IMAGING OF THE PATHOLOGY THAT AFFECTS THE EXTRINSIC OCULAR MUSCULATURE
Luís B. Cardoso
Objective: To review the radiological findings of normal extraocular muscles and of the pathologies that might compromise them.
Materials and methods: We searched for the cases of orbital pathology studied at our hospital and selected those that were representative of different processes that can affect direct or indirectly the extraocular muscles.
Results: Two cases of orbital metastasis: a 60-year-old woman with inferior rectus muscles metastasis of breast carcinoma and a 75-year-old man with lung cancer metastasis. A 70-year-old woman with lymphoma affecting the extraocular muscles. A 51-year-old woman with Graves-associated orbitopathy. Two cases of orbital pseudotumor; a 43-year-old woman with Wegener granulomatosis and a 48-year-old woman. A 5-year-old boy with a lymphangioma of the left orbit and a case of rectus muscle entrapment after craniofacial trauma.
Conclusions: Within the retrobulbar space there are six extraocular muscles that control eye movement; they insert at different distances from the limbus making the spiral of Tillaux and allowing eye movement over the three primary axes. A seventh orbital muscle, the levator palpebrae superioris, attaches to the upper tarsal plate. The involvement of extraocular muscles is unusual and clinically manifests as diplopia and exophthalmos. Most of the imaging studies of the orbit start with a helical-CT with thin slices that allows a proper diagnosis in most cases. Those cases on which the differentials include the possibility of a tumour should perform an MRI scan. The pattern of extraocular muscle disease on imaging, together with clinical findings, can often lead the radiologist towards a specific diagnosis.