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Specialty Boards Prep > Deck 7 > Flashcards

Deck 7 Flashcards

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1
Q

Explain T1 and T2 relaxation. What are the alternative names?

A

T1 — time taken for the proton to move from the transverse plane to the longitudinal plane; spin-lattice

T2 — time taken for the protons to lose coherence; spin-spin

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2
Q

Explain the difference between T2 relaxation and T2* relaxation.

A

T2 — loss of coherence due to the tissues themselves

T2* — loss of coherence due to the tissues AND due to external / magnetic field inhomogeneities

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3
Q

What is the purpose of the 180 RF pulse applied during spin echo sequences? When is it applied?

A

It helps reverse the effects of external magnetic field inhomogeneities.

It is applied halfway way between the initial 90 degree RF pulse and the TE (1/2 TE).

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4
Q

What type of pulse is this? Is the inversion time long or short?

A

FLAIR
Long inversion time

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5
Q

Identify this pulse sequence. Is the inversion time long or short?

A

STIR — short inversion time

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6
Q

What are the main differences in acquiring a GRE image compared to a SE image? What does this translate to in regards to the actual acquisition?

A

GRE images don’t use a 180 RF pulse, but instead use dual phasing and rephasing gradients. GRE images also utilize smaller flip angles than the standard 90 RF pulses in SE sequences.

This translates to faster sequences (TR is shorter), and images that are susceptible to the external / magnetic field inhomogeneities.

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7
Q

Fill in the blanks

A
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8
Q

In what direction is motion artifact? Chemical shift artifact?

A

Motion artifact is in the phase encoding direction. Chemical shift artifact is in the frequency encoding direction.

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9
Q

Explain what causes flow artifacts on MRI?

What can you do to correct for these artifacts?

A

Flow — protons in fast moving fluids (ie large blood vessels, turbulent CSF) are exposed to one, but not both, of the 90 and 180 RF pulses. Thus, they don’t generate signal in the transverse plane, and this registers as low signal, and you get a black spot. (This is called time of flight flow)

Can be corrected for by increasing slice thickness (protons are less likely to leave the excited slice if it is bigger) and can decrease TE (less time between the 90 and 180 RF pulses). You can also place a saturation bands as well.

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10
Q

What is entry zone phenomenon? What type of sequences is this artifact most common in? What is this concept the basis of?

A

This occurs when un-saturated protons (those with their full longitudinal magnetization vector) enter the selected slice, typically within a blood vessel. This allows these protons to generate more signal, and shows up as hyperintense.

More common in GRE sequences, where the TR is shorter, and the protons aren’t allowed to recover their full longitudinal magnetization vector between TRs (aka saturation).

This is the basis of magnetic angiography imaging.

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11
Q

What is the basis behind chemical shift artifact (of the first kind)?

Where does chemical shift artifact occur?

What are some things that can be done to correct for it?

A

The basis is that the protons in fat precess slightly slower than the protons in water.

Occurs at fat / water interfaces

Switch the frequency and phase encoding directions, increase receiver bandwidth, or use fat saturation techniques

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12
Q

What are three ways to address / verify partial volume averaging effects?

A

Decrease slice thickness
Look for the lesion in other planes
Verify accuracy of lesions using a FLAIR sequence

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13
Q

True or false — gadolinium lengthens T1 relaxation.

A

False — gadolinium shortens T1 relaxation — this means that tissues with gadolinium in them will regain their longitudinal magnetization vector faster, and have more signal to generate when flipped back into the transverse plane.

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14
Q

What breeds of dog are predisposed to this?

A

Staffordshire Bull Terriers and Miniature schnauzers are predisposed to corpus callosum agenesis.

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15
Q

How can you distinguish between epidural and subdural hemorrhages?

A

Shape — epidural is biconvex, while subdural is crescent shaped

Additionally, epidural hemorrhages can cross dural folds (falx and tentorium) but can’t cross suture lines, while subdural hemorrhages can’t cross dural folds but can cross suture lines.

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16
Q

Label the image.

A
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17
Q

What is bigger — the brainstem or the cerebellum?

What is the ratio used to identify cerebellar atrophy?

A

The cerebellum is bigger.

