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Small Animal Medicine > Neurodiagnostics > Flashcards

Neurodiagnostics Flashcards

1
Q

What imaging modalities are available for dogs and cats with CNS disease?

A
  • radiography
  • contrast radiography
  • ultrasonography
  • scintigraphy
  • CT
  • MRI**
  • thermography
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2
Q

What are the 5 major indications for radiography for diagnosing CNS disease?

A
  1. screening for bony lesions
  2. skull/vertebral tumors
  3. spinal fractures/luxations
  4. skull fractures
  5. diskospondylitis, vertebral physitis
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3
Q

How can image quality of radiographs be improved? How is it used to make diagnoses?

A

general anesthesia

  • prelude and screen before myelography and MRI
  • intraoperative implant positioning
  • NOT commonly used as a primary form of imaging
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4
Q

Although myelography is not commonly performed, what is considered some advantages? Disadvantages? What can it be combined with?

A

speed, availability, cost

side effects common, poor image quality compared to MRI

CT

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5
Q

What are the 2 ways of injecting contrast for myelography? What side effect is most common?

A
  1. cisternal
  2. lumbar - better quality images, safer

seizures, neurological deficits - most common in large dogs with neck issues

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6
Q

What is computed tomography? How does it work?

A

X-rays and computers used to create cross-sectional images with 3D reconstruction capabilities

different tissues will attenuate X-rays to different degrees, resulting in different linear attenuation coefficients (Hounsfield units)

  • bone = white (+1000 HU)
  • air = black (-1000 HU)
  • fluid = gray (0 HU)
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7
Q

How are CT images manipulated?

A
  • choose a central gray color to the HU of the tissue of interest = window level (WL)
  • choose number of shade allowed in the image = window width (WW)
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8
Q

What is the purpose of narrowing and widening WW of CT images?

A

NARROWING = soft tissue, like brain parenchyma, to improve contrast resolution (WL 35, WW 150)

WIDENING = tissues with good contrast already, like bone (WL 420, WW 1500)

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9
Q

What is the purpose of contrast CT?

A

administration of IV non-ionic iodinated contrast to highlight areas of BBB disruptions

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10
Q

What is the most common type of CT performed? How does this compare to conventional?

A

3rd generation - images acquired by rapid rotation of W-ray tube 360 degrees around the patient as the table moves = spiral-shaped continuous data set without any gaps

planar sections take of patient with gaps

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11
Q

What is CT especially helpful for diagnosing?

A
  • acute brain injuries
  • brain and spine imaging

(can be combined with myelography)

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12
Q

What are 4 advantages to CT imaging?

A
  1. fast
  2. less expensive to maintain than MRI
  3. good for imaging bone and acute hemorrhage
  4. 3D reconstruction capability
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13
Q

What are 3 disadvantages to CT imaging?

A
  1. ionizing radiation
  2. beam hardening artifact - low-energy photons are absorbed more than the high-energy photons, resulting in streaking and cupping
  3. less soft tissue detail compared to MRI
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14
Q

What are the 5 most common uses of CT imaging?

A
  1. acute brain injuries
  2. spinal trauma with fracture/luxation
  3. after hours emergency when MRI is not available
  4. pre-operative planning
  5. post-operative assessment of implants
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15
Q

What are the 2 major ways of obtaining a CSF sample? What can alter results?

A
  1. cisternal - C1-C2
  2. lumbar - L4-L5 larger, L5-L6 smaller
    (general anesthesia)

hemorrhage can increase cell count and protein levels

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16
Q

What are the 3 major indications for CSF evaluation?

A
  1. encephalopathies and myelopathies, especially is inflammatory causes are suspected
  2. meningitis suspected
  3. questionable imaging findigns
17
Q

What are the 3 contraindications for CSF taps?

A
  1. elevated ICP, especially with evidence of brain herniation on MRI
  2. general anesthesia risk - compromised older patients
  3. unlikely to contribute to diagnosis - obvious disk rupture on MRI
18
Q

What are the 3 anatomical landmarks for performing cisternal (cervical) CSF taps? What are the 5 steps?

A

external occipital protuberance, C2 spinous process, wings of C1

  1. palpate anatomic landmarks
  2. place patient in lateral recumbency with a flexed head
  3. keep patient parallel to table with a roll of paper towels under the neck
  4. use index finger to palpate the divot just cranial to the edge of C2 spinous process limit
  5. aim needle toward the angle of the mandible, slowly insert and check periodically
19
Q

What are the 6 steps for performing lumbar CSF taps?

A
  1. place patient in lateral recumbency with feet facing you
  2. push pelvic limbs cranially to open up the L4/L5 or L5/L6 spaces
  3. palpate caudal edge of L5 or L6 spinous process
  4. insert needle at 30-60 degree angle perpendicular to the spine
  5. legs and/or tail will twitch when entering the canal, indicating you’re in the right position
  6. advance needle to floor of the canal and withdraw styleet
20
Q

What are the normal WBC count and protein concentration of CSF? What is expected with blood contamination in dogs and cats?

A
  • WBC = <5 cells/uL
  • protein = <25 mg/dL cisternal, <45 mg/dL lumbar

DOGS = 500 RBCs to 1 WBC
CATS = 100 RBCs to 1 WBC
12000 RBCs required to elevate protein by 1 mg/dL

21
Q

When will CSF be visually turbid? What causes pleocytosis and albuminocytologic dissociation?

A

> 200 WBCs/uL

mixed suppurative, mononuclear inflammation

elevated protein with a low cell count

22
Q

When is ultrasonogaphy used for diagnosis and as a surgical tool for neurologic patients?

A

hydrocephalus, intracranial arachnoid cysts

locating intra-axial lesions

23
Q

What are the 2 most common uses of scintigraphy in neurologic patients?

A
  1. checking of PSS
  2. checking the patency of ventriculoperitoneal (VP) shunts used to correct hydrocephalus

(not commonly used)

24
Q

How does thermography work for neurologic patients? What are 5 potential uses?

A

sympathetic innervation to dermal vasculature is displayed with specialized cameras to show thermal patterns

  1. IVDD
  2. syringomyelia
  3. radiculopathy
  4. screening tool
  5. monitoring effects of therapy

Small Animal Medicine (52 decks)

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