Lecture: Neurodiagnostics

Question 1

Lab testing

Answer 1

• Fasted pre- and post -prandial bile acids
• ACTH stim test => cushings
• Dexamethasone suppression test => addisons
• Urine protein: creatinine ration (UPC) => glomerulus….?
• Paired insulin & glucose lesvels => Low BG, high Insulin = insulinoma

Question 2

Infectious testing:

Peripheral blood or serum

Answer 2

• Cryptococcus neoformans
• Endemic opportunistic fungus
• Respiratory entry, but neurotropic organism
• Latex Capsular Agglutination test (LCAT)
  
  • sensitive and specific
• Leptomeningitis
  
  • Eosinophils on CSF

Question 3

Infectious testing

Cerebrospinal fluid

Answer 3

• Toxoplasma gondii
• Neospora canis
• cryptococcus neoformans
• distemper virus (b/c of vaccines)

Question 4

Regional diseases

1. Coccidioides
2. Blastomyces
3. Hepatozoon canis

Answer 4

1. Coccidioides => Arizona
2. Blastomycoses => Ohio River Valley, +
3. Hepatozoon canis => Texas Gulf Coast

Question 5

Radiographs

Answer 5

• Anatomy => Normal?
• Boney lesions
  
  • Fractures
  • Luxations
  • Lysis
  • Proliferation
• Skull rads low yield
• won’t see neural structures
• won’t see discs unless mineralized

Question 6

Ultrasound

Answer 6

• Persistent fontanelle
• Sounds waves don’t penetrate bone

Question 7

Myelography

Answer 7

• Survey spinal radiographs
• Intrathecal injection
  
  • Cisternal or lumbar injections
  • Non-ionic iodinated contrast material

Question 8

Myelography complications

Answer 8

• Seizures
• Worsening neurological status
• Cardiac arrest

Question 9

Computed Tomography

Answer 9

• More sensitive than traditional rads
• rapid
• inexpensive
• can be done with sedation

Question 10

Magnetic resonance imaging

Answer 10

• signal comes from protons
• proton looks different depending on environment
• Sensitive for soft tissue resolution
• Slow
  
  • brain: < 45 minutes
  • T3-L3 study < 1 hour
• Requires general anesthesia
  
  • loud
  • no tolerance for motion

Question 11

MRI limitations

Answer 11

• can’t use with pacemaker
• can’t use on implants

Question 12

CSF collection

Considerations

Contraindications

Answer 12

• Considerations
  
  • Competency
  • Rapid degradation of cells
  • Requires general anesthesia
  • Usually more helpful to rule out other diseases
  • Very sensitive, not specific
• Contraindications
  
  • Increased intracrania pressure

Question 13

CSF is almost

Answer 13

• water (ultrafiltrate of plasma)

Question 14

CSF

Color and Clarity

Answer 14

• Normal: clear and colorless
• Xanthochromia
  
  • yellow tinge from prior hemorrhage (>10 hours)
  • Can last up to 10 weeks
• Turbidity
  
  • increased cellularity

Question 15

CSF

Cell counts

Answer 15

• Total nucleated cell count
  
  • < 5/microL, mononuclear
• RBC count
  
  • 0

*Pleocytosis?!

Question 16

Pleocytosis

Answer 16

Lots of cells

Question 17

CSF

Protein level

Albuminocytologic dissociation

Answer 17

• Protein level
  
  • Cisternal < 25 mg/dL
  • Lumbar < 40 mg/dL
• Albuminocytologic dissociation
  
  • elevated CSF protein concentration
  • normal CSF cell count

Question 18

Neuromuscular testing

Answer 18

• 2-M antibody titer
  
  • masticatory myositis
  • Serum sample
• Acetylcholine receptor antibody titer
  
  • Myasthenia gravis
  • Serum sample
• Electrodiagnostic testing
• Muscle and nerve biopsies

Question 19

Electrodiagnostic testing

Answer 19

• Electromyography
• Nerve Conduction Velocity
  
  • motor and sensory
• Repetitive Nerve stimulation
  
  • MG suspect
• F-waves
  
  • nerve root
• Brainstem Auditory Evoked Response
• Electroencephalography

Question 20

Electromyography

Answer 20

• Healthy muscle is electrically silent
• Abnormal discharges from
  
  • metabolic muscle
  • nerve disease
• When denervated, muscle becomes very sensitive to circulating acetylcholine

Question 21

BAER test

Answer 21

• Congenital deafness
• Determination of brain death
  
  • only in dogs with verified hearing abiilty