Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

Common intra orbital lesion where CT is used are24 :

1.Retinoblastoma of all stages, post radiation status, recurrence and intra cranial extension.

2.Rhabdomyosarcoma

3.Capillary haemangioma is best seen in contrast, may show calcification.

4.Optic nerve glioma with or without neurofibroma

5.Dermoids and teratomas

6.Pseudo tumours

7.Orbital cellulitis

CT may be a good diagnostic tool in optic neuritis. Moderate and symmetric enlargement is seen in raised intra cranial pressure.

In children dermoid cyst, rhabdomyosarcoma, optic nerve glioma, lymphangiomas give well circumscribed and sharply defined appearance. Capillary hemanioma, pseudo tumours, plexiform neuroma, leukaemia give ill defined view.25

Non ocular causes of loss of vision in one eye—optic neuritis, uniocular papilledema, ophthalmoplegia of unexplained origin. Conformation of ultrasonic findings are some other indications of CT of orbit.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging is a non invasive method of imaging that does not use ionising radiation used in common X-ray and computed tonography. The principle of MRI is that thin anatomic section similar to CT are viewed by exposing the patient to an intense magnetic field26. Besides magnetic field, a radio frequency wave and an atomic nuclei possessing an electric charge should also be available. Hydrogen atoms is used to generate MR signals because of its abundance in the body. The magnetic field is measured in a unit called Tesla

(T). Most of the MRIs uses 0.1 to 1.5 T of magnetic field. The process is not hampered by bone. It can very well differentiate between normal and abnormal tissue due to its high resolution. The metabolic profile of the tissue is also obtained.

Indications of MRI are ocular, orbital and neuro ophthalmic.

The ocular indication consists of ocular trauma, suspected nonferro magnetic intra ocular foreign bodies, growths obstructed by opacity in media. In such cases first choice should be ultrasonography but if ultrasonography findings are equivocal, the eye should be subjected to CT and MRI. Latter gives better view due to excellent resolution. The MRI can differentiate between retinoblastoma and intra ocular haemorrhage, exudates, Coats disease, choroidal efflusion and toxocariasis. Papilledema, optic neuritis, lens, vitreous and sclera do not normally enhance on post contrast MR.29

Orbital indication are—Proptosis of any kind, orbital cellulitis, pseudo tumours, neoplastic growths. Haemangiomas are well visualised in dye contrasted MRI. Magnetic resonance imaging is better than CT in evaluation of intra canalicular lesions. Orbital fat and optic nerve sheath do not enhance. MRI does not image bones well. MRI is contra indicated in suspected fero-magnetic foreign bodies. It should only be performed when such foreign bodies have been excluded by CT. MRI induced blindness in presence of metallic foreign body has been reported.29A

Neuro ophthalmic indications consists of :

Optic neuropathy of unknown origin, unexplained cranial nerve lesions, multiple sclerosis, paralytic squint, visual field defects not related to optic neuropathy. Lesions of sellaturcica, cavernous sinus and optic chiasma. It is widely used in suspected extension of retinoblastoma in the intra canalicular part of optic nerve and chiasma.

Some of the important indication of MRI in children are—evaluation of proptosis of sudden origin, suspected optic nerve sheath - complex lesions, organic foreign bodies, retinoblastoma with extra ocular extension. In children dermoid, rhabdomyosarcoma and glioma of optic nerve give well circumscribed image while capillary haemangioma, pseudo tumour, plexiform neuroma and leukaemia give ill defined image. The child may have to be sedated if not cooperative.

Advantages of MRI are :

1.The process is devoid of radiation hence it is safer than CT and X-ray. The child can be exposed to MRI for long period without any harm.

2.The procedure is not hampered by boney orbit.

3.Soft tissue image is seen better.

Ultrasonography with special reference to orbital diseases in children

General

Ultrasonography is one very important non invasive, non traumatic method. It does not use ionic radiation or magnetic field as used in X-ray, CT or MRI. Ocular ultrasonography does not have any side effect, can be used very frequently. It can be done as office procedure, bed side examination or in the operation theatre as this is a small handy instrument. It can be used in children with ease. However a non co-operative child should be suitably sedated by a trained anaesthetist.

