genetic material is gained or lost. Increased rate of unexplained fetal loss may be observed in MDS carriers with balanced translocations although they may be otherwise asymptomatic. However, they can become also unbalanced as they are passed to the next generation. Miller–Dieker syndrome is usually not inherited. The deletion event occurs randomly during gametogenesis (formation of eggs or sperm) or in early foetal development. Therefore, no history of the disorder is usually seen in their families. Diagnosis The disease may be diagnosed by cytogenetic techniques like fluorescence in situ hybridization (FISH), testing for a microdeletion at LIS1. Early detection With the use of prenatal ultrasonographic imaging, early detection of abnormal brain development in the fetus with MDS can be seen. At birth, facial dysmorphism can be present in the infant. Young children, when affected, can have feeding difficulties, severe intellectual disability, developmental delay, and seizures. MRI facilitates early detection of this syndrome in children by revealing a "smooth brain" image, also called lissencephaly. Children with this syndrome may remain underdiagnosed because of rarity and the prevalence of facial features that appear to be dysmorphic. The syndrome shares distinct external features (phenotype) similar to more common syndromes. Lack of relevant family history may delay diagnosis. FDNA provides a service that in turn increases the chances of detecting these distinct characteristics, which, when shown to a geneticist, can assist in reaching the right medical diagnosis. If a couple has had one child with MDS, they can be offered prenatal screening in future pregnancies. This option is particularly important for the 20% of MDS families where one parent carries a balanced chromosome rearrangement. The risk of these couples having another child with MDS depends on the exact type of chromosomal rearrangement present and may be as high as 25–33%. For families in which both parents' chromosomes are normal, the risk of having another child with MDS is low (1% or less). Either chorionic villus sampling (CVS) or amniocentesis can be used early in a pregnancy to obtain a small sample of cells from the developing embryo for chromosome studies. Early prenatal diagnosis by ultrasound is not reliable because the brain is normally smooth until later in pregnancy. Couples who are considering prenatal diagnosis should discuss the risks and benefits of this type of testing with a geneticist or genetic counselor. Visuals of the brain The brain is usually grossly abnormal in outline when