Corticospinal Fibers
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Visualization of the Pyramidal Decussation Utilizing Diffusion
OPEN ACCESS RESEARCH Visualization of the pyramidal decussation utilizing diffusion tensor imaging: a feasibility study utilizing generalized q-sampling imaging Erik H Middlebrooks1,*, Jeffrey A Bennett1, Sharatchandra Bidari1, and Alissa Old Crow1 1Department of Radiology, University of Florida College of Medicine, Gainesville, Florida, USA *corresponding author ([email protected]) Abstract Background: The delineating point of the end of the brainstem and beginning of the spinal cord is known as the cervicomedullary junction (CMJ). This point is defined by the decussation of the pyramidal tracts. Abnormal configuration and location of the CMJ have both been implicated in disease processes such as Chiari malformation. Unfortunately, the CMJ is not directly visualized on contemporary imaging techniques. Diffusion tensor imaging (DTI) has given us the ability to directly visualize white matter tracts, but suffers from difficulties with visualizing crossing fibers. Many advanced techniques for visualizing crossing fibers utilize substantially long imaging times or non-clinical magnet strengths making clinical applicability limited. Objective: This study inves- tigates the use of generalized q-sampling imaging with diffusion decomposition on standard DTI acquisitions at 3 Tesla to demonstrate the pyramidal decussation. Methods: Three differing DTI protocols were analyzed in vivo with scan times of 17 minutes, 10 minutes, and 5.5 minutes. Data was processed with standard DTI post-processing, as well as generalized q-sampling imaging with diffusion decomposition. Results: The results of the study show that the pyramidal decussation can be reliably visualized using generalized q-sampling imaging and diffusion decomposition with scan times as low at 10 minutes. Conclusion: Utilizing generalized q-sampling post-processing, the pyramidal decussation can be reliably visualized using clinically feasible DTI sequences with scan times as low as 10 minutes. -
Auditory and Vestibular Systems Objective • to Learn the Functional
Auditory and Vestibular Systems Objective • To learn the functional organization of the auditory and vestibular systems • To understand how one can use changes in auditory function following injury to localize the site of a lesion • To begin to learn the vestibular pathways, as a prelude to studying motor pathways controlling balance in a later lab. Ch 7 Key Figs: 7-1; 7-2; 7-4; 7-5 Clinical Case #2 Hearing loss and dizziness; CC4-1 Self evaluation • Be able to identify all structures listed in key terms and describe briefly their principal functions • Use neuroanatomy on the web to test your understanding ************************************************************************************** List of media F-5 Vestibular efferent connections The first order neurons of the vestibular system are bipolar cells whose cell bodies are located in the vestibular ganglion in the internal ear (NTA Fig. 7-3). The distal processes of these cells contact the receptor hair cells located within the ampulae of the semicircular canals and the utricle and saccule. The central processes of the bipolar cells constitute the vestibular portion of the vestibulocochlear (VIIIth cranial) nerve. Most of these primary vestibular afferents enter the ipsilateral brain stem inferior to the inferior cerebellar peduncle to terminate in the vestibular nuclear complex, which is located in the medulla and caudal pons. The vestibular nuclear complex (NTA Figs, 7-2, 7-3), which lies in the floor of the fourth ventricle, contains four nuclei: 1) the superior vestibular nucleus; 2) the inferior vestibular nucleus; 3) the lateral vestibular nucleus; and 4) the medial vestibular nucleus. Vestibular nuclei give rise to secondary fibers that project to the cerebellum, certain motor cranial nerve nuclei, the reticular formation, all spinal levels, and the thalamus. -
Cerebral Cortex