Ultrasound

Speed of sound in vacuum is far less than that of light which is 3x1010 cm/sec or 186,000 mile/second. Ultrasound is produced in the transducer mechanically at a rate of 20,000 cycle per second (20 kHz). This is not audible to human ears. Diagnostic ophthalmic ultrasonography uses 10 omega hertz (10Mhz). Ultrasonography of other parts of the body use 2.5 to 5 MHz. Higher the frequency of ultra sound, lower is the penetration. Thus, to measure corneal thickness or depth of AC 12-15 MHz are used while that for globe is 10 MHz and orbit is 7 MHz. The ultrasound behaves more or less like light wave, it is reflected, absorbed and refracted. Maximum ultrasonic waves are reflected when it falls at right angles. Ultrasound can also disrupt a target tissue and generate heat, the later two are used in treatment and not diagnosis.

Basically a diagnostic system consist of (1) a tranducer, (2) a black box that detects the reflected beam and prepare for display, (3) Display.

The transducer (The probe)

This part of the system is most important and has been called the heart of the system. It is both a transmitter as well as a receiver. The transducer is made up of either quartz crystal or a ceramic plate, which send out sound wave when charged electrically. The same crystal picks up the returning waves and prepare it for visual display and photography. The

mechanism is called piezoelectric effect. This converts one form of energy to another form, in ultrasound it converts electrical energy to sound energy, which is again converted to visible electric form. The transducer of A scan is called stationary because there is no moving part inside the probe. Though the probe itself is moved by the examiner to scan various parts of the eye. In the transducer of B. Scan, the crystal inside the probe moves to and from. The pulse is focussed and directed into the ocular tissue. The pulse after striking the tissue travels back to the probe. This process is repeated may times each second.

The distance of the target tissue can be calculated by noting the time to travel the echo from the tissue, if the velocity of the sound is known. In A scan this is processed by a built in computer that automatically measure the distance and displays on the screen, which can be photographed for future reference. The resolution depends upon the frequency. Higher is the frequency, greater is the resolution but as frequency increases penetration decreases.30

The electronically amplified sound wave signal received by the probe is called its sensitivity or gain. When the sensitivity is more, the spikes of A mode are taller and the dots of B mode are brighter.

Other factors on which the height of A Scan and brightness of B. Scan depend are— angle of sound beams when it strikes the tissue, relative difference between the two tissues, the size and shape of the inter-face.

Sometimes some echoes are noted during ultrasonography, which are not produced by anatomical structures, these are called artifacts. Commonest artifact is an air bubble either in the probe itself, in the coupling medium used during ultrasonography or in the eye. Air bubble can get into the eye either by accident as in penetrating injury. It can be produced by gas forming organism or may be introduced deliberately as part of surgery. Intra ocular foreign bodies sometimes bounce back and forth waves inside the eye causing a chain of echoes behind the foreign body. This phenomenon is called reverbation. The foreign bodies that produce such artifacts are - intraocular lens, glass particles or steel pieces. Air is a potent reflector of sound in case of a penetrating injury. It is often difficult to differentiate echo produced by retained intra ocular foreign body and air bubble.31

Modes of display30

There are two modes of display on screen that can be photographed as well. They are A and B modes also called A Scan and B Scan respectively.

A Scan. A scan is a simple instrument but findings are more difficult to interpret. This mode is called time amplitude. The picture produced is unidimensional. The spike has a base line and a vertical deviation. The spike is a triangular configuration, base of which is formed by the base line and the point where two slanting arms meet is the apex. The distances between the two arms on the base line is called width of the spike. The left arm is called ascending limb while the other arm is called descending arm. The height of each vertical deflection is proportional to intensity of the echo. The base line represents the distance and depends on the time required for the sound to reach the target, to be bounced back to reach the probe.

