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III./4.4.: Diagnosis
III./4.4.1.: Liquor evaluation
If petechias, sinusitises, pneumonia, endocarditis, cranial trauma can be revealed parallel to a headache with fever, the diagnosis is not hard. Despite this diagnostic mistakes are frequent. The diagnosis should always be based on liquor findings.
A lumbalis punctio során az ágy mellett végezhető a liquor fehérje-kémlelése (Pándy-reagenssel), és mérni kell a liquor nyomást. Bakterológiai vizsgálatra steril kémcsőbe kell gyűjteni néhány ml liquort. A liquort May-Grünwald-Giemsa és metilénkék oldat keverékével festjük, majd a sejteket Fuchs-Rosenthal-kamrában mikroszkóp alatt a 3 vonallal határolt „nagy négyzetben” számoljuk, az eredményt szorozzuk 16-tal. Nagyobb sejtsűrűség esetén az egy vonallal határolt kis négyzetben számolunk, az eredményt 256-tal (16 x 16) szorozzuk. A sejtszámot n/3 törtben adjuk meg (a kamra űrtartalma 3 µl). A Sayk-módszerrel ülepített liquorsejteket tárgylemezhez fixáljuk, majd festjük. Bakteriális meningitisben a liquorban az akut szakaszban több ezer sejtet találunk mm3-enként, főként szegmentált magvú leukocytákat és macrophagokat. Napokkal a magas láz után főként macrophagok, majd lymphocyták jelennek meg.
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During lumbar punction liquor proteins can be checked with a bedside tool (Pandy’s reagent), and the liquor pressure should be monitored. A few millilitres of liquor should be collected to a sterile test-tube for bacteriological testing. The liquor is stained with a combination of May-Grünwald-Giemsa stain and methylene blue stain. The number of cells is counted under a microscope in a Fuchs-Rosenthal counting chamber, in the ‘big squares’ which are bordered by triple lines. The result then should be multiplied by 16. In case of a higher cell density the counting should be performed in the squares bordered by a single line and the result should be multiplied by 256 (16x16). The cell number should be given in n/3 fractional (the cubic capacity of the chamber is 3µl). Liquor cells precipitated with the Sayk method are being fixed on a slide and then stained. In the acute phase of bacterial meningitis thousands of cells are found per mm3, mainly leukocytes with a segmented nucleus and macrophages. Days after the high fever mainly macrophages and then lymphocytes occur in the liqour. Meningococci and Staphylococci can be made visible in the liquor and in macrophages with Gram staining. In case of viral meningitis and encephalitis the number of lymphocytes and plasma cells in the liquor is not higher than a couple hundred cells. In case of infections caused by parasites eosinophil cells are present in the liquor. Liquor protein level is high in bacterial meningitis, while sugar is low (<40 mg/dl). Bacteria and fungi can be demonstrated with staining, cultures, complement binding reactions and neutralization tests. Antiviral antibodies can be detected with ELISA (enzyme-linked immunosorbent assay). Serological reactions can be used in case of Borrelia and Treponema pallidum, while tuberculosis, herpes, borreliosis, cytomegaloviral and other viral infections can be detected with liquor PCR. Pneumo/Meningo/Streptocossus can be demonstrated in the liquor with a quick antigene test.
In case of a suspected TB the acid resistant bacteria can be studied either in a smear or with molecular methods. Bacterial and viral meningitises can be differentiated with a good probability based on the liquor lactate and lactate dehydrogenase levels. In purulent meningitis the liquor sugar level lessens according to the rate of cell growth.
III./4.4.2.: Mikrobiological diagnosis
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Pathogen cultures from the blood and/or liquor are important for selective treatment options, but are often disturbed by previous antibiotic treatment. Liquor and blood samples should be analyzed to detect the presence of bacteria (Meningococcus, Pneumococcus, H. influenzae) and antigens. Resistance for the following antibiotics should be checked: penicillin, ceftriaxone, rifampicin, chloramphenicol, ciprofloxacin, azithromycin.
III./4.4.3.: Others diagnostics and aspects
CT scan in meningitis is usually negative, while it can show the oedema and the narrow ventricles. MR scans can reveal the effusion. EEG findings are non-specific, they usually help the differential diagnosis. Among laboratory findings leukocytosis is frequent. C-reactive protein level is elevated. With the help of PCR (polymerase chain reaction) bacterial DNA and specific antibodies can be demonstrated.
Lumbar punction has to be avoided even in the suspicion of meningitis if
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1) The patient is unconscious, or the consciousness is altering,
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2) The patient has suddenly appearing focal signs and/or symptoms of increasing intracranial pressure,
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3) If papilloedema or papillary bleeding is present.
General rule: If the patient with a fever develops delirium or the patient in a delirious state develops fever, meningitis has to be ruled out.
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