Cerebral Cortex • Research on the structure and function of the brain reveals that there are both specialized and diffuse areas of function • Motor and sensory areas are localized in discrete cortical areas called domains • Many higher mental functions such as memory and language appear to have overlapping domains and are more diffusely located • Broadmann areas are areas of localized function Cerebral Cortex - Generalizations • The cerebral cortex has three types of functional areas – Motor areas / control voluntary motor function – Sensory areas / provide conscious awareness of sensation – Association areas / act mainly to integrate diverse information for purposeful action • Each hemisphere is chiefly concerned with the sensory and motor functions of the opposite (contralateral) side of the body Motor Areas • Cortical areas controlling motor functions lie in the posterior part of the frontal lobes • Motor areas include the primary motor cortex, the premotor cortex, Broca’s area, and the front eye field Primary Motor Cortex • The primary motor cortex is located in the precentral gyrus of the frontal lobe of each hemisphere • Large neurons (pyramidal cells) in these gyri allow us to consciously control the precise or skill voluntary movements of our skeletal muscles Pyramidal cells • These long axons, which project to the spinal cord, form the massive Dendrites voluntary motor tracts called the pyramidal, or corticospinal tracts • All other descending motor tracts issue from brain stem nuclei and consists of chains of two, three, or -
Amyotrophic Lateral Sclerosis (ALS)
Amyotrophic Lateral Sclerosis (ALS) There are multiple motor neuron diseases. Each has its own defining features and many characteristics that are shared by all of them: Degenerative disease of the nervous system Progressive despite treatments and therapies Begins quietly after a period of normal nervous system function ALS is the most common motor neuron disease. One of its defining features is that it is a motor neuron disease that affects both upper and lower motor neurons. Anatomical Involvement ALS is a disease that causes muscle atrophy in the muscles of the extremities, trunk, mouth and face. In some instances mood and memory function are also affected. The disease operates by attacking the motor neurons located in the central nervous system which direct voluntary muscle function. The impulses that control the muscle function originate with the upper motor neurons in the brain and continue along efferent (descending) CNS pathways through the brainstem into the spinal cord. The disease does not affect the sensory or autonomic system because ALS affects only the motor systems. ALS is a disease of both upper and lower motor neurons and is diagnosed in part through the use of NCS/EMG which evaluates lower motor neuron function. All motor neurons are upper motor neurons so long as they are encased in the brain or spinal cord. Once the neuron exits the spinal cord, it operates as a lower motor neuron. 1 Upper Motor Neurons The upper motor neurons are derived from corticospinal and corticobulbar fibers that originate in the brain’s primary motor cortex. They are responsible for carrying impulses for voluntary motor activity from the cerebral cortex to the lower motor neurons. -
Quantifying Nerve Decussation Abnormalities in the Optic Chiasm T Robert J
NeuroImage: Clinical 24 (2019) 102055 Contents lists available at ScienceDirect NeuroImage: Clinical journal homepage: www.elsevier.com/locate/ynicl Quantifying nerve decussation abnormalities in the optic chiasm T Robert J. Puzniaka, Khazar Ahmadia, Jörn Kaufmannb, Andre Gouwsc, Antony B. Morlandc,d, ⁎ Franco Pestillie,1, Michael B. Hoffmanna,f,1, a Department of Ophthalmology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany b Department of Neurology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany c York Neuroimaging Centre, Department of Psychology, University of York, York, United Kingdom d York Biomedical Research Institute, University of York, York, United Kingdom e Department of Psychological and Brain Sciences, Program in Neuroscience and Program in Cognitive Science, Indiana University, Bloomington, USA f Center for Behavioral Brain Sciences, Magdeburg, Germany ARTICLE INFO ABSTRACT Keywords: Objective: The human optic chiasm comprises partially crossing optic nerve fibers. Here we used diffusion MRI Optic chiasm (dMRI) for the in-vivo identification of the abnormally high proportion of crossing fibers found intheoptic Albinism chiasm of people with albinism. Diffusion MRI Methods: In 9 individuals with albinism and 8 controls high-resolution 3T dMRI data was acquired and analyzed Functional MRI with a set of methods for signal modeling [Diffusion Tensor (DT) and Constrained Spherical Deconvolution Crossing nerves (CSD)], tractography, and streamline filtering (LiFE, COMMIT, and SIFT2). The number of crossing andnon- crossing streamlines and their weights after filtering entered ROC-analyses to compare the discriminative power of the methods based on the area under the curve (AUC). The dMRI results were cross-validated with fMRI estimates of misrouting in a subset of 6 albinotic individuals. -
