PREP2 TMS Protocol

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Purpose

To provide an overview of the specific use of TMS testing for PREP2. It is designed to follow the TMS Overview and TMS Safety Checklist sections, which ensure a good understanding of the mechanisms, physiology, side effects and contraindications to TMS.

More detailed TMS instructions can be downloaded here.


TMS testing sessions

Testing takes place on Day 3 – 7 post-stroke, once the patient has been screened and approved for testing. Testing performed outside these time-frames may affect the accuracy of predictions. TMS testing should be completed by day 7. If it is performed on Day 8 – 10 post-stroke you can only be confident to provide a prediction if the patient is MEP-. TMS testing performed after 10 days post-stroke is too late.

The testing is usually conducted by two staff members, with at least one being a trained TMS Operator, and the other having at least PREP2 Advanced certification. Testing takes about 20 minutes with the patient, with additional time before and after for setting up and putting away the equipment, and documentation. Testing can be done at the patient’s bedside, in a procedure room or similar location. Family may be invited to be present if this is what the patient wants.

Preparation

    • Screen the patient for contraindications to TMS using the TMS safety checklist. Ensure the TMS safety checklist has been completed and approved
    • Schedule the TMS appointment with the ward and the patient
    • Ensure all equipment and consumables are available

 

Explanation

    • Provide the patient and their family with an explanation of what the TMS testing is for, what it involves, and the possible outcomes. 
    • Once you’ve described the possible predictions, it’s a good idea to ask whether they would like to hear their prediction straight after the TMS test, or if they would rather wait if they’re not feeling ready for that discussion. This gives patients and their family the chance to manage the flow of information so they’re not overwhelmed. The prediction can be recorded in the notes and held until the patient and their family are ready for the discussion.

 

Set-up

    • The patient can be positioned supine, semi-reclined, or sitting in a chair or wheelchair, with their arms supported comfortably on a pillow
    • Position surface EMG electrodes over the paretic Extensor Carpi Radialis (ECR) and First Dorsal Interosseous (FDI) muscles. Further details of how to set up the electrodes can be found in the EMG technique module. Further details about how to set up the electrodes can be found in the EMG technique module.

 

TMS Description and Demonstration

    • Explain that TMS is painless and non-invasive, and that a member of their medical team has checked that it is safe for them to have this test.
    • Explain that you will hold a plastic-covered device gently against their scalp, and it will create a very brief magnetic field that can activate the area of the brain that controls their hand and arm.
    • Explain that the device makes a click sound, and they are likely to feel a light tap on their scalp each time it creates the brief magnetic field, but that it won’t be uncomfortable.
    • Explain that you will start at a low level of stimulation, and gradually increase it, while moving the device around to find the best position for sending a message to their weaker hand and arm.
    • Explain that may feel a brief twitch in their hand and arm muscles, which won’t cause any discomfort.
    • Explain that you will stick some sensors to the skin on their hand and arm, to detect the activity once it arrives at their muscles.
    • Explain that they can let you know if they have any concerns or feel uncomfortable at any stage, and the test can be stopped at any time.
    • Show the patient the TMS coil and discharge it while holding it away from them, so they can hear the click.
    • Position the TMS coil over the stroke affected hemisphere, so they can feel what it is like.
    • Let the patient know you will give them one ‘click’ as a ‘tester’, then deliver one stimulus at 30% maximum stimulator intensity (MSO), then check with the patient that they are comfortable to proceed with the rest of the test.

 

Coil Position

    • Testing is carried out by a certified TMS Operator, or a trainee under supervision of a certified trainer
    • Position the focal point of stimulation over the stroke affected hemisphere, approximately 2 inches lateral to the vertex on the inter-aural line. This position is shown in the picture on the left below. 
    • Ensure the coil is oriented to produce a posterior-to-anterior current flow in the underlying cortex. For a figure-of-eight coil this means having the handle pointing towards the back of the patient’s head, and at an approximately 30 – 45° angle to the mid-sagittal plane. This orientation is shown in the picture on the right below. 
    • Further examples of correct and incorrect coil positions can be found on the EMG and TMS training videos page.

 

 

Testing

  • Start at a low intensity like 30% deliver approximately 3-5 stimulations while systematically moving the coil in approximately 2cm steps (anterior, posterior, medial, lateral)
  • If no MEPs are elicited then increase the stimulator intensity by ~25% and repeat the same process of stimulating while systematically moving the TMS coil.
  • If MEPs are elicited at any stimulus intensity then the patient can be deemed MEP+ and the TMS session can end. 
  • If no MEP is observed at 100% MSO while the participant is at rest then you should ask the patient to perform active bilateral facilitation. Ask the patient to hug a pillow to their chest, using both upper limbs, attempting to activate the muscles of both upper limbs and hands to the greatest possible extent. An example of bilateral facilitation being performed can be found in a video here.

