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PubMed2003

Intraoperative three-dimensional visualization of the pyramidal tract in a neuronavigation system (PTV) reliably predicts true position of principal motor pathways.

BACKGROUND: This prospective study employs anisotropic diffusion-weighted (ADW) magnetic resonance imaging for the integration of individual spatial information concerning the principal motor pathways into the operating room during microneurosurgery in the central region. We hypothesize that the three-dimensional (3-D) visualization of the pyramidal tract position (PTV) in a neuronavigation system based on ADW provides valid information concerning the position and extension of the principal motor pathways. METHODS: A total of 13 consecutive patients with lesions adjacent to the pyramidal tracts and the central region underwent microneurosurgery with the help of pyramidal tract visualization (PTV). An ADW sequence obtained preoperatively was fused to an anatomic navigation sequence. The 3-D reconstructions of the precentral gyrus (PG), the pyramidal tract, and the tumor were available in a customized neuronavigation system during surgery. Intraoperatively the PG was identified on the basis of the aforementioned data. Electric motorcortex stimulation (CS) was used to directly verify the PG location and indirectly the fiber tract position. RESULTS: In 11 cases (92%) the prediction of the principal motor pathways' position was correct. In one case of a meningioma, according to PTV, the tumor was falsely localized postcentrally. In the case of a precentral cavernoma, no motor response could be elicited by cortical stimulation. CONCLUSION: Intraoperative PTV on the basis of ADW provides the neurosurgeon with reliable information concerning the position of the principal motor pathways during intracranial procedures as proved with intraoperative electrophysiological testing. The technique has the potential to reduce operative morbidity. PTV is straightforward and can be adapted to other customized neuronavigation devices.

Adult↗
PubMed2003

Involuntary stretching during yawning in patients with pyramidal tract lesions: further evidence for the existence of an independent emotional motor system.

A variety of associated movements have been described in patients with pyramidal tract lesions. We report three patients in whom involuntary stretching of an otherwise plegic arm could be observed during yawning. These patients had radiologically verified lesions at different levels of the pyramidal tract. As yawning and stretching are an automatic behavioural pattern in animals, it is likely that stretches during yawning in man are also an automatic motor pattern, usually inhibited in the presence of an intact corticospinal tract. The physiological function of yawning is unclear at present. Yawning might be the somatomotor manifestation of a particular emotional state characterized by boredom and fatigue. Our observation that movements of an otherwise plegic arm occur in patients with pyramidal tract lesions supports therefore the concept of an emotional motor system which has an independent input to motoneurones in the brain stem and the spinal cord.

Adult↗
PubMed1976

Further study on the excitation of pyramidal tract cells by intracortical microstimulation.

The effective spread of stimulating current for pyramidal tract (PT) cells and fibers was studied using a method of cancelling the shock artifacts and the following results were obtained: 1. The excitability of PT axon collaterals was as high as that of PT cells. 2. These axon collaterals extended as far as 1.0 mm horizontally from the PT cells. 3. The low threshold area for activation of a given PT cell was as wide as 3--4 mm2 on the surface of the cortex. 4. Intracortical microstimulation (ICMS) delivered to the PT cell layer produced direct (D) and indirect (I) descending volleys in the pyramidal tract, but ICMS to the superficial layer (III) produced only I-waves. 5. These I-waves grew significantly larger after 15--20 msec from the start of the train of stimuli. 6. It is concluded that either surface stimulation, or short train of ICMS is inadequate for delineating fine localization of motor function within the cortex. Longer train (30--40 msec) with high frequency pulses (300--400 cy/sec) can produce muscle contraction with much smaller currents, increasing the accuracy of measuring the localization of motor function.

Animals↗
PubMed1994

Extent of pontine pyramidal tract Wallerian degeneration and outcome after supratentorial hemorrhagic stroke.

