A 57-year-old man with painful ophthalmoplegia and cavernous sinus involvement: Why this is not Tolosa-Hunt syndrome.

Tolosa-Hunt syndrome (THS) is an idiopathic condition included in the differential diagnosis of painful ophthalmoplegia. Although this was once a common diagnosis, the increasing availability of tests reveals an alternative etiology in many cases. Exclusion of treatable disorders is important, because the prognosis may otherwise be poor. We here describe a patient who presented with painful ophthalmoplegia with an infiltrating lesion in the cavernous sinus. Initially suspected of THS, he had a fatal evolution, and postmortem evaluation revealed cervicocephalic actinomycosis. Actinomycosis diagnosis is often missed, and still represents a challenge to the clinician. We highlight pearls and pitfalls to establish a proper diagnosis to avoid missing a treatable condition in patients with suspected THS.