 

Interpretation

    • Determine whether the patient is MEP+ or MEP- to know their PREP2 prediction
    • MEP+: if MEPs are observed with FDI latency ≈ 20 – 30 ms, and ECR latency ≈ 15 – 25 ms.
    • MEP+ patients can be given a prediction of good recovery within the next 3 months.
    • MEP-: if MEPs are not observed with at rest or during bilateral facilitation at 100% MSO while systematically moving the TMS coil.
    • MEP- patients can be given a prediction of Limited or Poor recovery depending on their day 3 NIHSS score.
    • Refer to the Therapist’s section of the completed TMS Safety Checklist to see whether the patient wants to hear their test results straight away
    • Share the prediction if this has been agreed to by the patient

 

Pack-up

    • Remove the EMG electrodes and clean the underlying skin with an alcohol wipe.
    • Ensure all equipment is stored away

 

Document

    • Ensure the session is accurately documented in the patient’s clinical notes
    • If the prediction has been shared ensure that written prediction information is provided in the clinical notes

More detailed TMS instructions can be downloaded here.

 

Essential reading

Transcranial Magnetic Stimulation: A Primer

PREP2 TMS Instructions

 

FAQs

How important is the TMS? Can we skip this step and go straight to the NIHSS score?
The TMS step is important. We have found that people can be MEP+ even though they have a SAFE score as low as zero, and an NIHSS score greater than 7. Being MEP+ shows that the remaining descending motor pathways are still functioning. This means that these patients still have potential for a Good functional outcome. If the TMS step was skipped, the NIHSS score would put these patients in the Limited or Poor categories, which would underestimate their potential for recovery. If the pathways are functioning (MEP+), then it doesn’t seem to matter what their NIHSS score is.

The need for TMS has been shown by research from the PREP2 team at the University of Auckland, and a study in the US by Jessica Barth and colleagues (Barth et al., 2021). Barth and colleagues found that the overall accuracy of an algorithm using only age and clinical assessments (SAFE and NIHSS score) obtained within the first 2 weeks after stroke achieved a lower overall accuracy than PREP2 (61% vs. 75%). For patients with a SAFE score less than 5 the accuracy was only 50%. This is consistent with findings from the PREP2 team, who found that when TMS is removed from the prediction tool the prediction accuracy for patients with a SAFE score less than 5 drops to 55%. Together these findings highlight the importance of TMS to ensure more accurate predictions for patients who have a SAFE score less than 5.


Who needs to be trained in TMS?
The TMS protocol used in PREP2 can be carried out by trained staff, after safety screening and approval from the patient’s physician. The testing is usually conducted by two staff members. At least one needs to be a certified TMS operator to deliver the TMS, and at least one needs to have PREP2 Advanced certification to support the testing session. TMS testing is performed between days 3 – 7 post-stroke when a patient could be in either an acute or rehabilitation setting.


If a person had no responses to TMS 7 days after stroke, but responses returned at a later time, would they then have potential for a ‘good’ hand and arm outcome?
If a person has no responses to TMS 7 days after stroke, this indicates a greater degree of stroke damage to the descending motor pathways. This means that even if they do recover responses later, they are unlikely to have the potential for a good upper limb functional outcome.


Why is the TMS testing performed on Day 3 – 7? And what do I do if it’s not possible to test within this time-frame?
The research that has developed and validated PREP2 used TMS within this timeframe. The importance of testing by Day 7 has been confirmed by a study in Denmark by Camilla Biering Lundquist and colleagues (Lundquist et al., 2021). They found lower prediction accuracy compared to PREP2 (60% vs. 75%) when SAFE score and TMS testing were performed at 2 weeks. This indicates that if TMS is performed later, the predictions might not be as accurate. If TMS testing is delayed and performed on Day 8 – 10 you can only be confident to provide a prediction if the patient is MEP-. 

Differences in healthcare delivery models can create challenges for performing TMS testing within the specified time window. However, a recent US study by Yi-Ling Kuo and colleagues (Kuo et al., 2021) found that it was feasible to perform TMS testing at the bedside within 2 – 8 days post-stroke. They note that testing in this time frame was enabled by having a transportable TMS cart and efficient interdisciplinary communication.

 


Quiz

Click here for a practice quiz to assess your learning on the PREP2 TMS protocol.

Once the practice quiz has been completed with at least 70% correct you will be emailed a link to the final quiz for this section.

If you pass the final quiz with at least 80% correct you will be emailed a certificate of completion for the TMS for PREP2 section. There is no limit to the number of attempts for the practice or final quiz.

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