The term meningitis does not refer to a specific disease entity but rather to the pathologic condition of inflammation of the tissues of the meninges.
Enteroviruses are the most common causes of aseptic meningitis.
This form of meningitis occurs when pathogenic bacteria enter the subarachnoid space and cause a pyogenic inflammatory response. The incidence is age-related. Almost all bacterial infections of the meninges enter the nervous system after having invaded and infected another region of the body and then are spread by local extension, as from the sinuses, or through the blood, as in septicemia. The organisms gain access to the ventriculosubarachnoid spaces and the cerebrospinal fluid where they cause irritation of the tissues bathed by the fluid. Irritability and confusion occur early in the course of the disease, and convulsive seizures occur in about 25 per cent of patients.