Topographic Organization of Corticospinal Projections from the Frontal Lobe: Motor Areas on the Lateral Surface of the Hemisphere
The Journal of Neuroscience, March 1993, 133): 952-980 Topographic Organization of Corticospinal Projections from the Frontal Lobe: Motor Areas on the Lateral Surface of the Hemisphere San-Qiang He, Richard P. Dum, and Peter L. Strick Research Service, Veterans Affairs Medical Center, and Departments of Neurosurgery and Physiology, SUNY Health Science Center at Syracuse, Syracuse, New York 13210 We examined the topographic organization of corticospinal PMd that project most densely to upper cervical segments neurons in the primary motor cortex and in the two premotor were largely separate from those that project most dense/y areas on the lateral surface of the hemisphere [i.e., the dor- to lower cervical segments. Furthermore, we found two sep- sal premotor area (PMd) and the ventral premotor area (PMv)]. arate regions within area 4 that send corticospinal projec- In two macaques, we labeled corticospinal neurons that pro- tions primarily to the lower cervical segments. One of these ject beyond T7 or S2 by placing crystals of HRP into the regions was located within the classical “hand” area of the dorsolateral funiculus at these segmental levels. In another primary motor cortex. The other was located at the medial seven macaques, we labeled corticospinal neurons that pro- edge of arm representation in the primary motor cortex. ject to specific segmental levels of the spinal cord by in- These results provide new insights into the pattern of body jecting the fluorescent tracers fast blue and diamidino yellow representation in the primary motor cortex, PMd, and PMv. into the gray matter of the cervical and lumbosacral seg- Our findings support the classic distinction between the ments. -
White Matter Anatomy: What the Radiologist Needs to Know
White Matter Anatomy What the Radiologist Needs to Know Victor Wycoco, MBBS, FRANZCRa, Manohar Shroff, MD, DABR, FRCPCa,*, Sniya Sudhakar, MBBS, DNB, MDb, Wayne Lee, MSca KEYWORDS Diffusion tensor imaging (DTI) White matter tracts Projection fibers Association Fibers Commissural fibers KEY POINTS Diffusion tensor imaging (DTI) has emerged as an excellent tool for in vivo demonstration of white matter microstructure and has revolutionized our understanding of the same. Information on normal connectivity and relations of different white matter networks and their role in different disease conditions is still evolving. Evidence is mounting on causal relations of abnormal white matter microstructure and connectivity in a wide range of pediatric neurocognitive and white matter diseases. Hence there is a pressing need for every neuroradiologist to acquire a strong basic knowledge of white matter anatomy and to make an effort to apply this knowledge in routine reporting. INTRODUCTION (Fig. 1). However, the use of specific DTI sequences provides far more detailed and clini- DTI has allowed in vivo demonstration of axonal cally useful information. architecture and connectivity. This technique has set the stage for numerous studies on normal and abnormal connectivity and their role in devel- DIFFUSION TENSOR IMAGING: THE BASICS opmental and acquired disorders. Referencing established white matter anatomy, DTI atlases, Using appropriate magnetic field gradients, and neuroanatomical descriptions, this article diffusion-weighted sequences can be used to summarizes the major white matter anatomy and detect the motion of the water molecules to and related structures relevant to the clinical neurora- from cells. This free movement of the water mole- diologist in daily practice. -
How Does the Brain Produce Movement?
