Rare conjoined twins / twin research reviews / twins in the news.

490 Segal, N. L. (2011). News, views, and comments. Twin Research and Human Genetics, 14, 490–493. DOI 10.1375/twin.14.5.490 The May 29, 2011 issue of the New York Times Magazine published a fascinating article concerning 4-year-old conjoined twins, Krista and Tatiana Simms. These craniopagus twins (joined at the cranium vault, but otherwise separate) were born to Felicia Simms, a 20year-old mother of two living in Canada. Simms was informed early in her pregnancy that the twins were conjoined, but she chose to continue. She delivered the twins successfully and went on to have another child several years after the twins were born. Conjoined twins are rare, occurring in approximately 1 in 200 monozygotic twin births (Segal, 2000). Craniopagus twins are rarer still, estimated to occur in 0.6 to 2.5 million live births (Pietrini et al., 2005). What makes the Simms twins especially intriguing to scientists is their unusual brain structure: ‘Their brain images reveal what looks like an attenuated line stretching between the two organs, a piece of anatomy their neurosurgeon Douglas Cochrane of British Columbia Children’s Hospital has called a thalamic bridge, because he believes it links the thalamus of one girl to the thalamus of her sister. The thalamus is a kind of switchboard, a two-lobed organ that filters most sensory input and has long thought to be essential in the neural loops that create consciousness. Because the thalamus functions as a relay station, the girls’ doctors believe it is entirely possible that the sensory input that one girl Editor’s Note: Nancy L. Segal, the writer of the News, Views and Comments column has just published her third book, Someone Else’s Twins: The True Story of Babies Switched at Birth (Segal, 2011). A review will appear in a forthcoming issue of Twin Research and Human Genetics.