Normal Corticospinal Tract Research Articles

Exploring the Structural Plasticity Mechanism of Corticospinal Tract during Stroke Rehabilitation Based Automated Fiber Quantification Tractography.

Corticospinal tract (CST) is the principal motor pathway; we aim to explore the structural plasticity mechanism in CST during stroke rehabilitation. A total of 25 patients underwent diffusion tensor imaging before rehabilitation (T1), 1-month post-rehabilitation (T2), 2 months post-rehabilitation (T3), and 1-year post-discharge (T4). The CST was segmented, and fractional anisotropy (FA), axial diffusion (AD), mean diffusivity (MD), and radial diffusivity (RD) were determined using automated fiber quantification tractography. Baseline level of laterality index (LI) and motor function for correlation analysis. The FA values of all segments in the ipsilesional CST (IL-CST) were lower compared with normal CST. Repeated measures analysis of variance showed time-related effects on FA, AD, and MD of the IL-CST, and there were similar dynamic trends in these 3 parameters. At T1, FA, AD, and MD values of the mid-upper segments of IL-CST (around the core lesions) were the lowest; at T2 and T3, values for the mid-lower segments were lower than those at T1, while the values for the mid-upper segments gradually increased; at T4, the values for almost entire IL-CST were higher than before. The highest LI was observed at T2, with a predominance in contralesional CST. The LIs for the FA and AD at T1 were positively correlated with the change rate of motor function. IL-CST showed aggravation followed by improvement from around the lesion to the distal end. Balance of interhemispheric CST may be closely related to motor function, and LIs for FA and AD may have predictive value for mild-to-moderate stroke rehabilitation. Clinical Trial Registration. URL: http://www.chictr.org.cn; Unique Identifier: ChiCTR1800019474.

Teaching Video NeuroImage: Congenital Hemidystonia-Hemi-midbrain Atrophy Syndrome.

An 18-year-old man with normal birth and development and a negative family history complained of nonprogressive clumsiness and posturing of his left hand since early childhood. His left limbs were shorter than his right but showed no evidence of atrophy (eFigure 1, A-C, [links.lww.com/WNL/B902][1]). Examination revealed dystonic posturing with mirror dystonia of the left hand and subtle mirror movements in his feet (Video 1). MRI of the brain showed right hemiatrophy of the midbrain, bilateral cortical activation with unilateral finger taps on fMRI, and normal corticospinal tract decussation (Figure, A-F). Levodopa response was present, suggesting dopaminergic denervation due to a congenital hemi-midbrain insult.1 This case represents hemidystonia-hemiatrophy syndrome.2 Subtle limb shortening and mirror dystonia can aid in diagnosis. [1]: http://links.lww.com/WNL/B902

Clinical application of diffusion tensor imaging and fiber tractography in the management of brainstem cavernous malformations: a systematic review.

This study aimed to systematically review the literature to determine the clinical utility and perspectives of diffusion tensor imaging (DTI) in the management of patients with brainstem cavernous malformations (BSCMs). PubMed, Embase, and Cochrane were searched for English-language articles published until May 10, 2021. Clinical studies and case series describing DTI-based evaluation of patients with BSCMs were included. Fourteen articles were included. Preoperative DTI enabled to adjust the surgical approach and choose a brainstem safe entry zone in deep-seated BSCMs. Preoperatively lower fractional anisotropy (FA) of the corticospinal tract (CST) correlated with the severity of CST injury and motor deficits. Postoperatively increased FA and decreased apparent diffusion coefficient (ADC) corresponded with the normalization of the perilesional CST, indicating motor improvement. The positive (PPV) and negative predictive value (NPV) of qualitative DTI ranged from 20 to 75% and from 66.6 to 100%, respectively. The presence of preoperative and postoperative motor deficits was associated with a higher preoperative resting motor threshold (RMT) and lower FA. A higher preoperative CST score was indicative of a lower preoperative and follow-up Medical Research Council (MRC) grade. DTI facilitated the determination of a surgical trajectory with minimized risk of WMTs' damage. Preoperative FA and RMT might indicate the severity of preoperative and postoperative motor deficits. Preoperative CST score can reliably reflect patients' preoperative and follow-up motor status. Due to high NPV, normal CST morphology might predict intact neurological outcomes. Contrarily, sparse and relatively low PPV limits the reliable prediction of neurological deficits.

