Thin Corpus Callosum

Thin Corpus Callosum
Susan I. Blaser, MD, FRCPC
DIFFERENTIAL DIAGNOSIS
Common
  • Normal Variant
  • Immature Brain
  • Encephalomalacia
  • Multiple Sclerosis
  • White Matter Injury of Prematurity
  • Callosal Dysgenesis
  • Callosectomy/Callosotomy
  • Obstructive Hydrocephalus
Less Common
  • Hypomyelination
  • Injury (Any Cause)
Rare but Important
  • Susac Syndrome
  • Holoprosencephaly
  • Inherited Metabolic Disorders
  • Hereditary Spastic Paraplegia with Thin
  • Corpus Callosum (HSP-TCC)
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
  • Diffuse corpus callosum (CC) thinning can be normal
    • Newborn (immature brain)
  • Abnormally thin CC can be inherited or acquired
    • Broad spectrum of congenital malformations, inherited metabolic disorders can all result in thin CC
    • Check history for trauma, surgery, ischemia-infarction
  • Thin CC, normal signal hyperintensity
    • Normal variant, immature brain
    • Secondary to hemispheric white matter (WM) volume loss
    • Dysgenesis
  • Thin CC, abnormal signal intensity
    • Hypomyelination or demyelinating disease (chronic MS, Susac syndrome)
    • Injury (trauma, ischemia, radiation, toxic-metabolic insult)
    • Obstructive hydrocephalus
Helpful Clues for Common Diagnoses
  • Normal Variant
    • Focal thinning of corpus callosum at “isthmus” (junction between posterior body, splenium) is normal
    • Sagittal section slightly off-midline can make corpus callosum appear mildly thinned
  • Immature Brain
    • Hemispheric WM in newborn unmyelinated, corpus callosum thin and hypointense on T1WI
    • As myelination progresses, corpus callosum thickens, becomes hyperintense on T1WI
      • Corpus callosum splenium at 4 months
      • Corpus callosum genu at 6 months
      • By 8 months, corpus callosum essentially like an adult’s
  • Encephalomalacia
    • Holohemispheric WM volume loss, regardless of etiology, causes diffuse corpus callosum thinning
    • Focal WM loss can cause focal corpus callosum thinning
  • Multiple Sclerosis
    • Look for T2/FLAIR hyperintense lesions along callososeptal interface
    • Ependymal “dot-dash” sign along callosoventricular border occurs early
    • Longstanding MS with decreased hemispheric WM volume results in thinned corpus callosum
  • White Matter Injury of Prematurity
    • Corpus callosum thinning secondary to periventricular white matter infarction
    • Posterior corpus callosum disproportionately affected
  • Callosal Dysgenesis
    • Hypoplasia or absence of part or all of corpus callosum
      • Rostrum, splenium most likely deficient
      • Remnants vary in size, shape, and configuration
    • Most common abnormality associated with other malformations
      • Chiari 2 malformation
      • Heterotopias
      • Interhemispheric lipoma
      • Cephaloceles
  • Callosectomy/Callosotomy
    • History important!
    • Surgical disruption
    • Look for surgical changes of craniotomy, ventriculostomy
  • Obstructive Hydrocephalus
    • Causes 2 kinds of corpus callosum abnormalities: Stretching and intrinsic signal abnormality
    • As lateral ventricles enlarge, corpus callosum is stretched, appears thinned
      • Look for associated signal abnormality in corpus callosum (sagittal T2WI/FLAIR best)
    • Post-shunt decompression may show corpus callosum thinning, signal abnormality
      • Can appear bizarre, causing horizontal hyperintense “streaks” in corpus callosum on axial imaging
      • Can extend into periventricular WM
      • Theories: Impingement of corpus callosum against falx cerebri with resulting ischemia or axonal stretch
Helpful Clues for Less Common Diagnoses
  • Hypomyelination
    • Undermyelination, delayed myelin maturation
    • Diminished/absent WM myelination for age
    • Can be primary or secondary to other pathology
  • Injury (Any Cause)
    • Trauma (e.g., axonal injury, radiation-induced leukoencephalopathy)
    • Ischemia
Helpful Clues for Rare Diagnoses
  • Susac Syndrome
    • M < F
    • Classic triad
      • Encephalopathy (headache, confusion, memory loss)
      • Vision problems (retinal artery occlusions)
      • Hearing loss
    • Always involves corpus callosum
      • Central > callososeptal interface lesions
      • Middle callosal “holes” (subacute/chronic)
  • Holoprosencephaly
    • Many variants; often affect corpus callosum
  • Inherited Metabolic Disorders
    • Focal or diffuse atrophy
      • Focal: X-linked adrenoleukodystrophy
      • Diffuse: Many
  • Hereditary Spastic Paraplegia with Thin Corpus Callosum (HSP-TCC)
    • HSP-TCC is 1 of many hereditary spastic paraplegias
      • Autosomal recessive with SPG11 gene mutations on chromosome 15q13-15
      • Progressive neurodegenerative disorder
    • Clinical
      • Slow ↑ spastic paraparesis
      • Adolescent-onset cognitive decline
      • Pseudobulbar dysfunction
    • Imaging
      • Thin corpus callosum (especially genu, body) with progressive atrophy
      • Cerebral, cerebellar atrophy often associated
Image Gallery
Sagittal T1WI MR in a term infant imaged at 2 days of age shows a thin corpus callosum image with no discernible myelination. This is the normal appearance of an immature, largely unmyelinated brain.
Axial T1WI MR in 32-week-gestation premature infant shows a very thin corpus callosum genu image, reflecting total lack of hemispheric myelination.
(Left) Axial DWI MR in a newborn shows extensive diffusion restriction of the left hemisphere following perinatal stroke. Acute axonal degeneration of the corpus callosum image is present. (Right) Coronal T2WI MR at follow-up shows a large area of cystic encephalomalacia image and a very thin corpus callosum image.

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Aug 10, 2016 | Posted by in PEDIATRICS | Comments Off on Thin Corpus Callosum

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