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USAHS Neuroanatomy Test 1 > Neuroradiology and Neuroplasticity > Flashcards

Neuroradiology and Neuroplasticity Flashcards

1
Q

Focus on Common Images Modalities

A

Computerized Tomography- CT

Magnetic Resonance Imaging- MRI (T1 and T2, functional MRI)

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2
Q

Computerized Tomography (CT)

A
  • Developed from a conventional x-ray
  • Xray has a flat plate detector and radiation source
  • One single projection
  • CT uses the same mechanism but with 2 difference
  • CT slices are obtained simultaneously
  • Multiple x-ray beams are passing through the patient so the same structure image is captured from a variety of angles
  • The x-ray source moves really fast
  • Projections are mathematically combined to create a 2D or 3D image
  • Measures the density of tissues
  • Bone or calcification/dense structure appears white/lighter = hyperdense
  • Air/water/less dense structure appears darker = hypodense
  • Brain/intermediate structure appears gray = isodense
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3
Q

Hyperdense

A

Bone or calcification/dense structure appears white/lighter

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4
Q

Hypodense

A

Air/water/less dense structure appears darker

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5
Q

Isodense

A

Brain/intermediate structure appears gray

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6
Q

Abnormal Findings in CT

A
  • Hemorrhage
  • Acute Cerebral Infarction
  • Neoplasms
  • Mass Effect
  • Calcifications
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7
Q

Hemorrhage (abnormal findings in CT)

A

The appearance depends on the chronicity

  • Acute hemorrhage = Isodense
  • Two-three weeks post hemorrhage = Hypodense
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8
Q

Acute Cerebral Infarction (abnormal findings in CT)

A

Cannot be seen within first 6-12 hours

  • Cell death and edema occurs = hypodensity
  • After weeks/months = hypodensity (areas surrounding may shrink, enlarged ventricles)
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9
Q

Neoplasms (abnormal findings in CT)

A

Appear as hypodense, hyperdense, or isodense - Intravenous contrast dye is helpful in imaging these disorders

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10
Q

Mass Effect (abnormal findings in CT)

A

Anything that distorts the brain’s usual anatomy by displacement

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11
Q

Calcification (abnormal findings in CT)

A

Appears hyperdense

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12
Q

Intravenous contrast (CT)

A
  • Used to facilitate visualization of suspected neoplasm or brain abscess
  • The contrast contains iodine - which is denser than brain and appears as hyperdense (white)
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13
Q

Magnetic Resonance Imaging - MRI

A
  • Radio frequency magnetic waves are generated from an electrical coil that excites protons, causing some to flip their spins anti-parallel
  • Signal detected by reception coil
  • Multiple pulse frequency sequence will direct the protons to the patient and originates better images
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14
Q

Super Conducting Magnet (MRI)

A

Where pt needs to be positioned

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15
Q

Gradient Coils (MRI)

A

Perturbs the magnetic field to allow spatial localization

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16
Q

Different coil

A
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17
Q

Repetition Time (TR) (MRI Image: described in terms of intensity)

A

The amount of time between successive pulse sequences applied to the same slice.

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18
Q

Time to Echo (TE)(MRI Image: described in terms of intensity)

A

The time between the delivery of the RF pulse and the receipt of the echo signal.

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19
Q

T1 weighted MRI

A

-Looks like an anatomical brain section

Gray matter appears gray, white matter appears white

  • H20, CSF appears dark
  • Fatty tissue appears white
  • Air and bone appears black
  • “Spin-lattice” relaxation
  • White matter brighter than gray
  • Most lesions dark
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20
Q

T2 Weighted MRI

A

-Looks like a negative film

Opposite to T1

  • Gray matter appears light gray, white matter appears dark gray
  • Bone and air are black
  • CSF appears white
  • Myelinated areas appear dark
  • “Spin-spin” relaxation
  • Most lesions bright
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21
Q

MRI relates to brightness of the signal as compared to density in CT

A

Hyperintense = brighter areas
Hypointense = darker areas
Related to: Water content (dark in T1 and white T2), Fat content (white T1, dark T2)

22
Q

MRA and MRV

A

contrast to blood vessels

23
Q

CT Advantages

A
  • Low cost
  • It takes 5 – 10 min
  • Head trauma
  • Accessible in any ER
  • More bone detail
  • Screening test
24
Q

CT Disadvantages

A
  • Doesn’t detect brainstem and cerebellar stroke
  • Images not so clear
  • Radiation
25
Q

MRI Advantages

A
  • Clear images
  • More structures and tissue details
  • Detect brainstem and cerebellar stroke
  • No radiation
26
Q

MRI Disadvantages

A
  • High cost
  • It takes 20-45 min
  • Less accessible
27
Q

CT Indications

A
  • Acute neurological deficit/trauma
  • Subarachnoid hemorrhage
  • Acutely ill or unstable patient
  • Contradiction to MRI scan (ex. pacemaker)
28
Q

CT Contradiction

A
  • Pregnancy (we ask- you should)
  • Allergic reactions (contrast media)
  • Pediatric patient (radiation concerns)
29
Q

MRI Indications

A
  • Brainstem and cerebellar strokes
  • Normal CT and persistent clinical suspicion
  • Contraindications to CT (pediatric)
30
Q

MRI Contraindications

A
  • Certain implanted ferromagnetic devices
  • Claustrophobia (can be done with sedation)
  • Renal failure (when gadolinium necessary)
  • Early pregnancy (?)
31
Q

Structures

A
32
Q

Neuroplasticity

A

Definition: It is the adaptative capacity of the brain (CNS). The brain’s ability to reorganize itself by forming new neural connections throughout life. Mechanisms involve neurochemical, receptor, or neuronal structural changes.