Clinical and neuroimaging findings in patients with lissencephaly/subcortical band heterotopia spectrum: a magnetic resonance conventional and diffusion tensor study.

To clarify brain abnormalities on magnetic resonance imaging (MRI) and its clinical implications in lissencephaly/subcortical band heterotopia (LIS/SBH) spectrum patients. The clinical severity and classification according to Di Donato were retrospectively reviewed in 23 LIS/SBH spectrum patients. The morphological and signal abnormalities of the brainstem, corpus callosum, and basal ganglia were also assessed. The brainstem distribution pattern of the corticospinal tract (CST) was analyzed by diffusion tensor imaging (DTI) and categorized into two types: normal pattern, in which the CST and medial lemniscus (ML) are separated by the dorsal portion of the transverse pontine fiber, and the abnormal pattern, in which the CST and ML are juxtaposed on the dorsal portion of a single transverse pontine fiber. Correlations between MR grading score and potential additional malformative findings of the brain and clinical symptoms were investigated. All patients with grade 3 (n = 5) showed brainstem deformities, signal abnormalities of pontine surface and had atendency of basal ganglia deformity and callosal hypoplasia whereas those abnormalities were rarely seen inpatients with grade 1 and 2 (n = 18). For DTI analysis, the patients with grade 3 LIS/SBH had typically abnormal CST, whereas the patients with grade 1 and 2 LIS/SBH had normal CST. The classification was well correlated with CST and brainstem abnormalities and clinical severity. MR assessment including DTI analysis may be useful in assessing the clinical severity in LIS/BH spectrum and may provide insight into its developmental pathology.

Exploring Peritumoral Neural Tracts by Using Neurite Orientation Dispersion and Density Imaging.

Diffusion Tensor Imaging (DTI) tractography has been widely used in brain tumor surgery to ensure thorough resection and minimize functional damage. However, due to enhanced anisotropic uncertainty in the area with peritumoral edema, diffusion tractography is generally not practicable leading to high false-negative results in neural tracking. In this study, we evaluated the usefulness of the neurite orientation dispersion and density imaging (NODDI) derived tractography for investigating structural heterogeneity of the brain in patients with brain tumor. A total of 24 patients with brain tumors, characterized by peritumoral edema, and 10 healthy counterparts were recruited from 2014 to 2021. All participants underwent magnetic resonance imaging. Moreover, we used the images obtained from the healthy participants for calibrating the orientation dispersion threshold for NODDI-derived corticospinal tract (CST) reconstruction. Compared to DTI, NODDI-derived tractography has a great potential to improve the reconstruction of fiber tracking through regions of vasogenic edema. The regions with edematous CST in NODDI-derived tractography demonstrated a significant decrease in the intracellular volume fraction (VFic, p < 0.000) and an increase in the isotropic volume fraction (VFiso, p < 0.014). Notably, the percentage of the involved volume of the concealed CST and lesion-to-tract distance could reflect the motor function of the patients. After the tumor resection, four patients with 1–5 years follow-up were showed subsidence of the vasogenic edema and normal CST on DTI tractography. NODDI-derived tractography revealed tracts within the edematous area and could assist neurosurgeons to locate the neural tracts that are otherwise not visualized by conventional DTI tractography.

Joubert Syndrome Presenting With Normal Pyramidal Decussation: A Case Report.

Joubert syndrome (JS) is a rare genetic disorder characterized by a congenital malformation of the hindbrain, and accompanied by axonal decussation abnormalities affecting the corticospinal tract and the superior cerebellar peduncles. To the best of our knowledge, there are no reports of normal pyramidal decussation in JS. Here, we describe the case of an 18-year-old boy presenting midline-crossing corticospinal projections, which were considered normal corticospinal tract trajectories. Diffusion tensor imaging and motor evoked potential study analysis demonstrated the exclusive presence of decussating corticospinal projections in the patient. Based on these results, we suggest that JS might be associated with several, diverse corticospinal motor tract organization patterns.

