Statistics from Altmetric.com
Editor,—We present the case of a patient with unilateral lateral rectus muscle anomaly on computed tomography (CT) scan mimicking orbital pathology. A repeat scan 3 months later and a literature search confirmed this to be an anatomical variant of the involved muscle.
A 79-year-old man presented with a 4 day history of right side periocular swelling, erythema, and mild diplopia on upgaze. A clinical diagnosis of preseptal cellulitis secondary to maxillary sinusitis was made. In view of his diplopia and a possible right proptosis he underwent a CT scan examination of his orbits. This confirmed the preseptal soft tissue swelling on the right with no orbital involvement of the inflammation. The scan also revealed a linear opacity of soft tissue density lateral to the right lateral rectus muscle, probably arising from the proximal part of its belly and inserting onto the lateral orbital wall, raising the suspicion of a neoplastic plaque. As the patient’s cellulitis resolved on a 10 day course of oral antibiotics no further surgical intervention was considered at this stage. A repeat CT scan performed 3 months later showed no change in his previous orbital finding (Fig 1). A literature search confirmed this linear opacity to be an anatomical variant of the lateral rectus.
Anomalies of the extrinsic musculature of the human orbit are rare and their identification on postmortem dissections is difficult.1 A number of modifications in orbital connective tissue and muscular attachments have been reported and have been shown to vary between individuals.2 Bergman et al 3 demonstrated muscular fasciculi passing from the lateral rectus and inserting into the lateral wall of the orbit while Koornneef 4 described connective tissue attachments between the lateral rectus muscle and the lateral orbital wall. Other anomalous fibrous and muscular attachments of the lateral rectus muscle to the inferior tarsal plate, inferior rectus, medial rectus,3 and lateral canthus5 have also been reported. These anatomical variants are thought to influence eye movements and to have a stabilising role on lateral rectus action.
It is important to be aware of these rare orbital anomalies and recognise them on CT or magnetic resonance imaging scans. This would save the patient unnecessary further investigations.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.