Tolosa-Hunt syndrome (THS) is an idiopathic condition included in the differential diagnosis of painful ophthalmoplegia. Actinomycosis is a treatable, underrecognized condition that mimics neoplasia and other infections and may result in painful ophthalmoplegia with cavernous sinus involvement. Actinomycosis should be included in the differential diagnosis. PATIENT DE SCRIP TI ONA 57-year-old man presented with a 3-week history of refractory pain in the left jaw, which later involved the retroauricular, suboccipital, and retro-ocular areas. Due to the pain, he had several tooth extractions a few days after symptom onset. He had no prior known medical diagnoses.Physical examination disclosed left abducens nerve palsy with horizontal diplopia and decreased sensation to pinprick in the left V3 and V2 territories. Compression of the left trochlear, supraorbital, and infraorbital nerves was painful. There was mild monocytosis and a moderate elevation of C-reactive protein (21 mg/L) and erythrocyte sedimentation rate (48 mm/h). Brain magnetic resonance imaging (3 T) showed enlargement of the left cavernous sinus, occupied by a gadolinium-enhancing tissue with hypointense areas in its interior suggestive of necrosis (Figure 1a). The tissue extended into the extracranial area, following the path of the left V3 trigeminal branch, reaching the parapharyngeal and retroparotid space, where a softtissue lesion of 1.4 cm in diameter was evident (Figure 1b). A whole body computed tomography (CT) scan was normal. A 3-day course of methylprednisolone was ineffective.A lumbar puncture obtained acellular cerebrospinal fluid with normal glucose, protein increase of 60 mg/dl, no oligoclonal banding, normal IgG index, and negative culture. Flow cytometry ruled