“…Mental retardation is found in case reports of all three abnormalities (18p-, 18q-, and 18p tetrasomy), and in one study was estimated at 68% of all 18q deletion subjects [Semrud-Clikeman et al, 2005]. Abnormal EEG findings and epilepsy have been described in case reports for all three chromosomal disorders [Chudley et al, 1974;Wilson et al, 1979;Wilson and Al Saadi, 1989;Schinzel et al, 1991;Chudley et al, 1992;Krasikov et al, 1992;Poissonnier et al, 1992;Engelen et al, 1998;Tinkle et al, 2003;Linnankivi et al, 2006;Swingle et al, 2006;Brenk et al, 2007;Cody et al, 2007]. Many subjects with 18p or 18q deletions display delayed speech, mutism, or articulation difficulties [Thompson et al, 1986;Poissonnier et al, 1992;Grosso et al, 1999;Babovic-Vuksanovic et al, 2004;Wester et al, 2006;Brenk et al, 2007;Cody et al, 2007] and there has been one report of short Neuropsychiatric Genetics attention span in three out of three 18p-subjects [Thompson et al, 1986].…”