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PubMed2007

Pontine infarction in a dog with unilateral involvement of the trigeminal motor nucleus and pyramidal tract.

An unusual case of unilateral trigeminal neuronopathy in a dog is reported, in which the motor nucleus of the trigeminal nerve and the ipsilateral corticospinal tract were destroyed, apparently by a cerebrovascular accident (stroke). Hemiplegia did not occur. Neuropathological changes are described, including remyelination by Schwann cells in the central nervous system. The case illustrates the importance of central nervous system post-mortem examination when establishing causes of cranial nerve paralysis.

Animals↗
PubMed1994

Peroneal muscular atrophy with pyramidal tract features (hereditary motor and sensory neuropathy type V): a clinical, neurophysiological, and pathological study of a large kindred.

A large family with autosomal dominant inheritance of peroneal muscular atrophy, associated with extensor plantar responses in some cases, has been studied. Onset was usually in the first two decades and spasticity was not a feature. Nerve conduction studies in 21 cases and light and electron microscope findings on six sural nerve biopsies were similar to those in hereditary motor and sensory neuropathy type II.

Adolescent↗
PubMed2006

Implementation of fiber tract navigation.

OBJECTIVE: To implement fiber tracking in a common neuronavigation environment for routine clinical use to visualize major white matter tracts intraoperatively. METHODS: A single-shot, spin-echo diffusion weighted echo planar imaging sequence with six diffusion directions on a 1.5 T magnetic resonance scanner was used for diffusion tensor imaging. For three-dimensional (3-D) tractography, we applied a knowledge-based multiple volume of interest approach. Tracking was initiated in each voxel of the initial seed volume in retrograde and orthograde directions according to the direction of the major eigenvector by applying a tensor deflection algorithm. Tractography results were displayed as streamlines assigned direction encoding color. After selecting the fiber tract bundle of interest by defining inclusion and exclusion volumes, a 3-D object was generated automatically by wrapping the whole fiber tract bundle. This 3-D object was displayed along with other contours representing tumor outline and further functional data with the microscope heads-up display. RESULTS: In 16 patients (three cavernomas, 13 gliomas), major white matter tracts (pyramidal tract, n = 14; optic radiation, n = 2) were visualized intraoperatively with a standard navigation system. Three patients developed a postoperative paresis, which resolved in two in the postoperative course. Additional planning time for tractography amounted to up to 10 minutes. Comparing the tractography results with a fiber bundle generated on a different platform by applying a distortion-free sequence revealed a good congruency of the defined 3-D outlines in the area of interest. CONCLUSION: Fiber tract data can be reliably integrated into a standard neuronavigation system, allowing for intraoperative visualization and localization of major white matter tracts such as the pyramidal tract or optic radiation.

Adolescent↗
PubMed1996

Convergence of skin reflex and corticospinal effects in segmental and propriospinal pathways to forelimb motoneurones in the cat.

The organization of facilitatory convergence from cutaneous afferents (Skin) and the corticospinal tract (pyramidal tract, Pyr) in pathways to forelimb motoneurones of mainly distal muscles was studied in anaesthetized cats by analysing postsynaptic potentials (PSPs), which were spatially facilitated by combinations of stimuli to the two sources at different time intervals. Conditioning Pyr volleys facilitated Skin-evoked PSPs of fixed (1.2-3.6 ms) central latencies (Skin PSPs), suggesting that disynaptic and polysynaptic skin reflex pathways are facilitated from the pyramidal tract. The shortest latencies (1.2-1.7 ms) of pyramidal facilitation suggested direct connection of pyramidal fibres with last order neurones of skin reflex pathways. Conditioning Skin volleys facilitated Pyr-evoked PSPs of fixed, mostly disynaptic latencies (1.0-2.5 ms; Pyr PSPs), suggesting that pyramido-motoneuronal pathways are facilitated from Skin at a premotoneuronal level. The shortest pathway from skin afferents to the premotor neurones appeared to be monosynaptic. Although Pyr and Skin volleys were mutually facilitating, the facilitation curve of Pyr PSPs and that of Skin PSPs were discontinuous to each other, with the peak facilitation at different Skin-Pyr volley intervals. Transection of the dorsal column (DC) at the C5/C6 border had little effect on the latencies or amplitudes evoked by maximal stimulation and the pyramidal facilitation of Skin PSPs. In contrast, the facilitation of Pyr PSPs by Skin stimulation was greatly decreased after the DC transection, and the facilitation curve of Pyr PSPs was continuous to that of Skin PSPs, with no separate peak. Latencies of Pyr PSPs ranged similarly to those in DC intact preparations. More rostral DC transection (C4/C5 border) reduced Skin-facilitated Pyr excitatory PSPs (EPSPs) less than C5/C6 lesions, suggesting that the C5 segment also contains neurones mediating Skin-facilitated Pyr EPSPs. The results show that convergence from skin afferents and the corticospinal tract occurs at premotor pathways of different cervical segments. We suggest that corticospinal facilitation of skin reflex occurs mostly in the brachial segments and Skin facilitation of cortico-motoneuronal effects takes place largely in the rostral cervical segments and partly in the brachial segments.

