Neurological infection

Neurological infections can be broadly subdivided into chronic/subacute and acute. Chronic/subacute infection usually presents with global cognitive decline, with the prototypical disease being progressive multifocal leucoencephalopathy due to infection with the JC virus in immunocompromised patients. Acute neurological infections can be defined microbiologically, by the nature of the pathogen; clinically, by the presenting signs and symptoms and initial CSF findings; or anatomically. The anatomical definitions are those occurring intracranially (‘meningitis’, where infection involves the meninges overlying the brain; ‘encephalitis’, where the brain parenchyma is involved; or ‘cerebral abscesses’) and those affecting the spinal cord (‘myelitis’). However, there is often both clinical and histological overlap between these syndromes; consequently, the terms ‘meningoencephalitis’ and ‘encephalomyelitis’ are often used. Patients with acute intracranial CNS infections provide the greatest challenge to general physicians, because urgent investigation and appropriate treatment can save lives; they therefore form the focus of this chapter.