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| Number | Reference | Number of samples | IONM modalities used | Stimulation parameters | Muscles used to monitor MEP | Improvement criteria | Results |
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| 1 | Barley et al. [7] | One (15-month-old boy) | TcMEP and SSEP | C1-C2 scalp electrode positioning, current stimulation (145 mA to 187 mA for the left extremities and 175 mA to 200 mA for the right extremities) | Bilateral quadriceps femoris, tibialis anterior, gastrocnemius, sphincter, abductor pollicis brevis, and abductor hallucis | Not mentioned | TcMEP response of the left APB had an increment in amplitude. The patient had observable left upper extremity improvement |
| 2 | Voulgaris et al. [8] | 25 (2 had no IONM results) | TcMEP and EMG | C1-C2 with multipulse current stimulation, 0 mA to 200 mA, stimulus duration 0.2 ms to 0.5 ms | Not mentioned | >50% MEP amplitude improvement | 17 patients with >50% improvement had better VAS score improvement |
| 3 | Rodrigues et al. [9] | One (case report) | SSEP, MEP, and free running EMG | C3-C4 stimulation | Not mentioned muscles’ names specifically but monitoring covered L3-S2 myotomes | Not mentioned | MEP improved as much as 30%, and patient had returned to sports |
| 4 | Raynor et al. [10] | 386 patients had IOM signals improvement out of 12375 patients who had spinal surgeries over 25 years | DNEP, TcMEP, spontaneous EMG, triggered EMG, and dermatomal SSEP | C3-C4 TcMEP scalp electrode stimulation montage | Upper extremity TcMEP was recorded from deltoid, flexor/extensor carpi radialis, and/or abductor digiti minimi/abductor pollicis brevis. Lower extremity TcMEP was recorded from anterior tibialis, medial gastrocnemius, and/or extensor hallucis longus | Not mentioned | The results did not mention specifically TcMEP improvement, but out of the modalities used, 88.7% of patients had IOM signals improvement, but one patient out of this percentage had permanent neurological deficit |
| 5 | Visser et al. [11] | 74 patients | TcMEP | Cz-Fz with monophasic stimulation and C3-C4 with biphasic stimulation | For the lower limbs, the quadriceps muscle (L2-L4), the tibialis anterior muscle (L4-L5), the hamstrings (L5-S1), or the gastrocnemius muscle (S1–S2). For cervical, the bilateral trapezoid muscle (C2–C4), the biceps (C5–C6), and triceps muscle (C7–C8) of the arm; the extensor muscles of the forearm (C6–C7); or the abductor digitus V muscle (C6–C8) | >200% of amplitude increment | There is a correlation between the duration of symptoms onset and the MEP improvement. MEP improvement can be accurate if the symptoms’ onset duration is less than half a year |
| 6 | Wang et al. [12] | 59 patients who had cervical myelopathy who underwent laminoplasty or laminectomy | MEP and SSEP | Not mentioned | Not mentioned | Not mentioned | Patients who had MEP signals improvement had a significant mJOA improvement rate. MEP amplitude was found to be a more accurate parameter compared to MEP latency in predicting surgery outcome |
| 7 | Dhall et al. [13] | 32 | EMG, MEP, and SSEP (not used for the study) | 100 V–1000 V constant voltage stimulation, C1-C2 anodal stimulation, double train with a total of 9 pulses, 50 ms pulse width, 1.7 ms interstimulus, and 13.1 ms ISI | Not mentioned | Comparison with AIS grade and BASIC score of MRI images | MEP outcome (present) highly correlated with better AIS grade and BASIC grade |
| 8 | Piasecki et al. [2] | 18 | MEP and SSEP (not used for the study) | 50 V–150 V C1-C2 biphasic stimulation, 5 to 7 train pulses, 500 Hz, and 1 ms interstimulus pulse | One upper limb muscle (control), bilateral tibialis anterior/bilateral abductor hallucis | >20% of AUC MEP; > 50% of ZCQ score | The MEP improvement was related to the early follow-up functional outcome |
| 9 | Wi et al. (2019) [14] | 29 patients who had improvement in IONM signals out of 317 cases | MEP and SSEP | Not mentioned | Upper extremity TcMEP was recorded from deltoid, triceps, and thenar muscles. Lower extremity TcMEP was recorded from anterior tibialis and abductor halluces | Comparison with MISS, SF-36, JOA, NDI, and Oswestry Disability Index | The patients with MEP improvement had a better MISS improvement rate, while the patients with SSEP improvement only had a better SF-36 improvement rate |
| 10 | He et al. [15] | One (case report) | MEP and free running EMG | Not mentioned | Bilateral iliopsoas, rectus femoris, tibialis anterior, and medial gastrocnemius | Not mentioned | MEP improvement aligned with the patient’s relieved symptoms |
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