Background: Orbital cellulitis is characterized by the infective inflammation of orbital structures, usually posterior to the orbital septum. Extension of infection from the paranasal sinuses is the most common etiology for orbital cellulitis. Intracranial complications of orbital cellulitis include meningitis, subdural empyema, brain abscess, and cavernous sinus thrombosis.

Case presentation: A 33-year-old man presented with acute onset of foul-smelling mucopurulent nasal discharge and swelling of the left eye followed by altered sensorium. On examination of the left eye, chemosis, eyelid edema, and proptosis were present. Computed tomography (CT) of the brain revealed non-axial left proptosis with inflammatory reticulation in the intra- and extraconal fat alongside sinusitis. Magnetic resonance imaging of the brain confirmed the CT findings and additionally showed meningitis and subdural empyema along the left frontoparietal convexity with parenchymal signal changes, suggesting venous infarction in the left frontal lobe. Susceptibility weighted imaging (SWI) confirmed thrombus in the frontal polar vein on the left side, suggesting septic isolated septic cortical venous thrombosis (ICVT) as a complication of orbital cellulitis. Cerebrospinal fluid showed polymorphonuclear cell pleocytosis with elevated protein and lowered sugar. Blood and conjunctival swab cultures were negative. He was subsequently treated with intravenous broad-spectrum antibiotics and antifungals to which he responded and was discharged in stable condition.

Conclusions: Our case highlights the presentation of septic ICVT complicating orbital cellulitis and paranasal sinusitis. It also underscores the higher sensitivity of SWI as a crucial tool in diagnosing ICVT. Appropriate and prompt medical treatment in orbital cellulitis can prevent further complications.