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Radiology of demyelinating diseases

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Radiology of demyelinating diseases

  1. 1. Dr. Sunil Kumar Sharma Senior Resident Dept. of Neurology GMC Kota
  2. 2. Introduction  Demyelinating diseases comprise of diseases of central and peripheral nervous system in which disruption of myelin is a dominant feature.  Diseases affecting central nervous system (CNS) myelin can be classified on the basis of whether a primary biochemical abnormality of myelin exists(dysmyelinating) or whether some other process damages the myelin or oligodendroglial cells (demyelinating).
  3. 3. • Cell Body • Dendrites • Axons – Presynaptic terminals – Bundles of axons form nerves
  4. 4. Myelin sheath  Gray matter primarily contains neurons and their processes & the white matter is composed predominantly of myelinated bundles of axons  The oligodendroglial cell membrane is the source of the myelin sheath, which is a tightly wrapped, multilayered membrane which ensheathes axons
  5. 5. Myelin sheath Cholesterol, galactocerebroside, sphingomyelin, and phospholipids are the lipids found in fully formed white matter and account for the stability and strength . Transmission electron micrograph of a myelinated axon, myelin sheath, which is a tightly wrapped, multilayered membrane
  6. 6. Classification of diseases of myelin
  7. 7. Acute disseminated encephalomyelitis (ADEM)  Best diagnostic clue: Multifocal WM/basal ganglia lesions 7-14 days following infection/vaccination  Location: May involve both brain and spinal cord; predominantly WM but also gray matter (GM)
  8. 8. MRI Findings  T2WI: T2 abnormalities better seen with FLAIR FLAIR  Multifocal punctate to large flocculent FLAIR hyperintensities  Bilateral but asymmetric Involve peripheral WM/GM junction  Can involve brain stem and posterior fossa  Do not usually involve callososeptal interface  Tumefactive, mass-like lesions possible, yet with less mass effect than expected for size
  9. 9. ADEM… DWI  Variably restricted diffusion in acute lesions  Apparent diffusion coefficient (ADC): Increased In ADEM Due to extracellular water within demyelination
  10. 10. T1 C+  Punctate, ring, incomplete ring, peripheral enhancement  Cranial nerve(s) may enhance MRS  N-acetylaspartate (NAA) low within regions of prolonged T2  Other metabolites usually normal Best imaging tool-Contrast-enhanced MRI
  11. 11. Acute disseminated encephalomyelitis. A: SagittalT2-weighted image demonstrates high signal intensity of the majority of the spinal cord with mild expansion in the cervicothoracic region. B: Axial T2-weighted image of the cervical cord demonstrates involvement of both gray and white matter.
  12. 12. Inflammatory Demyelinating Pseudotumor  Clinical Features- Demyelinating diseases occasionally present as solitary, focal, or ill-defined space-occupying lesions in the brain that closely mimic a neoplasm both clinically and radiologically.  These lesions can be found in all age groups but mostly in the third to fifth decades .  The clinical features are similar to those of postinfectious/postvaccinal encephalomyelitis, i.e. an acute onset of symptoms and dramatic response to steroids.
  13. 13.  In contrast to classic MS, there is no predilection for the periventricular white matter, optic nerves, or brainstem.  If the diagnosis of demyelination is considered, biopsy can perhaps be delayed and patients can be imaged after treatment with steroids to look for regression of MR findings
  14. 14. Inflammatory demyelinating pseudotumor- Axial FLAIR images demonstrate ill- defined high signal intensity within the right frontoparietal white matter (A) and effacement of adjacent gyri and extension along the length of the corticospinal tract, (B) the posterior limb of the internal capsule, and (C) the cerebral peduncle. Postcontrast axial T1-weighted image (D) shows ill-defined minimal enhancement. These findings mimic the appearance of a large infiltrative neoplasm. Biopsy confirmed the presence of demyelination.
  15. 15. Multiple sclerosis (MS) MR Findings TlWI  Acute: Iso-/mildly hypointense  Chronic: Hypointense center, hyperintense rim  Variable atrophy; mostly loss of WM T2WI  High convexity "sand-like“( < 2 mm diameter) Virchow- Robin spaces in recent-onset MS  Hypointense basal ganglia 10-20% chronic MS
