Meningitis.pptx epidemiology and diagnosis

Meningitis

1. M eningitis هومن بصیری 1403

2. INTRODUCTION Meningitis is an inflammatory disease of the leptomeninges, the tissues surrounding the brain and spinal cord, and is defined by an abnormal number of white blood cells in the cerebrospinal fluid (CSF ) Approximately 1.2 million cases of bacterial meningitis occur annually worldwide

3. EPIDEMIOLOGY    Bacterial meningitis can be community-acquired or healthcare-associated The major causes of community-acquired bacterial meningitis in adults in developed countries are Streptococcus pneumonia , Neisseria meningitides , and, primarily in patients over age 50 to 60 years or those who have deficiencies in cell-mediated immunity, Listeria monocytogenes The major causes of healthcare-associated bacterial meningitis are different ( usually staphylococci and aerobic gram-negative bacilli)  Healthcare-associated bacterial meningitis may also occur in patients with internal or external ventricular drains, or following trauma

4. CLINICAL FEATURES Patients with bacterial meningitis are usually quite ill and often present soon after symptom onset

5. Presenting manifestations The classic triad of acute bacterial meningitis consists of fever, nuchal rigidity, and a change in mental status, although an appreciable number of patients do not have all three features Most patients have high fevers, often greater than 38ºC but a small percentage have hypothermia Headache is also common However, virtually all patients have at least one of the findings of the classic triad of fever, neck stiffness, and altered mental status  the absence of all of these findings essentially excludes the presence of bacterial meningitis

6. Neurologic complications such as seizures, focal neurologic deficits (including cranial nerve palsies), and papilledema may be present early or occur later in the course Certain bacteria, particularly N. meningitides , can cause characteristic skin manifestations, such as petechiae and palpable purpura Arthritis occurs in some patients with bacterial meningitis

7. Examination for nuchal rigidity Passive or active flexion of the neck will usually result in an inability to touch the chin to the chest The classic Brudzinski's sign refers to spontaneous flexion of the hips during attempted passive flexion of the neck The Kernig's sign refers to the inability or reluctance to allow full extension of the knee when the hip is flexed 90º

8. LABORATORY FEATURES

9. Laboratory studies Routine blood work is often unrevealing. The white blood cell count is usually elevated, with a shift toward immature forms; however, severe infection can be associated with leukopenia. The platelet count may also be reduced

10. Blood cultures Blood cultures are often positive and can be useful in the event that CSF cannot be obtained before the administration of antimicrobials. Approximately 50 to 90 percent of patients with bacterial meningitis have positive blood cultures Two sets of blood cultures should be obtained from all patients prior to the initiation of antimicrobial therapy.

11. LUMBAR PUNCTURE Every patient with suspected meningitis should have CSF obtained unless lumbar puncture (LP) is contraindicated It is not uncommon for LP to be delayed while a computed tomographic (CT) scan is performed to exclude a mass lesion or increased intracranial pressure, which rarely leads to cerebral herniation during subsequent CSF removal. However, a screening CT scan is not necessary in the majority of patients

12. Indications for CT scan before LP a CT scan of the head before LP should be performed in adult patients with suspected bacterial meningitis who have one or more of the following risk factors Immunocompromised state ( eg , HIV infection, immunosuppressive therapy, solid organ or hematopoietic stem cell transplantation) History of CNS disease (mass lesion, stroke, or focal infection) New onset seizure (within one week of presentation) Papilledema Abnormal level of consciousness Focal neurologic deficit

13. If LP is delayed If LP is delayed or deferred, blood cultures should be obtained and antibiotics should be administered empirically before the imaging study, followed as soon as possible by the LP. In addition, dexamethasone (0.15 mg/kg IV every six hours) should be given shortly before or at the same time as the antibiotics if the preponderance of clinical and laboratory evidence suggests bacterial meningitis with a plan to stop therapy, if indicated, when the evaluation is complete. Adjunctive dexamethasone should not be given to patients who have already received antimicrobial therapy because it is unlikely to improve patient outcome

14. Opening pressure he opening pressure is typically elevated in patients with bacterial meningitis

15. CSF analysis The usual CSF findings in patients with bacterial meningitis are a white blood cell count of 1000 to 5000/ microL  (range of <100 to >10,000) with a percentage of neutrophils usually greater than 80 percent, protein of 100 to 500 mg/ dL , and glucose <40 mg/ dL  (with a CSF:serum glucose ratio of ≤0.4 ).

