Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord

Mendez, Alan; Islam, Riazul; Latypov, Timur; Basa, Prathima; Joseph, Ogeneitsega J.; Knudsen, Bruce E.; Siddiqui, Ahad M.; Summer, Priska; Staehnke, Luke J.; Grahn, Peter J.; Lachman, Nirusha; Windebank, Anthony J.; Lavrov, Igor

doi:10.1016/j.mayocp.2020.07.039

Cited by 28 publications

(31 citation statements)

References 33 publications

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“…We developed a tridimensional model representing anatomical structures of the cervical body and stimulation electrodes using Autodesk Inventor Professional 2021 (Autodesk Inc., USA) as illustrated in Figure 1. The geometry of the cervical body was designed based on the MRI reconstructed volume of the “virtual family” from a 34 year old male model “Duke” [28], and anatomical values from the literature [13,14,26,27,37–42]. Specifically, the geometry model included 27 components: white matter and gray matter [26]; dorsal and ventral rootlets, and the respective roots, from the right and left sides at C7 spinal level [27,37]; dorsal root ganglions [40]; left and right C7 spinal nerves designed until the clavicle level [39]; cerebrospinal fluid [38]; C5, C6, C7, and T1 spinal bones with C5-C6, C6-C7, and C7-T1 inter-vertebral spinal disks [28]; epidural fat [28]; general cervical body [28]; back muscles [28]; fat [41]; skin [42]; a cathode electrode (5×5 cm) placed over C7 spinal process [13–15]; and an anode electrode (7.5×10 cm) placed on the anterior side of the neck [13–16].…”

Section: Methodsmentioning

confidence: 99%

“…The geometry of the cervical body was designed based on the MRI reconstructed volume of the “virtual family” from a 34 year old male model “Duke” [28], and anatomical values from the literature [13,14,26,27,37–42]. Specifically, the geometry model included 27 components: white matter and gray matter [26]; dorsal and ventral rootlets, and the respective roots, from the right and left sides at C7 spinal level [27,37]; dorsal root ganglions [40]; left and right C7 spinal nerves designed until the clavicle level [39]; cerebrospinal fluid [38]; C5, C6, C7, and T1 spinal bones with C5-C6, C6-C7, and C7-T1 inter-vertebral spinal disks [28]; epidural fat [28]; general cervical body [28]; back muscles [28]; fat [41]; skin [42]; a cathode electrode (5×5 cm) placed over C7 spinal process [13–15]; and an anode electrode (7.5×10 cm) placed on the anterior side of the neck [13–16].…”

Section: Methodsmentioning

confidence: 99%

“…The anatomy of the cervical body and the lower trunk spinal cord around the lumbar vertebrae is considerably different [26–28], implying that nerve fiber activation mechanisms during lumbar and cervical tSCS are also different. For instance, the ventral and dorsal rootlets are shorter and more obtuse at the cervical body compared with the lower trunk [26,27]. Moreover, the curvature of the spinal cord, as well as the shape of the vertebral bones also differ between the two anatomical regions [29].…”

Section: Introductionmentioning

confidence: 99%

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Preferential activation of proprioceptive and cutaneous sensory fibers compared to motor fibers during cervical transcutaneous spinal cord stimulation: A computational study

Freitas

Capogrosso

Nomura

et al. 2022

Preprint

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Objective: Cervical transcutaneous spinal cord stimulation (tSCS) is a promising technology that can support motor function recovery of upper-limbs after spinal cord injury. Its efficacy may depend on the ability to recruit sensory afferents and convey excitatory inputs onto motoneurons. Therefore, understanding its physiological mechanisms is critical to accelerate its development towards clinical applications. In this study, we used an anatomically realistic computational model of the cervical spine to compare α-motor, Aα-sensory, and Aβ-sensory fiber activation thresholds and activation sites. Approach: We developed a tridimensional geometry of the cervical body and tSCS electrodes with a cathode centred at the C7 spinous process and an anode placed over the anterior neck. The geometrical model was used to estimate the electric potential distributions along motor and sensory fiber trajectories at the C7 spinal level using a finite element method. We implemented dedicated motor and sensory fiber models to simulate the α-motor and Aα-sensory fibers using 12, 16, and 20 µm diameter fibers, and Aβ-sensory fibers using 6, 9, and 12 µm diameter fibers. We estimated nerve fiber activation thresholds and sites for a 2 ms monophasic stimulating pulse and compared them across the fiber groups. Main results: Our results showed lower activation thresholds of Aα- and Aβ-sensory fibers compared with α-motor fibers, suggesting preferential sensory fiber activation. We also found no differences between activation thresholds of Aα-sensory and large Aβ-sensory fibers, implying they were co-activated. The activation sites were located at the dorsal and ventral root levels. Significance: Using a realistic computational model, we demonstrated preferential activation of dorsal root Aα- and Aβ-sensory fibers compared with ventral root α-motor fibers during cervical tSCS. These findings suggest high proprioceptive and cutaneous contributions to neural activations during cervical tSCS, which inform the underlying mechanisms of upper-limb functional motor recovery.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Preferential activation of proprioceptive and cutaneous sensory fibers compared to motor fibers during cervical transcutaneous spinal cord stimulation: A computational study

