PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Pyramidal Tracts”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMedDate not supplied

Prognosis and MRI after ischemic stroke of the basal ganglia.

The clinical courses and long-term prognoses in 16 young patients with infarctions of the basal ganglia were evaluated and the recent magnetic resonance imaging findings in 9 of them were examined. Only 5 of 14 patients (35%) had motor sequelae, 4 had hemiparesis, and 1 had gait disturbance. Secondary dystonia occurred in 1 patient. Magnetic resonance imaging disclosed a circumscribed lesion in the basal ganglia, as reflected by T2 high- and T1 low-intensity signals, in all patients. The abnormal region on T2-weighted images usually was more extensive than that observed on T1-weighted ones. The hemiplegic patients each had an area of abnormal intensity in the internal capsule or corona radiata with relatively high signals on the T2- and proton-density-weighted images. Mild to moderate asymmetric atrophy of the midbrain on the side ipsilateral to the stroke lesion was observed in 8 of 9 patients. The mechanism involved may be remote transsynaptic neuronal death of the substantia nigra, as well as Wallerian degeneration of the pyramidal tract.

Adolescent↗
PubMed1996

Effects of judgement process on motor evoked potentials in Go/No-go hand movement task.

We examined the motor evoked potentials (MEP) of the forearm muscles following transcranial magnetic stimulation after the Go/No-go reaction-time hands movement in ten normal subjects. Facilitation of MEP of the agonistic muscles and suppression of MEP of the antagonistic muscles were recognized during the 'Go' session, while the MEPs of both muscles were markedly suppressed in the 'No-go' session. We considered that this MEP changes reflected the inhibition on the pyramidal tract during the 'No-go' session.

Adult↗
PubMed1978

Hereditary bimanual synkinesis combined with hypogonadotropic hypogonadism and anosmia in four brothers.

A new genetic syndrome of the combined occurrence of hypogonadotropic hypogonadism, anosmia (Kallmann syndrome) and congenital mirror movements in four brothers is presented. Mirror movements were manifest only within the distal parts of the upper extremities and resembled congenital mirror movements described for isolated or familial cases or those occurring in combination with other genetic defects. The hypothesis is supported, that a midline fusion disorder with preponderance of uncrossed pyramidal tract fibers is a major pathogenetic factor for the occurrence of congenital mirror movements.

Adult↗
PubMed1996

Motor evoked potentials (MEPs): evaluation of the different types of responses in amyotrophic lateral sclerosis and primary lateral sclerosis.

We studied different motor evoked potential parameters: cortical threshold (CT), primary response (PR) latency and amplitude and central conduction time (CCT) at rest and after maximal voluntary contraction of the target muscles, silent period (SP) and late muscular responses (LMR) in 21 normal subjects 42- to 75-years old and compared the results to those of 17 patients with motor disease (10 amyotrophic lateral sclerosis, ALS and 7 primary lateral sclerosis (PLS). We report for the first time in patients affected by motor diseases, LMRs were similar to controls. We found abnormalities in both ALS and PLS: enhanced cortical threshold, reduced PR amplitude during maximal voluntary contraction of target muscles compared to rest and shorter SP. CCT was slightly different: in ALS it was normal or undetermined (because of lack of the PR), while it was normal, enhanced or undetermined in PLS. We conclude that except for LMR, additional parameters would be useful for studying motor diseases: CT (reflecting excitability of the central cells), PR amplitudes and SP (disclosing inhibitory pathway disturbances in pyramidal tract diseases).

Adult↗
PubMed1987

The Florey lecture, 1987. Corticomotoneuronal projections: synaptic events related to skilled movement.

During infancy, children develop an expanding repertoire of movement skills in parallel with the maturation in their brains of direct nerve-fibre connections between the cerebral cortex and motoneurons in the spinal cord. These corticomotoneuronal connections are characteristic of primates and can be studied in monkeys; in these animals, refinement in the control of movements of the hand is also associated with increasing development of corticomotoneuronal connections. In monkeys, motoneurons innervating distally acting muscles are preferentially excited by convergent activities in corticomotoneuronal fibres. This excitation has been demonstrated to be effective in natural functional states when a conscious monkey is performing learned movement tasks. Extensive intraspinal arborizations of individual corticomotoneuronal fibres could permit the engagement of large numbers of local motoneurons and related interneurons by each of these fibres. Abolition of corticomotoneuronal influences, after section of the pyramidal tracts, causes a permanent deficit in fractionation of use of muscles of the forelimb and an inability to carry out independent movements of the fingers.

