Is cerebrospinal fluid drainage safe and of potential therapeutic benefit after acute traumatic spinal cord injury?

Abstract

Following acute neurotrauma, including traumatic brain injury (TBI) and spinal cord injury (SCI), the primary mechanical trauma is followed by a series of pathological events including ischemia, oxidative cell injury, glutamatergic excitotoxicity, apoptosis, inflammation, and edema.2 In acute severe TBI, standard clinical management involves placing an intraventricular catheter that can be used to measure intracranial pressure and drain CSF.7 Of note, this approach has not been used in the setting of acute SCI, for a variety of reasons including concerns that release of CSF below a swollen, compressed cord could result in neurological deterioration.3 However, there are some theoretical advantages to placing a lumbar subarachnoid catheter following acute SCI: 1) there is evidence that drainage of CSF may enhance neurological recovery following ischemic cord injury in the setting of aortic surgery;1,5 2) measurement of spinal CSF pressures could allow targeted hypertensive therapy directed at maintaining spinal cord perfusion pressures (SCPPs) above a critical threshold; and 3) in the future, measurement of critical biomarkers in the CSF may provide prognostic and therapeutic information.4 To resolve issues related to the safety of lumbar spinal subarachnoid catheter placement and drainage of CSF following acute SCI, Kwon and colleagues6 undertook a prospective randomized clinical trial in 24 patients with ASIA Grade A–C cervical and thoracic SCI. Two patients were excluded from the analysis for technical reasons. Lumbar subarachnoid catheters were introduced 21 hours after injury and maintained for 72 hours. Patients were randomly assigned to undergo drainage or no drainage, and 11 patients were assessed in each group. The authors evaluated CSF laboratory studies, ITP, pressure waveforms, amount of drainage, motor outcome, and adverse events related to drainage and SCPP. There did not appear to be any serious permanent adverse events associated with placement of the catheters, monitoring of ITPs, or CSF drainage, although the numbers in this study were too small to exclude a low rate of serious complications. One patient (see Fig. 5) developed an epidural hematoma, although it is unclear whether this was related to placement of a lumbar subarachnoid catheter and release of CSF (which can occur around a catheter also). Interesting data were obtained with regard to ITP and CSF pressure waveforms. The ITP rose in all but one case after surgical decompression, which suggests that there was a subarachnoid block at the injury site that dampened transmission of CSF pressures. Unfortunately there was not a standardized protocol for mean arterial blood pressure (MABP) management. This was reflected in differences in the MABPs between the drainage and no-drainage groups, which rendered the small changes in apparent SCPP difficult to interpret. Peak ITP in the postoperative period was significantly higher than the peak intraoperative value in the no-drainage group but not in the drainage group. The CSF waveforms were dampened at initial placement of the lumbar subarachnoid catheters but assumed a more robust appearance after surgical decompression. In some clinical cases, spinal cord swelling or an epidural hematoma also contributed to a delayed attenuation of the waveform. Cerebrospinal fluid drainage was not associated with improved neurological recovery at 6 months, although the amount of CSF drained was fairly minimal (in 7 of 11 patients < 51 ml was drained). This reflected a conservatism by the authors against draining excessive amounts of CSF for fear of causing harm, technical issues related to the catheter, and the presence of relative subarachnoid block due to cord swelling. In summary, the study by Kwon and colleagues6 suggests that lumbar subarachnoid catheters can be placed safely in patients with acute SCI, particularly if spinal cord decompression is undertaken. This provides the opportunity to assess CSF for biomarkers that could provide prognostic and therapeutic insights. However, it is unclear whether measurement of lumbar ITP will provide meaningful acute physiological data given the high rate of subarachnoid fluid block that occurs after traumatic SCI (and which may persist in the initial acute period, even with extradural cord decompression—as shown in some of the MR imaging studies in the article). Although this study failed to show any therapeutic benefits to CSF drainage after acute SCI, the amounts of CSF drained were minimal. I look forward to further prospective studies of CSF drainage from this group to address some of the key outstanding issues raised by this small pilot study. In particular, elucidation of the potential role of CSF biomarkers will be of great interest to the field. i 179 18 , See the corresponding article in this issue, pp 181–193.