Craniopagus twins are conjoined twins who are fused at the skull. The union may occur on any portion of the cranium, but does not primarily involve either the face or the foramen magnum; the two brains are usually separate, but they may share some brain tissue. Conjoined twins are genetically identical and always share the same sex. The thorax and abdomen are separate and each twin has their own umbilicus and umbilical cord.
The condition is extremely rare, with an incidence of approximately 1 in 2.5 million live births. An estimated 50 craniopagus twins are born around the world every year , with only 15 twins surviving beyond the first 30 days of life. Relatively few craniopagus twins survive the perinatal period; approximately 40% of conjoined twins are stillborn and an additional 33% die within the immediate perinatal period, usually from organ abnormalities and failure.
However, 25% of craniopagus twins survive and may be considered for a surgical separation; several such attempts occur annually worldwide. Advances in neuroimaging, neuroanesthesia, and neurosurgery have demonstrated that a successful outcome is possible. Among all conjoined twins, craniopagus twins account for a mere 2% to 6%.
Classification
The first classification system was developed by O'Connell in 1976, where craniopagus twins were classified as total and partial. In the former, twins shared an "extensive surface area with widely connected cranial cavities", while in the latter, only a "limited, superficial surface area" was connected.
In 2006, Stone and Goodrich came up with a more nuanced classification system, which is the "most commonly used" system. Partial CPT was defined as "lacking substantial shared dural venous sinuses", whereas total CPT "share a large portion of their dural venous sinuses and present with pronounced brain compression, which leads to distortion within the cranium".
Total Total craniopagus twins share a large portion of dural venous sinuses and present with pronounced brain compression, leading to distortion within the cranium. Stone and Goodrich also defined two main subtypes, based on whether the long-axis angle between the twins was angular or vertical. The angular subtype has a higher rate of comorbidities than the vertical subtype.
Vertical craniopagus calvaria is continuous and is further subdivided on the basis of intertwin axial facial rotation: Type 1: both children face in the same general directional axis so that the angle between twins is less than 40 degrees. These twins show relatively symmetric superior bi-parietal or vertex compressional flattening. Type 2: both children face opposite directions so that the deformity shows an axial rotation between 140 and 180 degrees. Type 3: in this variety axial rotation is intermediate between the first two types with a rotation of being between 40 and 140.
Another classification system divides total craniopagus twins into four categories: Frontal: twins are facing each other with the axis of the bodies forming an acute angle Temporoparietal: joined immediately above the external auditory meatus Occipital: twins are connected in the occipital lobe causing the twins to face away from each other Parietal: twins fuse at the vertex with the axis of the twins forming an obtuse angle; this leads to a situation where the twins share the most veins, lobes, and neural circuitry and thus is often described as one brain shared by two individuals
Having this kind of juncture means that there would be one common continuous cranium housing four cerebral hemispheres. An incomplete dural septum typically separates the flattened cerebral hemispheres. In total vertical craniopagus, the major cerebral arterial supply is usually confined to each respective twin and in some cases conjoined brain tissue may contain a larger artery. Within this category there are three smaller subdivisions that basically outline the different rotational symmetry of the junction.
Partial Stone and Goodrich define partial craniopagus twins as lacking substantial shared dural venous sinuses, with limited surface area involvement, with either intact crania or cranial defects. It is less common than total craniopagus twins.
In partial craniopagus twins, the unions are usually frontal and less commonly occipital and vertical. Angular frontal junctions occur when the two twins are joined at any part of the forehead. Occipital twins are joined at the occipital lobe in the back of the head and vertical are joined on the top of the head and usually face opposite directions. The junctional diameter is often smaller in partial forms and occasionally an incomplete layer of bone may be present between the twins. Each child maintains independent calvarial convexities except at the common area of skull junction. The dura of both children may be intact or deficient and cortical gyri may interdigitate. Additionally, shared dural venous sinuses is usually absent, or, if it is present, negligible. These twins usually undergo successful separation and both twins may live to lead normal lives.
Gestation and embryology
The exact nature of how conjoined twins develop in utero remains unclear. Embryologists have traditionally attributed identical twinning as "splitting or fission" of either the inner cell mass of pleuripotent cells or early embryonic disc at 13–14 days of gestation just before the primitive streak. Some theorists suggested that conjoined twins develop as a result of the failed division (fission) of a single fertilized ovum. However a new hypothesis suggests that cranial fusion occurs between two separate embryos before the end of the 4th week of gestation. This can happen because the cranial neuropore is still open, which is responsible for the ultimate fusion and formation of the brain stem and central nervous system. Furthermore, this secondary fusion of embryonic discs could implicate that intact skin will not fuse to other intact skin, including the ectoderm of the embryo. This means that two embryonic discs could only unite in locations where the ectoderm is absent. Moreover, the fusion occurs from neural folds of two separate, dorsally oriented embryonic discs, and the union can occur only after the ectoderm is disrupted to allow the neural and surface ectodermal layers to separate from each other.
