Snapshot A 59-year-old man presents to the emergency department with a headache. He has never had headaches in the past and reports his headache worsens with cough. He describes his headaches as severe and located on the right-side of his head. His headaches are unresponsive to over the counter analgesics. Medical history is remarkable for recent manipulation of his ventriculoperitoneal shunt due to malfunction. Physical examination is notable for 4-/5 power in the left-sided upper extremity. An MRI brain with contrast demonstrates a ring enhancing lesion in the right primary motor cortex. Neurosurgery has been consulted for removal of the mass in order to time empiric antibiotic administration. Introduction Definition focal purulent collection in the brain parenchyma Epidemiology Risk factors infection of contiguous structures otitis media dental infection mastoiditis sinusitis skull trauma or surgery (e.g., ventriculoperitoneal shunt) endocarditis leading to hematogenous spread immunocompromised state Etiology Pathogens include (note that infections are often polymicrobial) Streptococcus (most common) Staphylococcus aureus and epidermidis gram-negative enteric organisms Pathophysiology Immune-mediated response to the microbial pathogen Presentation Symptoms headache (main chief complaint) Physical exam fever (not a reliable clinical indicator) focal neurological deficit (e.g., extremity weakness) seizures Imaging MRI brain with contrast indication imaging study of choice in patients which there is a strong suspicion for brain abscess CT head with contrast can also be used findings round-like encapsulated mass with central necrosis and surrounding edema comment differential diagnosis for a ring-enhancing lesion is MAGIC DR Metastasis Abscess Glioblastoma Infarct and inflammatory (e.g., neurocysticercosis and tuberculoma) Contusion Demyelinating disease Radiation necrosis or resolving hematoma Studies Making the diagnosis can be suggestive based on neuroimaging but confirmed with surgical removal and histopathology Differential Neurocysticercosis differentiating factors significantly elevated opening pressure encapsulated yeast forms on India ink when testing the cerebral spinal fluid Glioblastoma differentiating factors biopsy results demonstrate cellular polymorphism and microvascular proliferation with a central area of necrosis Treatment Medical empiric antibiotics indication a component of the mainstay of treatment for brain abscess medications ceftriaxone or cefotaxime with metronidazole vancomycin can be considered if the patient is at risk of developing Staphylococci infection (e.g., recent brain surgery) Operative neurosurgical removal indication a component of the mainstay of treatment for brain abscess approach stereotactic neurosurgical aspiration surgical excision (less commonly used) Complications Seizures Brain herniation Ventriculitis secondary to abscess rupture and seeping in ventricles Meningitis