Brainstem to cerebellar area (on a mid-sagittal T2W image)

The cutoff of this ratio is 89%, with anything greater than this indicating cerebellar atrophy.

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18
Q

What percentage of choroid plexus carcinomas have imaging features of intra-ventricular / sub-arachnoid metastasis?

What percentage have detectable malignancy on CSF analysis?

A

35%

Up to 50%

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19
Q

What is the normal shape of the spinal cord at C7-T1?

A

Trapezoid

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20
Q

What percentage of dogs with FCEM have contrast enhancement? When it is most likely to detect contrast enhancement?

A

12%

5-7 days later

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21
Q

Per DaCosta, what is the T2W hyper-intensity of the disc associated with?

A

Proteoglycan content (not water concentration)

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22
Q

What are three things that the presence of spinal cord signal changes were associated with in dogs with wobblers?

A
  • chronicity of clinical signs
  • presence of neurologic deficits
  • more significant spinal cord compression
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23
Q

What is the toxic sphingolipid that accumulated in globoid cell leukodystrophy? What cell type is this byproduct toxin to?

A

Psychosine - toxic to oligodendrocytes and Schwann cells

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24
Q

Palpable enlargement of what nerves are common in fucosidosis?

A

Ulnar and vagus nerves

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25
What is the toxic material that is accumulated within the human and canine brains associated with cognitive dysfunction?
Beta-amyloid, forms plaques; the amount of plaque correlates with the severity of clinical signs
26
How much has omeprazole been shown to reduce the production of CSF in dogs?
26%
27
What portions of the skull and neck are formed together? What is the clinical significance of this?
Occipital bone, C1 and C2 Abnormal development of this unit explains the occurrence of craniocervical junction abnormalities
28
Per Dewey, the narrowing of which foramen could contribute to the development of intracranial hypertension and syringomyelia in COMS patients? What vessel leaves this foramen?
Jugular foramen — exit of the sigmoid sinus / internal jugular vein is at this foramen, which is a major way that venous blood leaves the cranial vault
29
What is the correlation between CSF TNCCs and COMs patients?
Higher TNCCs occur in dogs with syringes than those without, and that syrinx size is proportional to a higher TNCC.
30
What is the mechanism of action for gabapentin / pregabalin when treating dogs for syringomyelia pain?
It binds to the alpha 2 delta-1 subunit of voltage gated calcium channels within the dorsal grey horn of the spinal cord.
31
Which one — dermoid or epidermoid cyst — is T1 hyper-intense? What sequence can be used to differentiate these cysts from a SCAF / arachnoid diverticula?
Dermoid cysts are T1 hyper-intense FLAIR sequences — suppression will occur for arachnoid diverticula but not cysts.
32
What are the two main neurotransmitter imbalances associated with hepatic encephalopathy?
Increased GABA tone Decreased glutamine tone
33
Deposition of what substance in the lentiform nuclei accounts for the T1 hyperintensity?
Manganese
34
Define gliomatosis cerebri and glioblastoma multiforme.
Gliamotosis cerebri = “diffuse” glioma, involving at least three lobes and often both hemispheres Glioblastoma multiforme = grade IV astrocytoma
35
Most common presenting complaint in dogs with brain tumors? Cats?
Dogs — seizures Cats — behavioral changes
36
What two findings on CSF analysis can help differentiate between a choroid plexus tumor and choroid plexus carcinoma?
Visualization of metastatic cells on cytologic analysis, and a protein content higher than 80 mg/dL are consistent with a carcinoma.
37
True or false: brain tumor location is important for prognosis.
True — in a study evaluating palliative care for dogs with all type of brain masses, dogs with supratentorial masses lived ~5-6 months, whereas those with infratentorial masses only lived a month.
38
MST for dogs with meningiomas treated using an ultrasonic aspirator during surgery?
~1200 days
39
What is a common receptor located in canine meningiomas?
Progesterone
40
What breed of dog and what breed of cat are apparently predisposed to developing CNS cryptococcosis?