Animals↗
PubMed1992

Localization of mRNA for c-kit receptor and its ligand in the brain of adult rats: an analysis using in situ hybridization histochemistry.

Localization of mRNA for the c-kit receptor and its ligand (Sl factor) in the brain of adult rats was studied using in situ hybridization histochemistry. The mRNA for the c-kit receptor was detected in the forebrain, the lower brain stem and the cerebellum. In the forebrain, the c-kit mRNA signals were detected in the olfactory bulb, the caudate-putamen, throughout the superficial cortex, the accumbens nucleus, the nucleus of vertical limb diagonal band, the bed nucleus of anterior commissure, Ammon's horn, the entopeduncular nucleus, the subthalamic nucleus, the dorsal raphe nucleus, the parasubiculum, the presubiculum, the ventricular nucleus of lateral lemniscus, and the entorhinal cortex. In the lower brain stem, the signals were detected in the inferior colliculus, the spinal vestibular nucleus, the spinal tract nucleus of trigeminal nerve, and the pyramidal tract. In the cerebellum, the signals were detected in the molecular layer of the cortex and cerebellar nuclei. By contrast, the signals of mRNA for Sl factor were detected in the forebrain and the cerebellum. In the forebrain, the signals were detected in the olfactory bulb, the endopiriform nucleus, the septohippocampal nucleus, the habenular nuclei, and most of the thalamic nuclei. In the cerebellum, the signals were detected in Purkinje cells. Several pairs of structures were found in which mRNA of either the c-kit receptor or the Sl factor was expressed and between which the synaptic connection had been reported, suggesting that the interaction between the c-kit receptor and the Sl factor may play some roles in the development of such synaptic connections.

Animals↗
PubMed1996

Diffusion tensor MR imaging of the human brain.

PURPOSE: To assess intrinsic properties of water diffusion in normal human brain by using quantitative parameters derived from the diffusion tensor, D, which are insensitive to patient orientation. MATERIALS AND METHODS: Maps of the principal diffusivities of D, of Trace(D), and of diffusion anisotropy indices were calculated in eight healthy adults from 31 multisection, interleaved echo-planar diffusion-weighted images acquired in about 25 minutes. RESULTS: No statistically significant differences in Trace(D) (approximately 2,100 x 10(-6) mm2/sec) were found within normal brain parenchyma, except in the cortex, where Trace(D) was higher. Diffusion anisotropy varied widely among different white matter regions, reflecting differences in fiber-tract architecture. In the corpus callosum and pyramidal tracts, the ratio of parallel to perpendicular diffusivities was approximately threefold higher than previously reported, and diffusion appeared cylindrically symmetric. However, in other white matter regions, particularly in the centrum semiovale, diffusion anisotropy was low, and cylindrical symmetry was not observed. Maps of parameters derived from D were also used to segment tissues based on their diffusion properties. CONCLUSION: A quantitative characterization of water diffusion in anisotropic, heterogeneously oriented tissues is clinically feasible. This should improve the neuroradiologic assessment of a variety of gray and white matter disorders.

Adult↗
PubMed1992

Axonal and transsynaptic (transneuronal) spread of Herpesvirus simiae (B virus) in experimentally infected mice.

