In Reply: Ultrasound in Traumatic Spinal Cord Injury: A Wide-Open Field.

Abstract

To the Editor: We thank Dr Abulla and colleagues for their interest in our article.1,2 Novel applications of ultrasound are vast and ever increasing. We limited our review to studies that applied ultrasound to the spinal cord because of the shear breadth and depth of ultrasound research in spinal cord injury (SCI). We acknowledge that ultrasound has been studied extensively outside of the spinal cord in the setting of SCI. Abulla et al2 have mentioned ultrasound-based diagnosis and monitoring of hematoma, deep vein thrombosis, and muscle atrophy.1 In addition, studies have applied ultrasound to enhance the management of pressure ulcers, bladder dysfunction, and musculoskeletal and vascular conditions in patients with SCI.3-5 Ongoing research and development efforts are leveraging ultrasound's versatility to target multiple systems to improve both functional outcome and quality of life of patients with SCI. This trend supports our belief that ultrasound technology is well-poised to become a powerful multifaceted adjunct in the management of acute and chronic SCIs. In the context of neurorehabilitation after SCI, we agree with Abdulla et al that a robust closed-loop system based on physiologically and functionally sound and meaningful feedback signals is paramount to success. One promising avenue is neurofeedback. Neurofeedback is the ability to record neurobehavioral data and present it as sensory stimuli to the subject for self-regulation of responses.6 Neurofeedback has been used in a wide range of neurological and neurobehavioral disorders including stroke, traumatic brain injury, autism, and pain disorders.7 Neurofeedback has been studied in SCI, most commonly with electromyography (EMG) recordings delivered as audiovisual feedback for muscle training.8 Electroencephalogram has also been used to modulate neuropathic pain.9 Although no study has used ultrasound for neurofeedback in SCI motor rehabilitation, this method could have distinct advantages over EMG for accessibility, signal fidelity, cost-effectiveness, and noninvasiveness. Ultrasound has been shown to detect differences in functional muscle status with real-time video monitoring after SCI.10 Capabilities that enable ultrasound to generate multisensory input signals already exist, and future studies should investigate their utility in neurorehabilitation settings. Ultrasound-based wearable technology also holds great promise. We are excited to see how ultrasound will revolutionize the way we care for our patients with SCI in the near future.