Abnormal Shape/Configuration of Corpus Callosum

Susan I. Blaser, MD, FRCPC

DIFFERENTIAL DIAGNOSIS

Common

Normal Variant
Callosal Dysgenesis
Callosotomy
Neoplasm
- Lipoma
- Glioblastoma Multiforme
- Lymphoma, Primary CNS
Decreased White Matter Volume
- Hypomyelination
- Periventricular Leukomalacia
- HIE, Term
- Cerebral Infarction, Chronic
- Diffuse Axonal Injury (DAI)
- Multiple Sclerosis
- Radiation and Chemotherapy
Obstructive Hydrocephalus

Less Common

Holoprosencephaly
Holoprosencephaly Variants

Rare but Important

Hypertensive Intracranial Hemorrhage
Marchiafava-Bignami

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Normal corpus callosum (CC) varies in thickness, shape
Isolated callosal dysgenesis not common
- Look for second lesion
- Associated CNS anomalies in > 50%
  - Heterotopia
  - Cortical dysplasia
  - Noncallosal midline anomalies
  - Abnormal brainstem or cerebellum
If not congenital, history crucial!

Helpful Clues for Common Diagnoses

Normal Variant
- Size, shape, thickness of normal CC vary
  - Splenium, genu are largest parts of corpus callosum
  - Narrowing between body, splenium (“isthmus”) is normal
  - Dorsal surface of fully developed, normally myelinated corpus callosum often “wavy”
- Immature corpus callosum is thin
  - Pre-myelination
  - Gradually thickens with progressive myelination
Callosal Dysgenesis
- One or all segments absent
  - Rostrum, splenium most likely deficient
  - Remnants vary in size, shape, configuration
- “Micro” CC
  - Small, but well-formed
  - Often syndromic
- “Mega”CC
  - Isthmus usually absent
  - Megalencephalic (bulky white matter)
  - Or small to normal brain (syndromic)
Callosotomy
- Surgical disruption
  - Focal: Approach to 3rd ventricle or suprasellar tumor
  - Diffuse: Surgery for intractable seizures
- Best seen on sagittal or coronal MR
Neoplasm
- Can be benign/focal or malignant/diffusely infiltrating
- Lipoma
  - 40-50% interhemispheric fissure
  - Common in callosal dysgenesis
  - Can be bulky, mass-like (“tubonodular” type, usually associated with CC agenesis; may extend through choroidal fissures into lateral ventricles)
  - Thin mass curving around CC body/splenium (“curvilinear” type, CC present but may be dysgenetic)
- Glioblastoma Multiforme
  - “Butterfly” glioma
  - Central necrosis + thick irregular rim enhancement
- Lymphoma, Primary CNS
  - Hyperdense on NECT
  - Strong, uniform enhancement
- Decreased White Matter Volume
  - Many causes (congenital, acquired)
  - All may result in focal or diffuse callosal thinning
- Hypomyelination
  - Chromosomal, inborn errors of metabolism
- Periventricular Leukomalacia
  - Premature infant
  - “Scalloped” lateral ventricles
- HIE, Term
  - Term infant with profound partial asphyxia → WM/cortex damaged
- Cerebral Infarction, Chronic
  - Axonal loss → focal/diffuse thinning CC
- Diffuse Axonal Injury (DAI)
  - 20% involve CC (splenium, undersurface posterior body)
- Multiple Sclerosis
  - Chronic, late
Obstructive Hydrocephalus
- Acute
  - Corpus callosum (CC) stretched
  - CC bowed upwards
  - Forniceal columns bowed downwards
- Chronic
  - Post-shunt encephalomalacia
  - Sequela of acute callosal impingement against falx

Helpful Clues for Less Common Diagnoses

Holoprosencephaly
- Corpus callosum absent in alobar
  - Large dorsal “cyst” often present
- Semilobar may have residual splenium
  - Frontal fusion & hypoplasia
  - Splenium may be present
- Lobar
  - Genu may or may not be present
  - Gray matter often crosses with genu
Holoprosencephaly Variants
- Middle interhemispheric variant
  - a.k.a., syntelencephaly
  - Splenium, genu present, body deficient
  - Middle CC body “dips”
  - Gray matter crosses at dip
  - If severe, add bilateral perisylvian polymicrogyria

Helpful Clues for Rare Diagnoses

Hypertensive Intracranial Hemorrhage
- CC rare primary site
Marchiafava-Bignami
- Middle-aged alcoholic
- CC demyelination, necrosis, atrophy

SELECTED REFERENCES

1. Pierson TM et al: Mega-corpus callosum, polymicrogyria, and psychomotor retardation: confirmation of a syndromic entity. Neuropediatrics. 39(2):123-7, 2008

2. Samaranch L et al: SPG11 compound mutations in spastic paraparesis with thin corpus callosum. Neurology. 71(5):332-6, 2008

3. Mataró M et al: Functional and magnetic resonance imaging correlates of corpus callosum in normal pressure hydrocephalus before and after shunting. J Neurol Neurosurg Psychiatry. 78(4):395-8, 2007

4. Hetts SW et al: Anomalies of the corpus callosum: an MR analysis of the phenotypic spectrum of associated malformations. AJR Am J Roentgenol. 187(5):1343-8, 2006

5. Rollins N: Semilobar holoprosencephaly seen with diffusion tensor imaging and fiber tracking. AJNR Am J Neuroradiol. 26(8):2148-52, 2005

6. Kinsman SL: White matter imaging in holoprosencephaly in children. Curr Opin Neurol. 17(2):115-9, 2004

7. Barkovich AJ et al: Callosal agenesis with cyst: a better understanding and new classification. Neurology. 56(2):220-7, 2001

8. Kier EL et al: The normal and abnormal genu of the corpus callosum: an evolutionary, embryologic, anatomic, and MR analysis. AJNR Am J Neuroradiol. 17(9):1631-41, 1996

9. Mendelsohn DB et al: Corpus callosum lesions after closed head injury in children: MRI, clinical features and outcome. Neuroradiology. 34(5):384-8, 1992

Image Gallery

Sagittal T1WI FS MR with a close-up view of the corpus callosum shows normal “wavy” dorsal surface. Note the focal thinning along posterior body

, a common normal finding.

Sagittal T1WI MR shows a normal neonatal corpus callosum

, thin due to age-appropriate lack of myelin maturation. The cingulate gyrus

is normal.

(Left) Sagittal T1WI MR shows callosal agenesis. Note radial array of paracentral gyri “pointing” to the 3rd ventricle as well as absence of identifiable cingulate gyrus. Hippocampal commissure is visualized posteriorly