Clin Lab: Neuro Diagnostics Flashcards
CT head Indications
- AMS
- Stroke-like symptoms
- Trauma to brain/spine
- Suspected subarachnoid hemorrhage (SAH)
- Recurrent headache/migraine
- Seizures
When to do a non-contrast CT head?
- Initial scan for stroke
- Suspected bleed
When to do a CT head w/ IV contrast?
- Suspected abscess or tumor
- Suspected MS
How will a normal brain look on CT head - non-contrast?
Bone
Pineal gland/choroid plexi
CSF
Air
Gray matter
White matte
- Bone = bright white
- Pineal gland & choroid plexi – bright white
- CSF – dark
- Air – dark
- Gray matter – lighter gray
- White matter – darker gray
What color is bone on MRI?
darker (not bright white)
Abnormal findings on non-contrast CT head
- Midline shift
- Blood
- Mass
- Edema
- Atrophy
- Lesions
Fresh blood on CT is…
bright
Clotted (chronic) blood on CT is…
dark
CTA of head/neck Indications
Evaluate vasculature of the head/neck
- Embolus/thrombosis
- Dissection
- Malformation (AVMs)
- Stenosis
CTA head/neck procedure
- Similar to CT head w/ IV contrast
- Timing b/t contrast injection & taking the images is different
- Enhances vessels
What is the imaging modality of choice for the brain in many circumstances except the ER?
MRI
Indications for an MRI brain
- Suspected infx
- Suspected mass/lesion
- Neurologic deficits
- Seizures
Normal MRI brain T1:
Gray matter
White matter
CSF = dark
Timing
- Gray matter = gray
- White matter = lighter gray
- CSF = dark
- Short time
Normal MRI brain T2:
Gray matter
White matter
CSF
Timing
Gray matter = light gray
White matter = darker gray
CSF = bright
Long time
Describe a flair MRI brain
- T2 weighted
- Decreases signal of CSF
- Sensitive for Edema
Describe a diffusion weighted MRI brain
- Rate of water diffusion
- Increased in areas of pathology (bright)
Indications for CT spine
- Acute trauma of spine
- Evaluation when MRI contraindicated
- Chronic back pain
Indications of CT spine non-contrast
Evaluate for fracture
Indications of CT spine w/ IV contrast (into vasculature)
- Suspected abscess or tumor
- Suspected MS
Indications for CT myelogram (into CSF)
- back pain or localized neurologic signs suggesting spinal canal narrowing (spinal stenosis)
- suspected tumors (cord, meningeal, etc), encroaching on the canal
Indications of MRI spine
- Back pain
- Bilateral neurologic deficits
- Incontinence
- Suspected infx
Indications for a Octreotide Scan
- ID & localize neuroendocrine primary & metastatic tumors
- Indicated in pts w/ known neuroendocrine tumors
- Used preop to direct the surgeon to primary & metastatic tumors (especially in the abdo)
- Used to monitor therapy
Contraindications of electronystagmography (ENG)
Pacemaker
Risk Factors
homocysteine
- elevated levels assoc w/ incr risk of AD
Supportive tests for neurodegenerative dz/Alz
- MRI
- PET scan w/ amyloid imaging
Stroke symptoms can be caused by
- ischemia (blocked flow of blood)
OR - bleeding (intracranial hemorrhage)
What other imaging should for ischemic stroke / TIA?
- CTA head & neck
- MRI brain
- MRA head/neck
Why do a CTA head & neck for ischemic stroke/TIA?
- Allows possible visualization of clot
- Possible tx options depending on location
Why do a MRA brain for ischemic stroke/TIA?
- More sensitive for edema assoc. w/ stroke than CT
- If unable to do MRI, repeat CT head in 48 hrs to visualize area of stroke
Why do a MRA head/neck for ischemic stroke/TIA?
if CTA head/neck not done already
What other imaging should be done to work up the possible causes of the stroke?
Echo
- Afib, plaques, clots
Dx tests/labs for AMS - confusion/coma
- ABG / EKG / CXR / ua / CBC / CMP / lactic acid / glucose
- Blood alcohol level
- Toxicology screen
- Serum osmolality and osmol gap
- Ketones
- Salicylate level
Blood Alcohol Concentration level
> 50mg/dL (0.5%) effects
impairment begins
Blood Alcohol Concentration level > 80mg/dL (0.08%) effects
- flushing
- slower reflexes
- impaired visual acuity
Blood Alcohol Concentration >100mg/dL (0.1%)
- CNS depression
- hypotension (rare, but important in trauma)
Drugs screened on a tox screen?
- opioids
- benzo
- methamphetamine
- marijuana
Toxicology screen Interpretation:
- (-) test doesn’t rule out some drugs (ie fentanyl)
- (+) test
Some tests may be (+) for days after use
(+) test doesn’t necessarily indicate that is the cause of AMS
Free water in the blood is ___ related to its osmolality.
inversely
What is a normal osmolality?
285 - 295
What the 3 most important solutes in the blood that predict calculated osmolality?
- Na+, glucose, BUN
Calculated Osmolality equation
(2 X Na) + Glu/18 + BUN/2.8
What is a normal calculated osmolality?
10 mOsm/L
What things can cause a high osmol gap (>10 mOsm)?
- Ethylene glycol
- Toluene
- Methanol, Isopropanol, Ethanol
What crystals are seen in ethylene glycol?
Ca++ oxalate crystals
What acid/base disorder occurs w/ methanol, Isopropanol, or Ethanol?
metabolic acidosis w/ HAGMA w/ high osmol gap
Immediate S/S of Salicylate OD
- Tinnitus
- lethargy
- confusion
- restlessness
- fever in moderate overdoses
Eventual S/S of Salicylate OD
- hyperreflexia
- seizures
- hallucinations
- stupor
- coma in severe overdoses
What should be done if you suspect a salicylate level?
- Tests should be performed immediately & at about 4 hrs after suspected ingestion
- Call Poison control
What are ketones assoc. with?
DKA or starvation ketoacidosis
–> HAGMA
What yields ketoacids?
fatty acid catabolism
Testing for ketones?
beta-hydroxybutyrate
CNS tumors imaging
- MRI w/ contrast
- CT w/ contrast
- PET scan
- CT myelogram
- CT chest/abd/pelvis w/ contrast
What will CSF analysis show in CNS tumors?
- incr PRO
- normal cells
Describe PNS tumors
Sympathetic nervous system ganglion tumors
Types of PNS tumors
- Paragangliomas
- Pheochromocytomas
- Neuroblastomas
What is released in from PNS - sympathetic nervous system ganglion tumors?
catecholamines
- will be elevated
Catecholamine testing
24 hr urine collection
What is measured in catecholamine testing?
- dopamine
- epi/norepi
- homovanillic acid (HMA)
- metanephrine
- normetaphrine
- vanillylmandelic acid (VMA)
