Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

Prisms help only in small degree deviations.

Steroids may be needed if there is element of rheumatoid disease.

Surgery is rarely indicated as many show - spontaneous improvement, no manifest strabismus and minimum head tilt.

Surgery is indicated in

Diplopia in primary position, Marked abnormal head posture, Decompensation of squint

Surgery is not very rewarding as it rarely corrects the ocular rotation. Surgery consist of stripping of superior oblique tendon sheath, removal of adhesion round the trochlea and recession of contra lateral superior rectus.

Superior oblique myokymia

This is an ocular dyskinesia not seen in children. The exact cause is not known, there is periodic vertical and torsional oscillopsia each lasting for few minutes.

There is no definite treatment for the condition.

Characteristics of abducent nerve palsy42,43

The sixth nerve supplies only lateral rectus on ipsilateral side. The lateral rectus is involved in one horizontal movement i.e. abduction.

The sixth nerve has a long intra cranial course second only to fourth nerve. Lesions extending from its nucleus to its end in the muscle may involve lateral rectus. There are two types of lesions of sixth nerve i.e. those

(1)That have other neurological signs in pons and

(2)Those that cause isolated sixth nerve palsy.

Isolated sixth nerve palsies are non specific and non localising. An isolated sixth nerve palsy is never nuclear.

The signs and symptoms of isolated sixth nerve palsy produce :

1.Convergent squint.

2.Head turned towards the affected muscle.

3.No change in position of chin or tilting of head.

4.There is limitation of lateral movement.

5.Homonomous horizontal diplopia that becomes worse on looking towards the involved side.

6.Bilateral paralysis of sixth nerve produces diplopia in all gazes.

7.Paralysis of lateral rectus is frequent in children. It may be unilateral or bilateral.

Common causes of sixth nerve palsy in children are

•Congenital

•Trauma

•Infection

•Inflammation

•Demyelination

Vascular lesions like haemorrhage, aneursym, ischaemia are rare in children but are major cause of sixth nerve palsy in adults.

Neoplasm of mid brain are also major causes of sixth nerve palsy in children. Majority of congenital cases are bilateral. The common congenital causes are :

1.Developmental anomaly of lateral rectus

2.Maternal infection

3.Birth trauma (common)

4.Hereditary.

In new borns, a transient lateral rectus palsy due to viral infection is seen occasionally developing one to three weeks after non specific upper respiratory tract infection. Isolated sixth nerve palsy in children without neurological features of headache, vomiting, papilledema, ataxia is caused due to :

1.Middle ear infection

2.Post viral status

3.Sinusitis

4.Raised intra cranial pressure

Topographic location of sixth nerve lesion Nuclear lesion

An isolated sixth nerve palsy can never be nuclear.

A nuclear lesion is associated with horizontal gaze palsy towards the side of the lesion due to involvement of pontine paramedian reticular formation. Involvement of seventh nerve loop round the sixth nerve nucleus causes ipsilateral facial palsy. Involvement of medial longitudinal fascicles cause ipsilateral inter nuclear ophthalmoplegia. Involvement of oculo sympathetic will cause ipsilateral Horner’s syndrome.

Fascicular lesion (Brain stem lesion or anterior inferior cerebellar artery syndrome) : This can cause three types of lesions :

1.Dorsal pons lesion—Millard Gubler syndrome

2.Dorso lateral pons lesion—Foville’s syndrome

3.Combination of the two—Raymonds syndrome.

Millard Gubeller’s syndrome consists of

1.Sixth nerve palsy

2.Ipsilateral seventh nerve palsy.

3.Contra lateral hemi paresis due to involvement of pyramidal tract.

Foville’s syndrome consists of :

1.Horizontal conjugate gaze palsy due to involvement of P.P.R.F.

2.Ipsilateral fifth, seventh and eighth nerve palsy

3.Ipsilateral Horner’s syndrome.

Raymonds syndrome consists of :

1.Ipsilateral sixth nerve palsy

2.Contra lateral hemiparesis.

The above lesions are generally seen in elderly persons with micro vascular lesion of diabetes, hypertension, athero sclerosis and not in children. Moreover such patients are seriously ill and first seen by neuro physician.

Basillar lesion

The three common causes of sixth nerve palsy in children at this level are :

1.Raised intra cranial pressure

2.Gradenigo syndrome

3.Trauma

Other causes like acoustic neuroma and nasopharyngeal tumors are seen in elders.

1. Raised intra cranial pressure. Raised intra cranial pressure pushes the brain stem down pulling the sixth nerve on each side. It stretches the sixth nerve in the Dorellos canal over the apex of the petrous bone. This produces bilateral sixth nerve palsy without any localising sign. The causes are posterior fossa tumor and pseudo tumor ceribri.

Gradenigo’s syndrome -

This is a common cause of unilateral sixth nerve palsy in children in developing countries. This is secondary to otitis media which leads to infection of petrous bone and extra dural abscess formation that comes in close proximity of the sixth nerve.

The syndrome consists of sixth nerve palsy, facial palsy, diminished hearing, facial pain in the distribution of first division of fifth nerve.