p CHAPTER 10 How Does the Brain Produce Movement? The Hierarchical Control The Basal Ganglia and of Movement the Cerebellum The Forebrain and Movement Initiation The Basal Ganglia and Movement Force The Brainstem and Species-Typical Movement Focus on Disorders: Tourette’s Syndrome Focus on Disorders: Autism The Cerebellum and Movement Skill The Spinal Cord and Movement Execution Focus on Disorders: Paraplegia The Organization of the Somatosensory System The Organization of the Somatosensory Receptors and Sensory Perception Motor System Dorsal-Root Ganglion Neurons The Motor Cortex The Somatosensory Pathways to the Brain The Corticospinal Tracts Spinal-Cord Responses to Somatosensory Input The Motor Neurons The Vestibular System and Balance The Control of Muscles Exploring the Somatosensory The Motor Cortex and Skilled System Movements The Somatosensory Homunculus Investigating Neural Control of Skilled Movements The Effects of Damage to the Somatosensory Cortex The Control of Skilled Movements in Other Species The Somatosensory Cortex and Complex How Motor Cortex Damage Affects Skilled Movement Movements Kevork Djansezian/AP Photo Micrograph: Dr. David Scott/Phototake 354 I p amala is a female Indian elephant that lives at the In one way, however, Kamala uses this versatile trunk zoo in Calgary, Canada. Her trunk, which is really very unusually for an elephant (Onodera & Hicks, 1999). K just a greatly extended upper lip and nose, con- She is one of only a few elephants in the world that paints sists of about 2000 fused muscles. A pair of nostrils runs its with its trunk (Figure 10-1). Like many artists, she paints length and fingerlike projections are located at its tip. -
Developmental Determinants at the Mammalian Optic Chiasm
- Feature Article Developmental Determinants at the Mammalian Optic Chiasm Ft. W. Guillery,’ C. A. Mason,* and J. S. H. Taylor’ ‘Department of Human Anatomy, University of Oxford, Oxford OX1 3QX, United Kingdom and *Departments of Pathology, Anatomy, and Cell Biology, Centre for Neurobiology and Behaviour, College of Physicians and Surgeons, Columbia University, New York 10032 The optic chiasm is the point at the ventral midline of the di- ber of mutants are known that show well-defined abnormalities encephalon where the nerve fibers from the two eyes meet. Clas- of the optic chiasm. The chiasm can no longer be regarded sim- sically, it has been known as the place where groups of retinal ply as the region where some axons cross their partners from axons segregate to pass into the optic tract on either the same the other eye, and others diverge into an uncrossed course. There or the opposite side of the brain (Figs. 1, 2). This segregation is is now an opportunity to look more closely at the cellular and dependent upon the retinal position of the ganglion cells from molecular events producing the characteristic and rigidly cho- which the axons arise: axons from the nasal retina all cross to reographed patterns of axonal growth. The development of the the opposite side, whereas many from the temporal or ventro- optic chiasm and the reorganization of retinotopic order that oc- temporal part of the retina (temporal crescent) remain uncrossed. curs within region of the chiasm can now be seen in terms of a This segregation of the axons into a crossed and uncrossed com- number of discrete steps, each probably relatively simple in it- ponent allows the appropriate bilateral connections that underlie self, which together produce the final developmental sequence. -
Decussation Geometries in the Goldfish Nervous System
Proc. Natl. Acad. Sci. USA Vol. 76, No. 8, pp. 4131-4135, August 1979 Neurobiology Decussation geometries in the goldfish nervous system: Correlation with probability of survival (brain asymmetries/lateralization of function/Mauthner's neuron/optic chiasm/natural selection) RICHARD L. ROTH Department of Biological Sciences, Stanford University, Stanford, California 94305 Communicated by Donald Kennedy, May 9, 1979 ABSTRACT In the goldfish, the optic nerve decussation assumed to be representative of goldfish available in the United occurs without intermingling of fibers from the two eyes. In States. The embryonic and larval specimens examined were two-thirds of juvenile and adult specimens, the left optic nerve derived from two lots of fertile eggs and, by the breeders' es- is dorsal at the midline. In about 60% of the specimens, the decussation of Mauthner's neuron also has a left-dorsal-to-right timates, represent the progeny of 9-14 spawning females.