The image above depicts a fetal head with significant malformations. Based on the visible findings, what is the most likely diagnosis?

Explanation

## Image Findings * Complete absence of the cranial vault superior to the orbits. * Exposed, malformed, and rudimentary brain tissue (often referred to as cerebrovasculosa) visible at the superior aspect of the head. * Relatively well-formed facial structures (eyes, nose, mouth) below the cranial defect. * Overall "frog-like" appearance of the head. ## Diagnosis **Key Point:** The image demonstrates **anencephaly**, characterized by the absence of the cranial vault and cerebral hemispheres. Anencephaly is a severe neural tube defect resulting from failure of closure of the anterior neural tube during the 3rd to 4th week of gestation. This leads to the absence of a major portion of the brain, skull, and scalp. The brain tissue that is present is typically rudimentary, disorganized, and exposed, often referred to as cerebrovasculosa. The facial structures, including the orbits, nose, and mouth, are usually relatively preserved, giving a characteristic "frog-like" appearance due to the exposed brain and prominent eyes. ## Differential Diagnosis | Feature | Anencephaly | Encephalocele | Hydrocephalus | Microcephaly | | :------------------ | :-------------------------------------------- | :---------------------------------------------- | :------------------------------------------------ | :-------------------------------------------- | | **Cranial Vault** | **Absent** (superior to orbits) | Defect with sac-like protrusion | Intact but often thinned and enlarged | Intact but abnormally small | | **Brain Tissue** | Rudimentary, exposed, disorganized | Protrudes through defect, often covered by skin | Intracranial, compressed by enlarged ventricles | Intracranial, small, often with gyral abnormalities | | **Head Size** | Appears small/deformed superiorly | Variable, depends on size of encephalocele | **Enlarged** | **Abnormally small** | | **Key Visual** | "Frog-like" appearance, no skull cap | Sac-like protrusion on head | Large head, prominent forehead, wide sutures | Small head, sloping forehead | ## Clinical Relevance **Clinical Pearl:** Anencephaly is a lethal condition, with affected infants typically stillborn or dying shortly after birth. Prenatal diagnosis is crucial for counseling and management. ## High-Yield for NEET PG **High-Yield:** Anencephaly is the most common lethal neural tube defect. **Key Point:** Folic acid supplementation (0.4 mg daily for women of childbearing age, 4 mg daily for high-risk women) before and during early pregnancy significantly reduces the risk of neural tube defects, including anencephaly. ## Common Traps **Warning:** Do not confuse anencephaly with encephalocele. While both are neural tube defects involving the brain and skull, anencephaly involves the *absence* of the cranial vault and cerebral hemispheres, whereas encephalocele involves a *protrusion* of brain tissue through a *defect* in the skull, with the rest of the skull generally intact. ## Reference [cite:Nelson Textbook of Pediatrics, 21st Ed, Ch 610]