A Scan is used to find out axial length of eyeball, AC depth and corneal thickness. It is most widely used to calculate power of the intra ocular lens. However intra ocular growths, intraocular foreign bodies and retinal detachment can also be seen by A mode. The difference between anterior corneal echo to retinal echo in a normal eye is the axial length of the eye. The cornea gives two spikes, one from the anterior surface and other from the posterior surface as the cornea is relatively thinner than other structures i.e. lens, IOL. The distance between the two is very small. The lens when clear also gives two sharp spikes, one from the anterior surface and other from the posterior surface in case of homogenous lens. In case of nuclear sclerosis, two additional echoes represent anterior and posterior surface of nucleus. In an aphakic eye, the corneal spike is followed by the retinal spike, however, if the posterior capsule has been left it gives one additional spike. Occasionally the aqueous, vitreous interface may also give a spike. A clear vitreous is echo free and gives widest gap between the two peaks. Floaters, haemorrhages, endophthalmitis, foreign bodies produce echo inside vitreous. A high sharp echo from the retina denotes a normal retina. To measure the axial length, the beam should pass through the centre of cornea and macula. A posterior staphyloma can also be seen on A Scan.

B Scan. This is a two dimensional display that is shown as dots of various brightness. Clinical interpretation depends on the brightness of the dot. A structure that produces a tall spike on A Scan will give bright picture on B Scan as well. The B Scan is said to reveal not only geometry of the structure but also its geography in the form of shape, size and position. It gives the information in all quadrant as the probe is moved all over the globe including the axial length. However for power calculation, A Scan should only be used. It is more useful than A Scan in diagnosis of vitreous opacity, vitreous haemorrhage, retinal detachment, intra ocular tumour, intra ocular calcification. B Scan is used to detect path of intraocular foreign body and occult rupture of the globe.

Following conditions show calcification on ultrasonography—(All ages)

Retinoblastoma, optic nerve sheathmeningioma, osteoma, choroid, haemangiomachoroid, toxocara, granuloma, chronic retinal detachment, drusen of optic nerve head, phthisis bulbae, intumescent and hyper mature cataract asteroid bodies in the vitreous.

Orbital inflammatory disorders in children

Orbit in children may have acute or chronic inflammation of contents of the orbit, periorbita or bones. Acute orbital inflammation is generally unilateral. Anatomically infections of orbit may be preseptal or orbital. A useful classification of orbital infection based on anatomical spaces is -

1.Preseptal or periorbital

2.Orbital cellulitis

3.Orbital abscess

4.Periorbital abscess

5.Cavernous sinus thrombosis

Preseptal orbital cellulitis (cellulitis lid) is very common, easy to diagnose and treat unilateral inflammation limited by skin anteriorly and orbital septum behind. Generally the

orbital contents are not involved. Pre auricular and sub mandibular glands are enlarged. Common organism that produce preseptal cellulitis are streptococcus, staphylococcus, pneumococcus and haemophilus influenzae. The last organism is more common in children below 3-4 years. It is associated with systemic involvement especially respiratory tract. It can prove to be both sight and life threatening.

Predisposing factors in preseptal cellulitis are—injury, insect bite, stye, acute sinusitis. The symptoms are mild, may have fever and malaise. It is more frequent in upper half than lower. Clinical pictures depend upon duration and severity of the condition. In a fully established case, the lid is swollen, hyperemic and tense, obliterating in palpebral fissure. It is impossible to evert the lid. In case of H. influenzae, the skin has a bluish pink tinge. There may be tender points on the lid margin denoting a stye. The swelling may spill over the midline, causing edema of the other side without infection. The pre auricular and sub mandibular lymph nodes are enlarged. Most of the time lid retractors are required to examine the eyeball. The eye is generally non congested, the cornea is bright and papillary reaction is normal, movements are not restricted and the vision is not reduced.

Treatment consist of—Hot fomentation, oral analgesic oral antibiotics in divided doses.

