• meningitis

When can the management of meningitis become difficult? Broadly speaking, there are three main potential areas of concern:

• Clinical diagnosis—The classical symptoms and signs of acute meningitis may be absent in the very young, the very old and the very sick. Chronic meningitis requires a degree of clinical suspicion, as again signs of meningism may be minimal or absent.

• Laboratory diagnosis—Difficulties may arise in patients whose cerebrospinal fluid (CSF) examination yields a typical “aseptic meningitis” picture (elevated white cell count, predominantly lymphocytic, no organisms on Gram stain, normal or elevated protein concentration, normal or reduced glucose concentration) because of the breadth of the differential diagnosis, both infective and non-infective (table 1). In these circumstances, it is particularly important to exclude or diagnose tuberculosis, cryptococcosis, and other fungal infections, partially treated pyogenic meningitis, neurosyphilis, and Lyme disease, because of the need for urgent treatment and the consequences of failure to treat.

• Treatment—Two vexed questions are the choice of antimicrobial drug in particular clinical settings, and the role of corticosteroid treatment.

In this article, the major causes of meningitis are considered in turn, highlighting the difficulties which may arise under these three headings. Finally, the syndrome of recurrent meningitis is discussed separately, as its causes and management may differ from those of an isolated attack of acute meningitis. Inevitably, there will be overlap between the content of this article and others in the present issue, but, whenever possible, the discussion here will be restricted to immunocompetent patients.