The union in craniopagus twins may happen at any portion of the calvarium. The juncture can involve either the entire diameter of the head or any portion of the head and can be positioned at a multitude of rotational angles. In fact, craniopagus twins are rarely found in a symmetrical union. Apart from this, the vertebral axes may have a straight line. Despite this, the angle of the vertebrae is the ultimate dictator in how the individuals heads actually face. The majority of twins face either the same way or the exact opposite direction.
Medical procedures Diagnosis Conjoined twins, including craniopagus twins, can be diagnosed using standard ultrasound procedures during a pregnancy. In part because treatment of conjoined twins varies largely, many parents make the decision to terminate pregnancy due to the prognosis and quality-of -life issues. If the parents choose to continue the pregnancy, mother and babies will be closely monitored. In almost all cases, a C-section delivery is planned, often two to three weeks before the due date.
Separation surgeries
After the twins are born, parents and doctors decide whether or not separation surgery is possible. The doctors also must consider the possibility of reconstructive surgery and the social and learning issues the twins may have to face after they are separated.
Due to advances in neuroimaging, neuroanesthesia, and neurosurgical techniques, successful separation operations have become more common. Physical traits like joined brain tissue, shared arteries and veins, as well as defects in the skull and dura mater complicate a separation operation.
Neuroimaging especially plays an important role because it is imperative in surgical planning to understand the shared vascular anatomy—including the brain parenchyma, calvaria, and dura mater—because separating shared vessels can lead to thrombosis, air embolism, cerebral infarction, and hemorrhage. Technologies such as CT scans, MRIs, and angiography are used to map the shared vascular structures.
Cases
In 1495, a Munster reported seeing a pair of female craniopagus twins, conjoined at their foreheads, in the village Brisant near Worms. The girls died at age 10; one sister died first, the second dying from an attempt to separate her from her dead twin. They were described by Ambroise Pare in Of Monsters and Prodigies. Emilie and Elisabeth Stoll were born on January 17, 1912. Their parents exhibited them until their death in July 1912. Their cause of death is unknown, but they were probably weakened by the stress of travelling and exhibition. Rodney and Roger Brodie were born in Rock Island, Illinois, in 1951. In December 1952 a medical team led by neurosurgeon Oscar Sugar attempted to separate the 15-month old twins in a surgery that lasted 12 hours. During surgery, the doctors discovered that the twins shared the superior sagittal sinus, the canal that drains blood from the brain to the heart. This vessel was retained by Rodney Brodie. Both twins survived the surgery, although Roger did not regain consciousness and died 34 days later. Rodney recovered but suffered neurological damage; because his skull was never closed, he wore a helmet until his death at age 11. This was the first case where craniopagual twins were separated and one survived. Teresa (1956–2017) and Virginia Bunton of Tennessee, separated in 1956 and the first craniopagus pair to be separated with both surviving. Lotti and Rosemarie Knaack, who were born in Germany in 1951, were separated at age 6, with Lotti dying in surgery. Rosemarie survived until 2008. Lori and George Schappell, 1961–2024, are believed to have been the longest-surviving craniopagus twins in recorded history. Ladan and Laleh Bijani, who were born in Iran, were separated in 2003 at age 29, only to die 90 minutes apart after surgery. Ahmed and Mohamed Ibrahim, who were born in Egypt, were successfully separated in Dallas, Texas, in October 2003, when they were two years old. Lea and Tabea Block, who were born in Germany in 2003, were separated in September 2004 at Johns Hopkins Hospital in Baltimore, Maryland. Tabea died of cardiac arrest an hour after separation. Anastasia and Tatiana Dogaru were born in 2004 with the crown of Tatiana's head joined to the back of Anastasia's. Doctors determined in 2007 that they could not be separated. Krista and Tatiana Hogan, born on October 25, 2006. After a series of tests doctors determined these twins could not be separated. Joseph and Luka Banda from Zambia, born in 1997, were separated successfully the same year in South Africa by a team of surgeons led by Ben Carson. Trishna and Krishna from Bangladesh born in December 2006, joined on the tops of their skulls and sharing a small amount of brain tissue. In 2009, they were separated in Melbourne, Australia. Ganga and Jamuna Shrestha, born in Kathmandu, Nepal in 2000, were successfully separated by Dr. Chumpon Chan and his team from the Singapore General Hospital in 2001. Rital and Ritaj Gaboura of Sudan, were separated at 11 months old in 2011 at the Great Ormond Street Hospital in London. As of 2019 they lived in Ireland. Jadon and Anias McDonald were separated at 13 months old in 2016 in a crowdfunded operation costing $2.5 million (USD) at Montefiore Hospital in New York. Jadon appears to be healthy, but Anias is severely disabled.