Craniopagus twins

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Craniopagus twins
CraniopagusTwins.jpg
Craniopagus twins
Specialty Neurosurgery, neuroimaging, medical genetics
Usual onsetIn utero
Diagnostic method Obstetric ultrasonography
Frequency1 in 2.5 million live births

Craniopagus twins are conjoined twins who are fused at the cranium. [1] 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. [2] The thorax and abdomen are separate and each twin has their own umbilicus and umbilical cord. [3]

Contents

The condition is extremely rare, with an incidence of approximately 1 in 2.5 million live births. [3] An estimated 50 craniopagus twins are born around the world every year as of 2021, with only 15 twins surviving beyond the first 30 days of life. [4] 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. [5]

However, 25% of craniopagus twins survive and may be considered for a surgical separation; several such attempts occur annually worldwide. [6] Advances in neuroimaging, neuroanesthesia, and neurosurgery have demonstrated that a successful outcome is possible. [3] Among all conjoined twins, craniopagus twins account for a mere 2% to 6%. [3]

Classification

Doctor performing an assessment on conjoined infants 13256 2016 1023 Fig2 HTML.jpg
Doctor performing an assessment on conjoined infants

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. [7]

In 2006, Stone and Goodrich came up with a more nuanced classification system, which is the "most commonly used" system. [3] 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". [8]

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. [8] The angular subtype has a higher rate of comorbidities than the vertical subtype. [3]

Vertical craniopagus calvaria is continuous and is further subdivided on the basis of intertwin axial facial rotation:

Another classification system divides total craniopagus twins into four categories:

Occipital lobe Occipital lobe animation small.gif
Occipital lobe

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. [7]

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. [8] 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

Dural venous sinus Gray568.png
Dural venous sinus

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. [10] 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. [2]

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. [3]

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. [3]

Cases

Munster's case, seen in 1495 Monsters & Prodigies 10.jpg
Munster's case, seen in 1495

Tatiana and Krista

Lateral surface of cerebral cortex Lateral surface of cerebral cortex - gyri.png
Lateral surface of cerebral cortex

In 2011, The New York Times Magazine covered a story of two craniopagus twin girls who share a brain and seem to show all different kinds of physiological and emotional responses due to their condition. [18] Imagery revealed an attenuated line stretching between the two brains and forming a "thalamic bridge", a bridge connecting the two thalami. Knowing that the thalamus acts as a major control panel within the body, it is believed that the girls share part of this 'control panel' and so when one girl drinks the other one feels it. A more recent report on the twins was released in November 2017. [30]

Although there is not an overwhelming amount of research surrounding how the union between craniopagus twins leads to different personality, cognitive and motor traits, there have been some studies exploring what it actually means to share a brain. In the case of Tatiana and Krista, it is possible that the twins shared some conscious thought. Studies of the thalamus' role in the brain provide neurological data that help explain these behavioral observations that these two twins experience.

Thalamo-cortico-thalamic circuits are the looped neural pathways that connect the thalamus to the cerebral cortex, and then the cerebral cortex back to the thalamus. Because the thalamus is mainly responsible for relaying sensory messages from the body to the brain, it is possible that there is a lot of overlap between the twins' sensory reception and the actual response it creates within the brain. One study examines this by studying the thalamus when it is at a persistent vegetative state that is when the patient is awake but not conscious. This study proved that the cortical activity on its own is not conscious and that all the activity between the loops of the thalamus, the cerebral cortex and the thalamus itself are all conscious actions. Another study of the thalamus reaffirms that the thalamus does not answer yes/no questions but instead acts as a mediator between different parts of the cerebral cortex and systemic sensory reception. [31]

These loops actually may account for the relationship between Tatiana and Krista. At the neuronal level, communication is dense network of neurons linked between themselves and the coordinator (in this case the thalamus) that finally sends a message to the cortex. On top of this, there are links between the cortex that send messages back through the coordinator and finally to the rest of the body. The brain's ability to function through loops and circuits is a good model to explain why Tatiana consciously feels what Krista is physically experiencing. Additionally there is some level of synchronization between the two twins. Another study found that for craniopagus twins, their connection to each other is comparable to our normal appendages and that their bodies have obvious overlap physically and psychologically. [32] Because most cases of craniopagus twins are unique, the research outlining general connections between craniopagus twins is limited. However, this example provides insight into the effects of a union between twins who essentially share the same sensory relay system in the thalamus.

History

Conjoined twinning is one of the oldest known birth defects in history and examples with human's fascination with twins is extremely evident throughout historical literature. Although there are cases of conjoined twins dating back to as early as the 10th century, it was not until 1491 that the first case was documented.

Apart from that, Sebastian Münster’s Cosmographia universalis provides the true first account of craniopagus twins who happened to live for ten years, exceeding many expectations during that time. [33] He describes the set of twins as being a unique malformation and a punishment from their mother's mistake. In French barber surgeon Ambroise Paré’s 16th-century book, On Monsters and Marvels, various types of "supernatural" twinning are illustrated and described as "monstrous and marvelous creatures that proceed from the judgment of God", suggesting that conjoined twins and specifically craniopagus twins were viewed as literal monsters in the 16th century. [34]

See also

Related Research Articles

<span class="mw-page-title-main">Conjoined twins</span> Medical condition

Conjoined twins, popularly referred to as Siamese twins, are twins joined in utero. It is a very rare phenomenon, estimated to occur in anywhere between one in 49,000 births to one in 189,000 births, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.

