DOCSLIB.ORG

Adult Leukodystrophies: a Step- By-Step Diagnostic Approach

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Adult Leukodystrophies: a Step- By-Step Diagnostic Approach This copy is for personal use only. To order printed copies, contact [email protected] 153 NEUROLOGIC/HEAD A Adult Leukodystrophies: A Step- by-Step Diagnostic Approach Lucas Lopes Resende, MD N Anderson Rodrigues Brandão de Paiva, Leukodystrophies usually affect children, but in the last several D NECK MD decades, many instances of adult leukodystrophies have been re- Fernando Kok, MD, PhD ported in the medical literature. Because the clinical manifestation Claudia da Costa Leite, MD, PhD of these diseases can be nonspecific, MRI can help with establish- Leandro Tavares Lucato, MD, PhD ing a diagnosis. A step-by-step approach to assist in the diagnosis I of adult leukodystrophies is proposed in this article. The first step MAGI Abbreviations: CADASIL = cerebral auto- is to identify symmetric white matter involvement, which is more somal dominant arteriopathy with subcortical commonly observed in these patients. The next step is to fit the infarcts and leukoencephalopathy, CTX = cere- N brotendinous xanthomatosis, FLAIR = fluid-at- symmetric white matter involvement into one of the proposed pat- G tenuated inversion recovery, X-ALD = X-linked terns. However, a patient may present with more than one pattern adrenoleukodystrophy of white matter involvement. Thus, the third step is to evaluate for RadioGraphics 2019; 39:153–168 five distinct characteristics—including enhancement, lesions with https://doi.org/10.1148/rg.2019180081 signal intensity similar to that of cerebrospinal fluid, susceptibility- Content Codes: weighted MRI signal intensity abnormalities, abnormal peaks at MR spectroscopy, and spinal cord involvement—to further narrow From the Neuroradiology Section, Instituto de Radiologia (InRad), Hospital das Clínicas, Facul- the differential diagnosis. dade de Medicina da Universidade de São Paulo © (HC-FMUSP), R. Dr. Ovídio Pires de Campos RSNA, 2019sradiographics.rsna.org 75, São Paulo, SP 05403-010, Brazil (L.L.R., C.d.C.L., L.T.L.); and Neurogenetics Unit, De- partment of Neurology, Hospital das Clínicas da Universidade de São Paulo, São Paulo, Brazil (A.R.B.d.P., F.K.). Recipient of a Certificate of Introduction Merit award for an education exhibit at the 2017 RSNA Annual Meeting. Received March 12, Leukodystrophies currently are defined as genetically determined 2018; revision requested May 8 and received July disorders that primarily affect the white matter of the central nervous 3; accepted July 23. For this journal-based SA- system, regardless of the structural white matter component, molec- CME activity, the authors C.d.C.L. and L.T.L. have provided disclosures; all other authors, the ular process, patient age group, and disease course involved. Genetic editor, and the reviewers have disclosed no rele- testing is of paramount importance (1). vant relationships. Address correspondence to L.L.R. (e-mail: [email protected]). Although these disorders primarily manifest in early infancy and childhood, they may also affect adults, who occasionally present with ©RSNA, 2019 clinical and imaging findings that are distinct from those observed in children (2,3). There is growing recognition that leukodystrophies SA-CME LEARNING OBJECTIVES may manifest initially during adulthood (4). After completing this journal-based SA-CME Adult leukodystrophies usually are progressive diseases. Patients activity, participants will be able to: may present with movement disturbance, vision problems, hearing ■ Discuss a framework that could help impairment, imbalance, memory loss, behavioral changes, and atten- radiologists and clinicians narrow the usually broad differential diagnosis for tion deficits (5–8). adult patients suspected of having leuko- Because the clinical manifestation of leukodystrophy can be non- dystrophy. specific, MRI has been used as a powerful paraclinical tool; it some- ■ Identify the imaging features of some of times can be the key to narrowing the diagnosis, even at the early the most prevalent adult leukodystrophies. stages of the disease in presymptomatic patients and carriers (5,7). ■ Describe the key image points that might Symmetric involvement in the white matter at MRI is an essential lead to a confirmed diagnosis in patients suspected of having adult leukodystrophies. finding in patients with adult leukodystrophies, because it commonly is associated with inherited disorders. However, the imaging pattern See rsna.org/learning-center-rg. of adult leukodystrophy can vary according to the disease and its time course (9,10). In addition to symmetry, many other MRI features can help in reaching a final diagnosis in patients who are presumed to have adult leukodystrophy or at least in narrowing the list of diagnoses for which to evaluate as part of the differential diagnosis. An algorithm that allows evaluation of all of these characteristics has been devel- oped to help differentiate among white matter diseases overall (11). 