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Y P Berenson-Allen Center for Noninvasive Brain Stimulation O - PowerPoint PPT Presentation

Apr 28, 2023 •280 likes •474 views

Y P Berenson-Allen Center for Noninvasive Brain Stimulation O Department of Neurology Beth Israel Deaconess Medical Center C Harvard Medical School T O Determining motor threshold N O Franziska Plessow, Ph.D. D Paula Davila-Prez,

  1. Y P Berenson-Allen Center for Noninvasive Brain Stimulation O Department of Neurology Beth Israel Deaconess Medical Center C Harvard Medical School T O Determining motor threshold N O Franziska Plessow, Ph.D. D Paula Davila-Pérez, M.D. E Ali Jannati, M.D., Ph.D. S Peter J. Fried, Ph.D. A E L Intensive Course in Transcranial Magnetic Stimulation, P 02/27/2017

  2. Y P Safety First!!! O C T O N • Screen for contraindications and side-effects O D • Earplugs must be worn by subject and operator E S A E L P Determining motor threshold 2

  3. Y P Motor threshold (MT) definition O C T O N  The minimum intensity (% of maximum machine output) O to elicit a motor response in at least 50% of trials D E S A E L P Determining motor threshold 3

  4. Y P Role of MT O C T  Objective measure of relative cortical excitability/reactivity O N - Reflects voltage-dependent ion channel function O - Highest test-retest reliability of any TMS measure D  Used to individualize intensity of further TMS E S  Consistent with safety limits (Rossini et al., 2009) A E L P Determining motor threshold 4

  5. Y P Types of MT O C Resting motor threshold (RMT) > Active motor threshold (AMT) T O N O D E S A E L P Determining motor threshold 5

  6. Y P Factors that influence MT O C  Subject factors: T O - Inter- and intra-individual variance N - Activity of brain/muscle - Coil-to-cortex distance O - CNS drugs D  Physical Parameters: E S - Device (stimulator and coil) A - Pulse waveform/shape/direction E - Navigated vs. Non-navigated TMS L - Method of determination (visible/EMG) P Determining motor threshold 6

  7. Y P Methods of determining MT O C Visual inspection Electromyography (EMG) T O N O D E S A + E L P Determining motor threshold 7

  8. Y P RMT with EMG O C Rossini-Rothwell method: T O  Minimum intensity to elicit motor evoked potentials (MEPs) of ≥ 50 μV peak-to-peak amplitude N in ≥50% of consecutive trials (typically 10) O D E S μV μV A E L P s s Determining motor threshold 8

  9. Y P Target muscle O C T O N O D E S A E L P Determining motor threshold 9

  10. Y P Penfield‘s motor homonculus O C T O N O D E S A E L P Determining motor threshold 10

  11. Y P Attaching EMG electrodes O C Identify T O N O Clean D E S A Attach E L P 11

  12. Y P Finding the “hot spot” with neuronavigation O C T O N O D E S A E L P Determining motor threshold 12

  13. Y P Finding the “hot spot” without neuronavigation O C ≈5 cm lateral from the vertex T O N O D E S A E L P (Jaspers, 1958) Determining motor threshold 13

  14. Y P Finding a starting location O C T O N 7cm O 5cm D E 5cm S A E L P 14

  15. Y P Finding the “hot spot” O C 1. Set intensity to 30% and deliver a couple of pulses T O 2. Go up in steps of 5-10% until MEPs are observed N 3. Deliver several pulses to ensure a consistent response is evident (suprathreshold) O 4. Test four spots around the location of the MEP D (north, east, south, west) E 5. Repeat Step 4 until the individual’s S “hot spot” is identified A E L Whatever you do, do it consistently. P Determining motor threshold 15

  16. Y P Finding the MT O C 1. Record 10 MEPs T O 2. Progressively lower intensity (1-2%) until ≥5/ 10 trials elicit an MEP of ≥ 50 μV (or visible twitch) N 3. Always check 1 intensity lower O D E S A E L P 16

  17. Y P Finding the MT O C  Alternatives under time constraints: T - ≥3/6 O - Adaptive MT determination/Parameter estimation by sequential N testing (PEST) with the TMS Motor Threshold Assessment Tool O (clinicalresearcher.org) D  Trouble shooting: E - No MEP detected (relaxation, AMT, silent period) S - MEP latencies = 20-30 ms A E L P 17

  18. Y P Safety First!!! O C T O N • Screen for contraindications and side-effects O D • Earplugs must be worn by subject and operator E S A E L P Determining motor threshold 18

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