L06: Neurodiagnostics (Carrera) Flashcards
Common lab tests
pre and post-prandial bile acids ACTH stim. Dex supression test Urine protein: creatinine ratio paired insulin & glucose lvls (confirms insulinoma)
test for Leptomeningitis
eos on CSF
Latex Capsular Agglutination Test (LCAT)
used for infectious testing and treatment monitoring
-very sensitive and specific
CSF can be used to test for what common infectious agents?
Toxoplasma gondii
Neospora canis
Cryptococcus neoformans
Distemper virus (will have inclusion)
3 “regional” diseases
coccidioides
blastomycoses
hepatozoon canis
imaging modalities
Rads - not helpful for DIRECT visualization U/S Myelography CT and CT-myelography MRI
Rads can detect what bony lesions?
fractures
luxations
lysis
proliferation
disadvantages of rads
-will not see neural structures or discs (unless mineralized)
disadvantage of ultrasound
sound waves don’t penetrate bone
myelography
- survey spinal rads with intrathecal contrast injection
- repeat rads after contrast
most likely differential for extradural mass
disc
complications of myelography
- seizures assoc. with injection location and volume
- worsening neuro status due to chemical meningitis
- cardiac arrest
advant. of CT
- more sensitive than rads
- contrast arises from differences in tissue density
- rapid, inexpensive
- can be performed under sedation (don’t need to be anesthetized)
how does MRI work?
signal comes from protons which behave differently depending on the medium they’re in (water, tissue, tissue w/o water, tissue w/ metal, etc.)
- very sensitive for soft tissue resolution
- slow
- requires gen. anesthesia
when cannot use MRI?
pacemaker
region of interest has prior implants
main enzyme required to form CSF
carbonic anhydrase
where is CSF drained?
by arachnoid villi into venous sinuses (@ lower end of spinal column)
contraindication of collecting CSF
increased intracranial pressure
where is CSF usually harvested?
cisterna magna or cerebellomedullary cistern
2ary: lumbar puncture: subarachnoid space (smaller)
relationship between meningeal or ependymal involvement and CSF
greater the meningeal or ependymal involvement, the more abnormal the CSF
- helpful to rule out other diseases, but is rarely diagnostic alone
- VERY sensitive, not specific
when is lumbar puncture to get CSF indicated?
if closer to the lesion.
-higher rate of blood contamination!
2 cases when CSF CAN be diagnostic
bacteria in CSF
lots of lymphocytes (–>lymphoma)
what things are evaluated in CSF?
ultrafiltrate of plasma
color and clarity (normal = clear, colorless)
total nucleated cell count (N= mononuclear)
RBC count (N=0)
Protein conc.
xanthochromia
yellow tinge to CSF
- usually from prior hemorrhage
- can last up to 4 wks
turbid CSF can indicate:
increased cellularity
pleocytosis =
too many cells in the CSF
albuminocytologic dissociation
elevated CSF protein conc. with normal CSF cell count
types of neuromuscular testing
2-M Ab titer (for masticatory myositis)
Ach receptor Ab titer (for myasthenia gravis)
Electrodiagnostic testing
Muscle and nerve biopsies
Types of electrodiagnostic testing
Electromyography
Nerve conduction velocity (motor and sensory)
Repetitive Nerve Stimulation (MG suspect)
F-waves (to test integrity of nerve root)
Brainstem Auditory Evoked Response (to test for hearing)
Electroencephalography (to determine if brain waves are normal if we think animal is having seizure)
Electromyography: N vs. Abn.
- Healthy muscle electrically silent
- Abn. discharges can occur from metabolic, m. or nerve disease
- m. becomes very sensitive to circulating Ach when denervated and can have spontaneous discharges
Nerve Conduction Studies
- Evaluate conduction (motor and sensory nerve fx) by evaluating latency, amplitude, conduction velocity.
- looks at M wave
- affected by age, limb temp, limb length
amplitude proportional to:
of axons
conduction velocity proportional to:
degree of myelination
Which breeds more susceptible to congenital deafness?
Dalmatian**
Australian cattle dog, Aussie, Bull terrier, Catahoula, English cocker spaniel, English setter
