CNS Infection & Lumbar puncture

Question 1

Bacterial

Answer 1

Meningitis

Tuberculosis

Neurosyphillis

Question 2

Viral

Answer 2

Encephalitis

Meningitis

Poliomyelitis

Rabies

HIV

Question 3

Protozoa

Answer 3

Malaria

Toxoplasmosis

Amoebic abscess

Question 4

Helminthic infections

Answer 4

Schistosomiasis
* Hydatid disease
* Cysticercosis
* Strongyloidiasis

Question 5

Meningitis

Answer 5

Inflammation of meninges surrounding the brain and spinal cord

• Inflammation of meninges results in irritation of the nerves that pass
  through the meninges

Question 6

Causes of meningitis

Answer 6

Bacteria
* Viruses
* Fungus

Question 7

Symptoms of meningitis

Answer 7

Fever, headache, irritability, delirium and loss of consciousness

Question 8

Signs of meningitis

Answer 8

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.

Question 9

Bacterial Meningitis

Causative bacteria

Answer 9

• Strep. pneumoniae
• Hemophilus influenzae
• Meningococcus

Question 10

Tuberculous Meningitis

Answer 10

• Hematogenous spread into CNS
• Small yellow nodules (tubers) on brain surface

Histology
* Langhan’s giant cells
* lymphocytes
* vasculitis

Question 11

Viral meningitis

Answer 11

Aka lymphocytic meniningitis

• Viruses
  -mumps
  -measles
  *-echoviruses
• Dense lymphocytic infiltration on microscopy
• CSF shows lymphocytes

Question 12

Investigation of meningitis

Answer 12

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

Question 13

Treatment of meningitis

Answer 13

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

Question 14

Complications of meningitis

Answer 14

Cranial nerve palsies
-due to fibrosis

Hydrocephalus
-blockage of aqueduct

Cortical atrophy
-due to vessel thrombosis, ↑ ICP
-mental retardation, blindness, deafness, paralysis

Question 15

Encephalitis

Answer 15

• 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

Question 16

Symptoms of Herpes simplex encephalitis

Answer 16

fever, chills, signs of ↑ ICP

Behavioral & personality changes
* Focal neurological signs (aphasia, hemiplegia)
* Seizures
* Drowsiness and coma

Question 17

Japanese encephalitis

Answer 17

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

Question 18

Investigations for encephalitis

Answer 18

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

Question 19

Treatment of encephalitis

Answer 19

Anticonvulsants
* Raised intracranial pressure
* Dexamethasone
* Mannitol
* Antivirals
* IV Acyclovir for herpes simplex encephalitis
* Poor prognosis
* 10 – 30% mortality
* Residual epilepsy or cognitive impairment

Question 20

Brain Abscess

Answer 20

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

Question 21

Treatment of brain abscess

Answer 21

Treatment: drainage and/or excision of the abscess
with IV antibiotic therapy

Question 22

Procedure of lumbar puncture

Answer 22

• Lateral position, flexed in fetal position
• Check for level of iliac crest – L3/L4 level

Question 23

Lumbar puncture

Answer 23

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)

Question 24

Procedure of lumbar puncture

Answer 24

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

Question 25

Opening pressure

Answer 25

• 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

Question 26

CSF Investigation

Answer 26

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