Types:Structural and Functional

33
Q

Structural/Neural Plasticity

A

Changes in the organization and numbers of connections among neurons.

  • Unmasking of “silent” synapses
  • Synaptogenesis: development of new synapses
  • Collateral sprouting
34
Q

Functional Plasticity

A
  • Changes in the efficiency or strength of synaptic connections.
  • It can happen during therapeutic intervention
35
Q

Neuronal Function (effect of injury)

A
  • Interrupting axonal projections from areas injured
  • Denervation of the population of neurons innervated by the injured neurons
  • Removing some neurons entirely
36
Q

Cellular Level (effect of injury)

A
  • Neuronal Shock: Diaschisis
  • Loss of synaptic effectiveness
  • Alternative mechanisms are substituted
37
Q

Factors That Affect Recovery

A
  • Genes
  • Age
  • Size, type and location of lesion
  • Onset time
  • Experience/your environment
  • Pharmacology
  • Use/training
38
Q

Principles of Neuroplasticity

A
  • Use it or lose it: Failure to drive specific brain functions can lead to loss of abilities
  • Use it and improve it
  • Specificity: Plasticity specific to the training
  • Repetition matters
  • Intensity matters
  • Time matters
  • Salience matters: The training experience must be meaningful
  • Age matters
  • Transference: Training experience can even lead to learning other similar skills
  • Interference: Brain changes that result in bad habits can interfere with learning good habits
39
Q

Neuromodulation

A

Used to promoting neuroplasticity.

  • Medications
  • Rehabilitation
  • Neuromodulation tools: TMS, tDCS, DBS
40
Q

Techniques that may prime motor learning

A
  • TMS (increase or decrease corticomotor excitability) used to drive motor learning. Pulsating magnetic fields on the scalp to induce an electrical current within the brain
  • tDCS
  • Deep Brain Stimulation
  • Aerobic exercise
  • Neuropharmacology
41
Q

tDCS (Neuromodulation tools)

A
  • Transcranial direct current stimulation
  • Delivers low-intensity direct electrical current to the brain
  • Delivers low-intensity direct electical current to the brain
  • Enhance neuronal excitability or inhibit overexcitability of neural networks
  • Cathodal inhibits, anodal excites
  • tDCS is a safer, more comfortable, easier to do, more affordable and produces a more robust response
42
Q

Deep Brain Stimulation/DBS (Neuromodulation tools)

A
  • Helps with tremor, rigidity, slowness of movement, balance

- Surgically implanted electrodes to provide electrical impulses

43
Q

Aerobic Exercise

A
  • Indirect Effects: Improves general health and fitness

- Direct effects: Increase in neurotrophic factors (such as BDNF) and neurotransmitters (dopamine, serotonin)

44
Q

Brain Derived Neurotrophic Factor (BDNF)

A
  • Protein encoded by BDNF gene.
  • Member of neurotrophin family
  • Involved in neuroprotection, neurogenesis, neuroplasticity
  • A key mediator of motor learning and getting the brain ready for neuroplasticity
  • Secreted by 2 mechanisms: constitutive and activity-dependent pathways (aerobic exercises)
  • Enhances BDNF levels and leads to increased BDNF gene expression in hippocampus, cerebral cortex and cerebellum.
45
Q

BDNF role in facilitating neuroplasticity

A
  • BDNF facilitates long term potentiation through an activity-dependent secretion: vital to neuroplasticity
  • Evidence supports in increase in BDNF benefits cognitive functions
  • Systemic levels of BDNF are increased for 10-60 minutes following a bout of aerobic exercise
46
Q

“Priming the system” with aerobic exercise

A
  • Timing: engage patient in aerobic exercise close in time to your therapy (training pair exercise)
  • Evidence: High intensity exercise before motor task enhanced performance in young adults
47
Q

Recommendation for practice FITT principle

A

Frequency: 4x/wk
Intensity: 70% max HR
Time: Aerobic session more 30 min
Type: combination aerobic exercise and resistance training

Evidence that 30 min at 60% max HR is effective for increasing BDNF in patients with chronic disorders

48
Q

Genetic Considerations

A
  • Genetic variations may influence the efficacy of rehab
  • Common single nucleotide polymorphism (SNP) on the BDNF gene (Valine replaced by Methionine) - VAL66MET Polymorphism
  • Patient with VAL66MET Polymorphism present 25% reduction in activity-dependent secretion of BDNF in the CNS
49
Q

Neural Plasticity

A
  • Can be “good” or “bad”
  • Occurs throughout the CNS
  • Occurs with motor learning
  • Occurs with recovery of function
50
Q

How is neuroplasticity detected?

A

Non Invasive Brain Stimulation

TMS: Measures excitability of motor cortex maps

51
Q

Aerobic Exercise Effects on Brain Function

A

Enhances BDNF levels and leads to increased BDNF gene expression in:

  • Hippocampus
  • Cerebellum
  • Cerebral cortex
  • Spinal cord-
52
Q

BDNF Gene VAL66MET Polymorphism

A

-30-50% of population have this SNP
-The presence of the MET allele results in a 25% reduction in activity dependent secretion of BDNF in the CNS
Associated with (abnormalities in brain structure and physiology):
-Decreased hippocampal activation
-Decreased motor system activation
-Increased gray matter atrophy
-Poorer memory function
-Pooreroutcomeafterstroke
-Poorer learning and memory

USAHS Neuroanatomy Test 1 (4 decks)

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