Cerebrospinal fluid (CSF) is an ultrafiltrate of plasma which circulates in the subarachnoid space, located between the pia and arachnoid membranes , It. Is largely produced by the choroid plexus ,while lesser amounts are produced by the ependymal cells lining the ventricles .The choroid plexus epithelium make up the blood – brain barrier and regulate the passage of substances into the CSF from blood. The arachnoid villi reabsorb the fluid .CSF contains glucose ,electrolytes, amino acidsand other small molecules found in plasma ,but has very little protein and few cells .CSF protects the central nervous system from injury , cushionsit from the surrounding bone structure , provides it with nutrients and removes waste products by returning them to blood .CSF is withdrawn from the subarachnoid space through a needle by a procedure called a lumbar puncture or spinal tap. CSF analysis includes tests in clinical chemistry , hematology , immunology and microbiology. Usually three or four tubes are collected .The first tube is used for chemical and/or serological analysis and the last two tubes are used for hematology and microbiology and spinal tests. This reduces the changes of a falsely elevated white cell count caused by a traumatic tap(bleeding into the subarachnoid space at the puncture site) , and contamination of the bacterial culture by skin germs or flora. Total CSF volume is 90-150 ml in adults and 10-60 ml in neonates. There is a constant turnover of about 14% of the volume per hour .About 300-500 ml of CSF are formed per 24 hours (0.35 ml per minute).CSF is obtained by lumber puncture with removal of fluid from the lumbar sac ,located at the L3-4 or L4-5 interspace .At this level , the needle can not injure the spinal cord , which in adults end at L1.So the aim of this review was to evaluate the theoretical background and provide guidelines for clinical uses of cerebrospinal fluid analysis in parasitic diseases |
