A 59-year-old woman presented with sudden-onset eyelid swelling, ptosis, diplopia, mild pulsation, and mild pain of the right periorbital area for 4 days. She had gone to a local hospital and received antihistamine treatment. She was referred to our hospital for further investigation. The patient had no known history of systemic diseases except for hyperlipidemia. She also denied previous trauma and allergies. Her vision was 6/6 in both eyes. Mild lid ptosis was noted in the right side. A Krimsky test revealed a 35-prism diopter of exotropia in the right eye. In addition, extraocular movement showed severe limitations in adduction, supraduction, and infraduction of the right eye (Fig. 27.1). Anterior segments and fundoscopic examination were normal. Pupils were symmetric and reactive to light. An MR imaging study showed an enhancing lesion over the right cavernous sinus (Fig. 27.2) and segmental stenosis of the right internal carotid artery (ICA). The patient was admitted for lumbar puncture which showed an opening and closing pressure of 78/55 mmH2O, respectively. CSF analysis showed no white blood cells and a normal protein level and IgG index (0.64). Pulse therapy with methylprednisolone was given. Her orbital pain was relieved after steroid treatment and eye movement improved gradually. Her eye position returned to orthophoric with a full range of motion observed 1 month later (Fig. 27.3).