Battle’s sign. This consists of bilateral sixth and seventh nerve palsy, bleeding or leak of CSF from external ear and ecchymosis over the mastoid. The cause of the condition is closed head injury. The skull is compressed in horizontal diameter, there is transverse fracture of the temporal bone or base of the skull.

Differential diagnosis of sixth nerve palsy

Differential diagnosis of sixth nerve palsy consists of many unrelated non neurological conditions that produce more or less degree of mechanical restriction of lateral rectus. The conditions can be congenital or acquired. They are :

1.Mobius syndrome

2.Duane’s retraction syndrome

3.Fractured medial wall of the orbit

4.Strabismus fixus

5.General fibrosis syndrome

6.Alternate day esotropia

7.Conjunctival shortening syndrome

8.Spasm of near reflex

9.Break in fusion of congenital esophoria

10.Infantile esotropia

11.Nystagmus blockage syndrome

Besides these myasthenia and thyroid myopathy are two systemic conditions that may masquerade any motor palsy.

Mobius syndrome44,45

This is a multi systemic congenital anomaly where bilateral sixth nerve palsy with bilateral seventh nerve palsy are the two constant features. The Bells phenomenon is retained. The eyes can not be moved in horizontal direction, both duction and version are equally affected. Vertical movements are retained. There are no pupillary changes. No vestibular nystagmus can be demonstrated by caloric or rotatory tests. Occasionally there may be esotropia. Rarely there may be exotropia, A and V pattern is common. Involvement of other nerves from fifth to twelfth have been reported.45 Most probable cause is aplasia or hypoplasia of nuclei of various cranial nerves.

Other associated deformities are - Deafness, deformed tongue, dental defects, skeletal defects in hands, feet. General hypotonia of muscles, especially pectoral muscle, variable mental retardation.

Management

Associated error of refraction and amblyopia when present should be treated by standard method.

Lateral tarsorrhaphy may be required in presence of seventh nerve palsy.

Results of squint surgery are not very good. Maximum recession of medial rectus may be done.

Duane’s retraction syndrome

Duane’s retraction syndrome is a common motility disorders seen in children. The condition is congenital and sporadic. Though it is present at birth, it is generally not diagnosed before three years of age. The child is generally brought for squint or abnormal movements of the eye and lids. It is generally unilateral but can be bilateral. When unilateral the left eye is affected more often than right. It is more common in girls.

The essential features are :

•Narrowing of the inter palpebral fissure on adduction.

•Widening of IPA on abduction.

•Retraction of globe on adduction.

•Upshoot of the eyeball on adduction.

The eye may be orthophoric, esotropic or exotropic. A-V pattern is common. There are many classification of the condition based on clinical presentation and electro myographic findings.

Clinically there are three types :

1.Narrowing of IPA and retraction of globe with limited abduction, this is the commonest clinical type.

2.Other things remaining same as in type I, there is limited adduction.

3.Both adduction and abduction are limited. This is the rarest type.

The exact cause of Duane’s retraction syndrome is not known. Many congenital anomalies have been blamed for the condition alone or in combination. They are : 1. Mechanical, 2. Neural

The mechanical factors are :

1.Fibrotic, thin, non elastic lateral rectus

2.Relatively posterior insertion of medial rectus

3.Tight medial rectus acting as band

4.Abnormal attachment of lateral rectus

5.Muscles bound to the orbital wall

6.Abnormal attachment of medial rectus at its origin near the orbital apex

7.Fibrosis or atrophy of lateral rectus

The neural anomalies can be :

1.Absent sixth nerve nucleus

2.Poorly formed abducent trunk

3.The lateral rectus is partially supplied by third nerve

4.The lateral rectus is supplied by third nerve

5.Simultaneous contraction of medial and lateral rectus in an attempt to adduct with retraction of globe

The other classification is based on electro physiological changes in extra ocular muscle48

1.Paradoxical innervation of lateral rectus getting maximum impulses on adduction and diminished impulse abduction. This is the commonest type of Duane’s retraction syndrome.

2.Lateral rectus gets maximum impulse on abduction with normal medial rectus.

3.Innervation of both lateral or medial rectus in primary as well as adduction or abduction.

Duane’s retraction syndrome may be just an ocular anomaly which is very common. Involvement of other systems are not rare.

The ocular changes commonly seen with Duane’s retraction syndrome are microphthalmos, lid defects, crocodile tear, heterochromia of iris, lenticular opacities, dermoids, coloboma of choroid.

The auricular changes include - changes in external ear, external auditory meatus and defects in vestibular canals.

The skeletal system changes consists of changes in palate and vertebrae, hand and

feet.

The neural changes - mal-development of third, fourth and sixth nerve.

Variants of Duane’s retraction syndrome47

1.The retraction of globe is so minimal that the condition is called Duane’s retraction syndrome without retraction.

2.Similarly there may be very little narrowing of palpebral aperture.

3.There may be retraction of upper lid.

4.There may be hypotropia or hypertropia in primary position.

The term pseudo retraction syndrome is used to denote entrapment of medial rectus in fracture of medial orbital wall. There is retraction of globe in attempted abduction.

