D O Paired-pulse N on two brain regions O T C O P Y Paula - - PowerPoint PPT Presentation

▶
d
SMART_READER_LITE
LIVE PREVIEW

D O Paired-pulse N on two brain regions O T C O P Y Paula - - PowerPoint PPT Presentation

Mar 20, 2023 204 likes •365 views

Practical D O Paired-pulse N on two brain regions O T C O P Y Paula Davila Prez, MD Berenson-Allen Center for Noninvasive Brain Stimulation Beth Israel Deaconess Medical Center Harvard Medical School BA-CNBS: Paired-pulse on two

slide-1
SLIDE 1

BA-CNBS: Paired-pulse on two brain regions

Practical

Paired-pulse

  • n two brain regions

Paula Davila Pérez, MD Berenson-Allen Center for Noninvasive Brain Stimulation Beth Israel Deaconess Medical Center Harvard Medical School

D O N O T C O P Y

slide-2
SLIDE 2

BA-CNBS: Paired-pulse on two brain regions

Plans for the afternoon

  • Introduce ourselves
  • Physiological and technical aspects
  • Practice TMS!
  • Clinical aspects and applications

D O N O T C O P Y

slide-3
SLIDE 3

BA-CNBS: Paired-pulse on two brain regions

Basic concepts

  • Paired-pulse protocols
  • Intracortical
  • Intrahemisheric
  • Interhemispheric
  • Different brain structures
  • Paired-pulse in two brain regions
  • Test pulse (TP) MEP on target muscle
  • Conditioning pulse (CP)
  • Inter stimulus interval (ISI) (ms)

#1 CP #2 TP ISI

D O N O T C O P Y

slide-4
SLIDE 4

BA-CNBS: Paired-pulse on two brain regions

Physiological aspects: Transcallosal inhibition, but also…

INHIBITION: ISI 6-30ms Transcallosal inhibition (IHI)

  • To avoid mirror movement, allow unilateral movement, and hemispheric

specialization

  • To allow exchange of unilaterally represented information

But also FACILITATION at ISI 3-5 ms (inconsistent):

  • To allow transfer of information via the CC between the two hemispheres?

D O N O T C O P Y

slide-5
SLIDE 5

BA-CNBS: Paired-pulse on two brain regions

Corpus callosum:

  • 200 million fibers
  • largest white matter structure
  • GABAB interneurons

Transcallosal pathway: short latency studies in total or partial callostomy ± direct ipsilateral pathway (?) IHI has intracortical origin TES vs TMS (Ferbert et al. 1992)  I waves (Di Lazzaro et al. 1999)

Physiological aspects:

#1 CP #2 TP

D O N O T C O P Y

slide-6
SLIDE 6

BA-CNBS: Paired-pulse on two brain regions

Different parameters…

IHI dependent on:

  • Intensity of CS (↑ duration), TS (↑ depth) and increasing ISI (↑ 5-15 ms)
  • State of target muscle (→ control for muscle contraction!)
  • Contraction of muscle contralateral to the CS ↑ IHI
  • Effect disappears if the muscle contralateral to TS is also activated

And…

  • Hand dominance (studies are contradicting)
  • Gender differences (IHI women > men; ISI range well circumscribed in women)

D O N O T C O P Y

slide-7
SLIDE 7

Footswitch

Test pulse alone (RH)

Timer Input Input Output B Output A MEP Amplifiers Trigger Output Master: A Slave: B

D O N O T C O P Y

slide-8
SLIDE 8

Conditioning pulse (LH) & Test pulse (RH)

Master: A Slave: B Timer Input Input Output B Output A Footswitch MEP Amplifiers Trigger Output

D O N O T C O P Y

slide-9
SLIDE 9

BA-CNBS: Paired-pulse on two brain regions

Procedure to measure IHI

  • 1 right-handed subject
  • 2 to prepare the electrodes over the

two hands

  • 1-2 to prepare the cap and the marking
  • n the two hemispheres
  • 2 to find RMT on LH and RH
  • 2 to measure RH baseline (TS alone) (120%
  • f RMT, with the two coils)
  • 2 to apply the paired pulses from L->R

CP on LH and TS on RH (120 % of RMT) ISI of 8-12 ms (12 ms women, 10 ms men) Always monitor the relaxation of the muscle! IHI = 100*(PP MEP - TS alone MEP)/(TS alone MEP) We expect a decrease of 20 to 40% but it may not work today!

D O N O T C O P Y

slide-10
SLIDE 10

BA-CNBS: Paired-pulse on two brain regions

5 cm 5 cm Vertex M1 How to find FDI hotspot with a standard Magstim figure-of-eight coil

  • Monophasic coil
  • Handle pointed backwards 45º
  • Current directed posterior-anterior
  • Perpendicular to central sulcus

Safe coil and machine handling!

D O N O T C O P Y

slide-11
SLIDE 11

BA-CNBS: Paired-pulse on two brain regions

What are we going to do?

  • Mapping both M1 to find hotspot to determine RMT (FDI)
  • Baseline (TP alone, monophasic coil) at 120% of RMT
  • Paired-pulse: Conditioning pulse (CP) followed by test pulse (TP) (on
  • ptimal MEP site)
  • TP at 120% of RMT
  • CP at 120% of RMT
  • ISI = 8 - 12 ms
  • What do we get?

#1 CP #2 TP ISI

D O N O T C O P Y

slide-12
SLIDE 12

BA-CNBS: Paired-pulse on two brain regions

From a historical point of view

  • Various contradictory studies about callosotomies (“split-brain”)
  • Ferbert et al., 1992: first description
  • Vuilleumier et al., 1996: right parietal stroke followed by a left frontal

stroke

  • Geschwind & Kaplan, 1962: “deconnection syndrome” due to

callosal lesions

D O N O T C O P Y

slide-13
SLIDE 13

BA-CNBS: Paired-pulse on two brain regions

Clinical aspects How could we use it?

  • PD (↓)? Mirror movements? Dystonia? Cortical myoclonus (↓)?
  • MS: prolonged transcallosal conduction time
  • Stroke
  • IHI ↓ from affected to unaffected side (balance model)
  • IHI ↑ before movement onset (from unaffected to affected side)
  • Assess the efficiency of brain stimulation and/or rehabilitation?
  • Deconnection syndrome? Assess integrity of CC?

(Chen et al., 2008)

D O N O T C O P Y

slide-14
SLIDE 14

BA-CNBS: Paired-pulse on two brain regions

Outside M1… Be aware of network effects!

  • Cerebellum - M1: Suppression of MEPs at ISIs of 5-8 ms (Ugawa et al.,

1995)

  • FEF and extrastriate visual cortex (MT/V5): stimulation of FEF 20-40 ms

prior to stimulation of MT/V5 decreases the intensity needed to evoke a phosphene (Silvanto et al., 2006)

  • PPC and contralateral M1: stimulation of right caudal IPS facilitates MEPs

but stimulation of anterior IPS suppresses them. Directly or via homologous areas (Koch et al., 2009)

D O N O T C O P Y