Syntelencephaly

Syntelencephaly, also known as middle interhemispheric variant, is a mild subtype of holoprosencephaly that is characterized by an abnormal midline connection of the cerebral hemispheres between the posterior frontal and parietal regions. There is preserved interhemispheric separation of the basal forebrain, anterior frontal lobes, and occipital regions.

The images above show interhemispheric fusion of the gray matter and white matter across the midline and absence of the interhemispheric fissure in the posterior frontal and parietal lobes. The coronal image shows that the gyral pattern is abnormal with increased cortical thickness and irregularity of the cortical–white matter junction. On the sagittal view only the genu and splenium of the corpus callosum are present.

References

Simon EM, Hevner RF, Pinter JD, Clegg NJ, Delgado M, Kinsman SL, Hahn JS, Barkovich AJ. The middle interhemispheric variant of holoprosencephaly. AJNR Am J Neuroradiol. 2002 Jan;23(1):151-6.