BACKGROUND AND PURPOSE: Pyramidal tract Wallerian degeneration has been detected on magnetic resonance imaging (MRI) as T2-weighted high-intensity areas. We analyzed the relation between the extent of brain stem Wallerian degeneration and activities of daily living (ADL) after supratentorial hemorrhagic stroke. METHODS: Twenty-six patients with supratentorial hemorrhage were examined on the coronal T2-weighted image of the pons 3 months or later after stroke, and the percentage of Wallerian degeneration in the pons was calculated. The patients were divided into three groups. In group A (n = 6), MR films were taken 3 to 6 months from the onset, and the ADL assessment was done within 2 months from the MRI. In group B (n = 11), MR films were taken 3 to 6 months from the onset, and the ADL assessment was done within 10 months from the MRI (mean, 15.5 months from the onset). In group C (n = 9), MR films were taken after 10 to 17 months (mean, 12.0 months) from the ictus, and the ADL assessment was done simultaneously. Barthel Index score was used for quantitative ADL assessment. RESULTS: All patients showed various degrees of pontine pyramidal tract Wallerian degeneration associated with capsular involvement by the hematoma. In group A, the percentage of degeneration did not correlate with the Barthel Index score (r = .2101, P = .6895). An inverse relation between percentage of degeneration and Barthel Index score was seen in groups B (r = .7354, P = .0099) and C (r = .888, P = .0014). In groups B and C, Wallerian degeneration was higher in patients with Barthel scores less than 60 (P = .005). CONCLUSIONS: The extent of pontine Wallerian degeneration on MRI 3 months or later after the stroke correlated with the patient's Barthel Index score 1 year after the stroke.

Activities of Daily Living↗
PubMed1989

Differences in the fiber composition of the pyramidal tract in two- and 14-month-old rats.

The present study is aimed at an electron-microscopic morphometrical analysis of the pyramidal tract of 14-month-old rats at the level of the pyramis medullae and the second cervical segment, and a comparison with data obtained for rats of two months of age. Between 2 and 14 months of age there is, at the level of the pyramis medullae of the left pyramidal tract, a statistically significant increase of the number of myelinated fibers, from 91,000 to 118,000, whereas the total number of unmyelinated fibers decreases from 133,000 to 101,000. On the right side at the same level there is no statistically significant change in the number of myelinated fibers, whereas there is a significant decrease of unmyelinated fibers at this side, from 148,000 to 89,000. At the second cervical level, a statistically significant increase in the number of myelinated fibers has been noted at both sides (from 43,000 to 60,000) between 2 and 14 months, whereas the mean total number of unmyelinated fibers at this level decreases somewhat (from 35,000 to 28,000), but is not statistically significant. Several processes which might be involved in the age-related changes observed are discussed, including the possibility of a shift from unmyelinated fibers to myelinated ones, withdrawal of corticobulbar fibers and ongoing outgrowth of myelinated corticofugal fibers after two months of age, and a summarizing scheme is presented. We conclude that the pyramidal tract of the rat changes in composition after the age of two months and that continuing outgrowth of myelinated corticospinal fibers is an important aspect of this continuing development.

Aging↗
PubMed1990

Wallerian degeneration of the pyramidal tract in capsular infarction studied by magnetic resonance imaging.

Using magnetic resonance imaging, we studied 24 patients with ischemic infarction of the internal capsule. Magnetic resonance imaging detected wallerian degeneration of the pyramidal tract below the capsular lesion in 11 patients (45.8%); all 11 had clinical evidence of pyramidal tract damage. In six additional patients magnetic resonance imaging findings, present only on axial slices, were considered to indicate possible wallerian degeneration. When motor deficit was associated with posterior limb lesions, magnetic resonance imaging detected wallerian degeneration of the pyramidal tract in 78.6% (11) of 14 patients.

Aged↗
PubMed1959

Antidromic cortical response to stimulation of isolated pyramidal tract.

Direct electrical excitation of the intact medullary pyramids evokes a complex cortical response. When the pyramidal tract was dissected away from the bulb and stimulated in isolation. the antidromic cortical response consisted of a simple, positive potential, regardless of the stimulus parameters. This finding necessitates a reinterpretation of previous results obtained by stimulation of the intact pyramids.

Cerebral Cortex↗
PubMed1994

Motor cortex and pyramidal tract axons responsible for electrically evoked forelimb flexion: refractory periods and conduction velocities.

