PMC6308139_01
Neuroimaging and electrophysiological findings in "snake eye" appearance myelopathy. (A) Sagittal T2w image (above) and axial T2w image at C6 depicting a signal hyperintensity ("snake eye" appearance) located bilaterally in the central cord spanning about 3 segments. (B) Contact heat evoked potentials recorded at C4, C6, and T4 on the left, with an absent response at C6. (C) Pinprick evoked potentials recorded at C4, C6, and T4 on the left, with responses from all segments. (D) Somatosensory evoked potential recorded from the left ulnar nerve. (E) Schematic drawing indicating a spinal lesion (yellow) located around the spinal anterior commissure impairing conduction of crossing heat-sensitive pathways (dotted red line) while sparing noxious mechanosensitive pathways (black line). The color coding of the antero-lateral spinothalamic tract positions mechanical afferents (black) lateral and superficial to thermal afferents (red). Dorsal-column pathways are unaffected by the anteriorly located lesion (green line). Normal conduction is shown for supra- and infra-lesional stimulation indicating preservation of the antero-lateral quadrant where the spinothalamic tract ascends.
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F1
Magnetic resonance images revealed a multi-segmental (C5-C7), longitudinal "snake eye" appearance myelopathy (Figure 1A). Ulnar somatosensory evoked potentials (SEPs) and sensory nerve conduction studies were normal (Figure 1D). CHEPs were normal at C4 and T4 with high pain ratings to the heat stimulation, but almost complete loss of painful heat sensation and absent CHEPs at the level of C6 (Figure 1B). In contrast, PEPs remained preserved at all segments (Figure 1C).