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Medsci 317 > Lecture Five; Clinical applications of non-inasive brain stimulation > Flashcards

Lecture Five; Clinical applications of non-inasive brain stimulation Flashcards

1
Q

What is most TMS research focused on?

A

1) Depression
2) Stroke
3) Chronic Pain
4) Epilepsy

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2
Q

How can TMS be used in diagnosis?

A
  • Test the function of the corticomotor pathway

- Measure central conduction over time

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3
Q

How can TMS be used acutely in diagnosis?

A

Acute injuries

  • Stroke (not needed though)
  • Spinal cord injury
  • Peripheral nerve injury
  • Functional weakness. i.e no pathology, sudden loss of function, usually an underlying stressor
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4
Q

How can TMS be used in chronic diagnosis?

A

Chronic conditions

  • MS
  • Amytrophic Lateral Sclerosis
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5
Q

How can TMS be used on prognosis?

A
  • Predicting recovery of hand and arm function after stroke

- TRIO study at Auckland city hospital

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6
Q

Give an example of a stiuation where TMS could be used in prognosis?

A

i. e Mrs McIntyre
- 63
- Ischemic stroke 10 days ago
- Right sided weakness
- Grossly 1/5 upper limb (muscle power is flicker of activation hence 1 value)
- Works on a computer and watns to know if she will ever regain functionality

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7
Q

What is bad about the current system regarding functional recovery and outcomes?

A

Currently patients who have very similar clinical scores, can have very different recoveries and outcomes

i.e ARAT score (/57)
Arm Response Activity Test
Can have two patients with the same score and one can recover really well and the other mightnt at all.

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8
Q

What did studies show using experienced therapists to predict patients outcomes?

A

Experienced therapists could only predict clinical outcomes correctly 60% of the time. (on average across the three categories)

In short need need new system

= PREP!!

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9
Q

Describe the PREP 2 algorithm;

A

Look at notes…

FInal point is the predicted recovery of upper limb function at 12 weeks

First; Safe score (/10)

  • Safe >5 (->) < 80 yrs old? -> Yes -> Excellent
  • Safe >5 (->) < 80 yrs old? -> No -> Safe >8? -> yes = Excellent, No = Good (safe <8)
  • Safe <5 -> MEP +ve? yes -> = Good
    No (MEP -ve) -> NIHSS <7? -> Yes = Limited
    No NIHSS >7 = Poor
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10
Q

What is the SAFE score based on?

A

Strength
AB function
Finger Tensing

Within 72hrs of stroke

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11
Q

What is the NIHSS score?

A

Overall stroke severity

High number = bad

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12
Q

What were the conclusions from the TRIO study?

A
  • PREP algorithm info gave therapists more confidence and was correct for 75% of patients (PREP 2 higher)
  • More focused upper limb rehab, tailored to the recovery potential of individual participants, associated with shortened length of stay by ~ 1 week
  • PREP information may increase rehabilitation efficiency, with no negative effects on patient outcomes.
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13
Q

What are some types of TMS set ups and how is frequency important?

A 
repetitive TMS (rTMS) (High HZ = F)
theta burst TMS (TBS) (Intermittent TBS = F)
Paired associative stimulus (PAS) (~25ms = F)
Transcranial Direct Current Stimulation (TDCS) (Anodal TMS = Facilitation)

Hz is important because if either creates inhibition of facilitation.

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14
Q

What is the mechanism of TMS?

A

NMDA-R dependant
(effects are blocked by NMDA-R antagonists)

Ca influx

  • Rapid influx promotes LTP
  • SLow influx promotes LDP
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15
Q

What is important in the mechanism of rTMS?

A

The timing is important for fast or slow Ca influx and facilitation or inhibition.

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16
Q

Describe exactly how rTMS works;

A
  • Glutamate opens AMPA and NMDA (Remain Blocked though by Mg2+) receptors. AMPA receptors allow cation influx
  • Sufficient post synaptic neuron depolarisation results in removal of Mg ion
  • Thus allowing Ca influx
  • Rapid Ca influx will activate CAMKII and insertion of AMPA into the membrane (LTP)
  • Slow Ca influx will result in activation of calmodulin which will remove AMPA density and current.
17
Q

What does the study by Meullbacher show with the stimulus response curves?