American Cocker spaniel Siamese
41
What two anti-fungal medications are best at crossing the blood brain barrier?
Flucytosine and fluconazole
42
What are the three neurological presentations of canine distemper virus?
- Young dogs develop a non-inflammatory grey-matter disease, resulting in seizures & other signs of forebrain dysfunction. - Middle aged dogs develop an inflammatory demyelinating white matter disease affecting brainstem, cerebellum and spinal cord and associated dysfunction (often cerebellovestibular) - Older dogs can get “old dog encephalitis” characterized by forebrain dysfunction (behavioral changes, visual deficits and circling)
43
What is the route by which cats and dogs are exposed to pseudorabies virus? What are some of the common clinical signs?
Ingestion of pork It’s classically per-acute in the onset of clinical signs. They include seizures, obtundation, GI signs, and intense itching of the head/neck/shoulders.
44
What is the mechanism of action of cytarabine?
Nucleoside analog that crosses the BBB, and inserts itself into DNA molecules and causes premature chain termination in mitotically active cells.
45
What two breeds of dog are classically associated with NME? NLE?
NME - pug and maltese NLE - yorkies and frenchies
46
What percent of a pleocytosis needs to be met to consider a pleocytosis as eosinophilic?
10%
47
What are three reasons why a thalamic / midbrain stroke might result in vestibular dysfunction?
- interruption of the ascending pathways from the cerebellum (cerebrocerebellar & spinocerebellar pathways) / vestibular nuclei - interruption of the medial longitudinal fasciculus - damage to the medial geniculate nucleus / brachium of the caudal colliculus
48
Why does systemic hypotension potentiate increased intracranial pressure in traumatic brain injury patients?
It has to do with cerebral autoregulation. Even the injured brain will try to maintain constant, steady blood flow to the brain. To do so, intracranial blood vessels will either dilate or constrict in response to systemic blood pressure alterations (constrict when SBP is high, and dilate when SBP is low). Thus, if you have a hypotensive TBI patient, the blood vessels in the cranial vault will dilate in response to this, increasing how much blood is flowing into the brain, and thus increasing intracranial pressure.
49
What are the five proposed mechanisms of action for mannitol? Which one is presumed to work this quickest?
- decreases blood viscosity, which causes reflex vasoconstriction of blood vessels (works the quickest) AND increases perfusion by decreasing RBC membrane rigidity - decreased CSF production from choroid plexus - free-radical scavenging - removal of edema via osmotic effects
50
What are the three categories assessed in the modified Glasgow coma scale?
- motor activity - brainstem reflexes - level of consciousness
51
What is the definition of a refractory epileptic patient? What percent of epileptic dogs are refractory? What percent of epileptic dogs experience complete seizure control?
Refractory = appropriate serum concentrations of two anti-convulsants with poor seizure control 25-30% are refractory 15% experience seizure control
52
What is the term for when a partial seizure is associated with an impaired consciousness?
Complex focal seizure
53
What is the difference between the prodrome and the aura?
Prodrome — longer (hours to days), normal EEG Aura — quite short, abnormal EEG Abnormal / anxious behavior is characteristic of both of these.
54
What are some of the proposed MOAs of phenobarbital? What is the MOA for bromide? What is the MOA for zonisamide? What is the MOA for levetiracetam?
Pheno - Increasing neuronal responsiveness to GABA, anti-glutamate effects and decreasing calcium flow into neurons Bromide - neuronal hyperpolarization via traversing the chloride channels for which bromide has a 4x higher affinity for Zonisamide - blocking T-type calcium channels, blocking voltage gated sodium channels, binding to GABA mediated chloride channels, inhibiting glutamate release, free radical scavenging Levetiracetam- binding to synaptic vesicle protein 2A, unknown
55
What are the effects phenobarbital has on thyroid function testing?
Decreased total and free T4, and increases TSH
56
True or false — the target serum level for KBr is less when a patient is also on phenobarbital.
True — when on phenobarbital as well, the target serum level is 1-2
57
True or false — potassium bromide can result in pruritus
True
58