Management

Management consist of correction of any error of refraction when present, prevention and treatment of amblyopia. Some children have no visible change in primary position and maintain good binocularity with slight change in head posture.

Surgery

There are many types of surgeries performed to treat the condition. Each case seems to be requiring separate method. Multiple bilateral surgeries are required to strengthen the lateral rectus. Faden procedure may be used to correct abnormal head posture. This prevents up and down shoot with stabilising effect on horizontal muscles.

Commonest type of surgery advocated is bilateral medial rectus recession.

Strabismus fixus

This is a congenital condition of large bilateral esotropia due to anchoring of extra ocular muscles. The medial rectus is inelastic and replaced by a fibrous band, which is shorter than usual length of medial rectus. The muscle is inserted in a larger than normal area. Occasionally the lateral rectus and vertical muscles may also be affected. The eye is fixed in adduction. Forced duction test is positive. In an attempt to adduct, the globe retracts.

General fibrosis syndrome is more severe form of strabismus fixus. All the extra ocular muscles are fibrosed. There may be adhesion between Tenon’s capsule and the globe.

Alternate day esotropia (Intermittent cyclic esotropia)

This is an unusual form of squint that has rhythmic cycle of esotropia for twenty four hours followed by orthophoria for next twenty four hours. Making the squint to manifest every alternate day, such rhythm cycle may last for six months to one year, by then the esotropia becomes constant. Treatment is required when esotropia becomes constant and most commonly practiced surgery is bimedical recession.

Conjunctival shortening syndrome

This form of restrictive tropia is seen when conjunctiva is kept contracted for months as is seen in third nerve palsy, sixth nerve palsy, long standing concomitant squint or following trauma, surgery where conjunctiva has not been recessed well at the time of muscle surgery. The condition is also met with in thyroid eye disease.

There is limited ocular movement, forced duction test is positive.

Progressive external ophthalmoplegia

This is a rare chronic multi systemic disorder generally seen in second to fourth decade. Infantile and juvenile are also known.48 The exact cause of the disease is not known. It is said to be associated with micro chondrian mutation.49 Others consider it to be an abiotrophy.

It is a bilateral progressive disease that beigns with bilateral ptosis which is generally equal on both sides, gradually other extra ocular muscles also get involved. There is no fix pattern of involvement of the muscles, however, down gaze is unaffected for long time. At the end all the muscles loose function and the eye has a fixed position. The orbularis may also be involved. The iris and ciliary body are spared.

Kearns—Sayer syndrome is a triad of external ophthalmoplegia, retinal pigment degeneration and complete heart block.

Ophthalmploegia plus generally develops in childhood, there is no family history, CSF protein is elevated. The children have short stature, may have subnormal intelligence and hypogonadism.

The condition has to be differentiate from myasthenia, thyroid eye disease, orbital pseudo tumor, myotonic dystrophy, progressive supra nuclear palsy.

There is no known specific treatment.

Differential diagnosis of abducent palsy in children

Diagnosis of recent lateral palsy is not difficult. However, occasionally the child with esotropia may fail to abduct the involved eye in conditions other than sixth nerve palsy i.e. infantile esotropia. In such situation of simulated sixth nerve palsy it is essential to find out if the lateral rectus in question is really paralytic. The best way to demonstrate action of lateral rectus in such conditions is to patch the straight eye for few hours. This will move the eye laterally in cases of pseudo paralysis of lateral rectus but not in paralysed lateral rectus. The only exception is entrapment of medial rectus in fracture of the medial wall of the orbit, which is confirmed by forced duction test. The child with lateral rectus palsy has his face turned towards paralysed muscle to avoid diplopia. The other advantage of face turning is increased temporal field on the side of the paralysed lateral rectus. The child with prolonged lateral rectus palsy may cross fix with the paralysed eye like in infantile esotropia. The other test is Dolls eye movement which is negative in lateral rectus palsy.

Other conditions that simulate like lateral rectus palsy are—Duanne’s retraction syndrome, Mobieus syndrome, congenital fibrosis syndrome, pseudo tumor orbit, myasthenia. Investigation generally done to clinch the diagnosis of lateral rectus are—Ultrasonography of the orbit, CT, MRI, in cases of suspected myasthenia Tensilon test is positive. Forced duction test helps in finding out entrapment of the muscle and fibrosis syndrome.

Long term effect of extra ocular muscle palsy

1.Presentation of acute ocular palsy greatly differ from chronic palsies

2.Some cases may present with palsy of one particular muscle only to involve other muscles later. This happens frequently in thyroid eye disease and myasthenia.

3.Following are the changes that are seen in other muscle/muscles when one muscle is involved :

(a) Over action of ipsilateral antagonist

(b) On long term, the ipsilateral antagonist may end up in contracture (c) Secondary inhibition of contra lateral antagonist (under action)

(d) By the time secondary changes (sequel) take place, the other muscles get primarily involved.

(e) Compensatory head posture - The child may overcome diplopia by keeping the head in abnormal position.

(f) Suppression and amblyopia are common in children with manifest squint.

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