Beta-band intermuscular coherence: a novel biomarker of upper motor neuron dysfunction in motor neuron disease

In motor neuron disease, the focus of therapy is to prevent or slow neuronal degeneration with neuroprotective pharmacological agents; early diagnosis and treatment are thus essential. Incorporation of needle electromyographic evidence of lower motor neuron degeneration into diagnostic criteria has undoubtedly advanced diagnosis, but even earlier diagnosis might be possible by including tests of subclinical upper motor neuron disease. We hypothesized that beta-band (15–30 Hz) intermuscular coherence could be used as an electrophysiological marker of upper motor neuron integrity in such patients. We measured intermuscular coherence in eight patients who conformed to established diagnostic criteria for primary lateral sclerosis and six patients with progressive muscular atrophy, together with 16 age-matched controls. In the primary lateral sclerosis variant of motor neuron disease, there is selective destruction of motor cortical layer V pyramidal neurons and degeneration of the corticospinal tract, without involvement of anterior horn cells. In progressive muscular atrophy, there is selective degeneration of anterior horn cells but a normal corticospinal tract. All patients with primary lateral sclerosis had abnormal motor-evoked potentials as assessed using transcranial magnetic stimulation, whereas these were similar to controls in progressive muscular atrophy. Upper and lower limb intermuscular coherence was measured during a precision grip and an ankle dorsiflexion task, respectively. Significant beta-band coherence was observed in all control subjects and all patients with progressive muscular atrophy tested, but not in the patients with primary lateral sclerosis. We conclude that intermuscular coherence in the 15–30 Hz range is dependent on an intact corticospinal tract but persists in the face of selective anterior horn cell destruction. Based on the distributions of coherence values measured from patients with primary lateral sclerosis and control subjects, we estimated the likelihood that a given measurement reflects corticospinal tract degeneration. Therefore, intermuscular coherence has potential as a quantitative test of subclinical upper motor neuron involvement in motor neuron disease.

Abstract 2889: Neural Systems Injury Provides Insight Into Individual Behaviors While Global Injury Is Useful For Global Outcome In Chronic Stroke

INTRODUCTION: A key challenge in the treatment of patients with chronic stroke is identifying which patients are most likely to benefit from therapy. An assessment of stroke-related injury can help, but it remains unclear which are the most useful measures. This issue was examined in the current study bearing in mind that restorative therapeutics in chronic stroke often target modality-specific behavioral measures such as arm motor function or aphasia. The hypothesis is that deficits in modality-specific behaviors are better understood by measuring injury to the neural system underlying the behavior, while deficits in global outcome assessments are better understood by measuring a global measure of injury such as infarct volume. METHODS: Data were collected from pre-treatment assessments for patients enrolled in a study of robotic therapy for arm weakness after stroke (clinicaltrials.gov # NCT01244243 ). Entry criteria include age &gt;18 yr, arm motor deficits, and stroke 3-6 months prior. Pre-therapy measures included assessment of global impairment (total NIHSS score) as well as arm motor deficits (Fugl-Meyer scale (FM); Action Research Arm Test (ARAT), and Box and Blocks (B&amp;B)). Pre-treatment MRI (3T) included high resolution T1-weighted images, from which infarct volume was determined, and diffusion tensor imaging (DTI, 32 directions). DTI was used to determine corticospinal tract integrity by measuring fractional anisotropy (FA) within this tract. FA reflects the degree to which proton movements are directional, and so is higher in white matter tracts for which the axons are directional and intact, such as normal corticospinal tract. RESULTS: Of the 28 enrollees, 25 were able to complete MRI scanning. These 25 had mild-moderate global impairment (NIHSS = 4.5 +− 2.3, mean +− SD) associated with arm motor deficits that were variable but overall moderate-severe (FM score = 34 +− 15, range 14-60). Arm motor deficits correlated more strongly with FA in the affected cerebral peduncle (r=0.70, p=0.0001 for FM score; similar for ARAT and B&amp;B) than with infarct volume (r=-0.44; p=0.0546). Global impairment, however, correlated more strongly with infarct volume (r=0.66, p=0.002) than with FA in the affected cerebral peduncle (e.g, r=0-.57, p=.005 for FM). Note that in all cases, behavior/FA relationships were stronger with FA expressed as the ipsilesional/contralesional ratio, as compared to ipsilesional value alone. CONCLUSIONS: In patients with chronic stroke, measuring injury to a specific neural system provides insight into the behavior arising from that system, and does so better than a global measure of injury. On the other hand, a global measure of neural injury correlates better with global outcome. These findings are useful for understanding injury underlying the deficits targeted by restorative therapies and might be useful for matching the right patients with the right therapies.

