Constriction ring syndrome

Overview

Constriction Ring Syndrome (CRS), also known as Amniotic Band Syndrome or Amniotic Constriction Band Sequence, is a rare congenital condition in which fibrous bands form in the amniotic sac and entangle parts of the fetus, most commonly the limbs. These fibrous amniotic bands can constrict blood flow and tissue development, leading to a wide range of deformities that may include limb swelling, deep indentations, or even amputations. The condition is not genetic or inherited and can vary significantly in severity from mild ring-like depressions to life-threatening complications.

Causes

The exact cause of CRS is not fully understood, but the most widely accepted theory involves rupture of the inner lining of the amniotic sac (amnion) during pregnancy. This rupture leads to the formation of fibrous strands that float freely in the amniotic fluid and can entangle parts of the fetus, usually during the first trimester. These bands can constrict growing limbs or digits, restricting blood flow and tissue development. The condition is considered a random event and is not caused by genetic mutations or familial inheritance.

Symptoms

Symptoms and physical findings vary greatly depending on the timing, location, and severity of the constriction. Common features include:

• Constriction rings: Tight bands of tissue around fingers, toes, arms, or legs, often with deep grooves

• Swelling distal to the band: Due to restricted blood or lymphatic flow

• Limb abnormalities: Including clubfoot, shortened limbs, or bone deformities

• Amputations: In severe cases, bands can cut off circulation and lead to intrauterine amputation of fingers, toes, or limbs

• Syndactyly: Fusion of fingers or toes

• Cleft lip or palate: In rare cases where facial structures are affected

• Abdominal wall or craniofacial defects: In more complex presentations

Diagnosis

Constriction Ring Syndrome can be diagnosed either prenatally or after birth based on physical features and imaging studies:

• Prenatal ultrasound: May detect limb abnormalities, missing digits, or visible amniotic bands

• Postnatal physical examination: Identifies constriction rings, swelling, or limb defects

• X-rays or MRI: To evaluate bone and soft tissue involvement

• Differential diagnosis: Important to distinguish CRS from genetic syndromes with similar limb abnormalities

Treatment

Treatment of CRS depends on the severity of symptoms and the presence of functional impairments. A multidisciplinary team including orthopedic surgeons, plastic surgeons, and physical therapists is often involved. Treatment options include:

• Surgical release: Z-plasty or other reconstructive procedures to release constriction bands and improve circulation or function

• Amputation and prosthetics: In cases where parts of the limb are not viable or severely damaged

• Reconstructive hand or foot surgery: To improve mobility and function

• Physical and occupational therapy: To maximize limb function and aid in development

• Prenatal fetal surgery: In rare and severe cases, fetal intervention may be considered to release constricting bands before birth

Prognosis

The prognosis for individuals with Constriction Ring Syndrome depends on the location and severity of the bands and associated abnormalities. Many children with mild cases have normal development and function after surgical treatment. In more severe cases involving multiple limbs or amputations, lifelong rehabilitation and adaptive devices may be necessary. Overall, early intervention and supportive care can greatly improve functional outcomes and quality of life.