scholarly journals Lesion Area in the Cerebral Cortex Determines the Patterns of Axon Rewiring of Motor and Sensory Corticospinal Tracts After Stroke

2021 ◽  
Vol 15 ◽  
Author(s):  
Tokiharu Sato ◽  
Yuka Nakamura ◽  
Akinori Takeda ◽  
Masaki Ueno
Keyword(s):  
Cerebral Cortex ◽  
Brain Injuries ◽  
Corticospinal Tract ◽  
Cervical Spinal Cord ◽  
Neural Substrates ◽  
Neural Pathway ◽  
Lesion Area ◽  
Basic Principles ◽  
Corticospinal Tracts ◽  
Small Stroke

The corticospinal tract (CST) is an essential neural pathway for reorganization that recovers motor functions after brain injuries such as stroke. CST comprises multiple pathways derived from different sensorimotor areas of the cerebral cortex; however, the patterns of reorganization in such complex pathways postinjury are largely unknown. Here we comprehensively examined the rewiring patterns of the CST pathways of multiple cerebral origins in a mouse stroke model that varied in size and location in the sensorimotor cortex. We found that spared contralesional motor and sensory CST axons crossed the midline and sprouted into the denervated side of the cervical spinal cord after stroke in a large cortical area. In contrast, the contralesional CST fibers did not sprout in a small stroke, whereas the ipsilesional axons from the spared motor area grew on the denervated side. We further showed that motor and sensory CST axons did not innervate the projecting areas mutually when either one was injured. The present results reveal the basic principles that generate the patterns of CST rewiring, which depend on stroke location and CST subtype. Our data indicate the importance of targeting different neural substrates to restore function among the types of injury.

A critical reappraisal of corticospinal tract somatotopy and its role in traumatic cervical spinal cord syndromes

2021 ◽  
pp. 1-7
Author(s):  
Allan D. Levi ◽  
Jan M. Schwab
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Upper Extremity ◽  
Corticospinal Tract ◽  
Cervical Spinal Cord ◽  
Hand Function ◽  
Cervical Spinal Cord Injury ◽  
Pathophysiological Mechanism ◽  
Cord Injury ◽  
Central Cord Syndrome

The corticospinal tract (CST) is the preeminent voluntary motor pathway that controls human movements. Consequently, long-standing interest has focused on CST location and function in order to understand both loss and recovery of neurological function after incomplete cervical spinal cord injury, such as traumatic central cord syndrome. The hallmark clinical finding is paresis of the hands and upper-extremity function with retention of lower-extremity movements, which has been attributed to injury and the sparing of specific CST fibers. In contrast to historical concepts that proposed somatotopic (laminar) CST organization, the current narrative summarizes the accumulated evidence that 1) there is no somatotopic organization of the corticospinal tract within the spinal cord in humans and 2) the CST is critically important for hand function. The evidence includes data from 1) tract-tracing studies of the central nervous system and in vivo MRI studies of both humans and nonhuman primates, 2) selective ablative studies of the CST in primates, 3) evolutionary assessments of the CST in mammals, and 4) neuropathological examinations of patients after incomplete cervical spinal cord injury involving the CST and prominent arm and hand dysfunction. Acute traumatic central cord syndrome is characterized by prominent upper-extremity dysfunction, which has been falsely predicated on pinpoint injury to an assumed CST layer that specifically innervates the hand muscles. Given the evidence surveyed herein, the pathophysiological mechanism is most likely related to diffuse injury to the CST that plays a critically important role in hand function.

scholarly journals Segmental analysis in cervical spinal cord injury reveals the recovery potential of hand muscles with preserved corticospinal tract: Insights beyond impairment scales

2021 ◽  
Author(s):  
Gustavo Balbinot ◽  
Guijin Li ◽  
Sukhvinder Kalsi-Ryan ◽  
Rainer Abel ◽  
Doris Maier ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Muscle Strength ◽  
Evoked Potentials ◽  
Corticospinal Tract ◽  
Cervical Spinal Cord ◽  
Hand Muscles ◽  
Recovery Potential ◽  
Strength Recovery ◽  
Cord Injury

Cervical spinal cord injury (SCI) severely impacts widespread bodily functions with extensive impairments for individuals, who prioritize regaining hand function. Although prior work has focused on the recovery at the person-level, the factors determining the recovery potential of individual muscles are poorly understood. There is a need for changing this paradigm in the field by moving beyond person-level classification of residual strength and sacral sparing to a muscle-specific analysis with a focus on the role of corticospinal tract (CST) sparing. The most striking part of human evolution involved the development of dextrous hand use with a respective expansion of the sensorimotor cortex controlling hand movements, which, because of the extensive CST projections, may constitute a drawback after SCI. Here, we investigated the muscle-specific natural recovery after cervical SCI in 748 patients from the European Multicenter Study about SCI (EMSCI), one of the largest datasets analysed to date. All participants were assessed within the first 4 weeks after SCI and re-assessed at 12, 24, and 48 weeks. Subsets of individuals underwent electrophysiological multimodal evaluations to discern CST and lower motor neuron (LMN) integrity [motor evoked potentials (MEP): N = 203; somatosensory evoked potentials (SSEP): N = 313; nerve conduction studies (NCS): N = 280]. We show the first evidence of the importance of CST sparing for proportional recovery in SCI, which is known in stroke survivors to represent the biological limits of structural and functional plasticity. In AIS D, baseline strength is a good predictor of segmental muscle strength recovery, while the proportionality in relation to baseline strength is lower for AIS B/C and breaks for AIS A. More severely impaired individuals showed non-linear and more variable recovery profiles, especially for hand muscles, while measures of CST sparing (by means of MEP) improved the prediction of hand muscle strength recovery. Therefore, assessment strategies for muscle-specific motor recovery in acute SCI improve by accounting for CST sparing and complement gross person-level predictions. The latter is of paramount importance for clinical trial outcomes and to target neurorehabilitation of upper limb function, where any single muscle function impacts the outcome of independence in cervical SCI.