Complications are formation of a lid abscess and rarely cavernous sinus thrombosis. If a lid abscess develops fluctuation it should be drained through a horizontal incision and the pocket of pus broken. The wound may be packed with cotton gauze impregnated with antiseptic for twenty four hours.

Periorbital cellulitis

This is generally periostitis, there may be bony involvement9.36, 37. It may be peripheral, inflicting the orbital margin or may develop deep in the orbit near the apex of the orbit. The infection reaches the periostium either via veins that drain the paranasal sinuses or due to direct spread from the paper-thin walls of the sphenoid and ethmoidal sinuses. It may result following compound fracture of the orbital rim or due to penetrating injury.

There are two distinct types :

1.An acute stage due to strepto, staphyloor pneumococci or haemophilus influenza. This presents as tense swelling due to accumulation of pus between the rigid bony wall and periostmus. This is a painful condition, may push the eyeball to the opposite side, cause mild proptosis, is generally confused with acute orbital cellulitis. The diagnosis is confirmed by CT and MRI. The condition may subside following administration of broad spectrum antibiotic without any residual effect or the pus may find its way to the orbital margin, conjunctival fornix, inside the orbit or even the cranium. This may lead to a sinus formation.

2.The deep type of periostitis is associated with proptosis, extra ocular muscle palsy and optic nerve involvement generally mistaken for cavernous sinus thrombosis.

The chronic variety is generally seen in the orbital margin due to trauma, tuberculosis, unresolved acute peri orbititis. It presents with hard tender swelling on the orbital margin that is fixed to the bone. There may be an external sinus or a fistula. Sinus formation is more common with tuberculosis.

Treatment of the chronic tubercular lesion is treatment of the primary cause. Other causes require long term broad-spectrum antibiotic, drainage of the abscess and curettage of the sinus.

Orbital cellulitis32,33

Orbital cellulitis is common in children. It may be seen at any age but common at about five years.38 It is an acute purulent infection of contents of orbit that may involve more than one structure. It is a potentially sight threatening and sometimes may lead to loss of life due to involvement of central nervous system and septicimia.35

It is an unilateral condition caused by strepto, staphylo and pneumococci. It is generally single organism infection. H. influenza has emerged as a main causative organism especially in children under three years of age. The commonest route for organism to reach the orbit is via paranasal sinuses. All paranasal sinuses can cause orbital cellulitis, however, ethmoidal sinusitis is the most frequent source.39 Other common route is vascular spread from the sinuses, yet another mode of spread from the sinuses is dehiscence of the orbital wall of the sinus or its fracture. Generalised septicimia in a malnourished child and infection following penetrating injury can also introduce infection from outside. Occasionally septic teeth or acute dacryocystitis has also been observed to cause orbital cellulitis.

The infection is always acute. It starts with symptoms of fever, malaise, pain in the periorbital region and headache. The lids are swollen, in case of H. influenza the lid has a bluish red hue.

The lid itself is not primarily involved as the infections start in the orbit and is localised behind the orbital septum. Accumulation of pus, inflammatory substances and edema in a closed compartment cause sever pain, the eyeball is proptosed. As ethmoid and sphenoid are common source of primary infection. The eyeball is proptosed forward and laterally. The movements are restricted either due to edema of the muscles or paralysis of extra ocular muscle due to cranial nerve involvement. The conjunctiva is chemosed, however, the cornea is bright and AC does not show any reaction. Evidence of anterior chamber reaction denote uveal involvement. Dilated pupil is common with third nerve involvement. Fast deterioration of vision should warn about involvement of optic nerve that may be optic neuritis, central artery occlusion or central vein thrombosis.

Investigation show :

1.Leucocytosis

2.X-ray orbit shows a hazy orbit with hazy paranasal sinuses

3.CT and MRI shows fluid and air in the sinuses

4.Ultrasonography helps to differentiate other conditions that cause fast growing proptosis in a child. Swabs from conjunctiva or nasopharynx are seldom conclusive.

Differential diagnosis consist of cellulitis lid, cavernous sinus thrombosis, rhabdomyosarcoma, leukimic deposits, orbital deposit of neuroblastoma, retained intra orbital foreign body.

