Review

Authors: Verónica Murcia-Belmonte, Lynda Erskine

Retinal ganglion cells (RGCs) extend axons out of the retina to transmit visual information to the brain. These connections are established during development through the navigation of RGC axons along a relatively long, stereotypical pathway. RGC axons exit the eye at the optic disc and extend along the optic nerves to the ventral midline of the brain, where the two nerves meet to form the optic chiasm. In animals with binocular vision, the axons face a choice at the optic chiasm-to cross the midline and project to targets on the contralateral side of the brain, or avoid crossing the midline and project to ipsilateral brain targets. Ipsilaterally and contralaterally projecting RGCs originate in disparate regions of the retina that relate to the extent of binocular overlap in the visual field. In humans virtually all RGC axons originating in temporal retina project ipsilaterally, whereas in mice, ipsilaterally projecting RGCs are confined to the peripheral ventrotemporal retina. This review will discuss recent advances in our understanding of the mechanisms regulating specification of ipsilateral versus contralateral RGCs, and the differential guidance of their axons at the optic chiasm. Recent insights into the establishment of congruent topographic maps in both brain hemispheres also will be discussed.

Topics: Animals; Axons; Brain; Cell Lineage; Humans; Retinal Ganglion Cells; Vision, Binocular; Visual Pathways

PubMed: 31277365
DOI: 10.3390/ijms20133282

Authors: Amit Shah, Aadil Lodhi, Michael Bianco...

This manuscript describes the refinements of ipsilateral wire protection and bailout strategy for large-bore femoral access and especially transcatheter aortic valve replacement. This ipsilateral wire protection requires no additional expenses and can provide effective arteriotomy site protection without the need for contralateral femoral access, especially in cases when contralateral wiring and crossover are not feasible. Ipsilateral wiring can be done both as prophylactic protection and as bailout strategy. The exact steps required for ipsilateral protection and bailout are described. A comparison between ipsilateral wiring with conventional contralateral femoral and transradial wire protection is delineated.

Topics: Aortic Valve; Aortic Valve Stenosis; Femoral Artery; Humans; Transcatheter Aortic Valve Replacement; Treatment Outcome

PubMed: 34338655
DOI: 10.25270/jic/20.00651

Review

Authors: Brice T Cleland, Sangeetha Madhavan

Stroke-related damage to the crossed lateral corticospinal tract causes motor deficits in the contralateral (paretic) limb. To restore functional movement in the paretic limb, the nervous system may increase its reliance on ipsilaterally descending motor pathways, including the uncrossed lateral corticospinal tract, the reticulospinal tract, the rubrospinal tract, and the vestibulospinal tract. Our knowledge about the role of these pathways for upper limb motor recovery is incomplete, and even less is known about the role of these pathways for lower limb motor recovery. Understanding the role of ipsilateral motor pathways to paretic lower limb movement and recovery after stroke may help improve our rehabilitative efforts and provide alternate solutions to address stroke-related impairments. These advances are important because walking and mobility impairments are major contributors to long-term disability after stroke, and improving walking is a high priority for individuals with stroke. This perspective highlights evidence regarding the contributions of ipsilateral motor pathways from the contralesional hemisphere and spinal interneuronal pathways for paretic lower limb movement and recovery. This perspective also identifies opportunities for future research to expand our knowledge about ipsilateral motor pathways and provides insights into how this information may be used to guide rehabilitation.

Topics: Efferent Pathways; Functional Laterality; Humans; Lower Extremity; Stroke; Stroke Rehabilitation

PubMed: 33665910
DOI: 10.1002/jnr.24822

Review

Authors: Liliana Savin, Tudor Pinteala, Paul Botez...