Animals↗
PubMed1989

[Analysis of follow-up survey in spinocerebellar degeneration].

Spinocerebellar degeneration (SCD) is associated with other various degeneration of the nervous systems such as the optic tract, pyramidal pathway, extrapyramidal system, nuclei of the brain stem and autonomic nervous system as well as changes of heart. The clinical pattern, also have the great variability. We investigated the mode of progression of clinical symptoms and signs in 214 cases of SCD which were examined 2 times at intervals of about 10 years. 79 of 214 cases were reported to be died at the last examination. 135 alive cases included 3 with the Holmes type, 14 with late cortical cerebellar atrophy (LCCA) 10 with Menzel type, 18 with olive-ponto-cerebellar atrophy (OPCA), 33 with spinocerebellar form (SCF), 6 with Friedreich's ataxia, 18 with hereditary spastic paraparesis (HSP) and 33 with the other type. 79 dead cases included 0 with the Holmes type, 6 with LCCA, 5 with Menzel type, 32 with OPCA, 16 with SCF, 1 with Friedreich's ataxia, 4 with HSP and 15 with the other type. The disability of daily living in SCD revealed slower progression in the advanced stage than in the early stage. Every type of SCD had some different progression of disability each other. In the early stage, Friedreich's ataxia showed the highest progression of disability, but in the advanced stage, Holmes type and the OPCA did. Holmes type showed progression of ataxia without any remarkable change of other systems. LCCA showed increase of abnormality in the eye movements, pyramidal tract and autonomic nervous system in addition to the cerebellar system. OPCA involved multiple systems as ataxia worsening, but Menzel type had no remarkable changes of incidence in eye movement disorder.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2007

White matter fiber tracking computation based on diffusion tensor imaging for clinical applications.

Fiber tracking allows the in vivo reconstruction of human brain white matter fiber trajectories based on magnetic resonance diffusion tensor imaging (MR-DTI), but its application in the clinical routine is still in its infancy. In this study, we present a new software for fiber tracking, developed on top of a general-purpose DICOM (digital imaging and communications in medicine) framework, which can be easily integrated into existing picture archiving and communication system (PACS) of radiological institutions. Images combining anatomical information and the localization of different fiber tract trajectories can be encoded and exported in DICOM and Analyze formats, which are valuable resources in the clinical applications of this method. Fiber tracking was implemented based on existing line propagation algorithms, but it includes a heuristic for fiber crossings in the case of disk-shaped diffusion tensors. We successfully performed fiber tracking on MR-DTI data sets from 26 patients with different types of brain lesions affecting the corticospinal tracts. In all cases, the trajectories of the central spinal tract (pyramidal tract) were reconstructed and could be applied at the planning phase of the surgery as well as in intraoperative neuronavigation.

Adolescent↗
PubMedDate not supplied

[Protocol of intraoperative neurophysiological spinal cord monitoring].

INTRODUCTION: The consequences derived from medullar harm caused during several spinal cord surgical interventions can often be catastrophic for the patient, even more taking into consideration that many of them are young. DEVELOPMENT: This problem is observed specially at interventions of spinal malformations (kyphoscoliosis), but also during other surgical techniques like fractures, degenerations, spinal tumors and aortic lesions. The use of somatosensory evoked potentials (SEP) began at late 70's, as a method to monitorize spinal cord function during surgery; years later, motor evoked potentials (MEP) joined this option, giving us direct information about the functioning of posterior spinothalamic tract (posterior column) and lateral corticospinal tract (pyramidal tract), respectively. This has motivated that, although the degree of surgical difficulty and complexity of spinal instrumentation have raised, the actual percentage of neurological complications derived from them has decreased. CONCLUSIONS: This article describes the intraoperative spinal cord monitoring protocol followed at Hospital Clínico San Carlos of Madrid, Spain, which includes the making of SEP and MEP, the latest according to the translaminar stimulation technique.