154 January-February 2019 radiographics.rsna.org TEACHING POINTS In addition to recognizing symmetric white matter involvement, characterizing the white mat- ■ Symmetric involvement in the white matter at MRI is an es- ter involvement pattern is necessary to continue sential finding in patients with adult leukodystrophies, be- cause it commonly is associated with inherited disorders. with the differential diagnosis. ■ T2-weighted and fluid-attenuated inversion-recovery (FLAIR) MRI are the best sequences to use to determine white matter Step 2: Look for a White Matter involvement. Involvement Pattern ■ Sometimes the same patient presents with more than one The next step in the diagnostic approach is to pattern during the time course of the disease, and a given leu- look for the pattern of white matter involvement. kodystrophy may manifest with more than one of these pat- There are six patterns of white matter involve- terns. In this situation, searching for distinctive findings (step ment with which radiologists should be aware to 3) will help to restrict the conditions to consider in the dif- ferential diagnosis and target the specific confirmatory tests. reduce the list of possible diagnoses, as shown in ■ The periventricular pattern is probably the most prevalent of Figure 2. However, sometimes the same patient all patterns, and myriad distinct diseases, including diseases presents with more than one pattern during the other than leukodystrophies, can manifest with periventricular time course of the disease, and a given leukodys- involvement. trophy may manifest with more than one of these ■ MR spectroscopy might be used as a potential noninvasive patterns. In this situation, searching for distinc- biomarker of treatment response in treatable diseases such tive findings (step 3) helps to restrict the condi- as CTX. tions to consider in the differential diagnosis and target the specific confirmatory tests. The purpose of this review is to adapt this Parieto-occipital Pattern algorithm for adult leukodystrophies and to demonstrate the imaging features of some of the X-linked Adrenoleukodystrophy.—X-linked most prevalent forms of this disease. The ap- adrenoleukodystrophy (X-ALD), one of the most proach we propose here must be used mainly as common adult leukodystrophies, is caused by a a framework. The characterization of all possible mutation in the adenosine triphosphate–binding types of leukodystrophies and eventual atypical cassette subfamily D member 1 gene (ABCD1), presentations is beyond the scope of this review. which codes for an adenosine triphosphate–bind- ing cassette transporter and is located in the per- Step 1: Identify Symmetric White oxisomal membrane. The biochemical hallmark Matter Involvement of this condition is an elevation in serum levels Symmetric white matter involvement at MRI is a of very long-chain fatty acids, which also accu- typical finding in patients with leukodystrophies. mulate in neural tissues and in the adrenal gland. Thus, recognizing this involvement is important Molecular confirmation of X-ALD is performed when leukodystrophies are suspected, although by sequencing the ABCD1 gene (10,13,14). there are exceptions to this pattern (12). T2- In adults, there are different forms of X-ALD. weighted and fluid-attenuated inversion-recovery The most common is “pure” adrenomyeloneu- (FLAIR) MRI are the best sequences to use to ropathy, which manifests with slowly progres- determine white matter involvement, as shown in sive spastic paraparesis, sensory disturbances, Figure 1, which illustrates symmetric white mat- and bladder dysfunction. These patients usu- ter involvement compared with an asymmetric ally experience spinal cord atrophy, mainly in pattern. White matter lesions appear as hyperin- its