  16. 16. Multiple sclerosis (MS)… FLAIR  Bilateral, asymmetric linear/ovoid FLAIR hyperintensities  Perivenular extension; "Dawson finger“ Along path of deep medullary veins  Hyperintensities become confluent with severity DWI  Acute lesions-Concentric ring pattern on diffusion-weighted images with hyperintense rim
  17. 17. MS… Tl C+  Transient enhancement during active demyelination (> 90% disappear within 6 months)  Nodular (68%)  Ring (23%)  Semilunar, incomplete, "horseshoe-shaped" (9%)
  18. 18. MS… MRS  NAA (NAA/Cr), Choline (Cho/Cr)  MRS abnormalities found in NAWM  Only secondary progressive MS shows NAA in normal appearing gray matter (NAGM)  May allow early distinction between relapsing- remitting & secondary-progressive
  19. 19. MR diagnosis of MS requires  ≥3 discrete lesions ≥5 mm  Lesions in characteristic location  MS compatible clinical history Nuclear Medicine Findings  PET: Glucose utilization correlates with NAA in lesions and NAWM Imaging Recommendations  Best imaging tool: MRI  Protocol advice: Contrast-enhanced MR with sagittal FLAIR
  20. 20. Extensive cervical spinal cord lesions with multiple sclerosis. A: Sagittal T2-weighted image shows extensive irregular high signal within the cord substance. B: Axial T2-weighted image shows the typical peripheral location of the multiple sclerosis plaque.
  21. 21. C: A patient with multiple sclerosis shows an ill-defined lesion on T2-weighted image extending from the dorsal medulla to C2. D: Postcontrast T1-weighted image demonstrates minimal peripheral enhancement.
  22. 22. Differential Diagnoses for MS ADEM  Viral prodrome, monophasic illness  Assymetrical  CC not involved Autoimmune-mediated Vasculitis  Enhancing lesions spare callososeptal interface  "Beaded" angiogram appearance
  23. 23. Lyme disease  Can be identical to MS (skin rash common) Susac syndrome  Clinical presentation, course different from MS  Classic triad of Encephalopathy ,Branch retinal artery occlusions & Hearing loss.  Self-limited (2-4 y duration, then stabilizes),  Monophasic  Multifocal supratentorial WM lesions  Always involves CC
  24. 24. DDs. Of MS
  25. 25. Acute hemorrhagic leukoencephalitis (Hurst disease)  Acute hemorrhagic leukoencephalitis (Hurst disease) is considered a hyperacute or fulminant form of ADEM   This entity is typically seen in young  Patients have an abrupt onset of fever, neck stiffness, and progressive neurologic deficits often leading to coma and death within 1 to 5 days.
  26. 26. Acute hemorrhagic leukoencephalitis (Hurst disease)…  reported after viral respiratory infections, sepsis, ulcerative colitis and asthma, and as a manifestation of drug toxicity .  CSF -elevation of IgG and the presence of MBP.  clinical recovery are reported after the administration of high-dose steroids
  27. 27. Acute hemorrhagic leukoencephalitis (Hurst disease) Extensive abnormal signal involving the supraventricular white matter is present, with acute hemorrhage present as foci of marked hypointensity within the white matter lesions.
  28. 28. PML  PML is caused by reactivation of a latent infection by a papovavirus (JC virus).  Most cases of PML today occur as a complication of AIDS, and approx. 5% of all patients with AIDS ultimately develop PML  The non-AIDS population typically harbors an underlying disease affecting immunocompetence, such as leukemia, lymphoma, sarcoidosis, tuberculosis, or malignancy, or has received immunosuppressive therapy
  29. 29. PML…
  30. 30. HIV encephalopathy  HIV encephalopathy, also known as AIDS dementia complex, HIV dementia, and hiv-associated dementia complex is a progressive dementing illness of AIDS.  Occurs in patients with advanced immunosuppression.  The most common finding on imaging is atrophy of the brain.
  31. 31. HIV encephalopathy…  In early stages of the disease, small areas of high signal intensity are seen on the t2-weighted sequences in the periventricular white matter that lack mass effect or edema  Bilateral symmetric increased signal intensity on the T2-weighted sequences has been described in the basal ganglia (caudate and putamen) and thalamus and may also involve the brainstem
  32. 32. Human immunodeficiency virus encephalopathy in a patient with acquired immunodeficiency syndrome showing diffuse white matter involvement. A–D: FLAIR images progressing inferiorly to superiorly demonstrate diffuse white matter signal abnormality.