In order to study the pathogenesis of B virus infection of the nervous system, newborn and young mice were inoculated by four different routes: 1. Intramuscular (i.m.) in the forelimb; 2. I.m. in the hindlimb; 3. Subcutaneous (s.c.) in the abdominal wall; 4. Intraperitoneal (i.p.). Spread of virus was followed by immunohistochemical demonstration of viral antigen in tissue sections of the peripheral and central nervous system. Three distinct patterns emerged: 1. After i.m. limb inoculations, virus progressed along the ipsilateral dorsal column, the bilateral spinothalamic and bilateral spinoreticular systems and along central autonomic pathways. 2. After s.c. inoculation, the dorsal column was spared, otherwise the spread was similar to that following i.m. inoculations. 3. After i.p. inoculation, virus spread in the spinal cord bilaterally, mainly along spinothalamic and central autonomic pathways. The peripheral motoneurons were conspicuously spared, even in the i.m. inoculation mode. In the brain stem, B virus antigen appeared bilaterally, at multiple sites. In the cerebrum, virus infected cells appeared first in the thalamus, hypothalamus and the motor cortex. The mode of spread from spinal levels was mainly orthograde along the ascending systems (dorsal columns, spinothalamic, spinoreticular tracts), but also retrograde along descending systems (pyramidal tract, central autonomic pathways). Oligosynaptic systems transmitted virus more quickly than the polysynaptic ones. In the involvement of various neuronal systems in virus spread, a certain selectivity, sparing the peripheral motoneuron and the cerebellar systems, could be assessed.

Aging↗
PubMed2004

Ellen R. Grass Lecture: Motor evoked potential monitoring.

Because somatosensory evoked potentials (SSEPs) recorded from the brain are carried solely within the dorsal columns of the spinal cord, SSEP monitoring may fail to detect damage to the spinal cord motor pathways, and techniques for directly monitoring the motor pathways have been developed. Transcranial magnetic brain stimulation is useful for extraoperative evaluation of the motor system, but anesthetic effects on cortical synaptic activity limit its usefulness for intraoperative monitoring. Another proposed monitoring technique, rostral spinal cord stimulation with recording from peripheral nerves, predominantly reflects retrograde conduction within the dorsal columns; like SSEPs, this technique may fail to detect motor pathway damage. The true motor evoked potential (MEP) monitoring technique preferred by most institutions involves transcranial electrical brain stimulation. This stimulates the corticospinal tract axons directly, producing a D-wave in them. There may be additional corticospinal tract volleys, reflecting indirect activation of the pyramidal cells via synapses from cortical interneurons; these I-waves are largely suppressed by anesthesia. Temporal summation at the alpha motor neuron synapse is necessary to elicit myogenic MEPs (M-waves) under anesthesia; this is accomplished with brief trains of stimuli that produce multiple pyramidal tract volleys. High stimulus intensities are required to stimulate the brain through an intact skull; with proper precautions, this is acceptably safe. Myogenic MEPs are quite sensitive to anesthesia and show considerable run-to-run variability. Therefore, criteria for evaluating MEPs differ from those for SSEPs, and the anesthetic regimen and degree of neuromuscular blockade must be carefully controlled. SSEPs should be monitored concurrently with MEPs, because the dorsal columns may be affected without compromise of the motor tracts, and also because this provides redundancy, with two independent assessments of spinal cord function.

Brain↗
PubMed1985

Forelimb electromyographic responses to motor cortex stimulation during locomotion in the cat.

The forelimb motor cortex was stimulated via chronically implanted microelectrodes whilst electromyographic (e.m.g.) responses were recorded from muscles in the contralateral forelimb in cats walking steadily at 0.5 m/s. The stimuli were brief trains of 0.2 ms pulses (11 pulses at 330 Hz), intensity 5-20 microA and e.m.g.s were recorded from the following muscles: biceps brachii, brachialis, long and lateral heads of triceps brachii, latissimus dorsi, cleidobrachialis, extensor digitorum communis, palmaris longus and flexor and extensor carpi ulnaris. During locomotion, stimulation at 20 microA readily elicited brief, short-latency changes in the normal locomotor patterns of activity in all muscles studied. The changes included production of e.m.g. at times in the step cycle when the muscles are normally inactive and brief augmentations or diminution of the normal locomotor e.m.g.s. Individual electrodes usually influenced several muscles, and muscles acting antagonistically about the same joint were sometimes co-contracted. The first effect on locomotor flexor muscles (i.e. muscles active in relation to the swing phase of the step cycle) was almost always excitatory and such effects were often phase-dependent, usually occurring when the muscle was normally active or about to become active. Extensor muscles were excited from some cortical loci but inhibited from others (inhibitions were necessarily detectable only when the muscles exhibited locomotor-related e.m.g.s). Some micro-electrodes elicited excitation during swing (when the extensors are inactive) but elicited inhibition during stance. In several muscles the latencies of the excitatory e.m.g. changes could be as short as 6 ms measured from the first pulse in the stimulus train. In flexors, but not in extensors, latencies fluctuated according to the timing of the stimuli relative to the step cycle. Reduction in stimulus intensity reduced the amplitude of the e.m.g. changes, the number of muscles influenced and often increased the latency. However, both excitations and inhibitions were sometimes evident at 5 microA and thresholds for excitatory responses were, over-all, substantially lower than in the resting animal. Longer trains of stimuli were capable of resetting the step cycle. Response thresholds were greatly increased after pyramidectomy. These findings support the view that the natural bursts of impulses discharged by pyramidal tract neurones during steady locomotion are likely to contribute to regulating forelimb muscle activity on a step-by-step basis.

