Demyelinating Disease

Conditions Discusses

Marchiafava Bignami

• Demyelination of corpus callosum, most commonly secondary to alcoholism (M-B was an alcoholic to remember)

• Nonspecific presentation

• Imaging findings

  • Hyperintense corpus callosum (looks like it crosses midline but not masslike)

    • Starts in body of CC —> genu —> splenium (typically spares posterior aspect until late)

    • Affects central fibers and spares the dorsal and ventral fibers

    • So prefers center

      • Center of CC (body), and central fibers

  • T2 hyperintensities within the corpus callosum, T1 hyperintensities

  • Sandwich sign - central layers of corpus callosum affected first which will be T2/FLAIR hyperintennse, so you will have peripheral areas of hypo-intensity with a middle layer which is hyperintense and resembled a sandwich or just stripes I suppose

Acute Disseminated Encephalomyelitis (ADEM)

• Acute inflammation and demyelination of white matter

• Seen after viral infection or recent vaccination due to immune cross reaction, anti-MOG (myelin oligodendrocyte glycoprotein) IgG may be positive

• Imaging findings are typically identical to MS

• Full recovery common, sometimes persistent neuro deficits

• Imaging findings

  • Incomplete ring enhancing lesion

  • Typically large lesion (especially compared to MS)

  • Typically has surrounding edema - remember this is from acute demyelination from vaccination/viral illness so almost like a brain infection that is being self attacked so edema should be easy to remember

  • Asymmetric lesions

  • DWI - peripheral restricted diffusion but not centrally

• Hurst variant (acute hemorrhagic leukoencephalitis) - rapidly progressive form with death within days

  • T2 hyperintensities + multiple hematomas

DWI showing peripheral restriction without central restriction

Peripehral open ring restriction on DWI not always seen as evidenced below

Progressive Multifocal Leukoencephalopathy (PML)

• Demyelination after reactivation of JC virus which infects oligodendrocytes

• Seen in immunocompromised patients (AIDS < 200 CD4)

• Imaging findings

  • Asymmetric, multi-focal, bilateral lesions - really anywhere but key place is subcortical U fibers

  • T1: hypointense

  • T2: hyperintense

  • No enhancement on contrasted studies

  • Patchy areas of restricted diffusion

  • Milky way sign - multiple clustered punctate T2 hyperintense lesion (not to be confused with galaxy sign!)

    • Eh, not sure i really see this one, and no great examples online

  • Barbell sign - parieto-occipital lesions which crosses the splenium

  • Shrimp sign - T2 hyperintensity of the cerebellar white matter but which spares the dentate nucleus

Barbell sign

Image showing abnormally hyperintense dentate nuclei.

Note: This image is not PML it just shows anatomy of dentate nuclei well since they are so abnormally bright here,

Posterior Reversible Encephalopathy Syndrome

• Basically posterior circulation is not able to respond to changes in blood pressure and symptoms result

• Associations

  • High blood pressure (may seen in eclampsia/pregnancy)

  • Pregnancy

  • Chemotherapy use

• Vision issues (hence posterior) and encephalopathy

• Imaging Findings

• Bilateral - asymmetric - posterior lesions

  • Lesions typically of cortex and subcortical white matter

  • T1 hypo, T2 hyper

  • Everything is vague - may restrict/but also may not, may enhance/ but also may not, may have microhemorrhages/ but also may not

  • MRA - vessel irregularities, vasoconstriction

  • May have vasogenic edema

• Treatment - treat underlying cause, manage BP

Chronic Demyelinating Inflammatory Polyneuropathy (CDIP)

• Affects spinal nerves

• Repeated demyelination and remyelination leads to concentric rings looking like onion bulb

Neuromyelitis Optica (Devic Disease)

• Triad

  • Abs to aquaporin-4

  • Bilateral optic nerve disease

    • T2 hyper, enhancing

  • Long segment spinal cord myelitis

    • T1 hypo, T2 hyper, enhancing

• Does not affect the brain (well it can, but textbook is not to)

Multiple Sclerosis

• Demyelinating disease

• Lesions

  • Many different types

  • Can restrict diffusion in ACUTE phase

  • Perpendicular to the corpus callosum - dawson fingers

  • Involvement of callosal-septal interface is HIGHLY specific

  • Infratentorial plaque - very rare (although may be seen in kids)

  • Lesions will change location with time

  • If occurs in the cord will be short segment demyelination (1-2 vertebral bodies long)

• Relationship with EBV

• What looks similar

  • Vasculitis

    • Typically spares callosal-septal interface

    • Tends to preferentially affect basal ganglia

  • Lymes disease

    • Classically causes cranial nerve enhancement

Central Pontine Myelinolysis

• Location is key to diagnosis - look for lesion at center of pons

• Seen with rapidly corrected hyponatremia

• Almost always will see restricted diffusion

References:

• Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 2576 (ADEM)

• Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 39817 (ADEM)

• Case courtesy of Arthur Daire, Radiopaedia.org, rID: 31030 (PML)

• N. Adra, A.E. Goodheart, O. Rapalino, P. Caruso, S.S. Mukerji, R.G. González, N. Venna, J.D. Schmahmann, MRI Shrimp Sign in Cerebellar Progressive Multifocal Leukoencephalopathy: Description and Validation of a Novel Observation American Journal of Neuroradiology May 2021, DOI: 10.3174/ajnr.A7145 (PML shrimp)

• K.M. Bond, W. Brinjikji, L.J. Eckel, D.F. Kallmes, R.J. McDonald, C.M. Carr, Dentate Update: Imaging Features of Entities That Affect the Dentate Nucleus, American Journal of Neuroradiology Aug 2017, 38 (8) 1467-1474; DOI: 10.3174/ajnr.A5138 (dentate nuclei)

• Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 58883 (subcortical U fibers)

• Case courtesy of Paul Simkin, Radiopaedia.org, rID: 30476 (PRES)