* (L/R) configuration. Concordance for decussation geometry is Despite this limited sampling of embryos and larvae, the results greater than 80%, with smaller specimens accounting for a presented below indicate that they, too, provide an adequate disproportionate number of discordant cases. In embryos and basis for generalization. very young larvae, the L/R configuration occurs in slightly less For minimization of sampling bias, most of the Spanish moss than 50% of o tic chiasmata and in slightly more than 50% of into each Mauthner's cell chiasmata, and there is no significant tendency containing the eggs was teased and cut portions, toward concordance. However, larval specimens that survive bearing 50-75 eggs. -
Corticospinal Tract (CST) Reconstruction Based on Fiber
Corticospinal Tract (CST) reconstruction based on fiber orientation distributions (FODs) tractography Youshan Zhang Computer Science and Engineering Department Lehigh University Bethlehem, PA [email protected] Abstract—The Corticospinal Tract (CST) is a part of pyra- About 75%-90% of the CST fibers descend to the lateral midal tract (PT) and it can innervate the voluntary movement corticospinal tract by decussation of the pyramid, but a few of skeletal muscle through spinal interneurons (the 4th layer of fibers form the anterior corticospinal tract by not crossing the Rexed gray board layers), and anterior horn motorneurons (which control trunk and proximal limb muscles). Spinal cord the pyramid [9], [10]. The fibers, which first passed through injury (SCI) is a highly disabling disease often caused by the medial posterior spinocerebellar tract then went into traffic accidents. The recovery of CST and the functional the lumbosacral spinocerebellar tract, were not yet appeared reconstruction of spinal anterior horn motor neurons play an [11], [12]. The main function of the CST is innervating essential role in the treatment of SCI. However, the localization the voluntary movement of skeletal muscle through spinal and reconstruction of CST are still challenging issues, the accuracy of the geometric reconstruction can directly affect interneurons (the 4th layer of the Rexed gray board layers), the results of the surgery. The main contribution of this paper and anterior horn motorneurons (which control trunk and is the reconstruction of the CST based on the fiber orientation proximal limb muscles), then the CST terminates in the spinal distributions (FODs) tractography. Differing from tensor-based motor cells (which control the fine motor of small muscle tractography in which the primary direction is a determined in extremities) [13]. -
Vertical Gaze Palsy and Selective Unilateral Medial Longitudinal
Journal ofNeurology, Neurosurgery, and Psychiatry 1990;53:67-71 67 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.53.1.67 on 1 January 1990. Downloaded from Vertical gaze palsy and selective unilateral infarction of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) J Bogousslavsky, J Miklossy, F Regli, R Janzer Abstract Case report We report a clinico-pathological correla- A 60 year old housewife who was a smoker had tion study in a patient with basilar artery been investigated for ten years for arterial thrombosis, who developed tetraplegia hypertension, diabetes mellitus and elevated and combined up- and downgaze palsy blood cholesterol. Three weeks before admis- involving voluntary saccades and sion, she experienced transient dysarthria and visually-guided movements, but sparing dizziness and the day before had been unable to the oculocephalic responses. At necropsy, stand and experienced tingling in the left hand. apart from bilateral infarction in the One day later, she suffered acute rotatory basis pontis, there was a single unilateral vertigo with vomiting, diplopia, dysarthria, infarct selectively destroying the rostral and left-sided weakness and numbness. On interstitial nucleus of the medial longi- admission, the patient was well-oriented in tudinal fasciculus (riMLF) on the right. time and place but had severe dysarthria. Blood The posterior commissure and its pressure was 140/85 mm Hg. The visual fields nucleus, the nucleus of Cajal, the nucleus were normal. Eye movements were normal. of Darkschewitsch and the pontine The pupils could not be assessed, because of tegmentum were spared. We suggest that previous cataract operations.