Browsing by Author "Eblen-Zajjur, Antonio"

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    Non-Invasive Functional Evaluation of the Human Spinal Cord by Assessing the Peri-Spinal Neurovascular Network With Near Infrared Spectroscopy
    (2021) Valenzuela, Felipe; Rana, Mohit; Sitaram, Ranganatha; Uribe, Sergio; Eblen-Zajjur, Antonio
    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.
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    Peri-spinal Neurovascular Response Triggered by a Painless Electrical Nerve Stimulation in Patients with Chronic Arterial Hypertension
    (2023) Appelgren, Juan Pablo Gonzalez; Caulier-Cisterna, Raul; Oyarzun, Juan Esteban; Uribe, Sergio; Eblen-Zajjur, Antonio
    PurposeAlterations of the central nervous system are frequent complications in patients with chronic arterial hypertension (AHT). However, functional spinal cord lesions are not often detected in these patients despite diagnostic advances in neuroimaging and electrophysiology. Recently, a new non-invasive functional near infrared spectroscopy (fNIRS) application was developed for assessment of the peri-spinal neurovascular response (NVR) as a functional test of the spinal cord.MethodsThe continuous wave fNIRS technique was applied to detect changes in O(2)Hb concentration during the peri-spinal NVR triggered by non-noxious electrical stimulation of the median nerve at the wrist, and recorded at cervical and thoracic spinal levels using three different stimulation protocols in subjects with AHT treated with losartan (n = 22; 142.14 +/- 133.9 months of disease) and compared to healthy control subjects (n = 37). The body mass index (BMI) and the median nerve conduction velocity (NCV) were also recorded.ResultsThe NVR of patients with AHT showed a significantly lower amplitude (- 70.4%; cervical), longer rise time (+ 22.2%; cervical), and longer duration (+ 28.0%; thoracic) than the control group (p < 0.01). The stimulus intensity-response in the AHT group was - 53.5%, - 55.9%, and - 63% lower in amplitude than the controls (p < 0.05) for the increasing stimulus intensity steps (5; 7.5 and 10 mA, respectively) at the cervical level. Patients with BMI > 30 showed more intense changes. The median NCV was normal for both groups.ConclusionThese data show, for the first time, the difference in peri-spinal NVR between normal subjects and losartan-treated ATH patients, indicating the potential of a non-invasive fNIRS technique to find sensory functional abnormalities of the spinal cord in these patients.