Diagnosis

How Encephalocele Is Diagnosed Before Birth

Prenatal Ultrasound and Fetal MRI

· 2 min read · 306 words

In short: How Encephalocele Is Diagnosed Before Birth

  • Encephalocele is usually first detected on prenatal ultrasound, sometimes as early as 11–13 weeks.
  • Fetal MRI adds critical detail about sac contents and brain formation.
  • The AFP blood screen is often normal because most encephaloceles are skin-covered.
  • Detection leads to referral, detailed imaging, and multidisciplinary counseling.

Many encephaloceles are first found before birth, during routine pregnancy imaging. Understanding how diagnosis works can make the process less bewildering.

Ultrasound: the usual first clue

Encephalocele is most often discovered on a prenatal ultrasound, sometimes as early as the late first trimester (around 11–13 weeks) but frequently during the standard second-trimester anatomy scan. On ultrasound, it may appear as a sac-like protrusion along the midline of the skull, with a visible bony defect.

Fetal MRI: the detailed picture

If ultrasound suggests an encephalocele, your team may recommend a fetal MRI. MRI gives superior soft-tissue detail and can clarify:

  • The exact location and size of the defect
  • Whether the sac contains only fluid and membranes, or also brain tissue
  • How the rest of the brain has formed
  • Whether other findings (like hydrocephalus) are present

Fetal MRI is usually performed later in pregnancy (often after about 22 weeks), partly because the fetus is larger and easier to image. This detailed information is essential for counseling and for planning delivery and surgery.

Why the blood test is often normal

Many parents are surprised that the standard maternal blood screen (alpha-fetoprotein, or AFP) is often normal with encephalocele. The reason: most encephaloceles are covered by skin or a thin membrane, so the AFP that signals "open" defects like spina bifida doesn't leak out the same way. A normal AFP does not rule out encephalocele — imaging is the key tool.

What happens after detection

After an encephalocele is identified, families are typically referred to a fetal center or children's hospital for:

  • Detailed imaging and a full anatomy review
  • Counseling with maternal-fetal medicine, neurosurgery, and craniofacial specialists
  • Discussion of possible genetic testing
  • Delivery and treatment planning

Sources

  • Boston Children's Hospital — Encephaloceles (prenatal detection)
  • Nationwide Children's Hospital — Encephalocele (Fetal Center)
  • StatPearls (NCBI Bookshelf) — Encephalocele
  • Cleveland Clinic — Encephalocele

Questions people ask

My AFP was normal — could there still be an encephalocele??

Yes. Imaging, not AFP, is the main diagnostic tool for encephalocele. Is fetal MRI safe? Fetal MRI does not use radiation and is considered safe; your team will explain the specifics. Can ultrasound tell if there's brain in the sac? It can suggest it, but MRI usually gives the clearest answer.

Browse all 50 Encephalocele guides

Look up any Encephalocele term in the glossary — 265 plain-language definitions

Not sure which page you need? Put words to it with the symptom navigator

Print a Encephalocele booklet to take to an appointment

What AURORA is building for Encephalocele