Overview of Infective Syndromes of the Central Nervous System and Its Coverings: Decoding Chameleons and Mimics

Infections of the central nervous system (CNS), which include those of the brain’s cerebrum and cerebellum, spinal cord, optic nerves, and the membranes that cover them, are medical emergencies that are associated with high rates of morbidity, mortality, or long-term effects that can have detrimental effects on the quality of life of affected individuals. Acute CNS infections may be caused by microorganisms, such as bacteria, viruses, fungi, and parasites, or by trauma caused by fractures at the base of the skull or the cribriform plate, which can cause an opening between the CNS and the adjoining areas, such as sinuses, mastoid, middle ear, or nasopharynx, which may serve as a gateway for infections. Infections in the CNS can manifest as a subarachnoid space infection, such as meningitis, or a parenchymal infection, such as encephalitis, myelitis, or abscess. It is most usually disseminated hematogenously but it can also spread directly from nearby structures (otitis, sinusitis, and dental abscess) as well as invasive and non-invasive trauma (cranial fractures, foreign bodies, and ventricular shunt). CNS infection clinical syndromes may include acute meningitis: characterized by an acute onset of fever, headache, vomiting, meningismus, and impaired mental status in bacterial and viral infections; fast progression over hours to days; subacute or chronic meningitis: found in tuberculosis or fungal infections, with a low-grade fever that develops gradually over weeks; acute encephalitis that is caused by viruses manifests itself in two ways: (a) diffuse: changed mental condition and (b) focal: viral tropism for a single place; and encephalopathy caused by a systemic infection, such as Shigella, typhoid, malaria, Rickettsia, or endocarditis. Symptoms range from mild to severe and are frequently linked to mood swings.