Complications may vary from discharging sinus on the orbital margin to meningitis, brain abscess, cavernous sinus thrombosis. If the cornea is exposed due to proptosis, cornea may develop ulceration that may slough and perforate. Occasionally tenonitis may develop.

Management of orbital cellulitis

As the condition is potentially life and sight threatening efforts should be made to save both in consultation with ENT specialist and pediatrician. Treatment of choice is parentral administration of ampicillin in divided doses. If there is chance of penicillinase producing organism, the antibiotic should be methacellin. Other antibiotic generally used are—naficillin or oxacillin41.

With intense antibiotic administration the condition should subside in five to seven days. If the condition does not subside CT should be repeated to locate the pus and drain it. The abscess is drained through an area that shows maximal fluctuation near the lid margin avoiding trochlea, superior oblique and lacrimal gland. Proptosis, chemosis of conjunctiva and lateral rectus palsy of the contra lateral eye strongly suggest cavernous sinus thrombosis.

Orbital and sub periosteal abscess38,42

Primary abscess of orbital and periostial space is extremely rare. It is generally secondary to non resolving orbital and periosteal cellulitis. Accumulation of pus among the contents of orbit is known as orbital abscess and pus under periostium is called as sub periosteal abscess. The organisms are same as that cause orbital cellulitis and sinuses are generally the source of infection. There is always some proptosis depending upon the size and location of abscess. Periosteal abscess generally leads to eccentric proptosis. An orbital abscess in the vicinity of optic nerve can cause purulent optic neuritis and retinal vascular obstruction. If the lids fail to protect the cornea, there may be exposure keratitis, ulcer and perforation.

Diagnosis is conformed by CT and MRI.

Treatment consists of change of antibiotic and its dose. If there is palpable fluctuation, the abscess should be drained through the maximum area of fluctuation. Posteriorly placed abscess are best drained via ethmoid.

Cavernous Sinus Thrombosis

To understand the pathology of cavernous sinus, it is essential to know general outline of applied anatomy of cavernous sinus.

The cavernous sinuses are situated on either side of the sphenoid bone. The body of the sphenoid lies between the right and left halves of cavernous sinus. The sellaturcia lies above the sphenoidal sinus. The cavernous sinus starts at the end of the superior orbital fissure and ends posteriorly near the apex of petrous bone. The Gasserian ganglion comes in close proximity of the posterior end of the sinus. The sinus is formed by splitting of the dura and is traversed by trabeculae that gives it a spongy look. The sinuses of each side communicate with the sinuses of other side by transever sinuses of cavernous sinus.

The walls of the trabecular space are rough, making is vulnerable for thrombus formation. Each cavernous sinus is formed by superior ophthalmic vein, central retinal vein, part of inferior vein and spheno palatine sinus. Thus, the cavernous sinus is the reservoir of venous drainage from scalp, face, orbit and most part of the cerebrum. The superior and inferior petrosal sinuses drain backwards. The petrosal sinuses drain into sigmoid sinus that finally drain into juglar vein. The tributaries of cavernous sinus are valve less and are prone for infection to travel both ways.42

The contents of the cavernous sinus are internal carotid artery along with sympathetic plexus. The sixth nerve lies inferio lateral to the artery in the substance of the sinus making it more vulnerable than other cranial nerves. The other nerves lies in the lateral wall of the sinus in the posterior part. The third nerve is superior most followed by fourth and two divisions of fifth nerve. In the anterior part of the sinus, the fourth nerve changes its course to be superior to the third nerve. However this superior course of the fourth nerve is very short.42

Infection of the cavernous sinus is basically thrombo phlebitis which used to be almost cent percent fatal in pre antibiotic era. Even today it is common in malnourished and chronically ill children and remains sight threatening and life threatening condition. The cavernous sinuses can get infected as part of acute bacterial inflammation or by chronic granuloma. The former is generally refined to a cavernous sinus thrombosis while the later is known as anterior cavernous or superior orbital fissure syndrome. A third kind is known as a septic thrombosis that results following head injury and neuro surgical manipulation.44