Double-pulse methods are used here to measure the refractory periods and conduction velocities of the pyramidal tract axons which cause forelimb flexion in pentobarbital anesthetized rats. In the refractory period experiments, conditioning and test pulses were delivered to the motor cortex, the ipsilateral internal capsule, or the ipsilateral pyramid, and the maximum force exerted by the contralateral forelimb was measured at various conditioning-test intervals. The movements increased as conditioning-test interval increased from 0.5 to 1.0 ms in pyramid sites, from 0.6 to 1.5 in internal capsule sites, and from 0.6 to 2.0 ms in surface cortical sites, suggesting longer refractory periods for the substrates at more rostral sites. In cortical sites, as the conditioning-test interval increased from 4.0 to 20.0 ms, the movements decreased gradually to the single-pulse level, suggesting decreasing temporal summation at longer conditioning-test intervals. In the collision experiments, when conditioning pulses were delivered to one site and test pulses to a second site, the movements increased at conditioning-test intervals that were longer by 0.5-1.3 ms than the refractory periods in either site. This suggests that collisions occurred between orthodromic and antidromic action potentials in the pyramidal tract axons responsible for the limb movement. The collision-like increase was greater between internal capsule and pyramid than between cortex and pyramid, or between cortex and internal capsule. The estimated conduction times were 0.9-1.5 ms between cortex and pyramid, 0.4-0.8 ms between cortex and internal capsule, and 0.5-0.8 ms between internal capsule and pyramid. The range of conduction velocities, therefore, was quite narrow between all pairs (8.8-16.8 m/s). The largest pyramidal tract axons appear to be responsible for most of the force of forelimb flexion in pentobarbital anesthetized rats.

Animals↗
PubMed1991

[A case of HTLV-1 associated myelopathy with diffuse white matter lesion of the frontal lobe and continuous lesion of the pyramidal tract on cranial MRI].

In this report, the characteristic findings of cranial MRI of a case with HTLV-1 associated myelopathy (HAM) is described. The patient was a 62-year-old woman with 6 years history of paraplegia. Her main clinical signs were bilateral spastic paraplegia in the lower limb girdle muscles and extremities, paresthesia below the tenth thoracic cord level and urinary disorder. There was bilateral blepharoptosis. Hyperreflexia was observed in the examination of the cranial nerves and upper extremities. She showed no dementia or any other higher cortical dysfunctions. Positive anti-HTLV-1 antibody in the serum and cerebrospinal fluid established a diagnosis of HAM. T2 weighted MRI study revealed the symmetrical diffuse hyperintensity in the subcortical white matter of the frontal lobe and temporal lobe. The hyper-intensity was also observed in the bilateral internal capsule-peduncular base junction and pontine base, which indicated the continuous lesions in the intracranial pyramidal tracts. These MRI findings were different from those of reported cases of scattered lesion in central nervous system. There are some speculations for the nature of the diffuse lesion in the white matter, i.e., fusion of solitary gliosis and/or perivascular cuffing, or diffusely advanced spongy state. The continuous lesion of the pyramidal tract is suspected a systemic demyelination. Although the pathomechanism still remains uncertain, HTLV-1 infection generally affects the spinal pyramidal tract. It seems that this case is selectively affected in the pyramidal tracts in CNS.

Female↗
PubMed1995

Pyramidal tract and corticospinal neurons with branching axons to the dorsal column nuclei of the cat.