  33. 33. Human immunodeficiency virus encephalopathy with characteristic involvement of the basal ganglia. A: Axial FLAIR image demonstrates bilateral symmetric increased signal intensity within the basal ganglia and external capsules. B: Axial postcontrast T1-weighted image demonstrates no evidence of enhancement.
  34. 34. Neuromyelitis Optica  Neuromyelitis optica (Devic type) is a syndrome of acute onset of optic neuritis and transverse myelitis (LETM) that develop at approximately the same time  Classically, NMO patients have relapses consisting of optic neuritis and myelitis  The target of the NMO antibody is the Aquaporin-4 (AQP4).
  35. 35. Central Pontine and Extrapontine Myelinolysis (Osmotic Demyelination)  Central pontine myelinolysis describes demyelination usually isolated to the central pons; however, extrapontine sites of demyelination are not uncommon.  It is commonly found in association with alcoholism, chronic nutritional deficiency, and many other systemic disorders with electrolyte abnormalities including chronic pulmonary disease, liver and kidney diseases, diabetes mellitus, liver transplant, and neoplasia.
  36. 36.  The term “osmotic demyelination syndrome” has been proposed because of the common association with rapidly corrected hyponatremia.  The symptoms of central pontine myelinolysis include spastic quadriparesis, pseudobulbar palsy, changing levels of consciousness, and coma .  A significant proportion of patients progress to death, which may be preceded by a state of pseudocoma (locked-in syndrome).
  37. 37. Central pontine myelinolysis. A: T2-weighted axial image shows characteristic high signal intensity within the midpons, with a surrounding rim of normal-appearing pontine parenchyma and sparing of the corticospinal tracts. B: Sagittal T1-weighted image demonstrates a low-signal lesion within the pons.
  38. 38. Marchiafava-Bignami Disease  Marchiafava-Bignami disease is a rare condition in which demyelination and necrosis primarily affect the corpus callosum and sometimes also involve extracallosal regions.  It is almost exclusively found in male alcoholics and was originally described in Italian people who drank red wine .  In more recent years, it has been described in poorly nourished nondrinkers
  39. 39. Marchiafava-Bignami Disease… Sagittal T1-weighted image (A) demonstrates small areas of low signal intensity in the genu, body, and splenium of the CC
  40. 40. Subacute Combined Degeneration of the Spinal Cord  Vitamin B12 (cobalamin) deficiency may affect the CNS or peripheral nervous system but most commonly involves the spinal cord.  Subacute combined degeneration (SCD) refers to vitamin B12 deficiency with demyelination and vacuolation found in the posterior and lateral columns of the spinal cord
  41. 41. Subacute combined degeneration of the spinal cord (B12 deficiency). A: Sagittal T2-weighted image demonstrates a long segment of high signal intensity within the dorsal aspect of the cervical spinal cord. B: Axial T2-weighted image shows high signal intensity within the dorsal columns.
  42. 42. Hypertensive Encephalopathy (Reversible Posterior Leukoencephalopathy)  Hypertensive encephalopathy is a clinical entity that it is important to recognize early because the clinical and imaging findings are usually reversible.  Acute elevation of blood pressure (several hours to days before the onset of symptoms) is the most common precipitant  The syndrome can also be seen with renal decompensation, preeclampsia/eclampsia, fluid retention, and treatment with immunosuppressive drugs .  Cyclosporine ,tacrolimus, FK506, L-asparaginase, cisplatin, and mouse monoclonal antibody (OKT3)
  43. 43. Thank You
  44. 44. References  Magnetic Resonance Imaging of the Brain and Spine, 4th ed, 2009, Scott W. Atlas  Bradley ; neurology in clinical practice 7’th edition  Osborn Diagnostic Imaging Brain 2004

Notas del editor

  • Cell Body
    Contains the nucleus
    Dendrites
    Receptive regions; transmit impulse to cell body
    Short, often highly branched
    May be modified to form receptors
    Axons
    Transmit impulses away from cell body
    Axon hillock; trigger zone
    Where action potentials first develop
    Presynaptic terminals (terminal boutons)
    Contain neurotransmitter substance (NT)
    Release of NT stimulates impulse in next neuron
    Bundles of axons form nerves

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