Abstract
Current medical care lacks an effective functional evaluation for the spinal cord. Magnetic resonance imaging and computed tomography mainly provide structural information of the spinal cord, while spinal somatosensory evoked potentials are limited by a low signal to noise ratio. We developed a non-invasive approach based on near-infrared spectroscopy in dual-wavelength (760 and 850 nm for deoxy- or oxyhemoglobin respectively) to record the neurovascular response (NVR) of the peri-spinal vascular network at the 7th cervical and 10th thoracic vertebral levels of the spinal cord, triggered by unilateral median nerve electrical stimulation (square pulse, 5-10 mA, 5 ms, 1 pulse every 4 minutes) at the wrist. Amplitude, rise-time, and duration of NVR were characterized in 20 healthy participants. A single, painless stimulus was able to elicit a high signal-to-noise ratio and multi-segmental NVR (mainly from Oxyhemoglobin) with a fast rise time of 6.18 [4.4-10.4] seconds (median [Percentile 25-75]) followed by a slow decay phase for about 30 seconds toward the baseline. Cervical NVR was earlier and larger than thoracic and no left/right asymmetry was detected. Stimulus intensity/NVR amplitude fitted to a 2nd order function. The characterization and feasibility of the peri-spinal NVR strongly support the potential clinical applications for a functional assessment of spinal cord lesions.
Highlights
The spinal cord is a frequent target of traumatic, degenerative, tumoral, compressive, or vascular lesions, but is involved in neuropathic pain [1]
There is a relative lack of functional assessment of the spinal cord which contrasts to the well-developed structural evaluation by Magnetic Resonance Imaging (MRI) or Computed Tomography techniques [3]
General findings In the present study, the spinal neurovascular response (NVR) triggered by the unilateral median nerve electrical stimulation was recorded in 20 healthy participants for the first time, by a non-invasive Functional Near-Infrared Spectroscopy (fNIRS) system
Summary
The spinal cord is a frequent target of traumatic, degenerative, tumoral, compressive, or vascular lesions, but is involved in neuropathic pain [1]. There is a relative lack of functional assessment of the spinal cord which contrasts to the well-developed structural evaluation by Magnetic Resonance Imaging (MRI) or Computed Tomography techniques [3]. The spinal cord BOLD signal activation has been recorded at the corresponding spinal segment applying peripheral sensory stimulation in noxious intensity ranges [5], [7] or by long-lasting finger-tapping motor tasks [6]. Despite these paradigms, resulting BOLD signals showed low amplitudes compared with the baseline signal [5], [7]. Recent developments are gradually overcoming these challenges and increasing the potential clinical applications [8]-[11]
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