Infections Diseases and Meningitis Chapter 30 Paauw

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What is the definition of meningitis?: Meningitis is inflammation of the meninges from infectious (bacterial, viral, or fungal) or noninfectious causes (sarcoid, malignancy, or hemorrhage from vasculitis)
What is the more common cause of infectious meningitis: viral or bacterial?: Viral meningitis is much more common than bacterial meningitis.
Describe some of the viruses responsible for viral meningitis.: Enteroviruses account for 70% of all patients with viral meningitis.

Herpes simplex meningitis is usually associated with episodes of primary HSV II infection.

Acute HIV infection can cause meningitis and is under-diagnosed.
Describe some of the bacteria responsible for bacterial meningitis.: In adults with bacterial meningitis, the most common etiologic agent is Streptococcus pneumoniae, occuring in 30% to 50% of patients.

Neisseria meningitidis, meningococcus, is the second most common cause, occurring in 10%-35% of adult patients with bacterial meningitis.

H. influenzae, a very common cause of bacterial meningitis in children, is rare in adults, causing only 1%-2% of adult meningitis cases.
Causes of bacterial meningitis in adults.: COMMON: Strep. pneumoniae, Neisseria meningitidis

UNCOMMON: Haemophilus influenzae

SPECIAL CIRCUMSTANCES: Neurosurgical patients: Staphylococcus aureus and gram-negative rods

Alcoholics or immunosuppressed: Listeria
What are the typical symptoms of bacterial meningitis?: Classic symptoms seen in greater than 85% of adults include fever, headache, cerebral dysfunction, and meningismus.

***Presence of MENTAL STATUS CHANGE, occuring in 95% of patients, is the single strongest indicator of bacterial meningitis

Nonspecific symptoms include nausea, vomiting, rigors, profuse sweats, weakness, myalgias, and photophobia.

The presenting signs can be variable depending on the infecting organism and the underlying immune status of the patient.
What signs should I look for if I suspect meningitis?: Look for Kernig's and Brudzinski's signs.

Perform a careful skin exam, as 66% of patients with meningococcus have a violacecous rash
How do you perform Kernig's sign?: Attempt to extend the knee with hip flexed. This is positive when radicular pain in the back or leg causes resistance to further extension.

(see http://medlineplus.gov/ for pictures)
How do you perform Brudzinski's sign?: Flex the patient's neck. In a positive test, this maneuver produces flexion in the hip.

(see http://medlineplus.gov/ for pictures)
Where is a good website for meningitis information?: www.meningitis.org
What are the risk factors for **Streptococcus pneumoniae** causing causing bacterial meningitis?: Pneumococcal meningitis may occur in the presence of pneumococcal pnuemonia (15% to 25% of cases), otitis media, or CSF leaks following trauma.

Risk factors for pneumococcal meningitis, as for pneumococcal pneumonia, include alcoholism, cirrhosis, sickle cell anemia, asplenism, multiple myeloma, and chronic lymphocytic leukemia.
What are the risk factors for **Neisseria meningitidis** causing causing bacterial meningitis?: Neisserial meningitis usually occurs in young adults, is rare after age 45, and is the most common cause for epidemic bacterial meningitis.

Complement deficiency increases the risk, particularly with deficient terminal components (C-5 through C-8).
What are the risk factors for **Listeria** causing causing bacterial meningitis?: Listeria monoctyogenes is a gram-positive rod that is more prevalent in the setting of alcoholism, pregnancy or hematologic malignancy.

20% to 30% of adults with Listeria infections have no risk factors.
Does meningitis present differently in elderly and immunosuppressed patients?: The usual signs of meningeal inflammation, nuchal rigidity, headache, Kernig's and Brudzinski's signs, and fever may not be present in the elderly or patients with immune dysfunction, such as neutropenia or HIV disease.

