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Letter: Ultrasound in Traumatic Spinal Cord Injury: A Wide-Open Field

2022; Lippincott Williams & Wilkins; Volume: 90; Issue: 4 Linguagem: Inglês

10.1227/neu.0000000000001866

1524-4040

Jesse A. Stokum, Timothy Chryssikos, Phelan Shea, Joshua Olexa, Gary Schwartzbauer, Bizhan Aarabi,

Spinal Dysraphism and Malformations

To the Editor: We were very pleased to read the recent article by Dr Hwang et al1 titled “Ultrasound in Traumatic Spinal Cord Injury: A Wide-Open Field.” In their article, the authors reviewed the potential applications of ultrasound in patients with traumatic spinal cord injury (tSCI). We strongly agree that ultrasound holds great promise as a real-time imaging modality in both blunt and penetrating tSCIs. After tSCI, maladaptive secondary processes, including ischemia, inflammation, and upregulation of cationic channels,2 precipitate catastrophic injury to the endothelium at the injury epicenter and promote the expansion of intramedullary hemorrhage and spinal cord edema. This dynamic intramedullary lesion expansion3,4 occurs at a rate of 300 to 900 µm/hour and results in further compression of the swollen spinal cord within the spinal canal. As Dr Hwang et al1 state, currently, there are unfortunately no effective pharmacological treatments for tSCI. Adequate spinal cord decompressive surgery, therefore, represents the only effective neuroprotective intervention to reduce secondary injury. We and other groups have previously reported that the adequacy of spinal cord decompression, defined as the presence of cerebrospinal fluid surrounding the spinal cord5 after surgery, is strongly associated with AIS grade conversion.3,6-8 MRI currently represents the gold standard modality for evaluating spinal cord decompression.9 However, MRI is expensive, inconsistently available, and time-consuming. That many health care facilities throughout the world lack basic MRI technology at this time is well known. Ultrasound, on the other hand, is far less expensive and much more flexible, and several advantages provided by intraoperative ultrasound have been previously described in a variety of spine surgery settings.10 Dr Hwang et al1 have highlighted various applications of ultrasound in spinal cord injury, including measurement of spinal cord perfusion, molecular imaging, and focused ultrasound ablation and neuromodulation. Although we certainly agree that these future applications are exciting and advocate for their continued development, we believe ultrasound lends itself even more immediately to the basic problem of achieving de facto decompression of the injured spinal cord. The ability to use ultrasound intraoperatively is highly consequential, in that it can confirm spinal cord decompression in real time and in some cases serve as a guide to decision making. For instance, ultrasound may show that additional levels of decompression (ie, laminectomy) are required to adequately decompress the spinal cord. Ultrasound also provides the means to evaluate spinal cord decompression in patients with penetrating injuries in whom retained metallic fragments preclude MRI. If properly validated, intraoperative ultrasound could be implemented as a cost-effective alternative to postoperative MRI and extended to health care centers without access to it. The advantages of affordability and accessibility could greatly improve the care of patients with spinal cord injury. For these reasons, we have commenced an ongoing clinical investigation of the role of ultrasound for confirming spinal cord decompression intraoperatively and, secondarily, its role in guiding real-time decision making for achieving spinal cord decompression. For patients with traumatic cervical spinal cord injury who undergo laminectomy for decompression at the R Adams Cowley Shock Trauma Center, the surgical team's impression of the intraoperative ultrasound results are subsequently compared with the gold standard of postoperative MRI or computed tomography myelogram. To date, we have retrospectively evaluated 27 patients, and the results are promising (Figure). We have, therefore, started to prospectively recruit patients and aim to enroll at least 25 additional participants to validate the role of intraoperative ultrasound in the surgical management of spinal cord injury.FIGURE.: On August 31, 2021, at 11 am, this 44-year-old woman had an accidental fall from horseback riding and sustained an acute traumatic central cord syndrome. Her American Spinal Injury Association (ASIA) motor score at the time of admission was 44 and ASIA impairment scale D. Her multiplanar computed tomography scan of the cervical spine was negative for any fracture or dislocation. A, Preoperative T2W midsagittal image of the cervical spine indicating spinal stenosis from C4-C6 (arrow) and a 17.7-mm intramedullary lesion at the C5/C6 level. B, Preoperative T2W axial image of the cervical spine at the level of C5/6 indicating snake eyes high-intensity signal change with tight spinal stenosis. C, Midsagittal postoperative cervical MRI images 17 hours after C4-C6 laminectomy and posterior spinal fusion indicating spinal cord decompression and intramedullary signal change at the level of C5/6 (arrow). D, Postoperative T2W C5/6 axial images of the cervical spine indicating complete decompression of the spinal cord after laminectomy with high-intensity intramedullary signal change. E, Midsagittal intraoperative ultrasound view after laminectomy indicating complete spinal cord decompression of the spinal cord and an echogenic white signal where the intramedullary lesion was on MRI images (arrow). F, Intraoperative ultrasonographic axial image of the spinal cord after laminectomy indicating circumferential decompression of the spinal cord.Overall, we are enthusiastic about the myriad potential applications of ultrasound in spinal cord injury. We believe that this flexible and widely available imaging modality represents an important tool in the trauma neurosurgeon's arsenal. Further development of this technology, including the advent of an optimal probe for determining spinal cord decompression from anterior approaches, would further augment the utility of this remarkable technology.