Amniotic Band Syndrome

Amniotic band syndrome is a rare disorder [but not hereditary] that entrapment of fetus in strands of amniotic tissue and causes a variety of different birth defects.  The severity of amniotic band syndrome can range from a single, isolated finding to multiple, disfiguring complications.

It is advocated that it should be called a sequence, rather than a syndrome, because it results from an insult that can result from a variety of different causes whereas syndrome results from a single etiology (eg, Down syndrome is due to trisomy 21).

The severity of the defect varies from merely cosmetic band to limb or life-threatening conditions.

It is found approximately 1 in 1200 live births.

Amniotic band syndrome is also known by many other names. These are

• Amnion rupture sequence
• Amniotic bands
• Amniotic band sequence
• Amniotic deformity, adhesions, mutilations (ADAM) complex
• Congenital constriction rings
• Constriction band syndrome
• Limb-body wall complex
• Streeter anomaly
• Streeter bands
• Streeter dysplasia

The amniotic sac is the thin membrane that completely surrounds an embryo or developing the fetus. It contains a liquid called amniotic fluid which supports and protects a developing fetus.

Causes of Amniotic Band Syndrome

No single causative factor has been identified. The risk is believed to be increased in presence of blunt trauma to placenta [as in Chorionic villus sampling – a procedure where a sample of villi is obtained intrauterine] or misoprostol-induced uterine contractions.

The two main theories are given below

Extrinsic Theory states that the inner layer (amnion) of the amniotic sac ruptures or tears exposing the fetus to the strands of fibrous tissue that may float freely in the amniotic fluid. However, they could be in part attached to the amniotic sac. as well.

These bands can wrap around and constrict the fingers, toes, arms, legs and other parts of the developing fetus.

But the external theory does not explain the presence of intact amniotic sac in some infants with amniotic band syndrome and the presence of defects in the internal organs in some cases.

Intrinsic theory says that there is a vascular problem and the constriction bands result from a secondary effect of the impaired blood flow and damage to the fetus.

Clinical Presentation Amniotic Band Syndrome

No two cases of amniotic band syndrome have a similar presentation as the presentation depends on the sites of the defect.

However, three patterns have been identified with amniotic band syndrome

Limbs only are most commonly affected especially the distal part. Amputation, constriction bands and acrosyndactyly [conjoined finger tips] are common forms of presentation.

The hand is involved in almost 90% of cases. Middle, long, and index fingers are affected most commonly.

In the foot, the greater toe is most commonly involved in the foot.

The constriction could be just small indentation to severe compression leading to lymphatic and vascular compromise and child being born with a swollen engorged part distal to constriction.

Severe cases may require an immediate surgical release. In utero amputation is known. occurs

Acrosyndactyly [fused tips]  occur because fingers fuse again due to pressure from the band.

Anterolateral bowing of the tibia, tibial pseudoarthrosis, and clubfoot may be associated.

The patients may have leg length discrepancies.

Limb and body wall defects is another presentation where there are defects of the abdominal wall that occur in association with defects of the arms and legs and other abnormalities.

• Encephalocele
• Facial clefts
• Protrusion of the viscera through a fissure in the wall
  • in the abdominal wall (abdominoschisis)
  • the chest wall (thoracoschisis)
• Varied defects of the arms and legs.

A third pattern associated with amniotic band syndrome involves craniofacial abnormalities which include

• Cleft palate and/or lip
• Underdeveloped eyes (microphthalmia)
• Narrowing of the nasal passages (choanal atresia),
• Malformations affecting the size and shape of the skull.
• Neural tube defects
• Terminal transverse limb deficiencies – Missing portion or whole limb

Diagnosis

No laboratory test is available to detect its presence of amniotic band syndrome.

The typical diagnosis of amniotic band syndrome is soon after birth. The diagnosis is based upon characteristic presentation.

The prenatal ultrasound scan can reveal the swelling of digits or limbs distal to the constriction. Three-dimensional ultrasound and MRI can be used for more detailed and accurate diagnosis.

MRI can also be used for preoperative evaluation to evaluate the neurovascular status that could affect the surgical outcome.

Treatment of Amniotic Band Syndrome

Before the Birth

There is no drug treatment. For prevention, the drugs that may lead to spontaneous rupture of membranes, such as cocaine and mifepristone, should be avoided to decrease the potential risk.

When there are tight bands that risk constriction an loss of a limb or digit, fetoscopic surgery may be performed to cut the involved band

Treatment after Birth

The treatment of infants and children with amniotic band syndrome is symptomatic and supportive.

Mild cases may not require treatment.

But all cases should be monitored to watch for progressive constriction and swelling that may occur as the limb girth increases with growth.

Tight bands that cause distal engorgement or vascular compromise require surgical cutting.

The entire band is excised with 1-2 mm of normal skin to avoid recurrence.

Correction or repair associated deformities is done as required by the type of defect.

Physical and occupational therapy may also be necessary.

Severe lymphatic or venous congestion at the time of birth may lead to necrosis and gangrene if not urgently treated.

References

• Walter JH, Jr, Goss LR, Lazzara AT. Amniotic band syndrome. J Foot Ankle Surg. 1998;37:325–333. doi: 10.1016/S1067-2516(98)80070-7.
• Sentilhes L, Verspyck E, Patrier S, Eurin D, Lechevallier J, Marpeau L. Amniotic band syndrome: pathogenesis, prenatal diagnosis and neonatal management. J Gynecol Obstet Biol Reprod (Paris) 2003;32:693–704. K
• Awamura K, Chung KC. Constriction band syndrome. Hand Clin. 2009;25:257–264. doi: 10.1016/j.hcl.2008.10.007.