Lab tests Flashcards
What can cause elevated protein in CSF?
Infection, demyelination, tumor, sarcoidosis, and age
What does a positive EBV PCR from CSF in an AIDS patient (or immunocompromised) indicate?
Highly suggestive of a CNS lymphoma
What conditions can cause oligoclonal bands in CSF?
Demyelination (e.g. MS), infection (e.g. Lyme disease), noninfectious inflammatory processes (e.g. SLE)
What is 14-3-3 protein in the CSF suggestive of?
Creutzfeldt-Jakob disease
What is the most common complication of LPs?
Low-pressure HA. Treated by having patient lie flat and drink lots of fluids and caffeine
When should a CT be ordered before an LP?
Always, except in the setting of suspected bacterial meningitis (don’t want to wait).
When should an LP not be performed?
When CT indicates closure of the 4th ventricle and quadrigeminal cistern, increased ICP
What are evoked potentials?
Electrical potentials that are recorded from the brain, spinal cord, or peripheral nervous system in response to stimulus
How are visual evoked potentials (VEPs) elicited and what do they help diagnose?
A visual target is presented to the patient and the surface potentials are recorded over the occipital lobe. A delay in the P100 potential suggests dysfunction in the optic nerve (helpful for the diagnosis of optic neuritis and MS)
What do different electromyography (EMG) results indicate?
Reduced muscle activation is seen in CNS disease, reduced recruitment suggests PNS disease, early recruitment indicates myopathic disease
What labs should be done before administering tPA?
A CBC, blood glucose, and coagulation profile - to check that the patient is not at increased risk for hemorrhage or does not have an abnormal glucose level which may be causing their symptoms
What are lab findings of Wilson disease?
Increased serum copper and decreased serum ceruloplasmin. Increased 24-hour urinary copper excretion is the most sensitive screening test
What is normal ICP?
<15 mm Hg
What is the cerebral perfusion pressure (CPP)?
The difference between the MAP and ICP. A goal CPP is between 60 and 75 mm Hg
What is a normal opening pressure?
6-15 cm H2O
