Sampling of the cerebrospinal fluid is an extremely important procedure, since it is essentially the only neurodiagnostic technique that permits physicians to evaluate the biochemical and metabolic aspects of central nervous system functioning . However, it is imperative that the sample be properly collected and processed in order for the maximum information to be obtained. Before attempting to obtain cerebrospinal fluid, the physician should be aware of what information is desired from the study and how much cerebrospinal fluid is required for each laboratory test to be performed in order to collect and process the specimens properly. This chapter deals with the proper techniques used to sample cerebrospinal fluid and the techniques for subsequently handling the collected fluid . Cerebrospinal fluid may be collected by lumbar puncture, cisternal puncture, or lateral cervical puncture, or through ventricular cannulas (or shunts).
TECHNIQUE OF LUMBAR PUNCTURELumbar puncture, a procedure first introduced in the late nineteenth century [63], is the simplest, most convenient, and most widely used method for obtaining access to the subarachnoid space and for obtaining samples of cerebrospinal fluid (Figures 4.1 and 4.2). Below the level of the conus medullaris, the arachnoid continues as far as the second sacral vertebra to form a lumbar subarachnoid 'cul-de-sac' that contains cerebrospinal fluid and the roots of the cauda equina. Thus, a needle can be readily introduced through the inter-