Figure 7. Epidural volleys evoked by brainstem stimulation and lateral anodal stimulation in one anaesthetised patient undergoing surgery for an intramedullary tumour.
The epidural electrode is located at the D2 level. Each trace is the mean of ten sweeps. Lateral anodal stimulation evoked a single negative wave (L1) with a latency of 3.6 ms. The volley evoked by brainstem stimulation appeared 1.7 ms earlier.