CNS Infection & Lumbar puncture Flashcards
Bacterial
Meningitis
Tuberculosis
Neurosyphillis
Viral
Encephalitis
Meningitis
Poliomyelitis
Rabies
HIV
Protozoa
Malaria
Toxoplasmosis
Amoebic abscess
Helminthic infections
Schistosomiasis
* Hydatid disease
* Cysticercosis
* Strongyloidiasis
Meningitis
Inflammation of meninges surrounding the brain and spinal cord
- Inflammation of meninges results in irritation of the nerves that pass
through the meninges
Causes of meningitis
Bacteria
* Viruses
* Fungus
Symptoms of meningitis
Fever, headache, irritability, delirium and loss of consciousness
Signs of meningitis
Indicate presence of nerve irritation
- Neck stiffness - patient may feel pain; chin does not touch the sternum
- Kernig’s sign - trying to extend the flexed knee while the hip is flexed - causes spasm of the hamstring muscles
- Brudzinski sign - Severe neck stiffness causes a patient’s hips and knees to flex when the neck is flexed.
Bacterial Meningitis
Causative bacteria
- Strep. pneumoniae
- Hemophilus influenzae
- Meningococcus
Tuberculous Meningitis
- Hematogenous spread into CNS
- Small yellow nodules (tubers) on brain surface
Histology
* Langhan’s giant cells
* lymphocytes
* vasculitis
Viral meningitis
Aka lymphocytic meniningitis
- Viruses
-mumps
-measles
*-echoviruses - Dense lymphocytic infiltration on microscopy
- CSF shows lymphocytes
Investigation of meningitis
CT scan to exclude mass lesion in drowsy or unconscious patient
- Lumbar puncture – CSF contains:
-Neutrophils > 5000 cells/mm3 (lymphocytes in viral & tuberculous meningitis)
-Protein elevated
-Glucose reduced
-Gram stain may show organism - Blood culture
Treatment of meningitis
IV antibiotics
* depending on infecting organism
Supportive measures
Contacts
* of meningococcal meningitis require rifampicin prophylaxis
Vaccination
*quadrivalent vaccine A, C, Y, W135
* HIB vaccine against H. influenza B meningitis
Complications of meningitis
Cranial nerve palsies
-due to fibrosis
Hydrocephalus
-blockage of aqueduct
Cortical atrophy
-due to vessel thrombosis, ↑ ICP
-mental retardation, blindness, deafness, paralysis
Encephalitis
- Inflammation of the parenchyma of the brain by viruses
-herpes simplex, VZ, CMV, JE virus etc - Produces symptoms of focal dysfunction depending on organism
- Inflammation can occur in cortex, white matter, basal ganglia, brain
stem depending on type of virus
Symptoms of Herpes simplex encephalitis
fever, chills, signs of ↑ ICP
Behavioral & personality changes
* Focal neurological signs (aphasia, hemiplegia)
* Seizures
* Drowsiness and coma
Japanese encephalitis
Leading cause of viral encephalitis in Asia
* Vector
* culex mosquito
* Persons at risk
* rural residents in padi fields
* expatriates working in rural areas during transmission period
* Vaccine available
Investigations for encephalitis
CT scan
* Excludes mass lesion
* Localise site of lesion eg. temporal lobes in herpes simplex encephalitis
* Lumbar puncture
* Increased lymphocytes
* Protein elevated
* Glucose normal
* EEG
* Slow waves in temporal lobes in herpes simplex encephalitis
Treatment of encephalitis
Anticonvulsants
* Raised intracranial pressure
* Dexamethasone
* Mannitol
* Antivirals
* IV Acyclovir for herpes simplex encephalitis
* Poor prognosis
* 10 – 30% mortality
* Residual epilepsy or cognitive impairment
Brain Abscess
Localized collection of pus within the brain
parenchyma
*Usually from pus forming bacteria (pyogenic)
* Presents as space-occupying lesion and typically with
signs of infectious etiology
Treatment of brain abscess
Treatment: drainage and/or excision of the abscess
with IV antibiotic therapy
Procedure of lumbar puncture
- Lateral position, flexed in fetal position
- Check for level of iliac crest – L3/L4 level
Lumbar puncture
Diagnostic
* CNS infection – meningitis
* Thunderclap headache to rule out SAH when CT/MRI is normal or beyond 3
days
Therapeutic
* To evaluate for normal pressure hydrocephalus (with walk test)
Contra-indication
* Presence of infection in the tissues near the puncture site
* Presence of SOL
* Bleeding tendencies (plt < 80 or INR > 1.4)
Procedure of lumbar puncture
Clean/Drape
* Give lignocaine (5 to 10 mls)
*Wait for 3 mins
*Tap
*Measure OPENING PRESSURE
* Collect 15 drops (1ml) per bottle. Each drop 0.06ml
* Number each bottle in sequence
* Send for laboratory investigations
* Measure CLOSING PRESSURE
Opening pressure
- Normal: 10-18 cm H2O
- Elevated pressure
Infective – TB/bacterial/fungal
Hydrocephalus – Communicative type
Benign intracranial hypertension - Low pressure
Blockage – Spinal block but ICP is high
Intracranial hypotension
CSF Investigation
Never send 1st bottle for cell count and microscopy
* More likely to have high RBC
* Sent all bottles to Lab, but not all the test
Basic test first - Cell count, Gram stains, Cultures and Glucose
* Remember to check BSL
Compare with CSF glucose level
CSF glucose level low indicates bacterial infection
