The question asks to identify the term for a bulging sack-like lesion that contains both spinal fluid and elements of the spinal cord.

Myelomeningocele: Defining the Bulging Spinal Lesion

This condition describes a severe form of spinal bifida where the backbone and the spinal canal do not close before birth. This results in a sac protruding from the baby's back. Let's break down the options to understand why myelomeningocele is the correct answer:

Option 1: Meningocele

A meningocele involves the protrusion of the meninges (the membranes surrounding the brain and spinal cord) and cerebrospinal fluid (CSF) through an opening in the spine. However, it does not typically include the spinal cord itself or neural elements within the sac.

Option 2: Myelomeningocele

This is the most severe form of spina bifida. In myelomeningocele, the bulging sack contains the meninges, cerebrospinal fluid, and a portion of the spinal cord or nerve roots. This perfectly matches the description given in the question: a "bulging sack like lesion filled with spinal fluid and spinal cord element".

Option 3: Hydrocephalus

Hydrocephalus is a condition characterized by the buildup of excess cerebrospinal fluid in the brain's ventricles. It is primarily a condition affecting the brain's fluid dynamics, not a spinal lesion involving the spinal cord itself protruding externally.

Option 4: Spinal Bifida Occulta

Spinal bifida occulta is a milder, often hidden form of spina bifida. It involves a small gap in the spine where the vertebrae haven't fused completely, but the spinal cord and surrounding tissues remain in place. There is typically no bulging sac or protrusion visible externally.

Conclusion on Spinal Lesion Terminology

Based on the definitions, the presence of both spinal fluid and spinal cord elements within the bulging sack specifically points to Myelomeningocele.