OBJECTIVE: To report a case of cavernous sinus thrombosis, following paranasal sinusitis. The complex neurovascular anatomic relationship, the patient´s peculiar pneumatization of the sphenoidal sinuses, diagnosis, and management of this condition are discussed. CASE REPORT: C. E. C. L., a 15-year-old male patient, was admitted in the hospital with complaints of bilateral nasal obstruction, purulent rhinorrhea, and fever for 7 days. Two days before admission, his condition deteriorated, and he became increasingly unwell with swelling and ptosis of the right eye, a severe headache, and neck pain. In the physical exam, his prostate, oroscopy, and otoscopy were unchanged, ptosis and right eyelid edema were noted, and ocular motility was preserved. Nasofibrolaryngoscopy showed pus in both nasal cavities. A CT scan presented a soft tissue mass in the paranasal sinuses. The sphenoidal sinuses had significant hyperpneumatization that extended to pterygoid process, fully occupied by soft tissue density. MRI presented meningeal impregnation of the middle fossa and retroclival region, converging on the cavernous sinuses, and evidence of cavernous sinus thrombosis. We decided to perform a surgical approach, a left pansinusectomy and right sphenoidotomy with significant pus drainage. The patient presented at follow-up without symptoms and with a normal physical exam. CONCLUSION: Cavernous sinus syndrome is characterized by several cranial neuropathies, commonly caused by infections of sphenoid and ethmoid sinuses. The greater the degree of pneumatization, the more frequently the neurovascular structures bulge into the sphenoid sinus. Although cavernous sinus thrombosis is a rare situation, otolaryngologists should become familiar with its clinical presentation, diagnosis, and management.