Dear Sir/Madam,

I enjoyed the paper by Kao et al. [1]. My only concern is that the authors (in their algorithm at Fig. 3) say that if there is motor weakness immediately postoperatively the potential causes include the following: “screw malposition, root injury, neuropraxia, vascular compromise”. Although in their study no patient who had a significant postoperative spinal epidural haematoma (SEH) had immediate motor weakness postoperatively (the earliest symptoms occurred 1 h postoperatively), it is well recognised that SEH can present with deficits in the recovery area of theatre immediately on awakening from the anaesthetic. Lawton et al. [2] reported 12 patients with postoperative SEH of whom six (50 %) had new neurological deficits at the time of first assessment. Rodi et al. [3] reported a patient who had a postoperative SEH where there was loss of intraoperative evoked potentials and, immediately postoperatively, new neurological deficits. It is, therefore, the case that following spinal surgery, SEH can develop so quickly that there are new deficits when the patient awakens from the anaesthetic in the recovery area of theatre. This is an important message because there can be an assumption that new neurological deficits seen immediately postoperatively are probably a consequence of injury to neural structures intraoperatively which is something that cannot be reversed surgically and which may or may not improve with time. However, what the surgeon must do is immediately exclude any treatable cause of new neurological injury, the two most obvious of which would be SEH or malposition of instrumentation.