A 37-year-old man with no significant medical history presented to the emergency department with a headache. He described it as an insidious, constant severe pain that was initially localized occipital but progressed to a bitemporal distribution. His neurologic exam, extraocular movements, and visual acuity were all normal. The patient was given symptomatic treatment with compazine and Benadryl. He was responsive to therapy and discharged home after his headache symptoms resolved. Seven days later, however, he presented to the emergency department with a worsening headache, progressive altered mental status, fever, and bilateral proptosis. His temperature was of 103.9°F, blood pressure was 194/82 mm Hg, pulse rate was 87 bpm, and oxygen saturation was 98%. His exam was significant for profound bilateral periorbital edema with significant chemosis, drainage, and overlying erythema. (Figure 1.)Figure 1: Patient with profound periorbital swelling and significant chemosis with overlying erythema and drainage.The right eye was impossible to examine because of significant swelling. The extraocular muscles in the left eye were limited in all directions, and pupils were sluggish. Computed tomography without contrast of the head and orbit demonstrated an enlargement of the right superior ophthalmic vein, attenuation of the right sigmoid sinus, subtentorial collection, paranasal sinus disease, and severe bilateral proptosis with periorbital soft tissue swelling. (Figure 2.) The patient was treated empirically with intravenous antibiotics and admitted for suspected septic cavernous sinus thrombosis with periorbital cellulitis.Figure 2: Head and orbit computed tomography without contrast. A. Paranasal sinusitis including sphenoid and ethmoid sinuses (straight red arrows) with periorbital edema with proptosis (curved red arrow). B. Supraopthalmic vein enlargement. C. Hypoattenuation of right sigmoid sinus as compared with left. D. Extra-axial hypoattenuation under the right tentorium.Lateral canthotomy and cantholysis were performed after admission to relieve his elevated intraocular pressure, followed by an emergent orbital depression by total ethmoidectomy and sphenoid sinusotomy. The patient also suffered from meningitis and recurrent subdural empyemas, which required multiple subdural drains and neurosurgical interventions, including placement of a VP shunt for obstructive hydrocephalus. Cultures grew Streptococcus anginosis and Streptococcus viridins, and Propionibacterium, and antimicrobial therapy was titrated to penicillin G, which resulted in clinical improvement and infection clearance. The patient was discharged to a rehabilitation facility with complications, including blindness in the right eye and a permanent VP shunt. Dural venous thrombosis is caused by thrombosis of a cerebral vein or occlusion of dural sinuses. (Medicine 1986;65[2]:82; Arch Intern Med 2001;161[22]:2671.) The cavernous sinus is the most frequent dural sinus to become thrombosed secondary to infection because of its irregular trabecular structure that allows bacterial trapping. (J Neurosurg 1976;45[2]:169.) It is a rare disease with serious sequelae, including a 30 percent mortality rate, spread of infections such as meningitis and cerebral abscesses, persistent oculomotor weakness, blindness, hemiparesis, and pituitary insufficiency. (N Engl J Med 1983;309[19]:1149.) The prevalence of septic cavernous sinus thrombosis is most common among men (21% vs 10%), mainly because of a higher frequency of ear, nose, and throat infections in this population. (Stroke 2009;40[7]:2356.) Sinusitis, most commonly sphenoid and ethmoid infections, is a common nidus in infections that preclude cavernous sinus thrombosis. Facial infections drained by the ophthalmic vein and dental infections drained by the pterygoid venous plexus also put patients at risk for this complication. (Orbit 2006;25[1]:39.) Sphenoid sinus infections typically spread contiguously through the lateral air sinus wall, while ethmoid sinus infections extend laterally to the orbital cavity with subsequent extension to the ophthalmic veins. (N Engl J Med 1983;309[19]:1149.) The intricate structure of the cavernous sinuses creates a potential location for trapping, seeding, and proliferation of microorganisms. This results in thrombosis and stasis of dural venous return from the ophthalmic and cerebral veins. The venous status leads to increased capillary pressure with subsequent decreased cerebral perfusion, leakage into the interstitial parenchyma, and cytotoxic edema. (Neuroradiology 2002;44[6]:481; Arch Neurol 2001;58[10]:1569.) Early signs and symptoms of cavernous sinus thrombosis are nonspecific, and they usually mimic primary headache syndromes. Headaches are the most common early sign, followed by fever, proptosis, chemosis, altered mental status, and cranial nerve III and VI palsies. Brain MRI is the most sensitive and specific imaging modality for cavernous sinus thrombosis, but head CT scan and lumbar puncture are useful to evaluate the emergent or unstable patient. Mainstay therapy is broad-spectrum antibiotics with meningitis dosing, along with anticoagulation, glucocorticoids, and surgical drainage. (Pediatr Crit Care Med 2004;5[1]:86; J Laryngol Otol 2002;116[9]:667.) Septic cavernous sinus thrombosis is relatively rare but the prognosis of patients is relatively poor. Many patients can initially present with nonspecific symptoms, with the most common mimicking primary headache syndromes. Therefore, it is important for the emergency medicine physician to consider septic cavernous sinus thrombosis patients presenting with headache, especially in patients with a history of chronic sinusitis.