Presurgical Prediction of Motor Functional Loss Using Tractography

The usefulness of magnetic resonance imaging tractography is demonstrated in the presurgical planning of an 8-year-old girl with intractable epilepsy. Imaging and intracranial electrode monitoring suggested a left hemispherectomy for complete control of her seizures. Although this child was hemiplegic, she retained considerable motor function in her right hand, and her parents and the epilepsy team voiced significant concern that she would lose right-hand function after a hemispherectomy. Tractography indicated near-complete absence of her left corticospinal tract and a more robust than normal corticospinal tract in the right hemisphere. This finding suggested that her right motor function had reorganized to the right hemisphere and the ipsilateral corticospinal tract. After surgery, her seizures were completely controlled, and no change in right motor activity was evident compared with her presurgical status. Tractography helped determine the extent of cortical resection and predict the extent of motor functional loss.

A case of polymicrogyria in macaque monkey: impact on anatomy and function of the motor system

BackgroundPolymicrogyria is a malformation of the cerebral cortex often resulting in epilepsy or mental retardation. It remains unclear whether this pathology affects the structure and function of the corticospinal (CS) system. The anatomy and histology of the brain of one macaque monkey exhibiting a spontaneous polymicrogyria (PMG monkey) were examined and compared to the brain of normal monkeys. The CS tract was labelled by injecting a neuronal tracer (BDA) unilaterally in a region where low intensity electrical microstimulation elicited contralateral hand movements (presumably the primary motor cortex in the PMG monkey).ResultsThe examination of the brain showed a large number of microgyri at macro- and microscopic levels, covering mainly the frontoparietal regions. The layered cortical organization was locally disrupted and the number of SMI-32 stained pyramidal neurons in the cortical layer III of the presumed motor cortex was reduced. We compared the distribution of labelled CS axons in the PMG monkey at spinal cervical level C5. The cumulated length of CS axon arbors in the spinal grey matter was not significantly different in the PMG monkey. In the red nucleus, numerous neurons presented large vesicles. We also assessed its motor performances by comparing its capacity to execute a complex reach and grasp behavioral task. The PMG monkey exhibited an increase of reaction time without any modification of other motor parameters, an observation in line with a normal CS tract organisation.ConclusionIn spite of substantial cortical malformations in the frontal and parietal lobes, the PMG monkey exhibits surprisingly normal structure and function of the corticospinal system.

Assessment of the corticospinal tract alterations before and after resection of brainstem lesions using Diffusion Tensor Imaging (DTI) and tractography at 3 T

The purpose of the study was to investigate the role of Diffusion Tensor Imaging (DTI) and Diffusion Tensor Tractography (DTT) on the corticospinal tract alterations due to space occupying lesions in the brainstem before and after surgical resection. Pre- and post-surgical DTI data were acquired in 14 patients undergoing surgical resection of brainstem lesions. Patterns of corticospinal tract (CST) alteration on DTT were compared with the neurological exams of the patients pre- and post-operatively. DTT, especially in 3D movie format, seemed very helpful for evaluating the relationship of the lesions with the corticospinal tracts for surgical approach. None of the patients developed additional motor deficit related to surgery except one patient who presented with cerebellar ataxia after surgery. All of the patients with normal CST on DTT presented without motor deficit on neurological exam. The sensitivity, specificity, positive predictive and negative predictive values of DTT before surgery were 100%, 63.6%, 42.9% and 100%, and the corresponding values after surgery were 100%, 96%, 75% and 100% respectively. Although it has low specificity before surgery, DTT is a potentially useful technique in evaluating the effects of brainstem lesions and surgical resection on the relevant corticospinal tracts with high negative predictive value and higher specificity after surgery.