Evoked Potentials, Motor↗
PubMed1988

An electrophysiological study of single somatosensory neurons in rat granular cortex serving the limbs: a laminar analysis.

1. Recordings were made from 545 neurons in somatosensory granular cortex of anesthetized Sprague-Dawley rats. Of this sample, 32% were active spontaneously. Active neurons were not distributed uniformly throughout cortex but were most common in layer V. The highest mean spontaneous discharge frequency also was found in this layer. Cells with the lowest rates of spontaneous activity were located immediately above and below. One subset of spontaneously active neurons was characterized by an unusually high discharge frequency modulated by somatic stimulation. 2. Only 25.8% of the 534 neurons tested in granular cortex could be activated by somatic stimuli. Only 9.4% had cutaneous receptive fields, and 2.4% received deep inputs. The remainder (14.0%) were driven by higher intensity stimuli and could not be classified unequivocally as either cutaneous or deep. The 50 neurons with cutaneous receptive fields were located in the middle third of the cortex, and those with the largest receptive fields were found most superficially. Neurons driven by somatic stimuli were found most frequently in layer Vb, where 44.5% of the sample confirmed histologically to be in layer Vb could be excited. 3. The large proportion of neurons lacking demonstrable somatic inputs was attributed to the use of iontophoretically administered glutamate, which allowed the detection of many unresponsive neurons. This proportion was not reduced by the use of nitrous oxide and halothane as an anesthetic. 4. Neurons activated only by deep inputs were found on the medial and rostral edge of the hindlimb granular cortex, suggesting that deep and cutaneous inputs may be segregated in this species. 5. Electrical stimuli applied to the foot pads activated a sample of neurons differing from those driven by natural somatic stimuli in terms of depth, spontaneous activity, probability of somatic input, and probability of activation by the pyramidal tract. 6. Pyramidal tract neurons tended to be located in layer Vb, were active spontaneously, and had evidence of somatic inputs, although most required relatively intense stimuli to be excited. Other neurons activated synaptically from the pyramidal tract were located in the layers immediately above and below the pyramidal tract neurons. These cells were divided into two groups on the basis of action-potential latency, action-potential shape, and sensitivity to acetylcholine.

Animals↗
PubMed2002

T1 relaxation time mapping of white matter tracts in multiple sclerosis defined by diffusion tensor imaging.

T(1) relaxation time (T(1)) is a quantitative magnetic resonance measure that enables a global evaluation of white matter disease in multiple sclerosis (MS). We aimed to investigate whether mapping of T(1) values in critical white matter tracts, defined by diffusion tensor (DT) imaging, could provide a stronger surrogate marker of disability. 25 patients with relapsing-remitting MS and 14 healthy controls were imaged with a dual-echo T(2)-weighted sequence. Whole brain T(1) maps were acquired using a multi-slice inversion recovery sequence and DT images generated from a spin-echo, echo-planar diffusion weighted sequence. Trajectories were defined to follow the course of white matter fibre tracts in the pyramidal pathways and corpus callosum. T(1) values were sampled along these trajectories. Total white matter T(1) was sampled by defining white matter masks on axial slices of the T(1) maps. Median T(1) in the pyramidal tracts, corpus callosum and total white matter of MS patients was significantly longer than in controls (p < 0.0001). Median pyramidal tract T(1) correlated significantly with the pyramidal Kurtzke Functional Systems Score (r = 0.64, p = 0.0007) and the Expanded Disability Status Scale (r = 0.55, p = 0.005). By contrast, no correlation with disability was observed for corpus callosum T(1) or total white matter T(1). Our findings show that quantifying pathology within the pyramidal tracts, by utilizing T(1), provides a strong correlate of disability compared with the overall white matter burden of disease. Pyramidal tract T(1) may also provide an objective, sensitive measure for monitoring the progression of motor deficits and disability.

Adult↗