Main

Orbital myositis can be defined as a nonspecific localised orbital inflammatory process in which one or more of the extraocular muscles may be involved.1 Clinically, it is characterised by acute pain exacerbated by eye movement.2 Other symptoms such as ptosis,3 proptosis and peribulbar swelling 4 can also occur. Globe retraction on attempted eye movement away from the direction of the action of the involved muscle is a characteristic sign.1 Treatment with systemic steroids causes rapid resolution.2,5

Case report

A 6-year-old Caucasian boy was seen in the eye casualty complaining of a 2-day history of left-sided pain, photophobia and peri-orbital swelling. This was preceded by a fever a few days previously. There was no other ophthalmic history of note. He had no history of head injury, but there was a history of sinusitis. He was on no medication and had no known allergies. There was a family history of flu-like illness affecting all the members of the family in the preceding weeks. On examination, he was apyrexial. His visual acuity was 6/6 in each eye. Colour vision using the Ishihara colour plates was normal. There was mild oedema of the left upper lid and left lower lid, but no evidence of erythema. A partial left-sided ptosis was present that covered the left pupil. Levator function on that side was poor.3 Clinically, a mild left-sided proptosis was also present. Cover test revealed a small divergent squint and left hypertropia present for near and distant. On lifting the ptotic left lid, the patient complained of horizontal and vertical diplopia in primary position. Ocular motility examination revealed limitation of the left eye on dextroversion, elevation and depression, and all ocular movements of the left eye were very painful. Anterior segment examination was satisfactory. There was no relative afferent pupillary defect (RAPD). Dilated funduscopy was normal and, in particular, there was no evidence of disc swelling.

B-scan showed increased orbital fat density and volume around the superotemporal orbital rim. There was also a suggestion of hypertrophy of the superior and lateral recta. There was no evidence of thickened sclera and sub-tenon's space was normal.

ENT review suggested a high probability of orbital cellulitis secondary to sinusitis. The patient was admitted and treated with intravenous antibiotics.

A CT scan performed revealed evidence of sinus disease. The muscle bellies as well as the tendons of the medial and inferior recta were diffusely thickened. This suggested orbital myositis rather than thyroid eye disease. No evidence of sub-periosteal abscess or collection could be found and the cavernous sinuses were clear.

Results of FBC and U&E and blood film were normal. Coagulase negative staphylococcus was isolated from the blood cultures. It was never ascertained if these were contaminants.

Even 48 h after admission and treatment with IV antibiotics, the patient was still complaining of diplopia and the ptosis was still present. He was started on prednisolone 10 mg OD and continued on the IV antibiotics for a further day before changing to oral treatment. The next day, the swelling of the eyelids, the ptosis and diplopia had improved significantly. A week later all symptoms had settled fully. Examination including orthoptic assessment was satisfactory.

Comments

Orbital myositis has been described secondary to orbital cellulitis. We felt this case was one such classic case. The rapid response of signs and symptoms to low-dose oral steroids was typical of orbital myositis.

Orbital myositis has been associated with a variety of other systemic problems in adults and children. In children there has been a report of orbital myositis associated with the Lyme disease6 and Crohn's disease.7 In adults, the associations are with raised thyroid antibodies,8 herpes zoster infection,9 as a paraneoplastic syndrome in non-Hodgkin's lymphoma,10 metastasis from a small cell carcinoma,11 giant cell myocarditis,12 cysticercosis,13 systemic lupus erythematosus and autoimmune disorders.14 Opinions vary as to which patients presenting with orbital myositis should be investigated for associated systematic diseases.2,8

In summary, this was a case of a 6-year-old Caucasian boy who presented with classic signs and symptoms of orbital cellulitis. Despite appropriate treatment, however, he was left with residual ipsilateral ptosis and diplopia. These resolved rapidly after administration of low-dose oral steroids.