Neuro diagnostics

Question 1

radiographs

Answer 1

• fasted pre- and post-prandial bile acids
• ACTH stim test
• Dexamethasone suppression test
• urine protein:creatinine ratio
• paired insulin and glucose levels

Question 2

infectious testing: peripheral blood or serum

Answer 2

• Cryptococcus neoformans (cats)
• endemic opportunistic fungus
• respiratory entry, but neurotropic organism
• Latex Capsular Agglutination Test (LCAT)-very sensitive and specific
• Leptomeningitis-eosinophils on CSF

Question 3

infectious testing: CSF

Answer 3

• toxoplasma gondii
• neospora canis
• cryptococcus neoformans
• distemper virus

Question 4

infectious testing: regional diseases

Answer 4

Coccidioides, Blastomycoses, Hepatozoon…

Question 5

infectious testing: PCR panels

Answer 5

respiratory (cats), neurological (dogs)…

Question 6

radiographs

Answer 6

• survey analysis
• other systemic disease
• anatomy
• boney lesions
• will NOT see neural structures
• will NOT see discs (unless mineralized)

Question 7

ultrasound

Answer 7

• sound waves do NOT penetrate bone
• persistent fontanelle-a window

Question 8

myelography

Answer 8

• survey spinal rads
• intrathecal injection
• repeat radiographic series
• complications
  
  • arrest
  • seizures (higher if >20 kgs or cisternal)
  • worsening neuro status (chemical meningitis)
• non-ionic, iodinated, low osmolality

Question 9

computed tomography

Answer 9

• more sensitive than conventional rads
• contrast arises from different degrees of attenuation of x-rays (tissue density)
• rapid, inexpensive, can be performed under sedation

Question 10

magnetic resonance imaging

Answer 10

• signal comes from protons which behave differently depending on environment
• very esnsitive for soft tissue resolution
• slow
• requires general anesthesia
• can’t use with pacemaker or region of interest has prior implants
• gadolinium-based contrast, paramagnetic

Question 11

when to MRI

Answer 11

• most brain diseases
• intramedullary spinal diseases, tumors
• non-chondrodystrophoid or Type II IVDD

Question 12

when to CT

Answer 12

• fractures, boney disease
• mineralized, Type I IVDD
• poor for caudal fossa and lumbosacral area

Question 13

CSF

Answer 13

• bathes brain and spinal cord
• produced by choroid plexus
• carbonic anhydrase
• drained by arachnoid villi into venous sinuses
• ultrafiltrate of plasma (almost water)

Question 14

CSF tap

Answer 14

• considerations
  
  • competency
  • requires general anesthesia
  • rapid degradation of cells
• very sensitive, not specific
• greater meningeal or ependymal involvement, the more abnormal CSF

Question 15

CSF tap contraindications

Answer 15

• increased intracranial pressure
• lack of comfort/competency with procedure

Question 16

CSF collection-cisternal puncture

Answer 16

(dog, cat, horse…)

• cerebellomedullary cistern, cisterna magna
• landmarks
  
  • occiput
  • spine of C2
  • wings of C1
• spinal needle-stylet

Question 17

CSF collection-lumbar puncture

Answer 17

• subarachnoid space
  
  • L5-6 in dog
  • L6-7 or L7-S1 in cat
• higher rate of blood contamination
• indicated if closer to lesion

Question 18

CSF analysis

Answer 18

• color and clarity (clear and colorless)
• total nucleated cell count (<5 uL, mononuclear)
• red blood cell count (0)
• protein concentration (cisternal <25 mg/dL, lumbar <40 mg/dL)
• rarely gives definitive diagnosis
• must be interpreted in light of other findings

Question 19

xanthochromia

Answer 19

• yellow tinge
• usually from prior hemorrhage (>10h)
• can last up to 4 weeks

Question 20

turbidity

Answer 20

usually from increased cellularity

Question 21

pleocytosis

Answer 21

too many cells

Question 22

albuminocytologic dissociation

Answer 22

elevated CSF protein concentration in the face of a normal CSF cell count

Question 23

neuromuscular testing

Answer 23

• 2-M antibody titer
  
  • masticatory myositis
  • serum sample
• Acetylcholine receptor antibody titer
  
  • Myasthenia gravis
  • serum sample
• electrodiagnostic testing
• muscle and nerve biopsies

Question 24

electrodiagnostic testing

Answer 24

• electromyography
• nerve conduction velocity: motor and sensory
• F-waves: nerve root
• brainstem auditory evoked response
• repetitive nerve stimulation: MG suspect
• electroencephalography

Question 25

electromyography

Answer 25

• healthy muscle is electrically silent
• abnormal discharges can occur from metabolic, muscle or nerve disease
• when denervated, muscle becomes very sensitive to circulating ACh
• insertional acitivty
• spontaneous discharges

Question 26

nerve conduction studies

Answer 26

• evaluate conduction (speed and strength)
  
  • motor and sensory
  • latency
  • amplitude (number of axons)
  • velocity (degree of myelination)
• M wave
• affected by age, limb temp, limb length

Question 27

F wave

Answer 27

• evaluate the nerve root, only motor
• both orthodromic and antidromic stimulus
• orthodromic stimulus reaches muscle fiber, it elicits a strong response indicative of muscle contraction (M wave)
• antidromic stimulus evokes a small proporition of the muscle fibers causing a small, second CMAP called the F wave

Question 28

BAER

Answer 28

• measure of conductive, sensorineural hearing and brainstem function
• up to 7 waves
• skull thickness and muscle mass reduce amplitudes
• I, II, V reliable
• congenital deafness