Extracellular single activity was recorded from pericruciate neurons in anaesthetized, paralysed, artificially ventilated cats. A total of 309 neurons were identified antidromically by stimulation of the dorsal column nuclei (229 from the nuneate nucleus and 80 from the gracile nucleus). The study addressed the question whether pericruciate-dorsal column nuclei neurons (corticonuclear cells) sent collaterals to the ipsilateral red nucleus and/or to the contralateral nucleus reticularis gigantocellularis. Also, the ipsilateral pyramidal tract was stimulated at mid-olivary level, as was the crossed corticospinal tract at C2, Th2 and L2 levels in order to know whether the corticonuclear cells sent their axons to the spinal cord and if so to which level. It was found that more than 95% of the corticonuclear fibres coursed through the pyramidal tract. A significant (28.4%; 88/309) proportion of the the corticonuclear neurons sent collaterals to the red nucleus and/or to the nucleus reticularis gigantocellularis. About 68% (209/309) of the corticonuclear cells did not send their axons to the spinal cord and the remainder were corticospinal neurons. Most of the corticospinal fibres terminated at the cervical level (72/100) and the remaining ended at thoracic (18/100) and lumbar (10/100) segments of the cord. While 63.4% (123/194) of the corticonuclear fibres coursing through the pyramidal tract and ending at supraspinal levels were slow conducting, the great majority of the corticospinal neurons were fast conducting (91/100). The non-corticospinal neurons were significantly slower conducting than the corticospinal cells. The corticogracile neurons were slower conducting than the corticocuneate cells. Of the 88 corticonuclear neurons that sent at least a branch to the sites tested, 50% branched into the red nucleus, 35.2% into the nucleus reticularis gigantocellularis and 14.7% into both nuclei, without significant difference between non-corticospinal and corticospinal cells. Most of the main axons of the corticonuclear cells ended at bulbar and cervical levels (281/309 or 90.9%). The data indicate that pericruciate-dorsal column nuclei neurons form a particular substrate within pyramidal tract cells. They can serve precise functions in motor coordination associated with the selection of their own sensory input. The results are discussed from this point of view.

Animals↗
PubMed1994

Effects of 2,5-hexanedione on rat spinal pyramidal tract.

The present study was undertaken to investigate central axonal neuropathy caused by 2,5-hexanedione (2,5-HD) administration. The effects of 2,5-HD on rat pyramidal tract were studied electrophysiologically and histopathologically. Male rats were given 0.5% 2,5-HD in their drinking water for 4, 6 or 8 wk. Spinal motor conduction velocity was measured by direct electrical stimulation and was examined histopathologically by electron microscopy. Rats treated with 2,5-HD had reduced spinal motor conduction velocity at 6 wk and their pyramidal tract axons had decreased cross-sectional areas at 4 wk. The mean number of neurofilaments in myelinated axons of rats treated with 2,5-HD for 8 wk was 42.1% of that found in control rats, but the number of microtubules was not significantly different. The ratio of neurofilaments to microtubules in rats treated with 2,5-HD for 4 wk was less than 1.0 in 30.9% of myelinated fibers, while in control rats it was greater than 1.0 in all axons. These changes in spinal pyramidal tract were detected relatively early after 2,5-HD administration. These results in rats indicate the need for further studies of 2,5-HD neurotoxicity in the human central nervous system.

Animals↗
PubMed1998

Paw and limb use in skilled and spontaneous reaching after pyramidal tract, red nucleus and combined lesions in the rat: behavioral and anatomical dissociations.

The pyramidal tract and red nucleus send prominent projections to the spinal cord and are thought to co-operate in producing skilled movements. In the present study, skilled reaching for food located on a shelf and spontaneous grasping, handling and eating pieces of pasta were video-recorded and analyzed in control rats, rats with unilateral ibotenic acid lesions of the red nucleus (RN), unilateral pyramidal tract lesions (PT) and combined lesions. The behavioral results suggest that skilled movements are organized as action patterns, easily recognizable and distinctive for each task. In both skilled and spontaneous reaching, PT lesions reduced success more than RN lesions, suggesting a greater role for the PT in guiding limb movements. Both lesions impaired rotatory movements including limb aiming, pronation and supination. RN lesions additionally abolished the arpeggio movement by which the paw is oriented for searching and grasping. Combined lesions were additive as rats lost both rotatory movements and arpeggio. Nevertheless, even after combined lesions, the rats were able to advance the limb, grasp food and withdraw the limb. The sparing following combined lesions suggests that other neural systems as well as compensatory adjustments assist the impaired limb. The results are discussed in relation to the possible distinctive contributions of the rubrospinal and corticospinal tract to the action patterns that comprise skilled movements in rats.

Animals↗
PubMed1995

Magnetic resonance signal abnormalities along the pyramidal tracts in amyotrophic lateral sclerosis.

Magnetic resonance imaging (MRI) studies of the brain were reviewed in 16 patients with amyotrophic lateral sclerosis (ALS), representative of a large and homogeneously studied series, 11 of whom showed signal abnormalities along the pyramidal tracts. These were more frequent in patients with more severe upper motor neuron signs but did not correlate with disease severity. Our study suggests that MRI signal abnormalities along the pyramidal tracts are common in ALS and may reflect the severity of pyramidal tract degeneration.