thoracic segment, but the brain shows no tensity on T2-weighted and FLAIR MR images abnormalities. The cerebral manifestation of and hypo- or isointensity on T1-weighted images. X-ALD is less frequent in adults and is char- Depending on the cause and stage of the disease, acterized by psychiatric features followed by signal intensity may vary. Familiarity with typical dementia, ataxia, seizures, and even death. In manifestations is important (13). these patients, MR images of the brain are simi- Important exceptions to this rule are geneti- lar to those observed in children with ALD, and cally defined vasculopathies, such as CADA- the spinal cord shows no abnormalities. Other SIL, in which abnormalities in signal intensity patients present with intermediate forms of the (ie, increased signal intensity on T2-weighted disease that include involvement of the spinal or FLAIR MR
Load more

Recommended publications
  • Magnetic Resonance Imaging of Multiple Sclerosis: a Study of Pulse-Technique Efficacy
    691 Magnetic Resonance Imaging of Multiple Sclerosis: A Study of Pulse-Technique Efficacy Val M. Runge1 Forty-two patients with the clinical diagnosis of multiple sclerosis were examined by Ann C. Price1 proton magnetic resonance imaging (MRI) at 0.5 T. An extensive protocol was used to Howard S. Kirshner2 facilitate a comparison of the efficacy of different pulse techniques. Results were also Joseph H. Allen 1 compared in 39 cases with high-resolution x-ray computed tomography (CT). MRI revealed characteristic abnormalities in each case, whereas CT was positive in only 15 C. Leon Partain 1 of 33 patients. Milder grades 1 and 2 disease were usually undetected by CT, and in all A. Everette James, Jr.1 cases, the abnormalities noted on MRI were much more extensive than on CT. Cerebral abnormalities were best shown with the T2-weighted spin-echo sequence (TE/TR = 120/1000); brainstem lesions were best defined on the inversion-recovery sequence (TE/TI/TR =30/400/1250). Increasing TE to 120 msec and TR to 2000 msec heightened the contrast between normal and abnormal white matter. However, the signal intensity of cerebrospinal fluid with this pulse technique obscured some abnormalities. The diagnosis of multiple sclerosis continues to be a clinical challenge [1,2). The lack of an objective means of assessment further complicates the evaluation of treatment regimens. Evoked potentials, cerebrospinal fluid (CSF) analysis , and computed tomography (CT) are currently used for diagnosis, but all lack sensitivity and/or specificity. Furthermore, postmortem examinations demonstrate many more lesions than those suggested by clinical means [3).
    [Show full text]
  • Brainstem: Structure & Its Mode of Action
    Journal of Neurology & Neurophysiology 2021, Vol.12, Issue 3, 521 Opinion Brainstem: Structure & Its Mode of action Karthikeyan Rupani Research Fellow, Tata Medical Centre, India. Corresponding Author* The brainstem is exceptionally little, making up around as it were 2.6 percent of the brain's add up to weight. It has the basic parts of directing cardiac, and Rupani K, respiratory work, making a difference to control heart rate and breathing rate. Research Fellow, Tata Medical Centre, India; It moreover gives the most engine and tactile nerve supply to the confront and E-mail: [email protected] neck by means of the cranial nerves. Ten sets of cranial nerves come from the brainstem. Other parts incorporate the direction of the central apprehensive Copyright: 2021 Rupani K. This is an open-access article distributed under the framework and the body's sleep cycle. It is additionally of prime significance terms of the Creative Commons Attribution License, which permits unrestricted within the movement of engine and tangible pathways from the rest of the use, distribution, and reproduction in any medium, provided the original author brain to the body, and from the body back to the brain. These pathways and source are credited. incorporate the corticospinal tract (engine work), the dorsal column-medial lemniscus pathway and the spinothalamic tract [3]. The primary part of the brainstem we'll consider is the midbrain. The midbrain Received 01 March 2021; Accepted 15 March 2021; Published 22 March 2021 (too known as the mesencephalon) is the foremost prevalent of the three districts of the brainstem. It acts as a conduit between the forebrain over and the pons and cerebellum underneath.
