Definition of Fingers, six
Fingers, six definition - medical term The presence of an extra finger, a very common congenital
malformation (birth defect).
This condition is called hexadactyly. The word hexadactyly literally means six
digits. In medical usage, hexadactyly does not specify whether the six digits are
fingers or toes (although in Greek "dactylos" is without equivocation a finger).
The 6th digit can be located in three different locations: on either side of
the extremity or somewhere in between. With the hand for example, the extra finger
can be out beyond the little finger (which is called ulnar hexadactyly) or out beyond
the thumb (radial hexadactyly) or, finally, between two of the normally expected
fingers (intercalary hexadactyly).
Far and away the most frequent form of hexadactyly is ulnar (postaxial) hexadactyly.
Next comes radial (preaxial) hexadactyly. And far and away the rarest form of hexadactyly
is intercalary hexadactyly.
Hexadactyly in itself can be innocuous, absolutely harmless and very easily remedied,
when the hexadactyly is an isolated finding and the baby is otherwise entirely normal.
Ulnar hexadactyly with just a rudimentary tag of a sixth digit, for instance, can
be very simply treated by tying it off with one suture.
However, hexadactyly can also be one of a number of congenital malformations
affecting the baby. In this case, treatment may not be so simple and the prognostic
outlook may not be as good.
Hexadactyly can be seen on some prenatal ultrasound scans. To present a real
case, an ultrasound scan showed "a rudimentary 6th digit on both hands." A more
detailed ultrasound confirmed "a 6th digit on ulnar side of each hand" and showed
that 6th digit "is small and just a floppy skin tag." No other morphological (physical)
abnormalities of the fetus were visible. Another ultrasound with even greater resolution
revealed "a rudimentary digit/skin tag on the palmar surface of the hand lying between
the 4th and 5th digits." Again, no abnormality was seen elsewhere on the baby.
The differential diagnostic list of disorders causing hexadactyly is pretty long.
But many were excluded by the absence of other malformations. It also seemed a particular
type of hexadactyly. If it were an intercalated extra digit (with the extra finger
situated between the other fingers), the list would be much smaller and only a very
few entities such as the Pallister-Hall syndrome and Greig syndrome (but there would
usually be other things to see in either of these 2 syndromes). The final diagnosis
in this case has not yet been made. We have present the case to convey the quandary
that can occur when hexadactyly is discovered antenatally (before birth) today.
Hexadactyly is the most frequent form of polydactyly, a diagnosis that encompasses
all cases of extra digits, irrespective of the number of extra digits in a particular
case.
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