The clinical photographs of a newborn shown above demonstrate a severe congenital anomaly characterized by the absence of the cranial vault and exposed, malformed brain tissue. What is the most likely diagnosis?

Explanation

## Image Findings * **Absence of the cranial vault:** The top part of the skull is completely missing. * **Exposed, malformed brain tissue:** Irregular, reddish, vascularized tissue (area cerebrovasculosa) is visible where the brain should be, without any skin or meningeal covering. * **Prominent, 'frog-like' eyes:** Due to the absence of the frontal bone and shallow orbits. * **Relatively normal facial structures:** The lower face, including the nose and mouth, appears formed. * **Body appears otherwise normal:** No other gross congenital anomalies are evident in the visible parts of the body. ## Diagnosis **Key Point:** The complete absence of the cranial vault and exposed, dysplastic brain tissue is pathognomonic for **anencephaly**. Anencephaly is a severe neural tube defect resulting from the failure of the anterior neural tube to close during the third and fourth weeks of gestation. This leads to the absence of a major portion of the brain, skull, and scalp. The remaining brain tissue is typically a rudimentary mass of neural and vascular tissue, known as the **area cerebrovasculosa**, which is directly exposed to the amniotic fluid and often appears hemorrhagic and necrotic. Infants with anencephaly are stillborn or die shortly after birth. ## Differential Diagnosis | Feature | Anencephaly | Encephalocele | Hydrocephalus | | :---------------- | :-------------------------------------------- | :---------------------------------------------- | :--------------------------------------------- | | **Cranial Vault** | Absent (complete or nearly complete) | Defect in skull, but often localized | Intact, but enlarged | | **Brain Tissue** | Exposed, malformed (area cerebrovasculosa) | Protrudes in a sac, usually covered by skin/meninges | Intact, but compressed by CSF | | **Head Size** | Variable, often appears small/deformed | Variable, may have a mass | Enlarged head circumference | | **Prognosis** | Lethal | Variable, depends on size/contents of sac | Variable, can be managed with shunting | ## Clinical Relevance **Clinical Pearl:** Anencephaly is one of the most common severe neural tube defects, with a prevalence of approximately 1 in 1,000 live births globally. Prenatal diagnosis is crucial and often made via ultrasound in the first or second trimester, showing absence of the cranial vault and brain tissue. ## High-Yield for NEET PG **High-Yield:** Folic acid supplementation (400 mcg daily for women of childbearing age, 4 mg daily for women with a history of NTD-affected pregnancy) significantly reduces the risk of neural tube defects, including anencephaly. **Key Point:** Anencephaly is a lethal condition, and affected infants typically do not survive beyond birth or for more than a few hours/days. ## Common Traps **Warning:** Distinguish anencephaly from encephalocele. While both are neural tube defects involving the cranium, anencephaly involves the *absence* of the cranial vault and *exposed* brain, whereas an encephalocele is a *protrusion* of brain and/or meninges through a *defect* in the skull, usually covered by skin or a membrane. ## Reference [cite:Nelson Textbook of Pediatrics, 21st Edition, Chapter 611: Neural Tube Defects] [cite:Robbins & Cotran Pathologic Basis of Disease, 10th Edition, Chapter 27: The Central Nervous System]