    [Show full text]
  • Adult Onset) an Information Sheet for the Person Who Has Been Diagnosed with a Leukodystrophy, Their Family, and Friends
    Leukodystrophy (Adult Onset) An information sheet for the person who has been diagnosed with a leukodystrophy, their family, and friends. ‘Leukodystrophy’ and the related term ‘leukoencephalopathy’ The person may notice they trip more easily, particularly on refer to a group of conditions that affect the myelin, or white uneven ground or steps. matter, of the brain and spinal cord. Other symptoms that people with adult-onset Leukodystrophies are neurological, degenerative disorders, leukodystrophy may experience include: sensitivity to and most are genetic. This means that a person’s condition extremes of temperature, such as difficulty tolerating hot is caused by a change to one of the genes that are involved summer weather; pain or abnormal sensation, particularly in in the development of myelin, leading to deterioration in the legs; shaking or tremors; loss of vision and/or hearing; many of the body’s neurological functions. The pattern headaches, and difficulty with coordination. of symptoms varies from one type of leukodystrophy to People with leukodystrophy often experience long delays another, and there may even be some variation between before receiving a correct diagnosis. This is partly because different people with the same condition, however all are the symptoms can be quite vague and associated with described as progressive. This means that although there many different disorders. Leukodystrophies are rare, and may be periods of stability, the condition doesn’t go into it is routine medical practice to rule out more common and ‘remission’ as may be seen in some other neurological treatable causes before testing for rarer conditions. There conditions, and over time the condition worsens.
    [Show full text]
  • Child Neurology: Hereditary Spastic Paraplegia in Children S.T
    RESIDENT & FELLOW SECTION Child Neurology: Section Editor Hereditary spastic paraplegia in children Mitchell S.V. Elkind, MD, MS S.T. de Bot, MD Because the medical literature on hereditary spastic clinical feature is progressive lower limb spasticity B.P.C. van de paraplegia (HSP) is dominated by descriptions of secondary to pyramidal tract dysfunction. HSP is Warrenburg, MD, adult case series, there is less emphasis on the genetic classified as pure if neurologic signs are limited to the PhD evaluation in suspected pediatric cases of HSP. The lower limbs (although urinary urgency and mild im- H.P.H. Kremer, differential diagnosis of progressive spastic paraplegia pairment of vibration perception in the distal lower MD, PhD strongly depends on the age at onset, as well as the ac- extremities may occur). In contrast, complicated M.A.A.P. Willemsen, companying clinical features, possible abnormalities on forms of HSP display additional neurologic and MRI abnormalities such as ataxia, more significant periph- MD, PhD MRI, and family history. In order to develop a rational eral neuropathy, mental retardation, or a thin corpus diagnostic strategy for pediatric HSP cases, we per- callosum. HSP may be inherited as an autosomal formed a literature search focusing on presenting signs Address correspondence and dominant, autosomal recessive, or X-linked disease. reprint requests to Dr. S.T. de and symptoms, age at onset, and genotype. We present Over 40 loci and nearly 20 genes have already been Bot, Radboud University a case of a young boy with a REEP1 (SPG31) mutation. Nijmegen Medical Centre, identified.1 Autosomal dominant transmission is ob- Department of Neurology, PO served in 70% to 80% of all cases and typically re- Box 9101, 6500 HB, Nijmegen, CASE REPORT A 4-year-old boy presented with 2 the Netherlands progressive walking difficulties from the time he sults in pure HSP.
