Midline interhemispheric variant of holoprosencephaly (MIH) or syntelencephaly is a form of holoprosencephaly (HPE; see this term) characterized by non-separation of the posterior frontal and parietal lobes, normally-formed callosal genu and splenium, absence of the callosal body, normally-separated hypothalamus and lentiform nucleus, and frequent heterotopic gray matter.
About 2% to 15% of HPE patients have MIH type.
Patients have rather mild dysmorphic facial features such as ocular hypotelorism, flat or narrow nasal bridge or a relatively normal facial appearance.
MIH has mainly been reported in patients with ZIC2 (13q32) mutations.
Prognosis is better than in classical forms of HPE.
Last update: October 2011
- Dr Sandra MERCIER
- Pr Sylvie ODENT