Spinal cord representation of motor cortex plasticity reflects corticospinal tract LTP

2021 ◽  
Vol 118 (52) ◽  
pp. e2113192118
Author(s):  
Alzahraa Amer ◽  
Jianxun Xia ◽  
Michael Smith ◽  
John H. Martin
Keyword(s):  
Spinal Cord ◽  
Motor Cortex ◽  
Corticospinal Tract ◽  
Cervical Spinal Cord ◽  
Long Term Potentiation ◽  
Dependent Manner ◽  
Term Potentiation ◽  
Spinal Cord Segment ◽  
Spinal Interneuron ◽  
Activity Dependent

Although it is well known that activity-dependent motor cortex (MCX) plasticity produces long-term potentiation (LTP) of local cortical circuits, leading to enhanced muscle function, the effects on the corticospinal projection to spinal neurons has not yet been thoroughly studied. Here, we investigate a spinal locus for corticospinal tract (CST) plasticity in anesthetized rats using multichannel recording of motor-evoked, intraspinal local field potentials (LFPs) at the sixth cervical spinal cord segment. We produced LTP by intermittent theta burst electrical stimulation (iTBS) of the wrist area of MCX. Approximately 3 min of MCX iTBS potentiated the monosynaptic excitatory LFP recorded within the CST termination field in the dorsal horn and intermediate zone for at least 15 min after stimulation. Ventrolaterally, in the spinal cord gray matter, which is outside the CST termination field in rats, iTBS potentiated an oligosynaptic negative LFP that was localized to the wrist muscle motor pool. Spinal LTP remained robust, despite pharmacological blockade of iTBS-induced LTP within MCX using MK801, showing that activity-dependent spinal plasticity can be induced without concurrent MCX LTP. Pyramidal tract iTBS, which preferentially activates the CST, also produced significant spinal LTP, indicating the capacity for plasticity at the CST–spinal interneuron synapse. Our findings show CST monosynaptic LTP in spinal interneurons and demonstrate that spinal premotor circuits are capable of further modifying descending MCX control signals in an activity-dependent manner.

Trauma

2020 ◽  
pp. 131-170
Keyword(s):  
Traumatic Brain Injury ◽  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Brain Injury ◽  
Severe Traumatic Brain Injury ◽  
Brain Injuries ◽  
Cervical Spinal Cord ◽  
Trauma Patients ◽  
Cervical Spine Injuries ◽  
Cord Injury

This chapter discusses traumatic spinal cord and brain injuries. The first three studies review the background and key findings of the third National Acute Spinal Cord Injury Study (NASCIS) trial, examine the efficacy of the Canadian C-Spine Rule in the evaluation of cervical spine injuries in alert and stable trauma patients; and describe the development of the Thoracolumbar Injury Classification and Severity Score (TLICS) classification system. The next two studies assess the effect of early surgical decompression in patients with traumatic cervical spinal cord injury and delineate the role of secondary brain injury in determining patient outcome in severe traumatic brain injury. The following set of four studies evaluates the efficacy of phenytoin in preventing posttraumatic seizures, as well as the efficacy of intracranial pressure monitoring, induction of hypothermia, and decompressive craniectomy for severe traumatic brain injury. The last study, which is of historical value, identifies predictors of outcome in comatose patients with traumatic acute subdural hematoma.

scholarly journals Cortical thickness analysis – The methods

2015 ◽  
Vol 2 (1) ◽  
pp. 52-64
Author(s):  
Ann Mari Gransjøen
Keyword(s):  
Cerebral Cortex ◽  
Medical Imaging ◽  
Cortical Thickness ◽  
Complex Analysis ◽  
Basic Principles ◽  
Software Applications

Over the course of the last century, the cerebral cortex has been of interest for neuroscientists, and the work with mapping and measuring the cortex started in the early 1900s (Brodmann 1909).The advances in medical imaging over the recent decades has given the opportunity to measure the cortex in vivo, and several algorithms and types of software applications has been developed for this purpose. These software applications can be used to execute complex analysis to determine both cortex thickness and density.The algorithms and software applications presented in this paper are the ones most utilized to measure cortical thickness today, and include four software applications and two algorithms. The basic principles of these tools will be outlined, as well as their strengths and weaknesses.

scholarly journals The method of meningostomy and its application in the study of the brain in animals

2021 ◽  
Vol 27 (8) ◽  
pp. 820-821
Author(s):  
A. I. Smirnov ◽  
P. D. Olefirenko
Keyword(s):  
Cerebral Cortex ◽  
Electric Current ◽  
Brain Stimulation ◽  
Thermal Effects ◽  
Brain Injuries ◽  
The Other ◽  
Surgical Methods ◽  
The One ◽  
The Brain ◽  
Gain Access

All surgical methods used in the study of the brain in animals can be combined into two groups: 1) methods of direct and indirect shutdown of a particular part of the brain and 2) methods of non-mediocre brain stimulation by electric current or by mechanical, chemical or thermal effects. In the hands of different experimenters, depending on the goals and objects of research, these basic methods varied to one degree or another. All modifications were aimed at, on the one hand, to avoid brain injuries during trepanation as much as possible, and on the other hand, to gain access to the cerebral cortex without exposing it at the time of the observation itself. As can be judged from the literature collected from E. Abderhalden in Handbuch der biolog. Arbeitsmethoden to a certain extent this has already been achieved.

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