16. Gram stain Gram-positive diplococci suggest pneumococcal infection Gram-negative diplococci suggest meningococcal infection) Small pleomorphic gram-negative coccobacilli suggest Haemophilus influenzae infection Gram-positive rods and coccobacilli suggest listerial infection

17. Polymerase chain reaction Nucleic acid amplification tests, such as the polymerase chain reaction (PCR), have been evaluated in patients with bacterial meningitis

18. GENERAL PRINCIPLES OF THERAPY

19. Avoidance of delay Antibiotic therapy, along with adjunctive dexamethasone when indicated, should be initiated immediately after the performance of the lumbar puncture (LP) or, if a computed tomography (CT) scan of the head is to be performed before LP, immediately after blood cultures are obtained

20. Choice of regimen Antibiotic selection must be empiric immediately after CSF is obtained or when lumbar puncture is delayed. In such patients, antibiotic therapy needs to be directed at the most likely bacteria based upon patient age and underlying comorbid disease Once the CSF Gram stain results are available, the antibiotic regimen should be tailored to cover the most likely pathogen

21. Route of administration Because of the general limitation in antibiotic penetration into the CSF, all patients should be treated with intravenous antibiotics

22. Adjunctive dexamethasone Early intravenous administration of glucocorticoids (usually dexamethasone ) has been evaluated as adjunctive therapy in an attempt to diminish the rate of hearing loss, other neurologic complications, and mortality

23. Empiric regimens

24. REGIMENS BASED UPON GRAM STAIN

25. VIRAL MENINGITIS

26. Enteroviruses Aseptic meningitis occurring during the summer or fall is most likely to be caused by enteroviruses ( eg , Coxsackie, echovirus, other non-poliovirus enteroviruses), the most common cause of viral meningitis The presenting signs and symptoms of enteroviral meningitis are not distinctive Cerebrospinal fluid (CSF) findings are typical of other viral meningitides and include a white blood cell (WBC) count that is generally less than 250 cells/ microL , a modest elevation in CSF protein concentration (generally less than 150 mg/ dL ), and a normal glucose concentration

27. HIV infection The CSF profile characteristically has a lymphocytic pleocytosis , an elevated protein concentration, and normal glucose concentration

28. Herpes simplex meningitis Primary HSV has been increasingly recognized as a cause of viral meningitis in adults. In contrast to HSV encephalitis, which is almost exclusively due to HSV-1, viral meningitis in immunocompetent adults is generally caused by HSV-2 There is no standard approach to the treatment of HSV meningitis For hospitalized patients, we prefer intravenous acyclovir at 10 mg/kg administered every eight hours. Patients can be switched to an oral agent on discharge for a total of 10 to 14 days of treatment.

29. Recurrent (Mollaret's) meningitis The most common etiologic agent in Mollaret's meningitis is HSV-2, although some patients do not have evidence of genital lesions at the time of presentation

30. Mumps  The most frequent manifestations are headache, low-grade fever, and mild nuchal rigidity. The onset of meningitis is variable and can occur before, during, or after an episode of mumps parotitis The CSF profile typically reveals fewer than 500 WBC/ microL  with a lymphocytic predominance, but more than 1000 WBC/ microL  and an early neutrophil predominance can occasionally be seen. The CSF total protein is generally normal or mildly elevated and the CSF glucose levels may be mildly depressed.