From OMIM
Features of the Miller-Dieker syndrome include classic lissencephaly (pachygyria, incomplete or absent gyration of the cerebrum), microcephaly, wrinkled skin over the glabella and frontal suture, prominent occiput, narrow forehead, downward slanting palpebral fissures, small nose and chin, cardiac malformations, hypoplastic male extrenal genitalia, growth retardation, and mental deficiency with seizures and EEG abnormalities. Life expectancy is grossly reduced, with death most often occurring during early childhood (summary by Schinzel, 1988). Lissencephaly means 'smooth brain,' i.e., brain without convolutions or gyri. Deletion of or mutation in the LIS1 gene (PAFAH1B1; 601545) appears to cause the lissencephaly because point mutations have been identified in this gene in isolated lissencephaly sequence (ILS; see 607432). Facial dysmorphism and other anomalies in Miller-Dieker patients appear to be the consequence of deletion of additional genes distal to LIS1. Toyo-oka et al. (2003) presented evidence that the gene whose deletion is responsible for the greater severity of Miller-Dieker syndrome compared to isolated lissencephaly is the gene encoding 14-3-3-epsilon (YWHAE; 605066).  http://www.omim.org/entry/247200

From MedlinePlus Genetics
Miller-Dieker syndrome is a condition characterized by a pattern of abnormal brain development known as lissencephaly. Normally the exterior of the brain (cerebral cortex) is multi-layered with folds and grooves. People with lissencephaly have an abnormally smooth brain with fewer folds and grooves. These brain malformations cause severe intellectual disability, developmental delay, seizures, abnormal muscle stiffness (spasticity), weak muscle tone (hypotonia), and feeding difficulties. Seizures usually begin before six months of age, and some occur from birth. Typically, the smoother the surface of the brain is, the more severe the associated symptoms are.

In addition to lissencephaly, people with Miller-Dieker syndrome tend to have distinctive facial features that include a prominent forehead; a sunken appearance in the middle of the face (midface hypoplasia); a small, upturned nose; low-set and abnormally shaped ears; a small jaw; and a thick upper lip. Some individuals with this condition also grow more slowly than other children. Rarely, affected individuals will have heart or kidney malformations or an opening in the wall of the abdomen (an omphalocele) that allows the abdominal organs to protrude through the navel. People with Miller-Dieker syndrome may also have life-threatening breathing problems. Most individuals with this condition do not survive beyond childhood.  https://medlineplus.gov/genetics/condition/miller-dieker-syndrome