What is the electromyographic characteristic of a tremor?
Rhythmic bursts of motor neuron activity in opposing muscle groups
59
What is the pathophysiology of Scottie cramp and Spike’s disease (epileptoid cramping in Border terriers)?
Deficiency in serotonin, an inhibitory neurotransmitter
60
What is the age of onset of clinical signs in Lafora’s disease in wire-haired miniature Dachshunds? What are the main clinical signs? What is the associated genetic mutation?
6-13 years of age Myoclonic seizures in response to various stimuli Mutation of the EPMB2 gene encoding for the protein malin
61
What is an alternative name to the medial vestibulospinal tract?
The spinal portion of the medial longitudinal fasciculus
62
True or false — the rate of the nystagmus can be useful in differentiating between central and peripheral causes of vestibular dysfunction.
Per Dewey, this is true. Peripheral often has a higher rate than central.
63
Most common CNS fungal infection in dogs?
Cryptococcus
64
Metronidazole toxicity is thought to occur secondary to inhibition of this neurotransmitter?
GABA
65
Which tract is the medial cuneate nucleus associated with? Lateral?
Medial = fasciculus cuneate associated with conscious GP information Lateral = spinocuneocerebellar associated with subconscious GP information
66
Efferent fibers leaving the rostral cerebellar peduncle influence which UMN tracts? Caudal peduncle?
Rostral peduncle — rubrospinal and corticospinal Caudal peduncle — vestibulospinal And I think both influence both reticulospinal tracts
67
Lesions of the vermis / fastigial nuclei will result in what classic sign of cerebellar disease? Lateral hemisphere?
Vermal / fastigial = titubation (spinocerebellum) Lateral hemisphere / dentate = intention tremor (cerebrocerebellum)
68
What is one of the primary clinical signs in dogs with neuroaxonal dystrophy?
Cerebellar dysfunction
69
Which type of glioma is more likely to have surface contact?
Oligodendroglioma
70
What medication can be used to treat the orthostatic tremor of young Great Danes? What is the frequency of the muscle tremors?
Phenobarbital 13-16 (or up to 21) Hz
71
What is the main pathology associated with Wobblers?
Vertebral canal stenosis — can be absolute or relative (predisposing patient to myelopathy in the future)
72
What is this a picture of? What other locations can be affected? What are the main clinical signs?
Rottweiler leukoencephalomyelopathy Optic nerves / tracts, brainstem and cerebellum Progressive tetraparesis (reflective of cervical myelopathy) in young adult Rotties
73
What percent of CKCS have asymptomatic syringomyelia?
70%
74
What is the pathogenesis of dermoid sinuses? What are the classifications? Predisposed breed?
Incomplete separation of the ectoderm from the neuroderm Type 1 — broad connection to the supraspinous or nuchal ligament Type 2— broad start with narrow connection to the supraspinous or nuchal ligament Type 3 — more superficial, no obvious connection with the vertebral column Type 4 — broad extension into the vertebral canal with attachment to the dura Type 5 — true “dermoid cyst”’ with no deeper connection or skin opening Type 6 — broad connection initially to supraspinous / nuchal ligament, with narrow connection to dura Rhodesian ridgeback
75
What breed of dog can get FCEM at a juvenile age?
Irish wolfhounds (8-13 weeks!)
76
What breed of dog is pre-disposed to diffuse idiopathic skeletal hyperostosis? What is the criteria to diagnose DISH?
Boxers (and maybe flat-coated retrievers) Ossification extending for at least four contiguous vertebrae
77
What are the two nuclei within the POMC, and what are their functions?
Medial nucleus— excite parasympathetic neurons and inhibit somatic neurons (facilitates urination) Lateral nucleus — excite somatic neurons (facilitates filling)
78
Describe the clinical features of hereditary polyneuropathy of Alaskan Malamutes and Greyhounds. What is the associated genetic defect?
- young age of onset (malamutes 10-18 mos, greyhounds 3-9 mos) - pelvic limb signs first, with progression overt tetraparesis, muscle atrophy and and signs of laryngeal and esophageal weakness - typically euthanized within 6 months Mutation is in the NDRG1 gene locus
79
This dog has a normal gait, no pain, and this type of posture. What is its disease process and prognosis?
Dancing Doberman disease (neuromyopathy of the gastrocnemius m / tibial n) Prognosis is good as signs are very slowly progressive / minimal
80
Describe hypertrophic neuropathy? What breed of dog is affected by this? Who else can be affected by this disease?
