tumors Melanocytic conjunctival tumors Vascular conjunctival tumors Xanthomatous conjunctival tumors Lymphoid/leukemic conjunctival tumors

Non-neoplastic lesions that simulate conjunctival tumors

Conclusions