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Kelly Siberine
Lori and Reba Schnapell
Krista and Tatiana Hogan
Clarence and Carl Agurirre
(seperated craniopagus conjoined
twins)
“OMG!! Absolutely fantastic. Unbelievable.
Unprecedented as far as I know.” -Todd
Feinberg, professor of clinical psychiatry and
neurology at Albert Einstein College of Medicine
“ridiculously compelling.” neuroscientist in Kelowna
Conjoined Twins
• Identical twins joined in utero
• As known as Siamese twins
• Occurrence ranges from 1 in 50,000 births to 1 in
100,000 births
• Survival rate: 25%
• 40 sets born in the United States each year
• Share a single common chorion, placenta, and
amniotic sac (characteristics not exclusive to conjoined
twins)
Fission vs. Fusion
• 2 contradicting theories:
– Fission: fertilized egg splits partially
– Fusion: fertilized egg completely seperates,
but stem cells (looking for similar cells) find
like-stem cells on the other twin and fuse
together
How They Become Conjoined
• Embryo starts to divide but
does not complete the
process
• Area where the embryo
stop dividing is where the
twins become one
• Malformation believed to
occur first 13th & 15th days
after separation
• Inner mass of cell split into
equal halves (each capable
of forming an individual)
• Complete separation of
inner cell mass of chronic
vesicle doesn’t occur +
non-separated areas
remained fused through
development
• In normal embryo and
fetus development, every
cell knows where it is in
the body due to chemical
messages
• If confused, conjoined
twins don’t work normally
and form a single
organism w/ 2 heads, 2
hearts, & 4 legs/arms
Types of Conjoined Twins
MOST COMMON
• Thoraco-omphalopagus
• Thoracopagus
• Omphalopagus
• Parasitic twins
• Craniopagus
LESS COMMON
• Cephalopagus
• Synecephalus
• Cephalothoracopagus
• Xiphopagus
• Ischiopagus
• Omphalo-Ischiopagus
• Parapagus
• Craniopagus parasiticus
• Pygopagus (Iliopagus)
Thoraco-omphalopagus
• 28% of cases
• Two bodies fused
from the upper chest
to the lower chest
• usually share a heart
• may also share the
liver or part of the
digestive system
Thoracopagus
• 18.5% of cases
• Two bodies fused
from the upper
thorax to lower
belly
• Heart always
involved
• Seperation rarely
attempted
Omphalopagus
• 10% of cases
• Two bodies fused at
the lower chest
• Heart is never
involved
• Often share a liver,
digestive system,
diaphragm, and other
organs
• Highest success rate
for seperation
Parasitic Twins
• 10% of cases
• Twins that are asymmetrically conjoined
• One twin is small and, less formed, and
dependent and the larger twin for survival
Craniopagus
• 6% of cases
• Fused skulls, but separate bodies
• Conjoined at the back of the head,
front of the head, or side of the
head
• Not conjoined on the face or base
of the skull
• Seperation possible depending on
amount of shared brian, but
extremely risky
• Krista and Tatiana Hogan
Seperation
• Surgery can range from simple to extremely
complex
• Usually results in the death of one or both of the
twins
• Success Rates
– twins joined at the base of the spine: 68% chance of
successful separation
– twins with conjoined hearts at the ventricular: no known
survivors
– 50% in general
Greatest Risks
• Anesthesia and surgical complications
greatest risk during and after surgery
• Complications include:
– Blood clots in newly constructed blood
vessels
– Intracranial bleeding
– Heart complications
– infections
•Critical period: 3-4 days after surgery