CASE REPORT

When the normal developmental process of the corpus callosum is dis-

turbed, it may be completely absent or partially formed (hypogenetic) 

(Fig. 1). When it is hypogenetic, the anterior portion (posterior genu 

and anterior body) will be formed, but the posterior portion (poste-

rior body and splenium) will not. One exception to this largely ante-

rior-to-posterior formation sequence is holoprosencephaly. The callosal 

anomalies seen in holoprosencephaly represent true callosal dysgenesis 

(defective development) (Fig. 2) rather than the more common callosal 

hypogenesis (incomplete formation). In holoprosencephaly the defect in 

the corpus callosum is seen anteriorly rather than posteriorly.1

1.   Barkovich AJ. Pediatric Neuroimaging, 3rd ed. Philadelphia: Lippencott Williams & Wilkins, 2000: 254 

255, 323-327. 

  

Corpus callosum hypogenesis versus dysgenesis

S J Przybojewski, MB ChB, MMed (Rad D),  
FCR Diag (SA), Dip PEC (SA) 

S Andronikou, MB BCh, FCR Diag (SA),  
FRCR (Lond), PhD

Department of Radiology, Tygerberg Hospital and University of Stellenbosch

PICTORIAL INTERLUDE

24         SA JOURNAL OF RADIOLOGY • June 2006

Fig. 1. Incomplete formation (hypogenesis) of the corpus callosum. 

Fig. 2. Defective development (dysgenesis) of the corpus callosum in a 
patient with lobar holoprosencephaly.

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