A

Stimulus response curve;

  • MP (motor practice) followed by a stimulus will enhance learning (MEP), especially the higher the stimulus is
  • Using rTMS-M1 (inhibition) , will detract from learning and decrease the MEP (inhibit learning), shifting the stimulus response curve downwards

i.e did motor practice then received sitmulus

18
Q

What does the study by Meullbacher show with the repetitive session?

A

Set up =
P(practice)1 , rTMS 1, P2, rTMS2, P3

motor practice was thumb movement

Using the supressive stimulus (rTMS-M1) would detract from learning such that each practice session the participant would have to start learning from scratch. (they would improve during the session but then the stimulus afterwards would reverse it)

However the other TMS would enhance learning

19
Q

What did the Huang study show regarding theta burst stimulation?

A

Intermittent TMS = Facilitation
Intermediate TMS = No change
Continuous TMS = Suppression

20
Q

How can repetitive TMS be used in depression?

A

When pharmacological treatments fail;

Repetitive TMS

  • Suppression of prefrontal cortex
  • Usually subthreshold 1Hz rTMS
  • Several session required
  • FDA approved treatment
21
Q

How can rTMS be used in stroke?

A

rTMS in stroke

  • Brain stimulation needs to be combined with physical therapy for motor rehabilitation
  • Most studies are at the chronic stage
    • Facilitate ipsilateral cortex
    • Suppress contralateral cortex (potentially at chronic stage)
22
Q

What is the logic behind using TMS in stroke patients?

A

In stroke patients the stroke part of the brain cant inhibit the good side.
- It cant facilitate it either

TMS can be used to equal interhemispheric inputs for balance

23
Q

What did the study by ackerley show regarding stroke and TMS?

A

The use of iTBS of the ipsilesional M1 resulted in facilitation of the bad side.

The use of cTBS of contralateral M1 resulted in supression of the good side

Therefore either specific facilitation or supression resulted in improved precision grip with the weak hand (BALANCE)

iTBS had greater results. (facilitation)

24
Q

Describe the study by fritsch;

A
  • 36 healthy adults
  • Squeeze to move a cursor to a target
  • 5 days training
  • BDNF gene
  • Anodal TDCS

MET vs VAL carries (BDNF natural variation)

25
Q

What did the skill measure and skill improvement graphs show for Fritsch’ study?

A

Skill measure;
- VAL carries improved greater than MET

Skill Improvement
- Val carriers improved more than MET

Conclusion;
- Non-inasive brain stimulation normalised brain learning for Met carries (i.e made up the difference)

Anodal TDS excites the brain / part of cortex.

26
Q

What did the stagg study show in regards to TDS and stroke?

A
  • 13 chronic stroke patients
  • Facilitation of ipsilesional M1 speeds up reaction times
  • This is related to increases in activity in sensory motor network (fMRI indicates this)
27
Q

What doe the Shekhawt study regarding tinnitus and TDCS indicate?

A

TDCS in tinnitus;

  • Can reduce the loudness and annoyance of symptoms
  • Anodal to facilitate left temporoparietal area
  • Dose response (longer + stronger current = greater improvement)
28
Q

How does TDCS help in amblyopia?

A

Can improve depth perception when combined with visual training

29
Q

How does interindivudal variability affect the response to non-invasive brain stimulation

A

Genetic influences

  • Influences response to treatment
  • iTBS works for Val/Val (facilitation)
  • cTBS suppresses Val/Val
30
Q

What are the strengths of non-invasive brain stimulation?

A
  • Can be targeted to specific parts of the brain

- Specific effects depending on protocol

31
Q

What are the limitations of non-invasive brain stimulation?

A
  • Equipment
  • Contraindications
  • Unknown what dose, n. repeats etc is best
32
Q

Whats the downside to non-invasive brain stimulation?

A

Its not a one size fits all

Suppressing contralateral M1 with cTDCS in stroke patients

  • Mild Patients got better
  • Worse patients got worse (temporarily)

Trying to use the good side of their brain to control the bad side and the suppression made it worse as was suppressing this function

Medsci 317 (32 decks)

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