Sacral agenesis was first described by Hohl in 1852. Sacral
agenesis is rare entity occurring in 0.01% -0.005% of the population. Duhamel coined the term caudal regression syndrome
to describe a spectrum of congenital malformation;
these range from simple anal atresia, to absence of sacral
(sacral agenesis), lumbar and possibly lower thoracic vertebrae
(caudal aplasia/dysplasia), to the most severe form with
fusion of the lower extremities and major visceral malformation
known as sirenomelia. There is also an increased frequency
of spinal cord abnormalities is seen in patients with
sacral agenesis, including syrinx, tethered cord, lipoma, and
lipomyelomeningocele.
Maternal Diabetes, genetic predisposition and vascular hypoperfusion
have been suggested as possible causative factors. A higher frequency, in the range of 0.1%-0.2%, has been
observed in children of diabetic mothers. Insulin injections
may have a teratogenic effect on the embryo. This view has
been supported by by Duraiswami (1950) who has experimentally
produced caudal regression in chickens by injecting insulin
into the eggs.
Typically child present with flattened buttocks and shortened
intergluteal cleft with absent lumbar lordosis .The pelvic ring
is completed with either direct apposition of the iliac bones
or with interposition of the lumbar spine replacing the absent
sacrum. Scoliosis occasionally occurs. Visceral abnormalities
such as anal atrasia, fused kidneys and congenital heart malformations
are not uncommon. The spectrum of sacral
agenesis can be categorized into four types.
In type 1, partial unilateral agenesis is localized to the sacrum
or coccyx.
In type 2, there are partial but bilaterally symmetric defects in
the sacrum. The iliac bones articulate with S1, and distal segments
of the sacrum and coccyx fail to develop.
In type 3, there is total sacral agenesis and the iliac bones
articulate with the lowest available segment of the lumbar
spineIn type 4, there is total sacral agenesis and the iliac bones are
fused posteriorly along the midline.
The diagnosis is often made late in pregnancy. Early detection
of caudal regression syndrome at 11 weeks of gestational age
by transvaginal ultrasound scanning was reported. In the first
trimester crown-rump length was found to be smaller than
expected in caudal regression using abdominal ultrasound.
CT scan is not contributory enough and shows lumbosacral
agenesis.MRI is the investigation of choice. The management
of these cases is symptomatic for each system, and the
treatment should start as soon as possible.
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