What type of spina bifida involves protective membranes around the spinal cord pushing out through the vertebrae, forming a sac filled with fluid?

The condition described in the question relates to a type of spina bifida known as meningocele. In this condition, the protective membranes that cover the spinal cord (the meninges) herniate through an opening in the vertebrae, forming a sac filled with cerebrospinal fluid. This sac does not typically contain neural elements, which distinguishes it from other forms of spina bifida that may involve nerve tissue.

Meningocele is characterized by the presence of this fluid-filled sac protruding through the bony defect in the spine. It typically presents as a more benign form of spina bifida compared to myelomeningocele, where the spinal cord and nerves also protrude, making it more severe due to potential neurological impairments.

Understanding this distinction helps clarify the nuances in the classification and manifestation of spina bifida forms.