Diagnosis of cavernous sinus thrombosis is straight forward when there is tenderness over the mastoid, proptosis, in 50% cases proptosis is bilateral, restricted movement of the globe, contra lateral sixth nerve palsy. Only condition that mimic cavernous sinus thrombosis is orbital cellulitis which is invariably unilateral. Presence of orbital cellulitis can be confirmed by CT and MRI. X-ray skull has no role in diagnosis of cavernous sinus thrombosis.

Management of cavernous sinus thrombosis is a medical emergency. The child should be hospitalised and put on heavy dos of parental antibiotic. The cornea should be protected by antibiotic ointment and lubricants.

Pseudo tumour orbit

Pseudo tumour orbit is the cause of proptosis in ten percent of all cases. It is generally seen in adult male in fourth and fifth decade. In adults, it is generally unilateral. About one tenth of proved cases of pseudo tumour of orbit however belong to the pediatric age group, where it is invariably bilateral.47 Early diagnosis of this benign growth in children is required because it mimics rhabdomyosarcoma, metastatic neuroblastoma and leukaemic infiltration, all of which pose a threat to the life of a child and mistaken diagnosis of pseudo tumour in a case of malignancy can cause death of the child.

The condition has been defined as an idiopathic localised inflammatory disease47. The disease acquires its name from the fact that it masquarades as neoplasm with a histopathological picture of inflammatory granuloma. The exact etiology is not known, the condition is perhaps multifactorial in which auto immune responses to antigens has been implicated.48

Vasculitis, myositis granuloma, thickening of tissue, lymphatic infiltration are com-

mon.9

The disease generally has a torpid course, it may have an acute onset or may linger for long time causing extensive fibrosis leading to a condition called frozen orbit. Children may show variable systemic symptoms.

The characteristic presentation is a slow growing proptosis which may be axial when the growth is intra conal or eccentric when it is extra conal. The growth may involve any part of the orbit from the lacrimal gland to apex of orbit. It may even invade anterior part of the

cavernous sinus. The proptosis is irreducible and does not change with posture or valselva manoeuvre. The mass is palpable between the orbit and the globe when it is anteriorly placed. The extra ocular muscle are involved in various combinations causing tropia resulting in diplopia or complete immobilisation of the globe. The conjunctiva is generally congested and chemosed. Corneal anaesthesia is a common feature due to involvement of fifth nerve otherwise cornea is bright and transparent unless it protrudes beyond the lid. In such cases, there may be exposure keratitis.

As multiple structures are involved, the symptoms are variable. Initial symptoms are redness of eye, headache and diplopia. The parents may complain of gradually developing enlargement of the eye, which turns out to be a proptosis. Pain in the distribution of fifth nerve is common. Squint and diplopia are invariably present, loss of the vision should draw attention to optic neuritis, a growth behind the globe pushes the posterior pole forwards leading to hypermetropia.

Diagnosis is by exclusion, confirmed by X-ray orbit + ultrasonography, CT, MRI, fine needle biopsy and excessional biopsy. A therapeutic trial by oral steroid is advocated in adults. It is avoided in children. The first step is to give proper attention to possibility of fatal conditions i.e. rhabdhomyosarcoma, leukaemia and metastatic neuroblastoma. Foreign body granuloma, unresolved orbital cellulitis and specific granuloma of the orbit are rare but possible differential diagnosis.

X-ray orbit may also show enlargement of the orbit.49,50 A high resolution CT is more helpful because it provides more information about periorbital structures as well.42 A Scan has no value in this condition. On B Scan a characteristic irregular mass in retro bulbar space is visualised. Other findings on CT are orbital myositis—thickening of the muscle, lateral and inferior recti are more involved, the insertion of the muscles also thickened. The posterior sclera and choroid may also show thickening.48 MRI is more sensitive and help to localise the small growth more precisely. Fine needle biopsy unless done by a person who is well versed with the procedure may be futile. Even in case of positive specimen, histopathologist may only be able to see if it is a malignancy or not but not the exact nature of the growth. Excisional biopsy under general anaesthesia through anterior orbitotomy or trans ethmoidal approach gives the best result to pinpoint the diagnosis.

