Commonest site of meningomyelocele is :
**Core Concept**
Meningomyelocele is a type of congenital defect in the neural tube, resulting from incomplete closure of the neural plate during embryonic development. This leads to herniation of the meninges and spinal cord through a defect in the vertebral column.
**Why the Correct Answer is Right**
The most common site of meningomyelocele is the lumbar region, specifically at the level of the conus medullaris. This is due to the natural curvature of the spine, which puts increased pressure on the neural tube during embryonic development. The lumbar region is also more prone to herniation due to its anatomical structure and the presence of a natural hiatus in the dura mater.
**Why Each Wrong Option is Incorrect**
**Option A:**
Not specified - this is not a valid option for the location of meningomyelocele.
**Option B:**
Thoracic region - while meningomyelocele can occur in the thoracic region, it is less common than in the lumbar region.
**Option C:**
Sacral region - meningomyelocele can also occur in the sacral region, but it is the least common site among the options listed.
**Clinical Pearl / High-Yield Fact**
The Chiari II malformation is often associated with meningomyelocele, particularly in the lumbar region. This malformation involves herniation of the cerebellum and brainstem through the foramen magnum, which can lead to hydrocephalus and other neurological complications.
**Correct Answer:** C. Sacral region