See: [RCH paediatric lumbar puncture](x-devonthink-item://39014410-F8EE-4024-9E53-0315630109CE), [Robert Hedges - Spinal Puncture](x-devonthink-item://31ACDC98-D2CC-48C5-BE69-E9B37E53FA8C?page=1426)
# indications
suspected:
- [[Meningitis]]/encephalitis
- delayed presentation [[Subarachnoid haemorrhage]]
- benign intracranial HTN
- idiopathic intracranial hypertension (IIH)
- infants with fever w/o focus
- [[Guillain-Barré syndrome|GBS]]
# contraindications
see [Robert Hedges - LP contraindications](x-devonthink-item://31ACDC98-D2CC-48C5-BE69-E9B37E53FA8C?page=1428)
**Absolute**
- GCS < 8 or deteriorating/fluctuating level of consciousness
- **elevated ICP** or suspicion of mass lesion
- ALOC
- papilloedema
- focal neuro defect
- ==a bulging fontanelle in the absence of other signs of ↑ ICP is NOT a contraindication==
- local cellulitis
- resp compromise
- purpura suspicious of meningococcal disease
- bleeding tendency
- **anti-coagulation**
- plts <50
- INR < 1.5
- (RCH lists above as "relative" contraindications)
- chiari malformation
**Relative **
- septic shock (relative per RCH; general contraindication per Dunn)
- seizure within previous 30 min
- new focal neurological signs
# who needs CT prior to LP?
- age > 60 y
- immunocompromised - risk of mass lesions
- possible raised ICP:
- focal neuro findings
- new onset seizures within last 7 days
- reducing LOC
- papilloedema
- possible alternative dx
- suspected focal CNS disease
- SAH
- history of CNS lesions
- seizure within last 7 days
***Mnemonic:*** **“TAP AS IF”**
- **T**rauma
- **A**ge > 60
- **P**apilledema (or other sign of increased ICP)
- **A**ltered mental status
- **S**eizure
- **I**mmunocompromised (HIV/AIDS)
- **F**ocal neurologic deficits such as hemiparesis or new anisocoria, which can be a sign of impending herniation, typically accompanied by severe altered mental status.
# equipment
> tip: bring an extra manometer if you expect opening pressure may be high (eg IIH, viral meningitis/encephalitis, etc)
- non-cutting needles (pencil point, or whitacre or sprotte) cause ↓ headache after dural puncture, likely because the tip of the needle tends to separate rather than cut dural fibres. usually these need an introducer needle due to the tip itself cutting less.
- smaller diameter needle also reduces post-puncture headache
![[Pasted image 20250407160131.png]]
![[Pasted image 20250407160850.png]]
# consent
**complications**
- \<5 % infection
- post LP headache → reduced with small gauge pencil point (aka Whitacre) needle
- uncal or tentoral herniation
- post LP headache
- spinal epidural haematoma
- intra spinal epidermoid cyst
- infection
- radiculopathy or nerve injury
# procedure
- spinal cord ends at L1-L2 in most adults
- superior aspects of iliac crest at level of L3-4
**anatomical layers traversed by LP**
1. skin
2. s/c fat
3. supraspinous ligament
4. interspinous ligament
5. ligamentium flavum
6. extradural space (fat and internal epidural venous plexus)
7. dura mater (continuous with epineurium of spinal nerves)
8. arachnoid mater (punctured simultaneously as dura mater during LP)
9. subarachnoid space (aka "lumbar cistern" inferior to termination of spinal cord)
![[Pasted image 20250102144006.png]]
![[Pasted image 20250102144101.png]]
![[Pasted image 20250102150323.png]]
**opening pressure**
- normal opening pressure 7-18 cmH2O (up to 25 can be normal in adults)
- 5 cm H2O in neonates
**collect CSF**
- 10 drops (0.5mL) per tube ; can do 1 mL / 20 drops in one tube
- use fluid from manopmeter to fill first tube
## paediatric needle length
> Median spinal cord depth has been correlated with weight:
> Neonates & infants (mm) = 2 x wt (kg) + 7
> children (mm) = 0.4 x wt (kg) + 20
| age | child height cm | needle length cm | Spinal cord depth (cm) |
| ------- | --------------- | ---------------- | ---------------------- |
| neonate | <50 | 2 | 0.9-1.7 |
| <2 y | 50-80 | 3 | 2.4 |
| 2-5 | 80-120 | 3-4 | 2.6 |
| 5-12 | 120-150 | 4-5 | 2.8-3.6 |
| >12 | 150-180 | 5-6 | 3.6-4 |
# tips
- oral sucrose in children < 3 months of age
- document neuro exam of lower limbs
- consent
# interpretation
#tables
> consider fungal or TB if epidemiological risks, [[Encephalopathy|Encephalitis]], ↑ opening pressure in the setting of lymphocyte predominance
| | opening pressure | protein | glucose | WCC | RBC |
| -------------------- | ---------------- | ----------- | ----------- | --------------------------------- | ---------------------- |
| normal | 5 - 20 | 20 - 50 | 2/3 serum | none | 0 - 5 |
| bacterial meningitis | > 30 | ↑ | ↓ 2/3 serum | > 1000<br>> 500 PMN | 0 - 5 |
| viral meningitis | normal or ↑ | normal or ↑ | normal | 100 - 1000<br>mostly lymphocytes | 0 - 5 |
| Fungal / TB | ↑ | normal or ↑ | normal or ↓ | 50 - 500 lymphocytes or monocytes | 0 - 5 |
| SAH | ↑ | ↑ | normal | 1:500 WBC:RBC | > 1000 (usually > 10k) |
![[Pasted image 20240309030611.png]]
![[Pasted image 20240724142604.png]]
## Opening pressure
- TB meningitis and cryptococcis associated with high opening pressures
- normal CSF pressure is between 7 and 20 cm H2O
- obese patients may have CSF pressure up to 25 cm H2O
- pressure is NOT usually measured in neonates because a struggling or crying child will have a falsely elevated pressure
***Causes of ↑ opening pressure:***
- infection (especially bacterial)
- brain expansion (oedema, haemorrhage, neoplasm)
- cerebral oedema may be associated with meningitis, CO2 retention, SAH, anorexia, congestive heart failure, or superior vena cava obstruction
- high altitude and DKA other cause
- false elevation in tense patient when head is elevated above plane of needle or obese patients
- overproduction of CSF (choroid plexus papilloma)
- defect in absorption
- obstruction of flow of CSF through ventricles
## SAH
> if tube 4 has >2000 RBCs, likely SAH
- \>100,000 RBC in last tube indicative of SAH
- \>10,000 in many cases
- \>2,000 and/or visual xanthochromia close to 100% sensitive
- <100 RBC rare
## meningitis
- \> 80% PMN sensitive for bacterial meningitis
## [[Guillain-Barré syndrome|GBS]]
- albuminocytologic dissociation
- presence of elevated CSF protein (>0.65g/L) in absence of CSF cells
- present in
- < 50% during the first week of illness
- 75% in the third week
- protein > 0.4 g/L
- in 90% by the end of the first few weeks of symptoms
- in 70% in the first 3 days
- the degree of protein elevation has no prognostic value
- CSF cell count
- normal
- if abnormal, think of alternative diagnosis, unless patient has HIV, such as Lyme disease or lymphoma
## [[Multiple Sclerosis]]
- oligoclonal bands
## traumatic tap
- RBC usually > 400-1000
- xanthochromia does not occur in traumatic tap