Transcranial stimulation excites virtually all motor neurons supplying the target muscle. A demonstration and a method improving the study of motor evoked potentials.

Transcranial stimulation has become an established method in the evaluation of corticospinal tract function. Clinical studies mainly address slowing of conduction through measurement of increased central conduction time (CCT) and 'failures' of conduction through observation of marked reductions in the size of the motor evoked potential (MEP). While CCT is of great interest in detecting subclinical slowing of conduction, the method discloses only gross failures of conduction, since the size of the MEP varies markedly between normal subjects and from one stimulus to another, leading to a broad range of normal values. Furthermore, transcranial stimulation does not appear to achieve depolarization of all spinal motor neurons leading to the target muscles, since in most normal subjects MEPs are smaller in amplitude than the responses evoked by peripheral nerve stimulation. We have developed a triple stimulation technique (TST) which, through two collisions, links central to peripheral conduction and suppresses desynchronization of MEPs. This technique shows that transcranial stimulation does achieve depolarization of all, or nearly all, spinal motor neurons supplying the target muscle in healthy subjects. Our data thus demonstrate that the amplitudes of MEPs are (i) smaller than those of peripheral responses, mostly due to phase cancellation of the action potentials caused by the desynchronization occurring within the corticospinal tract or at spinal cell level and (ii) variable between normal subjects and from one stimulus to another, mostly due to variability of this desynchronization. This technique provides new insights into normal corticospinal tract conduction. It will improve detection and quantification of central motor conduction failures.

Amyotrophic lateral sclerosis: correlation of clinical and MR imaging findings.

To determine the magnetic resonance (MR) imaging characteristics of amyotrophic lateral sclerosis (ALS) and to evaluate possible correlations between the disease severity and the MR imaging findings. The authors retrospectively reviewed MR images of the head in 17 patients with ALS (14 men and three women) and 17 age-matched control subjects. The corticospinal tract (CST) was analyzed for the following features: size, signal intensity, and number of sections and regions in which the CST could be seen. Patients with ALS demonstrated sharp, well-defined, round, symmetric lesions that were hyperintense to gray matter within the CST. The lesions were best seen at the level of the middle or lower internal capsule on T2-weighted images. Visualization of the CST on proton-density-weighted images (which occurred in eight ALS patients) is the most reliable MR finding. Low signal intensity was identified within the motor cortex in six patients. Positive MR findings correlated with average or rapid progression of the disease. Increased signal intensity in the CST on proton-density-weighted MR images is diagnostic for motor neuron disease and correlates with the rate of disease progression. Subtle ALS changes can be differentiated from the normal CST. Low signal intensity in the motor cortex on T2-weighted images is a useful finding.

Reorganization of the corticospinal tract following neonatal unilateral cortical ablation in rats

The corticospinal tract in the rat after neonatal ablation of the unilateral cerebral cortex was studied morphologically and histochemically using the retrograde and antegrade horseradish peroxidase (HRP) tracing methods. The normal corticospinal tract in the lumbar cord was composed of a number of small and some large axons. In the atrophic corticospinal tract related to the ablated cerebral cortex, the small axons were decreased in number two weeks after the operation. However, new myelinated small axons appeared around day 28 and their diameters increased gradually from after day 56 to day 84. The original large axon in the atrophic corticospinal tract was much more increased in size than that in the corticospinal tract of the non-operated-on control. When HRP was injected into the left cervical cord of the adult rat whose right cerebral cortex had been ablated during the neonatal period, a considerable number of HRP-labeled neurons was seen in the healthy left cerebral cortex. When the corticospinal tract was traced antegradely by injecting HRP into the healthy left cerebral cortex, an aberrant corticospinal tract reaching into the ipsilateral dorsal funiculus was observed. These results give a morphological basis for the well known fact that children who have had brain damage during the neonatal period and early infancy have the capacity for recovery of motor function.