Numerous studies report the success and outcomes of the total knee arthroplasty (TKA); however, few papers present patients with knee osteoarthritis and ipsilateral hip fusion. One controversy when treating patients requiring a TKA with prior ipsilateral hip fusion is whether to first perform a total hip arthroplasty (THA) of the fused hip, followed by the ipsilateral TKA, or to proceed with the TKA without replacing the hip; studies suggest that the position of the fused hip is a key factor when making this therapeutical decision. In addition, performing a TKA in patients with an ipsilateral fused hip may require modifications to the surgical technique generated by the lack of joint mobility in the hip. We identified 12 studies encompassing 30 patients with hip fusion and ipsilateral TKA in current orthopedic literature, but only six offered insights on patient positioning on the operating table during surgery. This study aims to review the current literature on patients with knee osteoarthritis and prior ipsilateral hip fusion and to present some technical considerations when performing a TKA on a 75-year-old patient with hip ankylosis who underwent a total ipsilateral knee arthroplasty in our clinic.

PubMed: 38138932
DOI: 10.3390/jpm13121705

Authors: Carmelo Lucio Sturiale, Alba Scerrati, Luca Ricciardi...

: A relationship between the geometry and symmetry of Willis' circle and intracranial aneurysms was reported for anterior communicating and posterior communicating (PCom) aneurysms. A similar association with the middle cerebral artery (MCA) aneurysms instead appeared weaker. : We reviewed 432 patients from six Italian centers with unilateral MCA aneurysms, analyzing the relationship between the caliber and symmetry of Willis' circle and the presence of ruptured and unruptured presentation. CT-angiograms were evaluated to assess Willis' circle geometrical characteristics and the MCA aneurysm side, dimension and rupture status. : The hypoplasia of the first segment of the anterior cerebral artery (A1) was in approximately one-quarter of patients and PCom hypoplasia was in almost 40%. About 9% had a fetal PCom ipsilaterally to the aneurysm. By comparing the aneurysmal and healthy sides, only the PCom hypoplasia appeared significantly higher in the affected side. Finally, the caliber of the internal carotid artery (ICA) and the first segment of MCA (M1) caliber were significantly greater in patients with unruptured aneurysms, and PCom hypoplasia appeared related to the incidence of an ipsilateral MCA aneurysm and its risk of rupture. : Although according to these findings asymmetries of Willis' circle are shown to be a risk factor for MCA aneurysm formation and rupture, the indifferent association with ipsilateral or contralateral hypoplasia remains a datum of difficult hemodynamic interpretation, thereby raising the concern that this association may be more casual than causal.

PubMed: 38792350
DOI: 10.3390/jcm13102808

Authors: Benjamin W Fait, Bianca Cotto, Tatsuya C Murakami...

The spinal cord receives inputs from the cortex via corticospinal neurons (CSNs). While predominantly a contralateral projection, a less-investigated minority of its axons terminate in the ipsilateral spinal cord. We analyzed the spatial and molecular properties of these ipsilateral axons and their post-synaptic targets in mice and found they project primarily to the ventral horn, including directly to motor neurons. Barcode-based reconstruction of the ipsilateral axons revealed a class of primarily bilaterally-projecting CSNs with a distinct cortical distribution. The molecular properties of these ipsilaterally-projecting CSNs (IP-CSNs) are strikingly similar to the previously described molecular signature of embryonic-like regenerating CSNs. Finally, we show that IP-CSNs are spontaneously regenerative after spinal cord injury. The discovery of a class of spontaneously regenerative CSNs may prove valuable to the study of spinal cord injury. Additionally, this work suggests that the retention of juvenile-like characteristics may be a widespread phenomenon in adult nervous systems.

PubMed: 39314356
DOI: 10.1101/2024.09.09.612115

Authors: Sónia A Alves, Marco Preuße, Hagen Hommel...

