Neuro Diagnostic Testing- lec 3

what are indications for lumbar puncture (LP)?

infx (meningitis, ecephalitis), subarachnoid hemorrhage, dementia, malignancy, MS

What are contraindications for lumbar puncture (LP)?

• suspected intracranial mass or elevated ICP (risk of herniation, check for papilledema & get head CT)

• infx at site of puncture

• coagulopathy

• brain abscess

• lack of pt cooperation

In what patients would you obtain a CT scan prior to a lumbar puncture?

• over 60

• immunocompromised

• known CNS lesion

• seizure w/in 1 week

• abnormal level of consciousness

• focal findings on neuro exam

• papilledema seen on PE w/ clinical suspicion of elevated ICP

What is the usual site for LP?

L3-4 or L4-5 interspace at level of posterior iliac crests to avoid spinal cord which terminates at L1-2

needle through longitudinal ligament & into subarachnoid space

What is the order of tube collection in LP?

tube 1: glucose, protein, lactate

tube 2: gram stain, bacterial and viral cultures

tube 3: cell count and differential

tube 4: held in reserve

What test is a noninvasive record of brains’ electrical activity/brain waves obtained from electrodes placed on scalp?

electroencephalography (EEG)

What are indications for EEGs?

• seizure

• brain death

• metabolic encephalopathy

• multifocal brain lesions

• dementia

• creutzfeldt-jakob dz

• herpes simplex encephalitis

• psychogenic coma

what are contraindications to EEGs?

none

What test records intrinsic electrical activity w/in a muscle to detect muscles w/ damaged nerve supplies?

electromyography (EMG)

What test stimulates a nerve at one point and records the response, measuring how fast the electrical impulse travels through them?

nerve conduction studies (NCV)

What tests are used for evaluation of neuromuscular disorders, peripheral neuropathy or nerve entrapment (conditions that cause pain, numbness, tingling, muscle weakness)?

EMG and NCV

What imaging study has 200x the radiation exposure of an average CXR?

CT scans

Children who have 2-3 CT scans are _____ as likely to develop a brain tumor or leukemia in the decade following their first scan.

3x

What are indications for CT scans?

stroke or subarachnoid hemorrhage (STAT non contrast), tumor (+/- contrast), trauma, dementia

what are contraindications to CT scans?

inability to lie flat/still, dye allergy or kidney dz (consider non contrast or pre-medicate)

What test measures resonance of protons, has no radiation, and is better for brain, spinal cord, and soft tissue?

MRI

What test can detect hemorrhages earlier?

MRI

What test is more sensitive in detecting atrophy in dementia?

MRI

What test is best for visualization of acoustic neuromas and pituitary tumors, sensitive in detecting edema and shows white matter lesions of demyelinating disorders (MS)?

MRI

What are disadvantages to MRIs?

• loud machine, tight space

• artifacts due to pt movement

• takes 45-90 min to complete, not for unstable pts

• no surgical clips or pacemakers

• inability to bring ferrous objects near magnet

• expensive

What test is a “functional” imaging study that demonstrates perfusion and metabolic activity, differentiates types of movement disorders, and is done prior to epilepsy surgery to identify where seizures start in brain?

PET scan

What test is an MRI technique to image blood flow and rapidly detects vascular stenosis, occlusion in acute stroke (espat carotid artery bifurcation) & aneurysms or bleeds in circle of willis?

magnetic resonance angiography (MRA)

What test is NOT helpful for soft tissue injury and disc herniations and should be done with MRI instead?

Spinal Xray

What test is used for initial evaluation of trauma, subluxation, DJD, and new low back pain?

spinal xray

What is bony disease seen better on?

CT

What test is an xray exam of the spinal canal using contrast dye performed under fluoroscopy and is used to display spinal cord, canal, nerve roots for suspected compression, injury, cyst, or tumors?

myelography

What tests can be used as an alternative for patients who cannot have an MRI?

myelography followed by CT

What test is a non-invasive evaluation of extracranial vessels in TIAs/strokes and measures velocity of blood flow through carotid artery up to the bifurcation?

carotid ultrasound

What should be done for brain tumors and degenerative dz when imaging studies are not helpful?

brain bx

what bx evaluates weakness?

muscle bx

what bx evaluates neuropathy?

nerve bx

what bx should be done for suspected giant cell arteritis/temporal arteritis?

artery bx