Action Potentials↗
PubMed1991

[Measurement of central motor conduction time (CMCT) in healthy Chinese subjects].

Transcutaneous electrical stimulation of the central nervous system was used to measure CMCT between the human cerebral cortex and spinal cord. 64 normal volunteers (46 healthy adult males and 18 females, age of 20-67 years, body height of 156-185 cm) were recruited as experimental subjects. Action potentials of muscles were recorded from upper limb (Thenar) and lower limb (Muscle tibialis anterior) following cortical and spinal stimulation. The cortical and spinal latent periods (Lcor., Lsp.) were measured and CMCT was obtained by subtracting Lsp. from Lcor. for each muscle. The CMCT between the cerebral cortex and the first thoracic (Th1) cord was 6.69 +/- 1.48 ms, while that between the cerebral cortex and the first lumber (L1) cord was 12.90 +/- 1.59 ms. Statistical analysis indicated that CMCT was not related to sex, age, body height and left or right side of the body as well. The motor conduction velocity in spinal cord (MCVsp) between Th1 and L1, [distance (Th1 to L1)/CMCT (Muscle tibialis anterior)-CMCT (Thenar)] was found to be 71.34 +/- 10.89 m/s, which corresponds to the conduction velocity of the large fibers in the pyramidal tract. The results of the present study are valuable in diagnosis and prognosis of motor system diseases in CNS.

Action Potentials↗
PubMed1996

Skilled forelimb movements in prey catching and in reaching by rats (Rattus norvegicus) and opossums (Monodelphis domestica): relations to anatomical differences in motor systems.

Traditional anatomical/behavioral classifications suggest that rats and opossums have simple motor systems and are impoverished with respect to their ability to make prehensile movements. Nevertheless, the motor system in rats and opossums represent extremes in relative size and complexity suggesting that a behavioral analysis of the movement competencies of these species will provide insights into the significance of such anatomical differences. This paper examines the movements that the two species use in catching crickets and in reaching for food items. Both species could use a single limb to reach out and grasp prey during prey catching and both could use a single limb to take food from a shelf. Both species could transport the food to the mouth by using a single paw. The food handling behavior of the rats was more complex than that of the opossums, however. They used a variety of prey catching movements and extensively manipulated the prey to remove the legs and wings before eating only the head and body. Additionally the rats made rotatory limb movements of aiming, pronation, and supination, when reaching. For both cricket catching and reaching, they used their digits more than did the opossums. The suggestion also emerged from the results that the movements of the opossums were more fixed and species-typical whereas those of the rats were more plastic and individualistic. Thus, the skilled movements of both species are more complex than is generally recognized and the greater complexity of the rat movements parallels their more complex motor system. These results are discussed in relation to anatomical differences in the motor system and, specifically, to differences in the terminal fields of the pyramidal tract. It is concluded that the motor abilities of nonprimate mammals have been vastly underrated.

Animals↗
PubMed1987

Review of descending motor pathways involved with transcranial stimulation.

The anatomical basis of the pyramidal tract is reviewed with respect to its proposed role in the conduction of the motor evoked potential. The fiber diameter profiles are discussed in relation to the measured conduction velocities of the corticospinal tract in humans. Stimulus parameters utilized to obtain the motor evoked potential are reviewed in relation to the laterality of response, response threshold, and properties of spatial and temporal summation. A discussion of the major descending tracts involved with walking as opposed to fine distal use of the digits is undertaken in the context of the possible prognostic capabilities of the motor evoked potential.

