Stroke Recovery: Walking After Corticospinal Damage

The corticospinal tract (CST) is the main descending motor pathway that connects the motor cortex of the brain to the spinal cord neurons. It is divided into anterior and lateral parts, with the lateral tract containing over 90% of the fibres. The CST is closely related to the recovery of limb function in patients with post-stroke spasticity (PSS) and is the only direct descending motor pathway that innervates the spinal motor neurons.

Stroke-induced brain injury may affect the integrity and conduction function of the CST, leading to disinhibition of the CST and abnormal excitation of lower motor neurons, resulting in PSS. The degree of CST damage in post-stroke patients is a significant predictor of motor deficits, and there is a significant correlation between motor function improvement and CST remodelling in patients with PSS.

Promoting axonal remodelling in the CST may help identify new therapeutic strategies for PSS. Therapeutic strategies to promote axonal regeneration of the CST include reducing inhibitory factors in the central microenvironment, such as astroglial scarring and its secreted neurotrophic factors, and increasing neurotrophic factors.

The corticospinal tract is the major motor pathway in humans

The corticospinal tract is a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord. It is also known as the pyramidal tract. The tract is formed of upper motor neurons that synapse with lower motor neurons in the spinal cord, which then make contact with skeletal muscle to cause muscle contraction. The corticospinal tract is one of the major pathways for carrying movement-related information from the brain to the spinal cord.

The corticospinal tract is involved in a variety of movements, including walking, reaching, and fine finger movements. It is especially important for fine finger movements, such as writing, typing, or buttoning clothes. The tract is also involved in controlling the movement of muscles in the limbs, trunk, neck, and shoulders. The lateral corticospinal tract controls the limbs, while the anterior corticospinal tract controls the trunk, neck, and shoulders.

The corticospinal tract has many functions, including controlling afferent inputs, spinal reflexes, and motor neuron activity. The most important function is the mediation of voluntary distal movements. The tract contributes to excitatory monosynaptic alpha motor neurons and polysynaptic connections onto gamma motor neurons, which are responsible for controlling muscle spindle length.

Damage to the corticospinal tract can lead to a collection of deficits known as upper motor neuron syndrome. Lesions in the tract can result in deficits on the contralateral or ipsilateral side, depending on the location of the lesion. Following a stroke, patients may experience contralateral motor deficits and may be able to regain the ability to make crude movements but may struggle with fine finger movements.

Stroke-induced brain injury may affect the integrity and conduction function of the CST

Stroke-induced brain injury may affect the integrity and conduction function of the corticospinal tract (CST) in several ways. The CST is the major motor pathway in humans, connecting the primary motor cortex (M1) with the spinal cord. The CST conveys signals from the motor cortex to the spinal cord, and direct damage to it leads to motor deficits including paresis and paralysis.

The lateral corticospinal tract is the major motor pathway in humans. The role of this tract on walking, however, is uncertain. The development of diffusion tensor tractography enables corticospinal tract status to be visualised at the subcortical level.

The integrity of the motor system post-stroke can be quantified by the amount of injury to the CST, defined as the percent of overlap between the stroke lesion and CST. Individuals with stroke who have greater CST injury have worse motor outcomes than those with lower CST injury.

The functional integrity of the motor system can be assessed using resting-state functional magnetic resonance imaging (rs-fMRI). Rs-fMRI measures the spontaneous fluctuations in neural activity when the brain is not engaged in any task. In healthy individuals, the blood-oxygen-level-dependent (BOLD) signal between left and right M1 are temporally coupled and are thus considered 'connected'. Individuals with stroke with damage to their motor system show disrupted resting-state connectivity between the left and right M1 relative to healthy controls.

The CST conveys signals from the motor cortex to the spinal cord, and direct damage to it leads to motor deficits including paresis and paralysis. CST injury primarily assesses the degree of motor impairment. The resolution of impairment is linked with the brain's true or spontaneous recovery in response to the stroke.

However, deficits in motor impairment and function are related, which may be a reason why our findings and those of others show a relationship between CST injury and motor function. An individual with motor impairment may be unable to perform some motor functions unless motor behaviours are adapted using compensatory strategies.

The CST has many functions, including the control of afferent inputs, spinal reflexes and motor neuron activity. The most important function is the mediation of voluntary distal movements.

When the upper motor neurons of the CST are damaged, it can lead to a collection of deficits sometimes called upper motor neuron syndrome.

The CST is closely related to the recovery of limb function in patients with PSS

The corticospinal tract (CST) is the only direct descending motor pathway that innervates the spinal motor neurons. It is an upper motor neuron and is closely related to the recovery of limb function in patients with post-stroke spasticity (PSS). The CST is the main pathway that innervates spinal motor neurons and is closely related to the recovery of limb function after stroke.

