[10.12] Diagnostic Modalities in Neurology V2.2.pdf

Careful history and examination

What is the primary basis for a neurological diagnosis?

Ancillary testing

What corroborates the clinical impression but does not replace history and exam?

Fractures, changes in skull contour, infections in paranasal sinuses, and destructive lesions

What are four primary findings determined by skull radiography?

Rule out foreign body

What must be done before proceeding to further neuroimaging in trauma?

Information regarding the brain itself

What does a skull radiograph not reveal?

Non-linear and nondisplaced lines

How do fractures appear on a skull X-ray?

Degenerative, neoplastic, dysplastic, infectious, fractures, and spondylolisthesis

What are six types of lesions identified by spine radiography?

Spinal cord examination

For what specific type of examination is spine radiography not ideal?

Bone spurs

What degenerative bone changes present as neck pain or limitations in movement?

CT Scan

What is the diagnostic modality of choice for acute bleeding?

Subarachnoid, parenchymal, and epidural

What three types of hemorrhages are differentiated by CT?

Hypodense

How do ischemic strokes and brain tumors appear compared to normal parenchyma on a CT scan?

Bone window

What CT setting allows for the determination of bone anatomy and fractures?

Needle biopsies

CT scans can serve as a guide for what neurosurgical procedure?

Hounsfield Units

What does the scale of densities in CT scans use as a measurement unit?

-1000

What is the Hounsfield Unit value for air?

-30 to -120

What is the Hounsfield Unit range for fat?

0

What is the Hounsfield Unit value for water and CSF?

+23 to +34

What is the Hounsfield Unit range for white matter?

+32 to +41

What is the Hounsfield Unit range for gray matter?

56 to 76

What is the Hounsfield Unit range for acute blood?

+130

What is the Hounsfield Unit value for contrast?

+140 to +200

What is the Hounsfield Unit range for calcification?

+400 or more

What is the Hounsfield Unit value for bone?

Higher HU measurements

What indicates that a finding is bone or calcification rather than blood?

Metal

CT is safer than MRI when what is present inside the body?

CT scan

Which modality has a lower cost and shorter examination time?

15 to 30 seconds

How long does a cranial CT scan typically take?

30 minutes

How long does an MRI typically take?

Larger aperture

What feature of a CT machine reduces patient claustrophobia?

Hemorrhages

CT scan is more sensitive than MRI in detecting what?

Calcium deposits, fat, and bone

CT scan offers superior visualization of which three substances?

Life support

CT scans are accomplished more readily if the patient needs what system?

Radiation exposure

What is a primary consideration/risk of CT scans?

Alopecia, leukomalacia, and neoplasia

What are three potential clinical consequences of radiation overexposure?

Pregnancy

During what condition should a CT scan generally not be performed?

Shield above the abdomen

What precaution is taken if a CT scan is essential during pregnancy?

Contrast

What can lead to an increase in creatinine or kidney injury in CT studies?

30

Contrast is withheld if the GFR is less than what value?

Glioblastoma and metastasis

What two tumors are indications for a contrast study?

Meningitis, brain abscesses, tuberculoma, and cryptococcal infections

What four infections indicate a contrast study?

Angiogram

Vascular abnormalities are an indication for what type of contrast study?

Sulci

In a normal contrast CT scan, where does the contrast usually fill up?

Circle of Willis

Where is a subarachnoid hemorrhage located in the middle area of a CT scan?

Intraparenchymal hemorrhage

What white area in the middle of a CT scan can displace midline structures?

Biconvex or lentiform

What is the characteristic shape of an epidural hematoma?

Crescent

What is the characteristic shape of a subdural hematoma?

Chronic

In what clinical profile should you prioritize a contrast study already?

Surrounding edema and a rim in the contrast

What two findings help differentiate a tumor from a hemorrhage on CT?

Magnets and radio waves

What does MRI use to produce topographic images?

Horizontal tube known as the bore

What is the structure of the magnet in an MRI machine?

Tesla and Gauss

What are the two units of magnet strength used in MRI?

10000 gauss

How many gauss are in 1 tesla?

0.5 to 3 tesla

What is the common range of tesla for MRI machines?

Radio frequency waves

What do MRI coils transmit into the patient body?

Hydrogen protons

Before imaging, which particles in the body are aligned in random directions?

Superconducting magnet

What aligns all hydrogen protons in the same direction?

Alignment recovery time

What is measured by the scanner after radio waves are turned off to assemble an image?

T1 weighted

Which MRI sequence uses a short relaxation time and short echo time?

Less than 1000 msec

What is the TR value for T1 weighted images?

Less than 30 msec

What is the TE value for T1 weighted images?

T2 weighted

Which MRI sequence uses a long TR and long TE?

Greater than 2000 msec

What is the TR value for T2 weighted images?

Greater than 80 msec

What is the TE value for T2 weighted images?

Anatomic detail

What is T1 weighted MRI best for?

Pathology detection

What is T2 weighted MRI best for?

GRE or SWI

What sequence detects artifacts from local disturbances of the magnetic field due to metal?

Hypointense

How does blood and calcium appear in a GRE or SWI sequence?

Bleed

If a hypointense finding is seen in GRE, it is more likely to be a what than a tumor?

MRI Angiography

What modality uses time of flight images of the Circle of Willis?

Time of flight

What refers to still images conjured by MRI to show structures and flow without contrast?

Gray

How does brain tissue appear on a T1 MRI signal?

Black

How does air appear on T2 MRI?

White

How does CSF appear on T2 MRI?

White

How does fat appear on T1 MRI?

Black

How does calcium appear on T1 MRI?

Black

How does bone appear on T2 MRI?

White

How does extravasated blood appear on T1 MRI?

White

How does edema appear on T2 MRI?

Gray or white

How does a tumor appear on a T2 MRI signal?

Gadolinium

What contrast agent is used to enhance tumors or inflammation on MRI?

Pacemakers and defibrillators

In which patients is MRI contraindicated?

Posterior fossa

Lesions near the skull base are seen with greater clarity on MRI than CT in which area?

Age

MRI is able to approximate what characteristic of hemorrhages and infarcts?

DWI

In what MRI sequence is a hyperacute ICH bright?

Dark

How does chronic ICH appear on a GRE sequence?

Neurons

An EEG displays the electrical activity created by what cells?

Seizures

What is the most common indication for an EEG?

Localized brain lesion

EEG can find a slowing of activity to aid in the diagnosis of what?

Decreased sensorium

EEG is used for patients with what condition due to hypoglycemia or hyperglycemia?

Brain death

EEG is used to determine what clinical state?

Narcolepsy and sleep apnea

What two sleep disorders are diagnosed using EEG?

10 20 system

What is the name for the placement of EEG electrodes?

Nasion to inion

Between which two points is the distance measured as 10 percent in EEG?

Beta rhythm

Which rhythm is 13 to 30 Hz?

Alpha rhythm

Which rhythm is 8 to 12 Hz?

Theta rhythm

Which rhythm is 4 to 7 Hz?

Delta rhythm

Which rhythm is less than or equal to 3 Hz?

Alpha

What rhythm represents normal resting adult activity?

Drowsiness

What does the Theta rhythm represent?