<span class="mw-page-title-main">Craniopagus parasiticus</span> Rare medical condition

Craniopagus parasiticus is an extremely rare type of parasitic twinning occurring in about 4 to 6 of 10,000,000 births. In craniopagus parasiticus, a parasitic twin head with an undeveloped body is attached to the head of a developed twin. Fewer than a dozen cases of this type of conjoined twin have been documented in literature.

<span class="mw-page-title-main">Dura mater</span> Outermost layer of the protective tissues around the central nervous system (meninges)

In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. The other two meningeal layers are the arachnoid mater and the pia mater. It envelops the arachnoid mater, which is responsible for keeping in the cerebrospinal fluid. It is derived primarily from the neural crest cell population, with postnatal contributions of the paraxial mesoderm.

<span class="mw-page-title-main">Great cerebral vein</span>

The great cerebral vein is one of the large blood vessels in the skull draining the cerebrum of the brain. It is also known as the vein of Galen, named for its discoverer, the Greek physician Galen.

<span class="mw-page-title-main">Cerebral circulation</span> Brain blood supply

Cerebral circulation is the movement of blood through a network of cerebral arteries and veins supplying the brain. The rate of cerebral blood flow in an adult human is typically 750 milliliters per minute, or about 15% of cardiac output. Arteries deliver oxygenated blood, glucose and other nutrients to the brain. Veins carry "used or spent" blood back to the heart, to remove carbon dioxide, lactic acid, and other metabolic products. The neurovascular unit regulates cerebral blood flow so that activated neurons can be supplied with energy in the right amount and at the right time. Because the brain would quickly suffer damage from any stoppage in blood supply, the cerebral circulatory system has safeguards including autoregulation of the blood vessels. The failure of these safeguards may result in a stroke. The volume of blood in circulation is called the cerebral blood flow. Sudden intense accelerations change the gravitational forces perceived by bodies and can severely impair cerebral circulation and normal functions to the point of becoming serious life-threatening conditions.

<span class="mw-page-title-main">Intracranial hemorrhage</span> Hemorrhage, or bleeding, within the skull

Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds, subarachnoid bleeds, epidural bleeds, and subdural bleeds.

The emissary veins connect the extracranial venous system with the intracranial venous sinuses. They connect the veins outside the cranium to the venous sinuses inside the cranium. They drain from the scalp, through the skull, into the larger meningeal veins and dural venous sinuses. They may also connect to diploic veins within the skull.

<span class="mw-page-title-main">Falx cerebri</span> Anatomical structure of the brain

The falx cerebri is a large, crescent-shaped fold of dura mater that descends vertically into the longitudinal fissure between the cerebral hemispheres of the human brain, separating the two hemispheres and supporting dural sinuses that provide venous and CSF drainage to the brain. It is attached to the crista galli anteriorly, and blends with the tentorium cerebelli posteriorly.

Clarence and Carl Aguirre are former conjoined twins born in Manila. They were conjoined at the top of the head and shared 8 centimetres (3.1 in) of brain. More than 1–2 centimetres (0.4–0.8 in) will affect brain functionality in one or both of twins. Without separation, they were expected to live around 6–8 months.

<span class="mw-page-title-main">Confluence of sinuses</span> Venous sinus in the skull

The confluence of sinuses, torcular Herophili, or torcula is the connecting point of the superior sagittal sinus, straight sinus, and occipital sinus. It is below the internal occipital protuberance of the skull. It drains venous blood from the brain into the transverse sinuses. It may be affected by arteriovenous fistulas, a thrombus, major trauma, or surgical damage, and may be imaged with many radiology techniques.

<span class="mw-page-title-main">Superior petrosal sinus</span> One of the dural venous sinuses located beneath the brain

The superior petrosal sinus is one of the dural venous sinuses located beneath the brain. It receives blood from the cavernous sinus and passes backward and laterally to drain into the transverse sinus. The sinus receives superior petrosal veins, some cerebellar veins, some inferior cerebral veins, and veins from the tympanic cavity. They may be affected by arteriovenous malformation or arteriovenous fistula, usually treated with surgery.

<span class="mw-page-title-main">Dural arteriovenous fistula</span> Medical condition

A dural arteriovenous fistula (DAVF) or malformation is an abnormal direct connection (fistula) between a meningeal artery and a meningeal vein or dural venous sinus.

<span class="mw-page-title-main">Cerebellar veins</span> Veins that drain the cerebellum

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Wirginia June Maixner is an Australian neurosurgeon and the director of neurosurgery at the Royal Children's Hospital in Melbourne, Australia. She is known for having performed the first auditory brainstem implant on a child in Australia in 2007, and later having separated the conjoined twins, Trishna and Krishna in 2009.

