Encephaloceles

Encephaloceles are a group of congenital neural tube defects characterized by herniation of intracranial contents through a defect in the skull, forming a sac. When brain tissue is involved in the herniation, it is typically referred to as an encephalocele or brain-containing meningoencephalocele; if the sac contains only meninges, the condition is known as a meningocele.

Most encephaloceles occur in the occipital region, but anterior and basal types also exist, including frontal, nasal, and nasofrontal forms. The distribution varies by population. The condition ranges in size and can involve only meninges, or both meninges and brain tissue, leading to a range of neurological outcomes.

Pathogenesis involves failure of neural tube closure early in development, with a resultant skull defect through which intracranial tissue herniates. Risk factors include maternal folate deficiency, poor maternal health, diabetes, fever or teratogenic exposures during early pregnancy, and other environmental factors. The etiology is commonly multifactorial, and encephaloceles may be associated with other brain anomalies such as hydrocephalus, microcephaly, or corpus callosum defects. Genetic contributions are recognized but not fully understood.

Clinically, a soft sac may be evident at birth, protruding through the scalp. Symptoms and prognosis depend on the amount of brain tissue involved and on accompanying anomalies; patients may experience hydrocephalus, seizures, or developmental delays. Diagnosis is aided by prenatal ultrasound, with postnatal imaging by MRI or CT to define tissue involvement and skull defects.

Management requires multidisciplinary care, usually with neurosurgical intervention to reduce the herniated contents, repair the skull defect, and restore CSF dynamics. Prognosis varies; larger defects with significant brain involvement have greater morbidity and mortality. Prevention focuses on folic acid supplementation prior to conception, which reduces the risk of neural tube defects in general.