Amyotrophic Lateral Sclerosis↗
PubMed1978

Dystopic myelination with hypertrophy of pyramidal tract.

In a case of hypertrophy of the pyramidal tract the cross section of the hypertrophic pyramids was 174% of controls with an increase (148%) in the total population of myelinated fibers. However, there was no commensurate increase in the density of Betz cells. Confined to the hypertrophic tract there was a peculiar anomaly consisting of tubes of thick myelin sheaths that encompassed columns of glial nuclei instead of axons. This type of change, along with the clinical data, may indicate that the lesion originated in the perinatal period when myelin formation is in progress and is susceptible to derangement.

Cell Count↗
PubMed2003

Complete and partial lesions of the pyramidal tract in the rat affect qualitative measures of skilled movements: impairment in fixations as a model for clumsy behavior.

Little is known about prenatal and perinatal brain injury resulting in subsequent clumsy behavior in children. One candidate motor system is the pyramidal tract. The tract traverses the entire central nervous system and, through direct and indirect connections to the brainstem and spinal cord sensory and motor nuclei, is involved in the learning and execution of skilled movements. Here, rats, either naive or pretrained on a number of motor tasks, were assessed for acute and chronic impairments following complete or incomplete pyramidal tract lesions. Postsurgery rats with complete lesions were impaired on the qualitative measures of limb aiming, supination, and posture. Impaired movements require fixations, complementary movements in different body segments. The impairment in fixations was manifest acutely and underwent no improvement with subsequent training/testing. The finding that complete and partial pyramidal tract lesions produce chronic impairment in fixations provides insight for understanding clumsy behavior in humans and its potential remediation via specific training in making fixations.

Animals↗
PubMed1989

Corticostriatal cells in comparison with pyramidal tract neurons: contrasting properties in the behaving monkey.

Antidromically identified neurons projecting to the putamen (CPNs) and pyramidal tract neurons (PTNs) were recorded from motor and premotor cortex of a monkey which performed a load-bearing task with the wrist. CPNs appeared as a uniform population with very slowly conducting axons and low spontaneous activity. In contrast to PTNs, they exhibited weak, mostly insignificant correlation with graded steady-state forces, responded to torque perturbations with remarkably long latency, and seemed to discharge much later with active movement. Collateral branching of PTNs to the putamen was found to be infrequent (1%). We suggest that the putamen receives a cortical message that is strikingly different from that sent down the pyramidal tract.

Animals↗
PubMed1984

Diameter of axons and thickness of myelin sheaths of the pyramidal tract fibres in the adult human medullary pyramid.

After perfusion fixation with a mixture of paraformaldehyde, glutaraldehyde, and potassium-chromate 4 adult human medullary pyramids were examined with the electron microscope. The myelin sheaths showed only mild signs of post mortal destructions. The periodicity of the lamellae is preserved and varies about 17 nm. For quantitative purposes specimens were taken at random from regions with an extend of half a mm2 on the cross section of the pyramid. On the average 62 lamellae (s = 5, n = 200) built up 1 micron myelin sheath in the 4 brains. The myelin sheath thickness and the inner circumference of the myelin sheath are measured. The axon diameter is calculated from the inner circumference. We obtained an average number of 66,000 fibres, s = 11,000 per mm2. Fibres with a total diameter below 4 microns amount to 87.9%, fibres from 4 to 10 microns to 10.77%, and larger than 10 microns to 1.4%. An axon diameter of about 0.5 micron combined with a thickness of the myelin sheath of 0.3 micron was most often found in all 4 cases. The fibres showed a broad variation of myelin thickness. In a given group of the small axons the thickest myelin sheath exceeded 3 to 4 times the value of the thinnest one. The coefficient of correlation between axon diameter and myelin sheath thickness was calculated as r2 = 0.56. No correspondence exists between frequency maxima and the ratio g, axon diameter to total diameter. Below a total fibre diameter of 5 microns the ratio g scatters broadly about 0.6, fibres larger than 5 microns exceed the value of 0.6. From the morphological data only large sized fibres can evoke a strong effect on compound action potentials if the method of reconstruction of the action potential from fibre size frequency distribution is employed.

Adult↗