Animals↗
PubMed1999

Dorsolateral infarction of the lower medulla: clinical-MRI study.

We describe a man with lateral medullary syndrome associated with a long-standing clumsiness of the ipsilateral upper limb. MRI showed that the clinical finding of ipsilateral clumsiness correlated with an extension of the infarction into the dorsal column nuclei but was not reflected in any involvement of the more ventral pyramidal tract. This deficit in movement control that appears superficially like a hemiparesis may result from a combination of lemniscal and spinocerebellar deficits.

Adult↗
PubMed2005

A method for obtaining tract-specific diffusion tensor MRI measurements in the presence of disease: application to patients with clinically isolated syndromes suggestive of multiple sclerosis.

The aim of this study was to investigate whether neurological symptoms related to a specific axonal fiber tract in brain white matter were associated with a higher degree of tissue damage in that region, in patients at presentation with clinically isolated syndromes (CIS) suggestive of multiple sclerosis. To this end, a magnetic resonance imaging (MRI) method to segment and evaluate the fiber bundle of interest was implemented, taking care to circumvent the problems caused by pathology. Diffusion tensor (DT) MRI tractography was used to construct, from healthy volunteer data, a probability map for the pyramidal tract (PYT), and this map was applied to patients to calculate DT-derived metrics inside the PYT. In CIS patients with clinical symptoms related to motor function, the DT-derived mean diffusivity and the lesion volume in the PYT were found to be increased, while the fractional anisotropy was no different, when compared to those patients without motor symptoms. These results may be explained by several microstructural changes in the damaged tissue, such as changes in the permeability of axonal cell membranes, decreases of axonal density and edema. The approach taken to analyze a specific fiber tract was possible because the axons in the tract have a high orientational coherence, allowing tissue structure changes to be isolated from the tissue architecture. Its extension to other white matter fiber bundles is therefore limited to bundles with high orientational coherence.

Adult↗
PubMed1975

Patterns of cortical projection to hindlimb muscle motoneurone pools.

This study was undertaken to examine the organization of the hindlimb area of the motor cortex. Two specific questions were posed. The first was: are the cortical neurones which control the excitability of a given motoneurone pool localized in a small zone of corjex or are they diffuse? The second question was: does microstimulation in the hindlimb area of the motor cortex activate spinal motoneurones in a reciprocal fashion, i.e., is cortically elicited facilitation of a muscle accompanied by inhibition of the antagonist? Intracortical microstimulation was used to condition monosynaptic reflexes of the cat hindlimb to study the organization of a cortical projection to lumbar motoneurone pools. Cortical neurones which produced facilitation or inhibition of a given monosynaptic reflex were localized within a small zone of the cortex. Facilitatory and inhibitory effective zones were found to have similar shape and size. Intracortical microstimulation elicited facilitation or inhibition of individual monosynaptic reflexes without eliciting reciprocal effects on the antagonists. The pyramidal tract was shown to play an important role in the mediation of cortically elicited facilitation as well as inhibition of the monosynaptic reflexes in the lumbar cord.

Animals↗
PubMedDate not supplied

[A case of cervical myeloradiculopathy with positive serum anti-GT1a antibody].

A 19-year-old man with cervical myeloradiculopathy is reported. He was admitted to our hospital because of acute muscle weakness of upper limbs, which developed two weeks after respiratory tract infection. Neurologic examination revealed prominent muscular weakness of upper limbs. Deep tendon reflexes showed hyporeflexia in upper limbs and hyperreflexia in lower limbs. Serum IgG anti-GT1a antibody was detected by thin-layer chromatography and immunoblotting. Neck MRI revealed T2-weighted high intensity legions and swelling in spinal cord at third to sixth cervical segment. The muscular weakness and the cervical legion in MRI improved two weeks after steroid treatment. These findings indicate the involvement of cervical pyramidal tract as well as that of cervical roots in the patient. Neurological symptoms of the present case differed from those of pharyngeal-cervical-brachial variant (PCB) of Guillain-Barré syndrome, although serum anti-GT1a antibody was positive.

Adult↗