    [Show full text]
  • Hereditary Spastic Paraparesis: a Review of New Developments
    J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.69.2.150 on 1 August 2000. Downloaded from 150 J Neurol Neurosurg Psychiatry 2000;69:150–160 REVIEW Hereditary spastic paraparesis: a review of new developments CJ McDermott, K White, K Bushby, PJ Shaw Hereditary spastic paraparesis (HSP) or the reditary spastic paraparesis will no doubt Strümpell-Lorrain syndrome is the name given provide a more useful and relevant classifi- to a heterogeneous group of inherited disorders cation. in which the main clinical feature is progressive lower limb spasticity. Before the advent of Epidemiology molecular genetic studies into these disorders, The prevalence of HSP varies in diVerent several classifications had been proposed, studies. Such variation is probably due to a based on the mode of inheritance, the age of combination of diVering diagnostic criteria, onset of symptoms, and the presence or other- variable epidemiological methodology, and wise of additional clinical features. Families geographical factors. Some studies in which with autosomal dominant, autosomal recessive, similar criteria and methods were employed and X-linked inheritance have been described. found the prevalance of HSP/100 000 to be 2.7 in Molise Italy, 4.3 in Valle d’Aosta Italy, and 10–12 Historical aspects 2.0 in Portugal. These studies employed the In 1880 Strümpell published what is consid- diagnostic criteria suggested by Harding and ered to be the first clear description of HSP.He utilised all health institutions and various reported a family in which two brothers were health care professionals in ascertaining cases aVected by spastic paraplegia. The father was from the specific region.
    [Show full text]
  • Spinal Cord Organization
    Lecture 4 Spinal Cord Organization The spinal cord . Afferent tract • connects with spinal nerves, through afferent BRAIN neuron & efferent axons in spinal roots; reflex receptor interneuron • communicates with the brain, by means of cell ascending and descending pathways that body form tracts in spinal white matter; and white matter muscle • gives rise to spinal reflexes, pre-determined gray matter Efferent neuron by interneuronal circuits. Spinal Cord Section Gross anatomy of the spinal cord: The spinal cord is a cylinder of CNS. The spinal cord exhibits subtle cervical and lumbar (lumbosacral) enlargements produced by extra neurons in segments that innervate limbs. The region of spinal cord caudal to the lumbar enlargement is conus medullaris. Caudal to this, a terminal filament of (nonfunctional) glial tissue extends into the tail. terminal filament lumbar enlargement conus medullaris cervical enlargement A spinal cord segment = a portion of spinal cord that spinal ganglion gives rise to a pair (right & left) of spinal nerves. Each spinal dorsal nerve is attached to the spinal cord by means of dorsal and spinal ventral roots composed of rootlets. Spinal segments, spinal root (rootlets) nerve roots, and spinal nerves are all identified numerically by th region, e.g., 6 cervical (C6) spinal segment. ventral Sacral and caudal spinal roots (surrounding the conus root medullaris and terminal filament and streaming caudally to (rootlets) reach corresponding intervertebral foramina) collectively constitute the cauda equina. Both the spinal cord (CNS) and spinal roots (PNS) are enveloped by meninges within the vertebral canal. Spinal nerves (which are formed in intervertebral foramina) are covered by connective tissue (epineurium, perineurium, & endoneurium) rather than meninges.
    [Show full text]
  • Autosomal Dominant Leukodystrophy with Autonomic Symptoms
    List of Papers This thesis is based on the following papers, which are referred to in the text by their Roman numerals. I MR imaging characteristics and neuropathology of the spin- al cord in adult-onset autosomal dominant leukodystrophy with autonomic symptoms. Sundblom J, Melberg A, Kalimo H, Smits A, Raininko R. AJNR Am J Neuroradiol. 2009 Feb;30(2):328-35. II Genomic duplications mediate overexpression of lamin B1 in adult-onset autosomal dominant leukodystrophy (ADLD) with autonomic symptoms. Schuster J, Sundblom J, Thuresson AC, Hassin-Baer S, Klopstock T, Dichgans M, Cohen OS, Raininko R, Melberg A, Dahl N. Neurogenetics. 2011 Feb;12(1):65-72. III Bedside diagnosis of rippling muscle disease in CAV3 p.A46T mutation carriers. Sundblom J, Stålberg E, Osterdahl M, Rücker F, Montelius M, Kalimo H, Nennesmo I, Islander G, Smits A, Dahl N, Melberg A. Muscle Nerve. 2010 Jun;41(6):751-7. IV A family with discordance between Malignant hyperthermia susceptibility and Rippling muscle disease. Sundblom J, Mel- berg A, Rücker F, Smits A, Islander G. Manuscript submitted to Journal of Anesthesia. Reprints were made with permission from the respective publishers. Contents Introduction..................................................................................................11 Background and history............................................................................... 13 Early studies of hereditary disease...........................................................13 Darwin and Mendel................................................................................
