Neurodiagnostics Flashcards
(30 cards)
Where is CSF produced?
Choroid plexus and leptomeningeal capillaries
How does CSF flow?
Lateral -> 3rd -> 4th -> central canal -> filum terminale
CSF collection
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
What equipment is used for a CSF tap?
1.5 to 3.5 inch needle, 20-22g
Stylet
Red top tube
Purple top tube
What are the landmarks for cisternal CSF collection?
Occipital protuberance
Spinous process of C2
How to perform lumbar CSF collection
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
Prior to collection
Be sure pt is deep enough Reevaluate the images and pts vital parameters - No ICP! Can remove 1mL per 5kg BW - 15gtt=1mL
T/F: CSF analysis often provides a definitive diagnosis
False; rarely
T/F: CSF analysis should be performed immediately after imaging
True
Interpret with imaging findings
How long after CSF collection do cells begin to degenerate?
30min
What are the components of a CSF analysis?
Gross physical characteristics (color, clarity)
Microprotein []
Cell counts
Cytology and differential count
What is seen in a normal cytology and differential count of CSF?
Predominately mononuclear cells - 60-70% small, well differentiated - 30-40% large phagocytes >2% N0 or eos May see ependymal cells in small clusters
Abnormal CSF
Albuminocytological dissociation Pleocytosis - Elevated WBC Other - Contamination - Myelin - Hemorrhage - Infection - Neoplasia - Degenerative diseases
What can rads be used for?
Bony tumors (need >50% bone loss to see)
Discospondylitis (advanced)
Displaced fx or luxations
Congenital vertebral anomalies
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
True; very important!
What are some of the advantages and disadvantages of rads?
Pros: low cost, readily available
Cons: poor soft tissue detail (unable to see CNS), low diagnostic yield in most neuro cases
What is myelography?
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
T/F: CSF MUST be collected prior to injecting contrast agent
True; agent will cause abnormal CSF readings for over a week
Myelography patterns
Normal
Extradural - something outside pushing on cord
Intradural/extramedullary - subarachnoid space
Intramedullary - within parenchyma, causing swelling cranial and caudal to lesion
What are the pros and cons of myelography?
Pros: Easily and rapidly visualize SC over rads, low cost Cons: Invasive - Meningitis - Seizures - Deterioration of signs
Not gold standard, not done often
CT
Images obtained in transverse plane and then reformatted to other planes
Numbers applied to tissues
Can obtained without contrast
- IV contrast
- Post myelography
What can be ID’ed with CT?
IVDD - Chondrodystrophic (mineralized NP) Lumbosacral Disc Dz Neoplasia Spinal trauma
Pros and cons of CT
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
MRI
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