In the elderly, confusion and mental status changes are the most reliable finds, 80%-90%, although these are very nonspecific as they occur with many other conditions.
What are they typical clinical features of viral meningitis?: Typical features include a prodrome of headache, malaise and fever with NORMAL mental status.

Viral meningitis is particularly common in individuals younger than age 40.
What are some signs you can look for on physical exam for viral meningitis?: Look for genital ulcers or blisters suggesting HSV II, generalized adenopathy suggesting HIV, or parotitis suggesting mumps.
Should I obtain a CNS imaging test before lumbar punctures? The question frequently arises whether CNS imaging is required preceding LP.: Obtain a CT scan or MRI prior to LP in any patient with the following signs and symptoms:

1. a focal neurologic exam
2. papilledema or loss of venous pulsations on funduscopic exam
3. seizures
4. HIV infection with CD4 count below 200.

HIV infected patients more commonly have mass lesions caused by toxoplasmosis, TB or lymphoma.
If you do get CNS imaging, what are you looking for?: Look for evidence of midline shift, indicating CNS mass lesion and increased intracranial pressure. If present, risk for herniation and subsequent death with LP is approximately 6%.
What tests do I order on CSF?: Send CSF for:
1. glucose
2. protein
3. cell count with differential
4. bacterial culture
5. Gram stain.

In patients at high risk for TB or fungal meningitis, test for TB with an AFB smear and culture and for cryptococcal disease with cryptococcal antigen and India Ink prep.

An important point here is that not all patients need AFB and fungal testing of the CSF.
What does the CSF look like in patients wtih bacterial meningitis?: CSF in bacterial meningitis shows:

1. greater than 500/mm3 PMNs
2. protein greater than 100 mm/dL
3. glucose less than 40% serum glucose.

About 80% of patients have a positive Gram stain (S. pneumoniae 83%, H. influenzae 76%, N. meningitidis 66%)
What tests are useful if you suspect bacterial meningitis and the gram stain and culture are negative?: Counter immunoelectrophoresis (CIE) can detect the presence of capsular polysaccharide from H. influenzae, S. pneumoniae, and N. meningitidis.

This is particularly useful for evaluating patients who have received antibiotics because the polysaccharide persists after bacterial lysis.
What does the CSF test look like in a patient with viral meningitis?: In contrast to the high PMN count of bacterial meningitis, the typical pattern of viral meningitis is:

1. a total cell count less than 500/mm3 with a mononuclear predominance
2. protein less than 80-100 mm/dL
3. normal glucose level

Note: Early in the course of viral meningitis, PMNs may predominate. A repeat LP within 6-8 hours often shows a shift to mononuclear predominance.
What therapy should be used for suspected bacterial meningitis?: With the increase in pneumococcal resistance to penicillin, empiric therapy for meningitis must cover penicillin-resistant organisms.

Vancomycin, in additional to a 3rd generation cephaolosporin (ceftriaxone or cefotaxime) is recommended.
If you suspect Listeria (or if this organisim is seen on Gram stain), what antibiotic do you add in addition to vancomycin, cetriaxone or cefotaxime?: ampicillin
What don't you use cefoperazone or ceftazidime?: They have very poor CNS penetration.
A 3rd generation cephalosporin alone is adequate in what patient populations?: 1. When meningococcus is seen on Gram stain
2. Elderly patients with probable gram-negative meningitis
3. Postneurosurgical patients in whom gram-negative meningitis or S. aureus meningitis is possible.
If you need to obtain a CT scan before a LP in a patient with a high suspicion index for bacterial meningitis, what should you do in terms of antibiotics?: Give antibiotics BEFORE sending the patient for the CT scan.
In terms of gram stain of CSF, what do you see in viral, bacterial, cryptococcal, TB or subdural or epidural abscess (etiologies of meningitis)?: Viral: no organisms
Bacterial: 80% Gram stain positive
Cryptococcal: Greater than 90% cryptococcal antigen; 50% india ink positive
TB: AFB smear positive
Subdural or epidural abscess: No organisms

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