CSF acid-fast smear and culture have relatively low sensitivity but yield is increased with multiple, large volume samples. Characteristic cerebrospinal fluid (CSF) findings of TBM include a lymphocytic-predominant pleiocytosis, elevated protein, and low glucose. TBM is typically a subacute disease with symptoms that may persist for weeks before diagnosis. The finding of oligoclonal bands is not specific as they may also be found in Guillain-Barré syndrome, CNS infections (including neurosyphilis and HIV infection), after cerebrovascular accidents and in other CNS disorders.Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis (TB) and has very high morbidity and mortality. The IgG/albumin ratio is also often increased in these patients, but the test is less sensitive than oligoclonal bands. The presence of oligoclonal bands in CSF, but not serum, is indicative of local immunoglobulin synthesis and occurs most commonly in multiple sclerosis (>90% of patients) and SSPE. Whenever there is pus or blood in the CSF.Īdjunctive tests in the investigation of demyelinating disorders, especially multiple sclerosis, SSPE. With local immunoglobulin production (eg, Multiple sclerosis) and With increased vascular (blood-brain) permeability (eg, Encephalitis, Guillain-Barré syndrome) With meningeal inflammation (eg, purulent or tuberculous meningitis) ![]() In conditions where CSF circulation is impeded (eg, spinal tumour) Raised levels may also occur with severe cerebral hypoxia or genetic lactic acidosis. In viral meningitis, lactate levels remain normal, even when neutrophils are present in the CSF. In bacterial and cryptococcal infection, an increased CSF lactate is found earlier than a reduced glucose. The recommended method, spectrophotometric scanning allows quantitation of haemoglobin (recent bleed, traumatic tap), methaemoglobin and bilirubin (bleeding several hours previously). May be indicated when it is suspected that xanthochromia is due to elevated CSF protein or is being masked by free haemoglobin. Xanthochromia (increased CSF bilirubin) may be seen within 12 hours of subarachnoid haemorrhage and may persist for up to three weeks. Glucose levels are usually normal in viral infections of the CNS. Low glucose levels, as compared with plasma levels, are seen in bacterial meningitis, cryptococcal meningitis, malignant involvement of the meninges and sarcoidosis. PCR amplification, followed by specific nucleic acid probes, provides a sensitive technique for detection of Mycobacterium tuberculosis, herpes simplex virus, enteroviruses, cytomegalovirus and Toxoplasma gondii and other organisms. If an anaerobic organism is suspected special cultures are required.Ĭultures for AFB may take four weeks or longer to become positive.Īntigen testing for Neisseria meningitidis, Haemophilus influenzae type b, Streptococcus pneumoniae or, in infants, Group B streptococcus, may be useful for the diagnosis of meningitis which has been partially treated. The Gram stain is positive in approximately 70% of patients with acute bacterial meningitis.Ī negative Gram stain and/or bacterial culture does not exclude infection, particularly when the patient has received antibiotics. The detection of malignant cells indicates meningeal involvement with carcinoma, lymphoma or leukaemia. Indicated for the detection of motile amoebae ( Naegleria fowleri or Acanthamoeba spp). Specific NAA for meningitis, ie, meningococcal, pneumococcal and Haemophilus influenzae.Ĭell count: 5 x 10 6/L, or if the specimen is from an HIV antibody-positive patient, an India ink preparation should be examined and cryptococcal antigen detection should be considered. IgG/albumin ratio (with simultaneous assays of albumin and IgG on serum) andĮlectrophoresis or IEF with immunofixation of IgG to detect oligoclonal bands. Glucose (with simultaneous measurement of plasma glucose) Specific serological testing (eg, syphilis) Ĭytological examination and/or immunophenotyping India ink preparation and cryptococcal antigen detection Macroscopic inspection: microscopy of wet film including cell count.īacterial culture and antigen detection by NAA ![]() 5-15 mL divided between three sterile plain tubes.Īt least 2 mL required for immunoglobulin studies.
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