The role of lumbar puncture as a diagnostic tool in 2005.

Analysis of cerebrospinal fluid (CSF) obtained by lumbar puncture (LP) is fundamental to the management of inflammatory disease of the central nervous system (CNS), particularly that due to infection. This review summarises the role of lumbar puncture, anatomy and pathophysiology of CSF, techniques of obtaining CSF, indications, contraindications and complications of LP, methods of analysis and some of the implications of specific changes in CSF. The CNS is protected by unique immunological barriers, and has some unique responses to processes that breach these barriers. While clues in the epidemiology, history and clinical features of potential CNS inflammatory disease may be important in guiding early empirical treatment which may obviate adverse outcomes, many pathological processes cannot be distinguished or appropriately treated without analysis of CSF. When appropriate assessments are made of the indications, risks and potential to alter management, LP is a relatively safe procedure with a high diagnostic yield. Optimal performance and use of LP requires individual skill and judgment, and often benefits from close liaison with several disciplines, including emergency, intensive care, diagnostic laboratory, clinical imaging, neurology and infectious/ communicable diseases specialists. Understanding of the sensitivity, specificity and variation of CSF testing is critical to its effective use. Some CSF testing is sensitive, specific and timely, but other CNS disease processes will generate obscure and ambiguous results, and interpretation may benefit from liaison with experienced specialists in several fields. Polymerase chain reaction (PCR) testing has changed the practice of LP and is likely to generate further evolution. Some findings on CSF analysis may have implications beyond the individual patient - the consequences of the diagnosis of meningococcal meningitis, emerging pathogens such as West Nile virus or Nipah virus, and the identification of anthrax meningitis in the USA may be quite profound on both a local and global scale.