Encephalocele

Encephalocele is a type of neural tube defect where the brain and its protective membranes push through openings in the skull, forming sac-like bulges. This happens when the neural tube fails to close fully during fetal development. The condition creates a groove along the middle of the skull, between the forehead and nose, or at the back of the skull. How severe it is depends on where the bulge is located.

Signs and symptoms often include craniofacial abnormalities or other brain malformations. Neurological issues, hydrocephalus (buildup of cerebrospinal fluid in the brain), spastic quadriplegia (paralysis of the limbs), microcephaly (abnormally small head), ataxia (uncoordinated movement), developmental delays, vision problems, mental and growth retardation, and seizures can all occur.

The exact cause remains unknown, though it has been studied since the 16th century. The defect stems from incomplete neural tube closure during development. Both environmental and genetic factors play a role. Some studies show a higher occurrence in female embryos, hinting at a genetic link. The gene CEP290 is associated specifically with occipital encephaloceles. Research suggests teratogens like trypan blue and arsenic can damage the developing fetus and cause the condition. Taking proper levels of folic acid before and early in pregnancy helps prevent such defects. Occipital encephaloceles often come with hydrocephalus, seen in 60–90% of patients.

Diagnosis usually happens right after birth because the deformities are noticeable, though a small encephalocele in the nasal or forehead area might go undetected. Physical and mental developmental delays can signal its presence.

Facial encephaloceles are classified as nasofrontal, nasoethmoidal, or naso-orbital, though overlap can occur. They can also appear anywhere along the cranial vault due to abnormal closure of cranial bones; the occipital region is the most common site. If the bulge contains only cerebrospinal fluid and membrane, it’s called a meningocele. If brain tissue is present, it’s a meningoencephalocele. When the head size is smaller than the herniating sac, it’s termed giant encephalocele. A disturbance in the separation of neural and surface ectoderm, leading to a lack of apoptosis in the midline, is considered critical for nasofrontal and nasoethmoidal types.