A six-year-old girl
was admitted with complaints of a swelling on the left periorbital region since
5-6 months. This was associated with proptosis and squint which was more prominent
on looking toward the left. There was no associated diplopia, diminution of
vision, headache, vomiting or focal neurological symptoms. Physical examination
revealed the left periorbital region to be swollen & tender. Slight conjunctival
congestion was noted. There was sixth nerve palsy with mild left ptosis and
restriction of medial movements of the left eye. Both pupils were equal bilaterally
and reacting to light. Fundoscopy showed pallor of the left disc. The right
eye was essentially normal. The rest of the general and systemic examination
was unremarkable.
A B-scan ultrasonogram of the left eye showed a mixed echogenic lesion - predominantly
hyperechoic located in the retro-orbital area with a central cystic component.
The lesion extended from the globe to the apex of the orbit. The other retro
orbital structures were not seen separate from lesion.(Fig. 1).
Fig.1
A plain CT Scan showed a hyperdense, lobulated mass lesion with a central cystic
component, in the superolateral aspect of the intraconal region of the left
retro orbital area (Fig. 2,3,4) There was no calcification. On injection of
contrast, there was a thick irregular enhancement of the mass. (Fig. 2,3,4).
The mass displaced the optic nerve medially and was in contiguity with the lateral
rectus muscle (Fig. 2,3,4). Anteriorly, it extended up to the globe and posteriorly
upto the apex and causing proptosis. No bone involvement was noted.(Fig. 5)
Sections through brain were normal. No nasal and paranasal extension of the
mass was noted. The right globe is normal (Fig. 2). The differential diagnosis
considered were pseudotumor, tuberculous granuloma, cycticercosis and lymphoma
.
Fig.2
Fig.3
Fig.4
Fig.5
A biopsy of the lesion showed inflammatory granulomatous lesion with central
caseation with a peripheral rim of Langherhan's giant cells. No neoplastic cells
were seen. On anti tuberculous treatment, resolution of the eye swelling & regression
of proptosis occurred over a period of six months
DISCUSSION:
The common causes of orbital masses in the pediatric age group include pseudotumour,
lymphoma, hemangioma, and dermoid cyst where as tubercular involvement of the
orbit is rare. Orbital tuberculosis may occur as a result of hematogenous spread
of infection from a distant site or by direct extension of infection from adjacent
sinus, the lacrimal apparatus or the eye itself. The pulmonary focus may not
be evident clinically or radiologically as was case in our patient.
The most common form of orbital tuberculosis is periostitis which tends to occur
during the first two decades of life when bony growth is still active. In the
vascularised spongy tissue of the outer margin of the orbit, the infection may
smolder for weeks to months producing local erythema and edema involving the
lids and conjunctiva. A cold abscess may form and discharge chronically through
a cutaneous fistula.
A tuberculoma of the orbit is a rare manifestation of disease usually occurring
in the middle age group, but in our case it appeared in a six year old girl,
where the chronic granulomatous mass appeared in the orbit presumably due to
an infection of hematogenous origin.
Other forms of ocular tuberculosis include nodular conjuctivitis, corneal ulceration,
choroidal tubercle and tuberculous panopthalmitis.
Orbital pseudotumor and lymphoma are homogenous mass of relatively high density
and sharp margin , which are more often seen in the anterior portion of the
orbit, retrobulbar area or the superior orbital compartment. In addition, a
pseudotumor may extend a variable distance posteriorly along the optic nerve.
A diffuse pseudotumor involves the entire globe, with a soft tissue mass extending
from the orbital apex to the posterior margin of the globe. The shared feature
of pseudotumor and lymphoma is that they respect the boundary of the orbit and
mould themselves around the orbital structures without any bony involvement.
Both pseudotumor and lymphoma may have an intermediate or hypointense signal
on T1W and PW MR images and appear isointense to fat in T2W MR images. Lymphoma
may be more hypointense in T1 images than pseudotumor.
Dermoid cysts are more frequently located on the superior temporal quadrant
of the orbit where they are fixed to the periosteum near the fronto-zygomatic
suture and lesions are isointense to fat on T2W MRI image.
An orbital schwanoma is rare in the pediatric age group. On CT scan, they appear
as sharply marginated, oval, fusiform - often intraconal - masses of increased
density that show moderate to marked enhancement.
This case emphasis that in endemic areas, tuberculosis should be considered
in the evaluation of a patient with orbital masses - especially with bone destruction.
Correlation of MRI, CT & histopathology is required to confirm diagnosis
