PMC9108512_01
MRI (T2 weighted image, sagittal and axial view). The arrow points towards the intramedullary hypointense lesion the level of the T8-T9 vertebral body. In the axial T2-weighted image the lesion was seen intramedullary, situated mostly on the right ventral side of the spinal cord and also a small T2-hyperintense edge was detected cranially.
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MRI revealed a hypointense lesion of the spinal cord both on T1 and T2-weighted sequences at the level of the T8-T9 vertebral bodies, showing no contrast enhancement (Fig. 1).
IONM monitoring SSEP and tcMEP. SSEP signal elicited on the right tibial nerve were absent (see column no. 3). The other SSEP recording were found normal. The tcMEP responses (left leg + left arm - right leg) were recordable over the left upper extremity, but were lacking over the right lower extremity and only a small amplitude (50-60 microV) MEP response was detectable over the left tibialis anterior muscle, using maximal stimulus intensity. TcMEP and SSEP amplitudes did not changes after hematoma evacuation. (The red SSEP lines represent the preoperative baseline, while the green lines the postoperative responses.). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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The tcMEP responses were recordable over the upper extremity, but were lacking over the right lower extremity and only a small amplitude (50-60 microV) MEP response was detectable over the left tibialis anterior muscle, using maximal stimulus intensity. (Fig. 2). TcMEP and SSEP amplitudes did not change after hematoma evacuation. (Fig. 2).
IONM monitoring, eMEP. The upper two curves present three consecutive normal eMEP response recorded with the proximal flexible electrode (p1-p2 and p1-p3) in cascade arrangement. The lower two curves represent four consecutive eMEP responses recorded with the distal flexible electrode (d1-d2 and d1-d3) in cascade arrangement. Moving the electrode cranially, the eMEP is gradually built up (please see the arrows pointing towards the gradually developed electrical response).
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Decreasing the distance between the two electrodes by moving the distal electrode closer to the proximal one, theoretically leads to the appearance of eMEP response at the distal electrode also. (Note: Due to technical difficulties, the surgeon decided to change the orientation of the electrode, leading to inverted eMEP response (Fig. 3)).
Hematoma evacuation. On the upper picture the scissor points towards the lesion identified with eMEP. Please note the lack of macroscopic signs. (right caudal - left cranial). The lower picture demonstrates the adequate localization of the hematoma with eMEP. The wide arrows point towards the eMEP electrodes, narrow arrows show the contacts of them.
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Surgical incision was made at this level and the hematoma was successfully evacuated. (Fig. 4).