Amniotic band syndrome

Amniotic band syndrome (ABS, also called amniotic band constriction, congenital constriction bands or rings, ADAM (amniotic deformity adhesions mutilations)) is a congenital disorder caused by entrapment of fetal parts (usually a limb or digits) in fibrous amniotic bands while in utero. Sideshow performer Jeanie Tomaini (nee Bernice Smith) had congenitally absent legs (congenital amputation), and deformed arms (dysmelia), due to ABS.

Epidemiology
Amniotic banding affects approximately 1 in 1200 live births. It is also believed to be the cause of 178 in 10,000 miscarriages. Up to 50% of cases have other congenital anomalies including cleft lip, cleft palate, and clubfoot deformity. Hand and finger anomalies occur in up to 80%.

Features
The constriction of appendages by amniotic bands may result in:


 * 1) Constriction rings around the digits, arms and legs
 * 2) Swelling of the extremities distal to the point of constriction (congenital lymphedema)
 * 3) Amputation of digits, arms and legs (congenital amputation)

A strong relationship between ABS and clubfoot exists. A 31.5% of associated clubfoot deformity and ABS can be correlated with 20% occurring bilaterally. Other abnormalities found with ABS include: clubhands, cleft lip, and/or cleft palate, and hemangioma.

Pathophysiology
ABS occurs when the inner fetal membrane (amnion) ruptures without injury to the outer membrane (chorion). Fibrous bands from the ruptured amnion float in the amniotic fluid and can entangle the fetus, reducing blood supply and causing congenital abnormalities. In some cases a complete "natural" amputation of a digit(s) or limb may occur before birth or the digit(s) or limbs may be necrotic (dead) and require surgical amputation following birth.

Diagnosis
Amniotic band syndrome is often difficult to detect before birth as the individual strands are small and hard to see on ultrasound. Often the bands are detected indirectly because of the constrictions and swelling upon limbs, digits, etc. Misdiagnosis is also common so if there are any signs on amniotic bands further detailed ultrasound tests should be done to assess the severity.

Treatment
Treatment usually occurs after birth and where plastic and reconstructive surgery is considered to treat the resulting deformity. Plastic surgery ranges from simple to complex depending on the extent of the deformity. Physical and occupational therapy may be needed long term.

In rare cases, if diagnosed in utero, fetal surgery may be considered to save a limb which is in danger of amputation or other deformity. This typically would not be attempted if neither vital organs nor the umbilical cord are affected.

Prognosis
The prognosis depends on the location and severity of the constricting bands. Every case is different and multiple bands may be entangled around the fetus.

Bands which wrap around fingers and toes can result in syndactyly or amputations of the digits. In other instances, bands can wrap around limbs causing restriction of movement resulting in clubbed feet. In more severe cases, the bands can constrict the limb causing decreased blood supply and amputation. Amniotic bands can also sometimes attach to the face or neck causing deformities such as cleft lip and palate. If the bands become wrapped around the head or umbilical cord it can be life threatening for the fetus.

The number of cases of miscarriage that can be contributed to ABS is unknown, although it has been reported that it may be the cause of 178 in 10,000 miscarriages.

Prevention
Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote. The cause of amnion tearing is unknown and as such there are no known preventative measures.

Literature