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Flashcards in Lumbar Puncture Deck (16):
1

What are the normal values in an LP:
- Opening pressure
- Protein
- RCCs
- WBCs
- Colour
- Glucose
- Gram stain

- Opening pressure: 8-20cm H20
- Protein: 0.15-0.45g/L
- RCCs: None
- WBCs: 0-4/mm3
- Colour: Clear
- Glucose: >1/3,

2

What are the LP values in an acute bacterial meningitis?
- Opening pressure
- Protein
- RCCs
- WBCs
- Colour
- Glucose
- Gram stain

- Opening pressure: Normal/increased (inflammation may create increased pressure
- Protein: Increased (inflammatory response)
- RCCs: Increased usually, due to inflammation of the meninges
- WBCs: Increased (often >300, neutrophil predominant)
- Colour: Clear / yellow / turbid if pus (high protein)
- Glucose: Decreased (bacteria use it for respiration)
- Gram stain: May be +ve or -ve, especially if recent antibiotics

3

What are the LP values in a viral meningitis / encephalitis?
- Opening pressure
- Protein
- RCCs
- WBCs
- Colour
- Glucose
- Gram stain

- Opening pressure: Normal / increased
- Protein: Normal / increased
- RCCs: Normal / increased
- WBCs: Increased (often

4

What are the LP values in a subarachnoid haemorrhage?
- Opening pressure
- Protein
- RCCs
- WBCs
- Colour
- Glucose
- Gram stain

- Opening pressure: Normal
- Protein: Normal / increased
- RCCs: V. increased - doesn't clear with multiple bottles
- WBCs: Increased slightly
- Colour: Clear / yellow (xanthochromia) / red
- Glucose: Normal
- Gram stain: -ve

5

What are the LP values in Guillain Barre Syndrome?
- Opening pressure
- Protein
- RCCs
- WBCs
- Colour
- Glucose
- Gram stain

- Opening pressure: Normal
- Protein: Increased
- RCCs: Normal
- WBCs: Normal
- Colour: Clear / slightly yellow
- Glucose: Normal
- Gram stain: -ve

6

When is a LP indicated? Give examples.

To exclude CNS infection, inflammation or bleeding into the subarachnoid space.
Examples - Meningitis, subarachnoid haemorrhage, encephalitis, multiple sclerosis, TB, Guillain Barre, CNS cancer, Pyrexia of unknown origin

7

What are the potential contraindications to performing an LP?

3 main groups:
1) Risk of introducing infection into the CSF - infected skin at LP site
2) Risk of increased bleeding - Warfarin therapy, severe thrombocytopenia, uncorrected haemophilia
3) A possibility of raised ICP giving a risk of cerebellar tonsil herniation 'coning' - uncontrolled seizures (no CT), reduced level of consciousness, papilloedema, cerebral tumour, cerebral abscess

8

What are the potential complications to having an LP?

- Failure to obtain CSF
- 'Traumatic' tap
- Post LP headache
- Local anaesthetic or latex hypersensitivity
- Bleeding into the spinal canal
- Infection
- Spinal cord injury

9

What is the most common cause of bacterial meningitis?

0 - 3 months
Group B Streptococcus (most common cause in neonates)
E. coli
Listeria monocytogenes

3 months - 6 years
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae

6 years - 60 years
Neisseria meningitidis
Streptococcus pneumoniae

> 60 years
Streptococcus pneumoniae
Neisseria meningitidis
Listeria monocytogenes

Immunosuppressed
Listeria monocytogenes

10

What is the empirical therapy for bacterial meningitis?

Age groups:

- Antibiotics: Cefotaxime 2g IV +/- ampicillin if immunocompromised. Administer as soon as possible, but if possible after drawing blood cultures
- Aggressive resuscitation measures - IV fluids etc.
- Early senior involvement - Reg / Consultant / ITU

Initial empirical therapy aged 50 years: Intravenous cefotaxime + amoxicillin
Meningococcal meningitis: Intravenous benzylpenicillin or cefotaxime
Pneuomococcal meningitis: Intravenous cefotaxime
Meningitis caused by Haemophilus influenzae: Intravenous cefotaxime
Meningitis caused by Listeria: Intravenous amoxicillin + gentamicin

11

What is the empirical treatment with a suspected viral meningo-encephalitis?

Antiviral medication e.g. aciclovir 10mg/kg TDS (aciclovir not indicated for a lymphocytic meningitis in the absence of confusion / behaviour change)
Have a low threshold for antibiotics.
Supportive - seizure control, intubation

12

What are the common infective causes of encephalitis?

Viral:
- Herpes virus: 1+2, VZV, EBV, CMV (immunocompromised), HHV-6+7 (immunocomprimised and children)
- Enterovirus
- Paramyxovirus: Measles, mumps
- Others: Influenza, adenovirus, rubella
- Travel associated: West Nile, Japanese encephalitis, Tick-borne, Dengue, Rabies

Bacteria:
- Mycobacterium tuberculosis
- Mycoplasma pneumoniae
- Chlamydophila

13

What happens to the sensitivity of CT to detect Subarachnoid Haemorrhage over time?

Reduces:
- 12hr 98-100%
- 48hr 86%
- 7 days 50%
- 3 weeks almost nil

14

How long after SAH should LP be performed?

Ideally 6-12 hours so red cells have time to lyse and produce bilirubin

15

What percentage of people presenting with the typical thunderclap occipital headache actually have SAH?

10%

16

What is the diagnostic criteria for Guillain Barre?

1) Progressive, symmetrical weakness of 2 or more limbs due to neuropathy
2) Areflexia
3) Disease course