    [Show full text]
  • White Matter Tracts - Brain A143 (1)
    WHITE MATTER TRACTS - BRAIN A143 (1) White Matter Tracts Last updated: August 8, 2020 CORTICOSPINAL TRACT .......................................................................................................................... 1 ANATOMY .............................................................................................................................................. 1 FUNCTION ............................................................................................................................................. 1 UNCINATE FASCICULUS ........................................................................................................................... 1 ANATOMY .............................................................................................................................................. 1 DTI PROTOCOL ...................................................................................................................................... 4 FUNCTION .............................................................................................................................................. 4 DEVELOPMENT ....................................................................................................................................... 4 CLINICAL SIGNIFICANCE ........................................................................................................................ 4 ARTICLES ..............................................................................................................................................
    [Show full text]
  • Hereditary Spastic Paraplegias
    Hereditary Spastic Paraplegias Authors: Doctors Enza Maria Valente1 and Marco Seri2 Creation date: January 2003 Update: April 2004 Scientific Editor: Doctor Franco Taroni 1Neurogenetics Istituto CSS Mendel, Viale Regina Margherita 261, 00198 Roma, Italy. e.valente@css- mendel.it 2Dipartimento di Medicina Interna, Cardioangiologia ed Epatologia, Università degli studi di Bologna, Laboratorio di Genetica Medica, Policlinico S.Orsola-Malpighi, Via Massarenti 9, 40138 Bologna, Italy.mailto:[email protected] Abstract Keywords Disease name and synonyms Definition Classification Differential diagnosis Prevalence Clinical description Management including treatment Diagnostic methods Etiology Genetic counseling Antenatal diagnosis References Abstract Hereditary spastic paraplegias (HSP) comprise a genetically and clinically heterogeneous group of neurodegenerative disorders characterized by progressive spasticity and hyperreflexia of the lower limbs. Clinically, HSPs can be divided into two main groups: pure and complex forms. Pure HSPs are characterized by slowly progressive lower extremity spasticity and weakness, often associated with hypertonic urinary disturbances, mild reduction of lower extremity vibration sense, and, occasionally, of joint position sensation. Complex HSP forms are characterized by the presence of additional neurological or non-neurological features. Pure HSP is estimated to affect 9.6 individuals in 100.000. HSP may be inherited as an autosomal dominant, autosomal recessive or X-linked recessive trait, and multiple recessive and dominant forms exist. The majority of reported families (70-80%) displays autosomal dominant inheritance, while the remaining cases follow a recessive mode of transmission. To date, 24 different loci responsible for pure and complex HSP have been mapped. Despite the large and increasing number of HSP loci mapped, only 9 autosomal and 2 X-linked genes have been so far identified, and a clear genetic basis for most forms of HSP remains to be elucidated.
