CSF interpretation Flashcards
what positions can an LP be performed?
- Lying in foetal: can get opening pressure
- Sitting hunched over table opens up spine
what landmarks do you follow to get correct LP place?
- Follow iliac crest gets to L3/4
why do you not want any higher than L2?
- Any higher would get spinal cord risk of nerve damage paralysis
- L2 and lower gets individual nerves cauda equina region
why do you insert LP needle at L3/4 region?
the nerves are all individual nerve roots - not the spinal cord any more
the needle is designed so that it can push nerve roots out of the way
what are the complications of a LP?
post LP headache
bleeding
infection
haemorrhage
dry tap
nerve damage
brain herniation
why does a headache occur and what can help?
- Post LP headache caused by low pressure dark room, lying down and caffeine can help. Usually occurs 24-48hrs post LP
due to the pressure change
why might there be local pain and bleeding with a LP?
- Local pain – needle. Disc herniation if needle is too far
- Bleeding – micro trauma by needle
what may cause haemorrhaging following a LP?
low platelets/ coagulopathies
why might you get a dry path within a LP?
: misplaced or dehydrated patient – not enough csf
how might nerve pain present and what is done to avoid it within a LP?
- Nerve damage: extremely rare as should be low enough not to hit nerves leg pain, electrical sensation
how can a LP cause a brain herniation?
- Brain herniation: caused by the drastic change in pressure – high intercranial pressure and low pressure in spinal cord and this causes brain to move down into brain stem potentially fatal
what is normal opening pressure of CSF?
12-18cm H20 in foetal position
which position and why can inly get opening pressure?
foetal only - as sitting gives higher csf pressure compared to brain due to gravity
what can elevated opening pressure and what is the cut off before worrying?
- Elevated if tense or anxious
- Higher if obese - <25
- Pathology: infection, idiopathic intercranial hypertension, hydrocephalus, SoL
normal CSF is clear and colourless, what would bacteria in csf look like?
- Pathology – turbid: bacterial
normal csf is clear and colourless what would turbid csf indicate?
fungal/ TB presence
what WCC is deemed normal within csf?
<5 x10^9
what might elevate WCC?
traumatic LP
bacteria
viral presence
what WCC would you expect with bacterial csf presence and what cell type?
100s to 1000s
mainly neutrophils
if there are viruses present in csf, what WCC and cell type would you expect?
100s to 500s
lymphocyte predominately
even with viral and bacterial presence what may have lower the WCC?
empirical ABx - the counts would be lower than expected
what is normal protein count in csf?
<0.5g/l
if a csf was normal, except a very high protein what could that indicate?
GBS
how would viruses effect csf protien levels?
slight increase
what would indicate a bacterial presence within csf?
1<
what would a low glucose in csf indicate?
Glucose: >2/3 of serum glucose
- Low: bacterial
what would show a bacterial picture?
bacteria eats all the glucose - very low
bacteria poos out the protein - very high (>1)
mainly neutrophils
when would xanthochromia present in csf?
bilirubin from heme breakdown
- Seen in LP performed 12hrs post SAH headache onset
when would oligoclonal bands be seen?
MS
- Can be seen in other inflam conditions eg sarcoidosis/ SLE
what are common bacterial causes of meningitis and which demographics are mainly affected?
N. menigitidis teens, uni students
- Strep. Pnuemoniae paeds, elderly
- Listeria: provides lymphocytic picture neonates, elderly, immunocompromised and pregnancy
- TB: provides lymphocytic picture immunocompromised, high prev areas
what can cause raised intercranial pressure?
- Idiopathic intercranial hypertension
- SoL
- Infection
- Venous sinus thrombosis
what can papilledema indicate?
raised intercranial pressure
what can cause optic neuritis?
MS, diabetes
anything causing peripheral neuropathy
how can hypercapnia affect the eyes?
can cause papilledema
what are RF for idiopathic intercranial hypertension?
females of childbearing age
RF: obesity, Venous sinus thrombosis (common after anti-coag therapy from bleeds)
- Drugs: tetracycline, minocycline, nitrofurantoin, vitA and isotretinoin, COCP
what investigations are needed with idiopathic intercranial pressure?
Investigations: need MRI
- LP: raised opening pressure and therapeutic drainage
how do manage idiopathic intercranial hypertension?
- Lifestyle: weight loss, remove causative medication
- Therapeutic LP: bring pressure below 20mmHg
- Drugs: acetazolamide, topiramate, loop diuretics, pred
- Surgery: lumbar-peritoneal shunt, optic nerve sheath fenestration
what are complications of intercranial hypertension?
visual loss
how does acetazolamide work?
carbonic anhydrase inhibitor helps reduce CSF production
what is viral encephalitis?
viral infection of brain parenchyma (cortex, white matter, basal ganglia, brainstem)
what are the most common causes of viral encephalitis?
HSV 1 most common in Europe – mostly affects temporal lobes
- HSV2: in immunosuppressed/ neonates
- CMV, EBV, VZV, HIV, Measles, mumps, rabies, tick borne, arbovirus
- Japanese B encephalitis – east asia and Australia
what is HSV1 and HSV2?
herpes simplex virus 1 - very common causes cold sores
HSV2 - genital herpes
how does viral encephalitis present?
- Headache, fever
- Focal neuro signs: hemiplegia and aphasia
- Seizures
- Reduced consciousness and confusion - acting very stupidly?
- Meningism
what is meningism?
meningitis symptoms without meninge inflammation – triad (headache, neckstiffness and photophobia)
what comes first investigations or treatment?
treat before investigations start base on clinical presentation then alter accordingly to results
what would an mri show indicating viral encephalitis?
- Brain imaging (MRI) : temporal lobe petechiae – small haemorrhages
what would a LP show to indicate viral encephalitis?
- LP: raised WCC – mainly lymphocytes, elevated protein, normal glucose
what would an EEG show to indicate viral encephalitis?
slow periodic waves
how do you manage viral encephalitis?
- IV acyclovir – HSV 2
- Steroids (dexamethasone) if raised ICP
- Supportive: anti-convulsants, resp support
what does gram positive diplococci indicate?
strep pnuemoniae
how common in guillan barre syndrome?
not very
1 to 2 in every 100,000
what is GBS linked to?
previous recent infection - last 2 weeks or so
coryzal, acute diarrhoeal, acute infection
: linked infections include – campylobacter, CMV, mycoplasma, HZV, HIV, EBV
what are the symptoms of GBS?
- Ascending symmetrical paralysis starting in lower legs
- Pain can occur but sensory less common
- Autonomic dysfunction: sweating, tachycardia, arrythmias, BP changes
- Lower motor neurone signs: hypotonia, facilitations, no reflexes
what is the miller fisher variant of GBS?
: opthalmoplegia (paralysis of eye muscles), ataxia and areflexia
what is the pathophysiology of GBS?
rare but serious post-infectious immune-mediated neuropathy. It results from the autoimmune destruction of nerves in the peripheral nervous system
what investigations are done for GBS?
MRI - rule out other pathology
CSF analysis: raised protein count
- Nerve conduction studies: reduced velocity – demyelination
- Resp function: FVC/ABG breath count – concerns due to paralysis of resp system
- Anti-ganglioside auto-antibodies – may be positive
- Investigate cause of infection – non priority