Growth of corticospinal axons on prosthetic substrates introduced into the spinal cord of neonatal rats

Nitrocellulose implants treated with biological materials known to support neurite growth in vitro were introduced at thoracolumbar levels of the neonatal rat spinal cord before the arrival of growing corticospinal tract (CST) axons. Implant placement was designed to interrupt the normal CST growth path and provide a potential, alternative growth path. Subsequent growth of CST axons within the spinal cord in the vicinity of the implants was evaluated by labeling the axons with the anterograde transport of horseradish peroxidase. Untreated implants either blocked further CST axon growth or deflected CST axons to abnormal positions. Implants bearing living cells from spinal cord primary cultures were able to support the adhesion and growth of CST axons. Similarly, acellular implants coated with laminin, but not with poly- l-lysine supported the adhesion and growth of CST axons, suggesting that laminin or some other adhesive factor produced by immature neuroglial cells may be normally involved in CST axon growth and guidance.

Plasticity of the corticospinal tract following midthoracic spinal injury in the postnatal rat.

Rats received a midthoracic spinal cord "overhemisection" including right hemicord and left dorsal funiculus at birth (neonatal operates, N = 15) or 21 days of age (weanling operates, N = 14). In a second experiment neonatal (N = 6), 6-day (N = 3), and 12-day (N = 7) rats sustained a right sensorimotor cortex (SmI) ablation to destroy the left corticospinal tract (CST) at the same time as the spinal injury (double lesion operates). Later (3-12 months) injections of 3H-proline and autoradiography were used to label the left or right CST. The results of the first experiment showed that most right CST axons failed to grow around the spinal lesion in neonatal operates (N = 9). There was an increase in the density of label, mainly to CST projection areas, in a 1-mm zone rostral to the lesion. However, left CST axons bypassed the lesion by growing through the intact tissue in neonatal operates (N = 6). These displaced axons were consistently located within the dorsal portion of the lateral funiculus (dLF) and remained within that location caudal to the lesion, an area normally containing only a few CST axons. In spite of this abnormal position, these axons terminated bilaterally throughout the remainder of the cord in normal CST sites. In weanling operates, CST axons severed by the lesion did not regenerate around the lesion site. An increased density of label over the few spared axons within the left dLF and in CST projection zones immediately caudal to the lesion site suggested axonal sprouting by these axons. The results of the second experiment showed that the lack of growth of right CST axons around this injury in neonatal operates was, at least partially, due to an interaction with left CST axons. In neonatal double lesion operates, right CST axons grew around the spinal injury for a varying distance within the left dLF and distributed bilaterally to normal CST sites. The number of right CST axons bypassing the lesion was related to the configuration of the lesion site. A smaller number of right CST axons bypassed the lesion in 6-day double lesion operates and most terminated within 2-3 mm of the lesion site. Right CST axons failed to grow around this injury in 12-day double lesion operates.(ABSTRACT TRUNCATED AT 400 WORDS)

Projections and termination of the corticospinal tract in rodents.

An examination of the precise mode of termination of the corticospinal system in the spinal cord of rodents has been conducted by use of light and electron microscope methods. This study confirms the position of the normal corticospinal tract in rodents in the ventralmost portion of the dorsal column white matter. Three to four days following unilateral sensorimotor cortex ablation, Nauta-Gygax and Fink-Heimer silver methods reveal a dorsomedial projection of degenerating debris into the dorsal horn from the contralateral corticospinal tract. Although the silver methods do not show degeneration at survival times earlier than two days, the electron microscope shows degenerating axons and synaptic knobs as early as 24 hours following cortical lesion. The degenerating synaptic knobs are found only in the dorsal regions of the dorsal horn subjacent to the substantia gelatinosa. They usually make synaptic contact with several small to medium sized dendrites. These terminals do not appear to participate in axosomatic or axoaxonal synapses. No degeneration is seen in the ipsilateral corticospinal tract, the lateral white columns, or the ventral horn of the spinal cord.