LAUSR

The central nervous system (CNS) primarily consists of the brain and spinal cord, which are enclosed within the surrounding meninges and bone structures such as the calvarium and spine. Infectious diseases of the CNS include a wide spectrum of infections caused by various pathogens affecting one or more of these components as well as the spaces between these components. Different components or compartments of the CNS are affected circumstantially; each of the disease entities will have different imaging pattern and characteristics according to their different transmission routes, locations and appearance, i.e. meningitis, brain abscess, septic emboli, spinal epidural empyema and osteomyelitis (OM). Despite the advances of modern medicine, accurate diagnoses of a specific disease entity of the CNS infections have proven to be very challenging as their clinical presentations are very general and nonspecific, such as fever, headaches, weakness, numbness or back pain. The infectious diseases of the CNS are most commonly caused by various types of bacteria or viruses. Other less common organisms include fungi or protozoans, etc. These pathogens enter the CNS through two main routes of transmission: hematogenous spread from distant infections such as endocarditis or urinary tract infection, or direct extension from infections of the adjacent structures such as sinusitis or mastoiditis. Hematogenous transmission tends to produce diffuse or multifocal lesions in different vascular distributions, such as diffuse meningitis or septic emboli. Direct extension of the infections usually gives rise to focal lesions, such as subdural or epidural empyema. Whenever local infection is identified, the adjacent anatomic structures (e.g., paranasal sinuses, mastoid air cells, middle ears) should be examined diligently to pinpoint the initial source. Extended involvement of other CNS compartments and vascular systems is not uncommon, as it can coexist or become complications of primary meningitis or encephalitis, such as ventriculitis or thrombophlebitis. Neuroimaging techniques are essential for diagnosing various CNS infections and help differentiate different disease entities. The two main utilized imaging modalities are computed tomography (CT) and magnetic resonance imaging (MRI), each with their own advantages and limitations. CT scanners are widely available in hospitals and clinics, being operated 24 hours a day. Nonenhanced CT (NECT) images can be acquired quickly and with little patient preparations. CT scan is highly sensitive to acute intracranial hemorrhages (parenchymal or extraaxial), calcified lesions or bony deformities. NECT of head often serves as a gateway for more advanced imaging or more complexed patients’ management, such as screening for lumbar puncture (LP) or used for CT-guide biopsy or drainage. Administration of intravenous contrast in CT usually increases the sensitivity of detecting an underlying abnormality and further delineating its characters. Vascular Editorial