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Rate CSF is produced
total volume
time to replace 100%
0.5 mL per minute
150 mL
every 5 hours
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Area of LP
Contraindications for LP
L3-L4 (level of ASIS)
any space occupying mass or increased ICP, local infection
-
Spinal cord ends at
L1-L2
-
Protein content of CSF
Normal opening pressure
40-50 mg/dL
60-150 mm H2O
-
define xanthochromia
yellow discoloration of the supernatant of spun CSF. Indicates intrathecal hemorrhage (vs traumatic tap)
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Interpretation of CSF findings...
polymorphs
bacterial or early viral infection
-
Interpretation of CSF findings...
lymphocytes
- infection (viral, fungal, mycobacterial)
- demyelination
- CNS lymphoma
-
Interpretation of CSF findings...
elevated protien
- infection (fungal, mycobacterial)
- demyelination
- tumor (meningioma, carcinomatous meningitis)
- sarcoidosis
- age
-
Interpretation of CSF findings...
low glucose
bacterial infection
-
Interpretation of CSF findings...
oligoclonal bands
- demyelination (MS)
- CNS infections (Lyme disease)
- noninfectious inflammatory processes (SLE)
-
Interpretation of CSF findings...
positive EBV PCR
CNS lymphoma in patients with AIDS or other immunosuppressed states
-
Interpretation of CSF findings...
14,3,3-protein
Creutzfeldt-Jakob disease
-
When is CT before LP contraindicated
when pt has meningitis
-
Most common complication of LP
low-pressure headache
tx with pt lying flat, increase intake of fluids and caffeine
-
CT measures...
degree of x-ray attenuation by tissue
best for demonstrating fresh blood (ex - contrast enhancement indicates disruption of local BBB), acute intracranial bleeding
contraindicated in pregnancy
-
MRI measures...
radiofrequency (RF) pulses instead of x-rays
especially good for seeing contents of posterior fossa and craniocervical junction
ok in pregnancy or in pts with contrast sensitivity (gadolinium is not nephrotoxic)
-
MRI...
T1
Fat is bright, myelinated white matter is bright
water is dark
usually used with contrast (gadolinium)
-
MRI...
T2
water is bright
useful for examining spinal cord
-
MRI...
FLAIR
T2 weighted but CSF signal has been inverted so it's dark. Best for almost everything...
-
MRI...
diffusion-weighted image (DWI)
demonstrates cellular toxicity with high sensitivity, so good for acute stroke
-
MRA
uses blood flow as contrast agent, so safer than angiogram, but not as sensitive or specific
-
PET scan
measures regional brain metabolism (good for seeing seizures)
-
SPECT scan
demonstrates increased blood flow during seizures
-
EEG normal frequencies
-alpha: 8-13 Hz. over posterior head regions in the relaxed awake state with eyes closed
-beta: 14-30 Hz. in frontal regions
-theta: 4-7 Hz. during drowsiness and sleep
-delta: 0.5-3.0 Hz. during drowsiness and sleep
-
EEG...
diffuse theta or delta activity during awake state...
suggests encephalopathy
-
EEG...
records the activity of...
cortical neurons
-
EEG...
interictal epileptiform EEG findings in how many pts with epilepsy
half
-
definition of coma
unarousable unresponsiveness
-
use to reverse common etiologies of coma
Note: use thiamine BEFORE glucose bc otherwise it will precipitate Wernicke's encephalopathy
-
Brainstem reflexes and associated CNs
- -pupillary (II, III)
- -oculocephalic (aka dolls eyes) (VIII - afferent - III, IV, VI - efferent)
- -corneal - (V1, VII)
- -gag - (IX, X, XI)
-
caloric testing can replace what brainstem reflex
oculocephalic
-
two main ways in which consciousness can be depressed
- -brainstem dysfunction
- -both cerebral hemispheres dysfunctional simultaneously
-
how to lower ICP
raise head of bed, hyperventilate, use mannitol
-
cause of locked in syndrome
large lesions in base of pons
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