This is a disease of the Tibetan mastiff where their Schwann cells are unable to maintain a stable myelin sheath, leading to demyelination and remyelination. This causes the nerves to be grossly enlarged. Tibetan mastiffs only 7-10 weeks old develop signs of pelvic limb weakness that rapidly progresses to non-ambulatory tetraparesis. Sensation is normal. Cats also develop this disease, usually around 1 year of age. Their signs are less severe, with tremors, hypermetria and plantigrade stance. They often have sensory deficits.
81
What breed of cat develops a distal polyneuropathy as a kitten? Does it affect just the PNS? What are the clinical signs?
Birman No, it affects the axons in both the PNS and CNS. Affected at 8-10 weeks of age, starting with pelvic limb plantigrade stance and hypermetria x 4. Typically slowly progressive.
82
What breed of dog develops a giant axonopathy? Why are they giant? What is the typical clinical course? What is a unique PE finding in these dogs?
German Shepherds — accumulation of neurofilaments Pelvic limb LMN signs are present around 15 months due to involvement of the sciatic, then tetraparesis occurs by 18-24 months due involvement of dorsal spinocerebellar and fasciculus gracilis tracts. Voice change, megaesophagus and fecal incontinence also slowly develop. Curly hair coat
83
Should you do a tie back in a young _______ (fill in the breeds) presenting with laryngeal paralysis? Why or why not?
Rottweiler and Dalmatian They have an inherited laryngeal paralysis - polyneuropathy complex that will also cause pelvic limb weakness and megaesophagus (more common in Dalmatians) that will show signs very soon after onset of breathing difficulty.
84
What breed of dog has two related, but different inherited distal polyneuropathy? What are the predominant clinical signs in these dogs?
Leonberger The classic signs are sciatic weakness and associated sciatic gait, and some will develop laryngeal weakness. Usually slowly progressive.
85
What is the stereotypic breed of dog to have an inherited laryngeal paralysis? What is the pathophysiology?
Bouvier des Flanders Neuronal degeneration in the nucleus ambiguus
86
What breed of dog gets optic nerve hypoplasia? Lack of a chiasm?
Miniature poodles German shepherds
87
What tumor type is classically associated with a polyneuropathy?
Insulinoma
88
What is the classic histopathologic finding in dogs and cats with chronic inflammatory demyelinating polyneuropathy?
Evidence of demyelination and remyelination
89
What is the mechanism of action of phenothiazine drugs?
Blockade of post-synaptic dopamine receptors
90
What is the MOA for vincristine toxicity?
Inhibition of neurotubules, preventing axonal transport mechanisms
91
What toxicity can cause a delayed polyneuropathy in cats? Measurement of what in the serum can help confirm exposure?
Organophosphate toxicity Decreased cholinesterase activity
92
What three chemotherapeutic agents result in a peripheral neuropathy?
Vincristine Vinblastine Cisplatin
93
What is the biological function of creatine kinase?
It replenishes ATP from ADP by cleaving a phosphate molecule off of phosphocreatine within the myocyte.
94
Explain the differences between type 1 and type 2 myocytes.
Type 1 - slow 1. Good blood supply 2. Rely on oxidative metabolism 3. Large amounts of myoglobin 4. Lots of mitochondria 5. Smaller fibers / nerve fibers 6. Lots of glycogen Type 2 - fast 1. Less blood supply 2. Rely on anaerobic metabolism/ glycolysis 3. Minimal myoglobin (white) 4. Less mitochondria 5. Larger fibers 6. Less glycogen
95
What blood work value may be elevated in anorexic cats?
CK
96
In muscular dystrophy, what is the most commonly affected protein? What does this protein normally do?
Dystrophin — it provides structural integrity for the myofibers
97
True or false — cats with muscular dystrophy experience generalized muscle hypertrophy instead of atrophy
True
98
Centronuclear myopathies affect type ____ myofibers preferentially, and affect which breeds of dog? Which breed typically has a good outcome?
Type 2 Labradors and Great Danes Labradors have relatively mild signs and often don’t progress after 1 year of age, while most Great Danes are euthanized.
99
What reflex is typically abnormal in a Labrador experiencing an EIC episode?
Patellar reflex
100
What is the recommended thickness for a fat graft? How much will these shrink during re-vasculaturization?
5-7 mm thick 30% reduction

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