Meningitis and CSF Analysis Flashcards
What is meningitis?
- Meningitis is an inflammatory disease of the meninges, the tissues surrounding the brain and spinal cord
- Meningitis is defined by an abnormal number of white blood cells in the cerebrospinal fluid
Common differential diagnosis of meningitis?
Most common subtypes
- bacterial meningitis
- viral meningitis
Uncommon differential diagnosis of meningitis?
- fungal meningitis
- TB meningitis
- parasitic meningitis
- CNS abscess
- drug induced meningitis e.g., NSAIDs, trimethoprim, sulfamethoxazole
- HIV
- neoplastic meningitis
- leptomeningeal carcinomatosis
- Lyme disease
- neurosarcoidosis
- neurosyphilis
- SLE
- vasculitis
Where is CSF formed?
choroid plexus - in pia mater
How much is the CSF in the body?
120 - 150 ml
In which direction does the CSF flow?
Unidirectional flow from ventricles to sub-arachnoidal space (cranium, myelum)
What is the normal CSF pressure?
6 - 20 cm H20
What causes CSF to increase?
- production vs. reabsorption imbalance
- cerebral edema
- mass lesions
Consequences of increased CSF pressure?
herniation of the:
1. cingulate gyrus
2. uncus of the temporal lobe, or
3. cerebellar tonsils
Clinical presentation of meningitis?
- Acute or Gradual presentation
- Fever
- General illness
- Head and neck ache
- Altered mental state
- Preceding illness: pneumonia, otitis
- Seizures
- Skin abnormalities
- Focal neurological manifestations e.g. photophobia
What are signs of meningeal irritation?
- Kernig sign
- Brudzinski sign
- Jolt accentuation of headache
Describe the maneuver of Kernigs signs?
place patient supine with hip flexed at 90 degrees and attempt to extend the leg at the knees
What is a positive Kernigs sign?
the test is positive when there is resistance to extension at the knee to >135 degrees or pain in the lower back or posterior thigh
Describe the Brudzinski sign maneuver?
place patient in the supine position and passively flex the head toward the chest
What is a positive Brudzinski sign?
the test is positive when there is flexion of the knees and hips of the patient
What is the jolt accentuation of headache maneuver?
patient rotates his/her head horizontally two to three times per second
What is a positive jolt accentuation of headache test?
the test is positive if the patient reports exacerbation of his/her headache with his maneuver
What is the skin manifestation in a patient with bacterial meningitis?
can start as a blanching rash and develops into a no-blanching red, purple or brownish petechial rash or purpura
- does not disappear when pressure is applied to the skin
Contraindications of a lumbar puncture?
- Local infection
- Anatomical deformities
- Hemorrhagic diathesis (coagulopathy) or anticoagulant therapy
- Herniation risk e.g. increased ICP
- Platelets <20000
What poses a herniation risk?
- clinical signs indicating herniation
- hypertension, bradycardia, irregular respirations - cranial mass lesion
- suspected in the presence of focal neurological deficits - increased intracranial pressure
Principles of anti-sepsis in LP?
- Sterile equipment
- Sterile gloves
- Disinfection
- Concentric circles away from the LP site
Complications of LP?
- Herniation
- Local pain
- Headache
- Bleeding
- CSF leak
- Infection
- Epidermal cyst (sub-arachnoid)
Describe the different appearances CSF can have?
- Normal: as water
- Cloudy - turbid: >200 WBCs or 400 RBCs /microL
- Bloody: 6000 RBCs /microL
What is xanthochromia?
Breakdown of RBCs (Hb) in CSF
- first to oxyhemoglobin (pink), later to bilirubin (yellow)
e.g. subarachnoid bleeding - 90% sensitive after 12 hours duration up to 4 weeks
Features of xanthochromia in CSF?
- Very high protein levels
- Systemic hyperbilirubinemia
Normal CSF contents?
- Up to 5 WBC (3 PMN)
- 5 RBC /microL
- avoid delays > reduces sensitivity - Protein level 0.20 to 0.40 g/L
- CSF-to-serum glucose ratio = 0.6
What does pleocytosis of WBCs mean in CSF?
- Pleocytosis WBCs suggests infection
- lymphocytosis suggests viral, TB, Cryptococcal
What to do when you find WBC in bloody CSF?
deduct 1 WBC for every ~ 500 RBCs
Increased protein in CSF could mean?
bacterial, TB and fungal meningitis
Low glucose levels in CSF could mean?
- bacterial, TB, fungal meningitis
- malignancies
- hypoglycemia
Cytology requires how much CSF for analysis?
10 - 15 ml
Microbiological tests you can do on CSF?
- gram stain
- bacterial/fungal culture
- AFB
- MTB Xpert (ultra)
- mycobacterial culture
- CRAG
Common causes of bacterial meningitis?
- Neisseria meningitidis
- streptococcus pneumoniae
- listeria monocytogenes
- coagulase-negative staphylococcus
- staphylococcus aureus
- gram-negative bacilli
- haemophilus influenzae
Complications of otitis media?
- Meningitis
- Brain abscess
- Epi- and sub-dural empyema
- Lateral sinus thrombosis
Microbiology of otitis media and meningitis?
- S pneumonia, H influenzae
- GN bacteria, especially in chronic OM
Prevalence otogenic cause among meningitis cases?
- <1% to 50% of meningitis cases
- As common in adults as in children
- Mainly acute OM, rarely chronic OM
Role of surgery in otitis?
drainage middle ear, any intracranial sites, mastoid
Which types of meningitis have the highest complication and mortality rates?
Bacterial, tuberculous and cryptococcal meningitis
