Teaching Case

A 14-year old boy with Gardner's Syndrome presents with a non-tender, cystic mass on the inner canthus of the right upper eyelid, resulting in proptosis and diplopia. There are no other opthalmic symptoms.

A 14-year old boy with Gardner’s Syndrome presented with a swelling on the inner canthus of the right upper eyelid. Swelling had begun 5 months previously, and had grown steadily. There was no conjunctival redness or tenderness. The boy complained of some diplopia, but otherwise vision was normal. On examination, the non-tender mass appeared cystic in nature, and was positioned on the inner canthus of the right upper eyelid. There was obvious lateral proptosis of the globe, although there remained good motility and no hypotrophia. Pupillary reflexes were intact and the fundus was normal. Examination under anaesthetic revealed that there was no optic nerve compromise. The patient is listed to undergo a prophylactic total colectomy in the next two months, as endoscopic surveillance recently revealed polyposis in his colon. At age 2 years, he underwent excision of a dermoid cyst from his right ankle. MR imaging of the head was undertaken and axial T2 images are shown in Figures 1a, 1b and 1c, and a sagittal T2 image in Figure 2. They show a mass which is predominantly cystic, but it is partially loculated with a slightly more solid mixed density component in the posterior part. The mass extends intracranially and displaces the cerebrum and frontal lobe, however the brain itself is intrinsically normal and the mass does not appear to be infiltrating it. From these images the lesion seems to arise from within the region of the frontal sinus, extending downwards into the orbit and displaces the ocular muscles. The downwards extension is also causing opacity of the ethmoid air sinus on the right. Above, it extends through the diploic space, but does not erode the skull vault. The appearances are those of a mucocele. CT was performed principally to identify the bony landmarks and the frontal sinus better. Figure 3 shows the lesion extending down into the right ethmoid sinus and infiltrating the wall of the orbit, displacing the globe laterally. It reveals that the lesion appears either bony or full of chondroid tissue as it extends into the ethmoid sinus. Plain film AP Skull X-ray, Figure 4, shows that the position of the two petrous bones is different, and that there is an opacity projecting into the region of the right ethmoid sinus. The patient underwent surgery with excision of the frontal bone space occupying lesion and reconstruction of the right orbital ridge/roof. The lesion was identified as a mucocele, and removed. An osteoma blocking the ethmoidal air sinus was observed and was remodelled to allow drainage again. The patient made a good recovery.

Gardner’s syndrome is an autosomal dominant disease characterised by a triad of gastrointestinal polyposis, multiple osteomas and various soft tissue tumours [Ref 1]. The genetic, pathological and clinical features of the disease include all the features of Familial Adenomatous Polyposis (FAP); patients with more prominent extracolonic manifestations continue to be classified as having Gardner’s syndrome for historical reasons. The incidence of FAP is between 1 in 7,000 – 24,000 live births [Ref 2]. Osteoma formation in Gardner’s syndrome is seen particularly in the membranous bones of the mandible, skull (particularly maxilla) and long bones [Ref 3]. They can be classified radiographically in sinuses as being diffusely dense without enhancement following intravenous contrast infusion [Ref 4]. The patient shown has developed an osteoma of the middle right concha, thereby blocking the drainage of the ethmoidal sinus. The subsequent accumulation of secretions has resulted in the formation of a mucocele. These are airless cysts lined with epithelium producing mucoid secretions. Eventually the continual secretion of mucin leads to pressure necrosis of the sinus wall, and in this case it has spread upwards into the frontal sinus, and subsequent destruction has occurred around the orbital ridge, causing proptosis of the globe. Plain film skull X-rays can help in the diagnosis of a paranasal sinus mass, and is used initially to define their extent, however cross-sectional imaging is required for full mapping. Bone erosion is best assessed by CT, but intracranial and transdural spread are best seen with MR.