From the Research
The standard montage for direct current motor evoked potentials (dcMEP) involves placing stimulating electrodes at C1/C2 or C3/C4 positions according to the International 10-20 EEG system, with recording electrodes placed in relevant muscle groups, as supported by the study 1.
Key Considerations
- For upper extremity monitoring, recording electrodes are typically placed in the abductor pollicis brevis, first dorsal interosseous, or abductor digiti minimi muscles.
- For lower extremity monitoring, recording electrodes are placed in the tibialis anterior, abductor hallucis, or gastrocnemius muscles.
- The stimulation parameters generally include a train of 5-7 pulses with an interstimulus interval of 2-4 ms, pulse width of 50-75 μs, and intensity ranging from 100-400V, as described in the study 1.
Rationale
The montage effectively activates the corticospinal tract by depolarizing pyramidal cells, allowing for assessment of motor pathway integrity during surgeries that put these pathways at risk, as demonstrated in the study 2. Proper electrode placement and parameter selection are crucial for obtaining reliable signals while minimizing stimulation artifacts and patient movement during surgical procedures. The study 1 provides evidence for the safety and efficacy of motor mapping utilizing short pulse train direct cortical stimulation, which is relevant to dcMEP.