Orbital dermoid mimicking a monocular elevation deficiency.

Dermoid cysts are choristomas (a mass of histologically normal tissue in an abnormal location), which originate from aberrant primordial tissue and are often evident soon after birth. It may occur anywhere in the body. Dermoid cysts account for about 3-9% of all orbital masses and 0.04-0.6% of primary orbital tumors. The frequent site of origin is the superotemporal quadrant of orbit. Depending on the location, size, and associated abnormalities of the cyst, the patient may have proptosis, diplopia, and restriction of eye movements. Monocular elevation deficiency (MED) is the inability to elevate one eye in abduction, adduction, or from primary position. We report this case of orbital dermoid in an adult female presenting as a monocular elevation deficiency with unilateral ptosis of right eye which was investigated and managed with good results.

Introduction

Dermoid cysts are choristomas, which originate from aberrant primordial tissue and are often evident soon after birth. Dermoid cysts account for about 3–9% of all orbital masses and 0.04–0.6% of primary orbital tumors.[1-4] The frequent site of origin is the superotemporal quadrant of orbit. Monocular elevation deficiency (MED) is the inability to elevate one eye in abduction, adduction, or from primary position. We report this case of orbital dermoid in an adult female presenting as a monocular elevation deficiency with unilateral ptosis of right eye which was investigated and managed with good results.

Case Report

A 22-year-old college girl presented to Ophthalmology outpatient department with a history of drooping of right eye upper lid since birth [Figure 1]. There was no diurnal variation in the symptoms. She denied any complaints of diplopia. There was no history of ocular trauma in the past. General examination of the patient did not reveal any abnormality. On ophthalmological examination, best corrected distant visual acuity was 20/20 and near vision was N6 in each eye. A slight chin elevation was noticed. Right eye upper lid showed severe ptosis with a palpebral fissure height of 3 mm, Margin-reflex distance (MRD) of 2 mm with poor levator action (2–3 mm) and fair Bell's phenomenon. Right eye showed 4 mm of proptosis on Hertel's exophthalmometry. Ocular motility showed restriction of elevation from the primary position and in adduction and abduction in the right eye. The cornea, anterior chamber and fundus examination were normal. Left eye examination showed normal findings. The patient was referred to squint clinic on the suspicion of monocular elevation deficiency (MED).

Figure 1

Initial presentation with right upper lid ptosis

Alternate prism cover test showed a right hypotropia of 25 prism diopters (PD) and exotropia of 12 PD in primary gaze for distance and near. Right eye upper lid showed fullness. On palpation, a soft tissue mass was felt in the right medial canthus near the trochlea, which was non-tender, soft in consistency, non-pulsatile and non- reducible. No palpable thrill could be felt. Valsalva maneuver showed no change in the size of the swelling. The patient was advised computed tomography (CT) scan of the orbit.

CT scan orbit revealed a well-defined hypodense fatty density soft tissue lesion measuring 20 × 20 × 12 mm in the extraconal space of right superior orbit extending from just behind the orbital rim up to the mid orbit level displacing the superior muscle complex inferiorly – possibly due to a dermoid [Figure 2].

Figure 2

Sagittal and coronal section of the right orbit showing the extent of orbital mass lesion

Excision biopsy of the cystic mass lesion was done in toto through the superior lid crease approach and sent for histopathological examination (HPE). HPE revealed the presence of fibrocollagenous tissue with hair follicles [Figure 3], sebaceous glands [Figure 4] and striated muscle fibers, which was consistent with the diagnosis of dermoid cyst. Surrounding structures showed infiltration of chronic inflammatory cells with multiple vascular channels.

Figure 3

Histopathology photograph of the dermoid; arrow pointing to a hair follicle

Figure 4

Histopathology photograph of the dermoid; arrow pointing to a pilosebaceous unit

Following cyst excision, the deviation in the right eye reduced to 15PD of hypotropia with a small exotropia [Figure 5]. Limitation of elevation persisted even after removal of the cyst [Figure 6]. After three months, a 4 mm inferior rectus recession was done in the right eye for correcting the vertical deviation prior to ptosis correction. Post-operatively, a flick right hypotropia with 10PD of exotropia was noted and the patient was advised to go ahead with the ptosis correction.

Figure 5

Residual hypotropia and exotropia following dermoid cyst excision

Figure 6

Persistent limitation of elevation of right eye from primary gaze and abduction

Right eye frontalis sling surgery with silicon rod was performed 3 weeks after squint correction to treat the ptosis. Palpebral fissure height improved to 8 mm and MRD was +3 mm with frontalis action. No lagophthalmos was noted post-operatively [Figure 7].

Figure 7

Patient after squint and ptosis correction showing good cosmesis

Discussion

Dermoid cyst is an ectodermal inclusion cyst which may occur anywhere in the body. Approximately 50% of tumors that involve the head are found in or adjacent to the orbit. Forty percent of orbital dermoids are diagnosed between 15 and 40 years of age. The most frequent site of origin is the superotemporal quadrant of orbit.[12] Dermoid cyst gradually increases in size through epithelial desquamation and glandular secretions. The slow enlargement of dermoid cysts, due to the accumulation of this debris within the lumen, probably leads to attenuation of the epithelial lining and leakage of lipids and keratin into the tissues of the cyst wall. Clinical presentation of orbital or intracranial dermoid cysts depends on the location, size, and associated abnormalities of cyst. Orbital dermoid cysts located superficially in and around the orbit present as subcutaneous or subconjunctival discrete well-circumscribed swellings in childhood.

In our case, the presentation was at 22 years, and the site was in the extraconal space of right superior orbit. Larger cysts that abut the globe or cysts that are located deep in the orbit may displace the globe and can compress the optic nerve and extraocular muscles leading to proptosis and restriction of eye movements.[356] In our case, there was mild proptosis and restricted elevation but there was no pressure effect. Pathology of dermoid cysts has been well documented.[37] The differential diagnosis of orbital cysts include choristoma (epidermoid, dermoid, dermolipoma), teratoma, the congenital cystic eye, and colobomatous cyst. Imaging modalities such as ultrasonography, CT scan, and magnetic resonance imaging (MRI) of the dermoid cyst are valuable in the diagnosis and characterization of benign lesion and also to demonstrate their intraorbital and intracranial extension.[3489] Treatment of dermoid cyst is surgical en bloc excision, which is indicated for cosmetic purposes, confirmation of diagnosis, to relieve the symptoms created by mass in periorbital region and to prevent complications in cases of intracranial extension.[10] Complete surgical excision with intact capsule is done to prevent dissemination of the contents which otherwise can incite an acute inflammatory response. This is also to avoid the deposition of cells that could form a new cyst at the operative site.[56] Orbital dermoid cysts are rare, but if untreated they can still lead to devastating complications. Malignant transformation is rarely seen.[1] Leakage of contents can cause an acute or chronic inflammatory response with, in some cases, phagocytosis of lipid by macrophages, giant cell and granuloma formation, and secondary fibrosis around the cyst. The present case is unusual in a few aspects - unusual location of dermoid cyst in the medial part of orbital roof which is uncommon, severe ptosis and restriction of elevation with no pressure symptoms. Preoperative diagnosis became easier with the availability of CT scan and excellent results could be achieved by appropriate surgical intervention.