    [Show full text]
  • Memory Loss from a Subcortical White Matter Infarct
    J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.51.6.866 on 1 June 1988. Downloaded from Journal of Neurology, Neurosurgery, and Psychiatry 1988;51:866-869 Short report Memory loss from a subcortical white matter infarct CAROL A KOOISTRA, KENNETH M HEILMAN From the Department ofNeurology, College ofMedicine, University ofFlorida, and the Research Service, Veterans Administration Medical Center, Gainesville, FL, USA SUMMARY Clinical disorders of memory are believed to occur from the dysfunction of either the mesial temporal lobe, the mesial thalamus, or the basal forebrain. Fibre tract damage at the level of the fornix has only inconsistently produced amnesia. A patient is reported who suffered a cerebro- vascular accident involving the posterior limb of the left internal capsule that resulted in a persistent and severe disorder of verbal memory. The inferior extent of the lesion effectively disconnected the mesial thalamus from the amygdala and the frontal cortex by disrupting the ventral amygdalofugal and thalamic-frontal pathways as they course through the diencephalon. This case demonstrates that an isolated lesion may cause memory loss without involvement of traditional structures associated with memory and may explain memory disturbances in other white matter disease such as multiple sclerosis and lacunar state. Protected by copyright. Memory loss is currently believed to reflect grey day of his illness the patient was transferred to Shands matter damage of either the mesial temporal lobe,' -4 Teaching Hospital at the University of Florida for further the mesial or the basal forebrain.'0 l evaluation. thalamus,5-9 Examination at that time showed the patient to be awake, Cerebrovascular accidents resulting in memory dys- alert, attentive and fully oriented.
    [Show full text]
  • White Matter Dissection and Structural Connectivity of the Human Vertical
    www.nature.com/scientificreports OPEN White matter dissection and structural connectivity of the human vertical occipital fasciculus to link vision-associated brain cortex Tatsuya Jitsuishi1, Seiichiro Hirono2, Tatsuya Yamamoto1,3, Keiko Kitajo1, Yasuo Iwadate2 & Atsushi Yamaguchi1* The vertical occipital fasciculus (VOF) is an association fber tract coursing vertically at the posterolateral corner of the brain. It is re-evaluated as a major fber tract to link the dorsal and ventral visual stream. Although previous tractography studies showed the VOF’s cortical projections fall in the dorsal and ventral visual areas, the post-mortem dissection study for the validation remains limited. First, to validate the previous tractography data, we here performed the white matter dissection in post-mortem brains and demonstrated the VOF’s fber bundles coursing between the V3A/B areas and the posterior fusiform gyrus. Secondly, we analyzed the VOF’s structural connectivity with difusion tractography to link vision-associated cortical areas of the HCP MMP1.0 atlas, an updated map of the human cerebral cortex. Based on the criteria the VOF courses laterally to the inferior longitudinal fasciculus (ILF) and craniocaudally at the posterolateral corner of the brain, we reconstructed the VOF’s fber tracts and found the widespread projections to the visual cortex. These fndings could suggest a crucial role of VOF in integrating visual information to link the broad visual cortex as well as in connecting the dual visual stream. Te VOF is the fber tract that courses vertically at the posterolateral corner of the brain. Te VOF was histori- cally described in monkey by Wernicke1 and then in human by Obersteiner2.
    [Show full text]
  • 1. 2. A) Explain the Compositions of White Matter and Gray
    Tfy-99.2710 Introduction to the Structure and Operation of the Human Brain, fall 2015 Exercise 1 1. 2. a) Explain the compositions of white matter and gray matter. White matter consists of glial cells and myelinated axons. It does not contain the cell bodies of neurons and acts as a signal pathway for the gray matter regions of the central nervous system. Gray matter consists of glial cells and unmyelinated axons. It contains neuronal cell bodies. b) Explain shortly the structure of a neuron. Neurons can be divided into three main parts: the cell body or the soma, the dendrites and the axon. The dendrites act as neuronal antennas in that they receive incoming signals. The cell body functions as the information processing unit of the neuron, and is responsible for sending signals forward. The axon is the signal pathway of the neuron; the signals sent by the cell body are transmitted along the axon to the axon terminals located away from the cell body. Signal transfer is along the axon is aided by the myelin sheath that covers the axon. c) Explain: Tfy-99.2710 Introduction to the Structure and Operation of the Human Brain, fall 2015 Exercise 1 i) myelin Membrane that wraps around axons. Formed from glial support cells: oligodendrogolia in the central nervous system and Schwann cells in the peripheral nervous system. Myelin facilitates signal transfer along axons by allowing action potentials to skip between the nodes of Ranvier (saltatory conduction). ii) receptor Molecule specialized in receiving a chemical signal by binding a specific neurotransmitter.
    [Show full text]