The CST is divided into anterior and lateral parts and belongs to the upper motor neurons, both originating from the cerebral cortex and ending directly or indirectly (via interneurons) in the anterior horn of the spinal cord. The CST of the lateral tract contains more than 90% of the fibres present in the CST, with spinal cortical fibres originating from the grey matter of the spinal cord. The CST contains fibres from the upper motor neurons for the synapses of the lower motor neurons.

The CST has many functions, including the control of afferent inputs, spinal reflexes, and motor neuron activity. The most important function is the mediation of voluntary distal movements. The CST may also act as a 'gate', modulating or inhibiting information that is deemed useful or irrelevant.

The CST is closely related to the pathological mechanisms of PSS. Stroke-induced brain injury may affect the integrity and conduction function of the CST. Cerebral ischemia damages the neural axons in the CST and leads to the loss of function of upper motor neurons. This results in diminished or lost inhibitory control of the CST, abnormal excitation of lower motor neurons, and increased muscle tone.

The integrity of the CST is probably the most important factor affecting the clinical function of patients. The degree of CST damage in post-stroke patients is a significant predictor of motor deficits. There is a significant correlation between improvement in motor function and CST remodelling in patients with PSS. The recovery of patients with post-stroke dysfunction is largely dependent on homologous CST axon integrity in stroke patients and experimental animals.

Strategies to promote axonal remodelling of the CST include the inhibition of inhibitors in the central microenvironment and an increase in neurotrophins. Astrocyte activation and the derived neurotrophin also enhance the axonal ability to promote the regeneration of CST axons.

The degree of CST damage in post-stroke patients is a significant predictor of motor deficits

The corticospinal tract (CST) is a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord. It is one of the major pathways for carrying movement-related information from the brain to the spinal cord and has approximately 1 million nerve fibres. The CST has many functions, including the control of afferent inputs, spinal reflexes, and motor neuron activity, but is most important for the mediation of voluntary distal movements and fine finger movements.

The degree of CST damage is a significant predictor of motor deficits in post-stroke patients. A study by Maraka et al. found that DTI-defined damage to the CST correlated with motor impairment at each phase of ischemic stroke (acute, subacute, and chronic). The combination of baseline CST damage and the NIHSS (National Institutes of Health Stroke Scale) predicted motor outcome. Another study by Zhu et al. found that CST-lesion load was a significant predictor of motor deficit in chronic stroke patients, with the integrity of the CST showing the most significant correlation with motor deficits.

In summary, the degree of CST damage is a significant predictor of motor deficits in post-stroke patients, and CST assessment could be used as a surrogate marker of motor impairment in stroke recovery clinical trials.

The integrity of the CST is probably the most important factor affecting the clinical function of patients

The corticospinal tract (CST) is a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord. The CST is one of the major pathways for carrying movement-related information from the brain to the spinal cord and has approximately 1 million nerve fibres. The CST has many functions, including the control of afferent inputs, spinal reflexes, and motor neuron activity, the most important being the mediation of voluntary distal movements.

The integrity of the CST is a key factor in determining the clinical function of patients, particularly in their ability to walk and perform fine finger movements. Damage to the CST can lead to a collection of deficits sometimes called upper motor neuron syndrome. The effect of a lesion to the CST causes more than just muscle weakness, it also affects synergistic movement patterns that impact dexterity, ambulation, and activities of daily living.

Studies have shown that the integrity of the CST is a strong predictor of clinical outcomes and can be used to determine the potential for clinical improvement in chronic stroke patients. The presence or absence of motor-evoked potentials (MEPs) in the affected upper limb, measured through transcranial magnetic stimulation (TMS), is a strong predictor of current upper limb function, with those having MEPs exhibiting better function than those without. In patients without MEPs, increasing fractional anisotropy (FA) asymmetry in the CST predicted lower function, with an FA asymmetry of >0.25 indicating a "point of no return" beyond which functional potential is severely limited.

Diffusion tensor imaging (DTI) has been used to visualize ischaemic regions within the CST and to quantify CST integrity by calculating FA within a region of interest. DTI can also be used to construct three-dimensional images of white matter tracts and has been shown to be effective in predicting motor outcomes in stroke patients, with larger asymmetries in FA associated with poorer motor recovery.

In summary, the integrity of the CST is a critical factor in determining the clinical function of patients, particularly their upper limb function and ability to walk. The combination of neurophysiological measures and imaging techniques can be used to evaluate CST integrity and inform the setting of therapeutic goals and the selection of individualized rehabilitation strategies for patients recovering from stroke.

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