A myelomeningocele (MMC) is a neural tube defect in which the spinal cord and meninges herniate through a defect in the vertebral column, usually in the lumbosacral region. It is the most common form of spina bifida and occurs in approximately 1 per 1000 births. On prenatal ultrasound, a myelomeningocele appears as a fluid-filled sac with neural tissue protruding from an opening in the spine, and associated findings include lemon sign (concave frontal bones), banana sign (curved cerebellum), and ventriculomegaly. Postnatal cranial ultrasound in neonates with myelomeningocele is used to assess for associated Arnold-Chiari malformation and hydrocephalus. Early surgical repair soon after birth is the standard treatment.
Sonography Term