Neurodiagnostics

Question 1

Where is CSF produced?

Answer 1

Choroid plexus and leptomeningeal capillaries

Question 2

How does CSF flow?

Answer 2

Lateral -> 3rd -> 4th -> central canal -> filum terminale

Question 3

CSF collection

Answer 3

Cerebellomedullary cistern
Lumbar
- L4-5, L5-6, or L6-7 (caudal in smaller pt)
- Collect CSF and save prior to myelogram
High risk if done incorrectly

Question 4

What equipment is used for a CSF tap?

Answer 4

1.5 to 3.5 inch needle, 20-22g
Stylet
Red top tube
Purple top tube

Question 5

What are the landmarks for cisternal CSF collection?

Answer 5

Occipital protuberance

Spinous process of C2

Question 6

How to perform lumbar CSF collection

Answer 6

Move legs cranial to open the interarcuate space
Insert needle lateral to midline at 30-60 degrees perpendicular to spine
Will likely get twitch
Advance needle to the floor of the spine then withdraw stylet

Question 7

Prior to collection

Answer 7

Be sure pt is deep enough
Reevaluate the images and pts vital parameters
- No ICP!
Can remove 1mL per 5kg BW
- 15gtt=1mL

Question 8

T/F: CSF analysis often provides a definitive diagnosis

Answer 8

False; rarely

Question 9

T/F: CSF analysis should be performed immediately after imaging

Answer 9

True

Interpret with imaging findings

Question 10

How long after CSF collection do cells begin to degenerate?

Answer 10

30min

Question 11

What are the components of a CSF analysis?

Answer 11

Gross physical characteristics (color, clarity)
Microprotein []
Cell counts
Cytology and differential count

Question 12

What is seen in a normal cytology and differential count of CSF?

Answer 12

Predominately mononuclear cells
- 60-70% small, well differentiated
- 30-40% large phagocytes
>2% N0 or eos
May see ependymal cells in small clusters

Question 13

Abnormal CSF

Answer 13

Albuminocytological dissociation
Pleocytosis
- Elevated WBC
Other
- Contamination
- Myelin
- Hemorrhage
- Infection
- Neoplasia
- Degenerative diseases

Question 14

What can rads be used for?

Answer 14

Bony tumors (need >50% bone loss to see)
Discospondylitis (advanced)
Displaced fx or luxations
Congenital vertebral anomalies

Question 15

T/F: in pt with congenital abnormalities in bones of spinal canal, the neck should not be ventroflexed for fear of impinging the spinal cord

Answer 15

True; very important!

Question 16

What are some of the advantages and disadvantages of rads?

Answer 16

Pros: low cost, readily available
Cons: poor soft tissue detail (unable to see CNS), low diagnostic yield in most neuro cases

Question 17

What is myelography?

Answer 17

Spinal rads or CT obtained following injection of radiopaque contrast agent into subarachnoid space

Non-ionic iodinated, water soluble contrast agents used

• Iohexol and iopamidol
• Administer slowly!
• 2-3mL/min

Not done often

Question 18

T/F: CSF MUST be collected prior to injecting contrast agent

Answer 18

True; agent will cause abnormal CSF readings for over a week

Question 19

Myelography patterns

Answer 19

Normal
Extradural - something outside pushing on cord
Intradural/extramedullary - subarachnoid space
Intramedullary - within parenchyma, causing swelling cranial and caudal to lesion

Question 20

What are the pros and cons of myelography?

Answer 20

Pros: Easily and rapidly visualize SC over rads, low cost
Cons: Invasive
- Meningitis
- Seizures
- Deterioration of signs

Not gold standard, not done often

Question 21

CT

Answer 21

Images obtained in transverse plane and then reformatted to other planes

Numbers applied to tissues

Can obtained without contrast

• IV contrast
• Post myelography

Question 22

What can be ID’ed with CT?

Answer 22

IVDD
- Chondrodystrophic (mineralized NP)
Lumbosacral Disc Dz
Neoplasia
Spinal trauma

Question 23

Pros and cons of CT

Answer 23

Pros:
Superior soft tissue contrast
Non contrast can be performed with sedation only
Less cost than MRI
More rapid than MRI
Bone and hemorrhage better visualized
Post imaging ability to change window settings and form 3D images
Cons:
Exposure to iodizing radiation
Limited soft tissue detail and can miss lesions in CNS
Imaging artifacts within the brainstem
More expensive and less available than rads

Question 24

MRI

Answer 24

Modality of choice for most neuro Dz
Hydrogen ions spin around axes and magnetic field rearranges the spin
Tesla = strength of field
Translates differences of tissue into image contrast

Question 25

MRI features of increased ICP

Answer 25

Subtentorial herniation

Foramen magnum herniation

Question 26

MRI Evaluation

Answer 26

Lesion: number, shape, location, margins
Signal intensity relative to normal gray matter
Contrast enhancement pattern
Contrast enhancement intensity
Mass effect
Parenchymal distribution
Meningeal contact
Meningeal enhancement

Hyper or hypointense

Question 27

MRI pros and cons

Answer 27

Pros:
Superior soft tissue contrast
Best for visualizing neuro pt
No iodizing radiation
Cons:
More expensive
Requires general anesthesia

Question 28

T1 is great for looking at __ while T2 is good at looking at ___ and ___

Answer 28

Fat (appears bright)

Fat and fluid

Question 29

What is FLAIR?

Answer 29

Suppressing free fluid but bound fluid becomes bright

Great for looking at edema

Question 30

T2*

Answer 30

Susceptibility imaging

Good for looking at hemorrhage (appears dark)