Freitas

Capogrosso

Nomura

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Placement of the cathode at T12 previously resulted in the perfect anatomical classification of L2–L3 and L5–S2 spinal cord segments in 34 participants with neurological disorders [ 10 ]. This is really important considering the vast variability in the lumbosacral segment length in healthy individuals [ 21 ].…”

Section: Discussionmentioning

confidence: 99%

Single Lead Epidural Spinal Cord Stimulation Targeted Trunk Control and Standing in Complete Paraplegia

Gorgey

Gouda

2022

JCM

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A 25-year-old male with T3 complete AIS A was implanted with percutaneous spinal cord epidural stimulation (scES; eight contacts each) leads and a Medtronic Prime advance internal pulse generator. The two leads were placed at the midline level to cover the region of the T11–T12 vertebrae. Five days after implantation, X-ray showed complete migration of the left lead outside the epidural space. Two weeks after implantation, reprogramming of the single right lead (20 Hz and 240 µs) after setting the cathode at 0 and the anode at 3 resulted in target activation of the abdominal muscles and allowed for the immediate restoration of trunk control during a seated position, even with upper extremity perturbation. This was followed by achieving immediate standing after setting the single lead at −3 for the cathode and +6 for the anode using stimulation configurations of 20 Hz and 240 µs. The results were confirmed with electromyography (EMG) of the rectus abdominus and lower extremity muscles. Targeted stimulation of the lumbosacral segment using a single lead with a midline approach immediately restored the trunk control and standing in a person with complete paraplegia.

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“…After unilateral lumbar deafferentation in spinalized animals, EES elicited locomotor activity only on the non-deafferented side when animals were suspended in air, while the sensory input from non-deafferented leg was able to trigger rhythmic movement on deafferented side in presence of EES (Gerasimenko and others 2002; Lavrov and others 2008). To achieve the optimal activation of the circuitry, precise positioning of the electrodes in relation to segment-specific spinal cord neuroanatomy is critically important (Mendez and others 2020), as the highest peak-to-peak motor responses were achieved with electrodes positioned in close proximity to the dorsal entry zone (Cuellar and others 2017). It should be also considered that reorganization of the spinal network may potentially lead to pathological consequences, including neuropathic pain (Kramer and others 2017), muscle spasticity (Roy and Edgerton 2012), and autonomic dysreflexia (Taylor 2018).…”

Section: Spinal Cord Reorganization After Scimentioning

confidence: 99%

The Translesional Spinal Network and Its Reorganization after Spinal Cord Injury

et al. 2020

Self Cite

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Evidence from preclinical and clinical research suggest that neuromodulation technologies can facilitate the sublesional spinal networks, isolated from supraspinal commands after spinal cord injury (SCI), by reestablishing the levels of excitability and enabling descending motor signals via residual connections. Herein, we evaluate available evidence that sublesional and supralesional spinal circuits could form a translesional spinal network after SCI. We further discuss evidence of translesional network reorganization after SCI in the presence of sensory inputs during motor training. In this review, we evaluate potential mechanisms that underlie translesional circuitry reorganization during neuromodulation and rehabilitation in order to enable motor functions after SCI. We discuss the potential of neuromodulation technologies to engage various components that comprise the translesional network, their functional recovery after SCI, and the implications of the concept of translesional network in development of future neuromodulation, rehabilitation, and neuroprosthetics technologies.

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Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord

Cited by 28 publications

References 33 publications

Preferential activation of proprioceptive and cutaneous sensory fibers compared to motor fibers during cervical transcutaneous spinal cord stimulation: A computational study

Preferential activation of proprioceptive and cutaneous sensory fibers compared to motor fibers during cervical transcutaneous spinal cord stimulation: A computational study

Single Lead Epidural Spinal Cord Stimulation Targeted Trunk Control and Standing in Complete Paraplegia

The Translesional Spinal Network and Its Reorganization after Spinal Cord Injury

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