A poster presentation to the American Society of Neurophysiologic Monitoring Annual Convention, May 5, 2019

1. Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
A Presentation by David Barnkow, Au.D., D.ABNM, CCC-A
for the
ASNM 2019 Annual Meeting,
Medically Interesting Case and Scientific Abstract Presentations,
May 5, 2019

2. Session Title: Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
Name of Speaker: David Barnkow, Au.D., D.ABNM, CCC-A
Disclosures
• Scientific advisory board: none
• Scientific research: none
• Speakers Bureau: none
• Stock options: none
• Company leadership/board of directors: none
• Product Royalties: none
• Travel: none
• Society leadership and IONM related boards: none
• Patents: none
• Employed by: Medsurant Health, LLC
• No off label use of products will be discussed in this lecture.
• No commercial product names will be used in this presentation.
ASNM Conflict Of Interest Required Slide

3. Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
The Case Presentation: A 58 year-old male with diagnoses of
C2 incomplete tetraplegia, post-traumatic tethered spinal
cord, myelocyst, spasticity, and central neuropathic pain. The
chief complaints were episodic syncopy, progressive
weakness, decreased ambulation, decreased sensation,
decreased range of motion, increased neuropathic pain, and
increased spasticity. The surgical treatment was cervical
decompressive laminectomies, microscopic spinal cord
untethering, and expansion duraplasty.
Table 1. Motor Strength Assessment
Muscle Grading Right Muscle Left
5 - Normal 1+ Brachioradialis 5
4 – Good 5 Ext. Carpi Radialis 5
3 – Fair 4- Pronator Teres 5
2 – Poor 5 Flex. Carpi Radialis 5
1 – Trace 3+ Add. Pollicus Brev. 5-
0 – No Power 4+ Add. Digiti Min. 4
5 Abd. Hallucis 5
Figure 1.
Sensory Assessment –
Pin-Prick
Figure 2.
Sensory Assessment –
Light Touch

4. Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
Figure 3. Left Side TceMEPs to C4 Anodal Stimulation. Threshold
Search using standard protocol of 100 ms post-stimulus recording
window, and 100 uV/div. Note the initial myogenic response is in
the left BR/ECR montage at 110 mA, and well-formed upper
extremity responses with anticipated absolute latencies at 130 mA.
Figure 4. Left Side TceMEPs to C4 Anodal Stimulation. The same
data as illustrated in Fig. 3 using a 200 ms post-stimulus recording
window, and 200 uV/div. Note the initial myogenic response in the
left BR/ECR montage at 40 mA with a prolonged latency of 95 ms,
complex waveform morphology, and larger response amplitudes.

5. Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
Figure 5. Bilateral TceMEPs to C4 Anodal Stimulation. The same data illustrated in Fig. 3 and Fig.4 but includes right side recording montages. Note the presence of a
right, ipsilateral, BR/ECR response at 30 mA, 80 mA less than the conventional, short-latency, contralateral response from the left BR/ECR. Also note the presence of
LLMEPs in all of the right side montages, with complex morphology and large amplitudes from the right upper extremity target muscles.

6. Long-Latency Motor Evoked Potentials (LLMEPs):
Open the TceMEP Recording Window for an Expanded View
Discussion:
This case study demonstrates that simply doubling the recording
window of the current standard TceMEP protocols to 200 ms
reveals an interesting, and essentially undescribed category of
responses, the LLMEP.
This author encourages all clinicians to consider expanding their
recording window to collect possible LLMEPs, and to publish and
share their LLMEP findings for a greater meta-analysis of this
interesting phenomenon.