James Tait Goodrich was an American neurosurgeon. He was the director of the Division of Pediatric Neurosurgery at Montefiore Health System and Professor of Clinical Neurological Surgery, Pediatrics, Plastic and Reconstructive Surgery at the Albert Einstein College of Medicine, and gained worldwide recognition for performing multiple successful separations of conjoined twins. He assisted in two craniopagus separations with Dr. Alferayan A in Riyadh, Saudi Arabia, with the first one done May 5, 2014 and the second one done February 14, 2016. Both pairs were successfully separated and are doing well.

Dr Noor ul Owase Jeelani BMed.Sci (Hons), BMBS, MRCS, MBA, MPhil, FRCS (NeuroSurg.) is a Kashmiri-British neurosurgeon and academic. He is a Consultant Paediatric Neurosurgeon at Great Ormond Street Hospital for Children (GOSH) and was the Head of the Department of Neurosurgery from 2012 until 2018. He is an Honorary Associate Professor at the Institute of Child Health, University College London. He leads the FaceValue research group in Craniofacial Morphometrics, device design, and clinical outcomes.

<span class="mw-page-title-main">András Csókay</span> Hungarian neurosurgeon

András Csókay, is a Hungarian neurosurgeon with international recognition in the field of neurosurgery for his development of a technique to enhance microsurgical precision in the vascular tunnel and for the separation of a pair of Bangladeshi (Islam) Craniopagus Twins.

<span class="mw-page-title-main">Cranial venous outflow obstruction</span> Medical condition

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References

  1. ↑ A. B. Todorov; K. L. Cohen; V. Spilotro; E. Landau (1974). "Craniopagus twins" (PDF). Journal of Neurology, Neurosurgery & Psychiatry. 37 (12): 1291–1298. doi:10.1136/jnnp.37.12.1291. PMC   1083642 . PMID   4448993 . Retrieved 6 September 2021.
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  9. ↑ Bucholz, Richard; Yoon, Kong-Woo; Shively, Raymond (1987). "Temporparietal Craniopagus". Journal of Neurosurgery. 66 (1): 72–79. doi:10.3171/jns.1987.66.1.0072. PMID   3783261.
  10. ↑ James Tait Goodrich; David A. Staffenberg (August 2004). "Craniopagus twins: clinical and surgical management". Child's Nervous System. 20 (8–9): 618–624. doi:10.1007/s00381-004-1001-8. PMID   15197566. S2CID   24176048 . Retrieved 6 September 2021.
  11. ↑ "The workes of that famous chirurgion Ambrose Parey". National Library of Medicine. Retrieved 2023-12-15.
  12. ↑ "Gallery of Famous Craniopagus Twins - Doc Zone - CBC-TV".
  13. ↑ Hardin, Rozella (2017-02-27). "Teresa Bunton, one of famed Siamese twins, dies at age 60". Elizabethton Star. Retrieved 2023-06-17.
  14. ↑ "Teresa Bunton Obituary 2017". Mountain City Funeral Home. Retrieved 2023-06-17.
  15. ↑ "Once-conjoined twins return to Dallas for checkups". San Diego Union-Tribune. September 16, 2009. Retrieved 2024-06-08.
  16. ↑ "Girl dies after separation surgery from her twin". NBC News. Associated Press. September 17, 2004. Retrieved 18 June 2024.
  17. ↑ "Two Lives, Entwined". Archived from the original on 2011-06-07. Retrieved 2012-11-19.
  18. 1 2 Dominus, Susan (29 May 2011). "Could Conjoined Twins Share a Mind?". The New York Times Magazine . Retrieved 21 July 2018.
  19. ↑ "Separating Twins". NOVA. PBS. 8 February 2012. Retrieved 2014-08-03.
  20. 1 2 "The battle to separate Safa and Marwa". BBC News. Retrieved 2019-07-17.
  21. ↑ "Beautiful moment conjoined twins see each other for the first time since they were separated". New Zealand Woman's Weekly . November 23, 2016. Retrieved November 27, 2016.
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  23. ↑ Maciel, Benedito Carlos, ed. (November 5, 2018). "HC divulga imagem de gêmeas após cirurgia de separação definitiva em Ribeirão Preto, SP" [HC publishes image of twins after definitive separation surgery in Ribeirão Preto, São Paolo]. Journal Electrónico Complexo Acadêmico de Saúde (in Portuguese).
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  28. ↑ "Hungarian doctors separate Bangladeshi twins joined at head". Medical Xpress. 2 August 2019. Retrieved 6 September 2021.
  29. ↑ "Conjoined twins separated with the help of virtual reality". BBC News . 2 August 2022. Retrieved 2 August 2022.
  30. ↑ "Inseparable: A Year in the Life of Tatiana and Krista Hogan, BC's Craniopagus Twins". CBC News . Archived from the original on 2023-06-07.
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  32. ↑ Murray, Craig D. (August 2001). "The experience of body boundaries by Siamese twins". New Ideas in Psychology. 19 (2): 117–130. doi:10.1016/S0732-118X(00)00018-0 . Retrieved 6 September 2021.
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