This study aimed to characterize ipsilateral loading and return to weight-bearing symmetry (WBS) in patients undergoing total hip arthroplasty (THA) during activities of daily living (ADLs) using instrumented insoles. A prospective study in 25 THA patients was performed, which included controlled pre- and postoperative follow-ups in a single rehabilitation center of an orthopedic department. Ipsilateral loading and WBS of ADLs were measured with insoles in THA patients and in a healthy control group of 25 participants. Measurements in the THA group were performed at 4 different visits: a week pre-THA, within a week post-THA, 3-6 weeks post-THA, and 6-12 weeks post-THA, whereas the healthy control group was measured once. ADLs included standing comfortably, standing evenly, walking, and sit-to-stand-to-sit (StS) transitions. All ADLs were analyzed using discrete methods, and walking included a time-scale analysis to provide temporal insights in the ipsilateral loading and WBS waveforms. THA patients only improved beyond their pre-surgery levels while standing comfortably (ipsilateral loading and WBS, < 0.05) and during StS transitions (WBS, < 0.05). Nevertheless, patients improved upon their ipsilateral loading and WBS deficits observed within a week post-surgery across all investigated ADLs. Ipsilateral loading and WBS of THA patients were comparable to healthy participants at 6-12 weeks post-THA, except for ipsilateral loading during walking ( < 0.05) at the initial and terminal double-leg support period of the stance phase. Taken together, insole measurements allow for the quantification of ipsilateral loading and WBS deficits during ADLs, identifying differences between pre- and postoperative periods, and differentiating THA patients from healthy participants. However, post-THA measurements that lack pre-surgery assessments may not be sensitive to identifying patient-specific improvements in ipsilateral loading and WBS. Moreover, StS transitions and earlier follow-up time points should be considered an important clinical metric of biomechanical recovery after THA.

PubMed: 35284427
DOI: 10.3389/fbioe.2022.813345

Review

Stimuli-evoked NOergic molecules and neuropeptides at acupuncture points and the gracile nucleus contribute to signal transduction of propagated sensation along the meridian through the dorsal medulla-thalamic pathways.

Authors: Sheng-Xing Ma

Numerous studies from different international groups have demonstrated that sensations can be propagated along acupuncture channel pathways. The propagated sensation along the channel pathway (PSCP) can be elicited by electroacupuncture (EA), transcutaneous electrical nerve stimulation (TENS), manual acupuncture (MA), and heat applied to distal acupuncture points (acupoints). Nitric oxide (NO) levels were reported to be elevated in the gracile nucleus and skin regions near to the EA sites, with higher levels at acupoints associated with an enhanced expression of NO synthase and transient receptor potential vanilloid type 1. The stimuli, EA, MA, TENS, and heat, have been used to elicit axonal reflexes, which increase local release of NO and neuropeptides such as calcitonin gene related peptide. Furthermore, the sensation of PSCP along the body surface occurs only ipsilaterally to the stimulated acupoints in various human studies, which does not support the involvement of the spinal-thalamic pathway, which would involve cross over transmission of the signals. The gracile nucleus receives ascending input from the sciatic nerve and responds to somatosensory stimulation mainly on the ipsilateral side via the dorsal column pathway. EA at Zusanli (ST36) increases NO release and expression of NO synthase mainly in the ipsilateral side of the gracile nucleus, while the cardiovascular effects and analgesic responses to EA at ST36 are changed by influences of l-arginine-derived NO synthesis in the ipsilateral gracile nucleus in rats. The stimuli-induced release of NOergic molecules and neuropeptides exist high levels in the acupoints, which contain rich neuronal components and blood vessels. Enhanced NOergic molecules at acupoints cause axon reflexes during the stimuli, which elevate cutaneous blood flow. Elevated NOergic molecules and local blood flow may spread over acupoints one after another along the meridian lines differing from nerve pathways following the stimuli to induce PSCP. The same types of stimulation also elicit NO release in the gracile nucleus, which contributes to the somatosensory signal transduction of PSCP through the dorsal medulla-thalamic pathways. Other substances such as serotonin and catecholamines are proposed to mediate responses and certain effects of acupuncture-like stimulation but their mechanisms are poorly-understood. In this review we summarize the current understanding of the neurobiological processes of PSCP research with an emphasis on recent developments of NO mediating stimulation-evoked axon reflexes and somatosensory signal transduction for PSCP perceptions through the dorsal medulla-thalamic pathways. Please cite this article as: Ma SX. Stimuli-evoked NOergic molecules and neuropeptides at acupuncture points and gracile nucleus contribute to signal transduction of propagated sensation along the meridian through the dorsal medulla-thalamic pathways. J Integr Med. 2024; 22(5): 515-522.

Topics: Humans; Acupuncture Points; Signal Transduction; Medulla Oblongata; Neuropeptides; Meridians; Animals; Thalamus; Sensation; Nitric Oxide

PubMed: 39214715
DOI: 10.1016/j.joim.2024.07.001