Management

Most important part of the management is to be sure that the case under consideration is not malignant. Rhabdomuosarcoma, which is the commonest malignant tumour of the orbit in children may present with feature of inflammation and may show initial regression with systemic steroid.

There is no specific treatment for pseudo tumour. The tumours completely regress under full dose of steroids orally over few months. Inter lesional steroids also give some relief but is difficult to administer in a child. While the child is under steroid careful watch should be kept on possible ocular and systemic side effects. The drug should be tappered over weeks.

Other methods used are—radiation and cytotoxic drugs in case of steroid resistant cases. Radiation consists of 15-25 Gy given in consultation with radiologist in divided dose. Cytotoxic drugs commonly used are cyclophosphamide, chlorumbucil, metho trex ate, cyclosporin

separately or in combination in collaboration with pediatric oncologist and physician. Complications of pseudo tumours are—recurrence, poor response to steroids, strabismus, amblyopia, exposure keratitis, optic neuritis, papilledema, frozen orbit, permanent diminished vision.

Tenonitis9,37

This is inflammation of Tenon’s capsule. It is rare in children except as complication of orbital cellulitis. Besides orbital cellulitis, severe scleritis and posterior uveitis can cause tenonitis in adults. The condition is painful, the eye is axially proptosed. There may be diplopia with restriction of ocular movement without paralysis of extra ocular muscles. There may be associated optic neuritis.

Diagnosis is confirmed by CT and MRI.

Management in children is meticulous treatment of orbital cellulitis.

Common orbital tumours in children

Tumours in children can be primary or secondary or extension from other structures

(retinoblastoma). The secondary tumours are always malignant. They may metastasise from a distant organ i.e. neuroblastoma, Ewings sarcoma, Wilm’s tumour or leukaemia. The primary tumours are mostly benign. The benign tumours inflicting orbit in children are—Neurofibroma, capillary haemangioma, dermoids, teratomas, optic nerve glioma.

Commonest type of primary malignant tumour of orbit in children is rhabdomyosarcoma.

Rhabdomyosarcoma54, 55

Rhabdomyosarcoma may develop at any age even at birth. In children it is the most common primary malignant tumour of the orbit. Average age of presentation is seven years. In adults it spares the orbit and develops in skeletal muscles. Surprisingly in children it does not develop from extra ocular muscles as it was thought to be in the past.45 However rhabdomyosarcoma may present as a mass in the lid.42 No race is immune, there is no predilection for right or left eye. It is unilateral. Boys have slightly more predilection. It is highly malignant and cent percent fatal when not treated. Mortality level has been considerably reduced due to radio therapy and chemo-therapy. It develops from pluri potential embryonal mesoderm which commonly differentiates to form rhabdomyoblast as seen in foetus.52 The growth may originate in the ethmoid and extend in the orbit. It may develop as second malignancy in case of retinoblastoma. Histopathologically there are three types of rhabdomyosarcoma—1. The embryonal, 2. Aluelar and 3. pleomorphic. The first is seen in about 70% of cases, the last is least common.

The tumour may arise anywhere in the orbit but commonest site is superio nasal quadrant. It starts as a painless rapidly growing mass that pushes the globe towards the opposite direction. However it may present with inflammatory signs and mistaken as orbital cellulitis or vice versa. The mass can be palpated by insinuating a finger between the globe and the orbital wall. The growth is non compressible. It does not invade the globe, which may otherwise be damaged and lost due to proptosis, exposure keratitis. The tumour may extend into surrounding structures by direct invasion. Distant metastasis is via blood stream. Lymphatic spread occurs when lid, conjunctiva and para orbital tissues are involved. In such case preauricular submandibular and neck glands may be involved.