An educational case on bacterial rhinosinusitis and brain abscess formation; and a review of the pathophysiology of infection seeding through the sinuses.

Acute bacterial rhinosinusitis (ABRS) is a common diagnosis affecting about 12% of adults in the United States each year. While it is often a self-limited disease, it may evolve if left undiagnosed and untreated. A feared complication of ABRS is the development of a brain abscess. Prompt imaging and aggressive therapy are necessary to reduce mortality and morbidity of brain abscesses. Through this case, we attempt to identify unique presenting factors that may have pre-disposed this patient to brain abscess which may aid in future risk stratification of ABRS. A 43 year old male with no significant medical history presented with 16 days of frontal headache, green nasal discharge, subjective fevers, nausea/vomiting, and left eye pressure. Physical exam in the ED revealed no neurological deficits. A CT sinus was performed which showed near complete opacification of all paranasal sinuses and features indicative of acute on chronic pansinusitis. Additionally, this scan revealed severe localized vasogenic edema with subfalcine herniation strongly suggesting a brain abscess. He was admitted to the neuro-ICU with a neurosurgery consult and started on aggressive antibiotic therapy and seizure prophylaxis. Two days after initial presentation, he was taken to the OR for open craniotomy and excision of the lesion with drainage. Repeat MRI showed worsening edema surrounding the site of excision. He returned to the OR for surgical aspiration that same day. Following clinical stabilization, he was discharged on a prolonged course of IV antibiotics. Contiguous spread of bacteria from the sinuses is the most common pathway for brain abscess formation, accounting for about ⅔ of cases. Brain abscesses may form after osteomyelitic destruction of bones around the sinuses resulting in seeding of infection from the sinuses to the brain. Brain abscess most commonly presents as headache, fever, and focal neurological deficit. Factors that increase the likelihood of brain abscess secondary to ABRS, including length of time between infection and treatment, anatomical defects, and immunosuppression to name a few. Delay of treatment for ABRS is the most common reason for brain abscess to occur. The diagnostic imaging of choice is a brain MRI as it is extremely sensitive for abscess, provides better image resolution, and detects brain abscess formation earlier than a CT of the head. CTH is the next choice and is still an excellent form of imaging to detect abscess. Treatment of brain abscess is aggressive empiric antibiotics. Surgery is indicated if there is evidence of increased intracranial pressure. Surgical aspiration or open craniotomy with excision are methods for treatment. ABRS is a common clinical diagnosis often resolving after a short course of antibiotics. Rarely, as in this case, it can progress to life threatening cases of brain abscess requiring immediate surgical intervention and long term antibiotic therapy. Such a potential for rapid clinical decline prompts further investigations of these rare cases to determine prognostic factors to aid diagnostic considerations. Routine CT head/sinus exams in the ED for sinusitis would most likely add to an already overwhelming burden of pending emergency studies.