Neurenteric cyst with associated butterfly vertebrae in a seven-month-old colt.

This research discusses a case of a seven-month-old colt with a neurenteric cyst and associated butterfly vertebrae, both outcomes of a condition called spinal dysraphism which can occur due to problems during the early stages of embryonic development.

Understanding Spinal Dysraphism

• Spinal dysraphism is a term that encapsulates conditions that arise from issues with the closing of the neural tube during embryonic development, particularly during the first weeks. This technical term also encompasses all congenital spinal disorders relating to anomalous differentiation or defects in the closure of dorsal midline structures.
• Spinal dysraphism has been categorized into open and closed types, depending on the exposure of neural elements. Previously, definitions such as spina bifida aperta or cystica for open, and spina bifida occulta for closed were used. However, the term ‘spina bifida’ should primarily be used for cases with defective closure of bony elements dorsal or posterior to the spinal cord.

Types of Spinal Dysraphism

• The prevalence of open spinal dysraphisms (OSDs) is notably higher than that of closed spinal dysraphisms (CSDs) in humans; these OSDs are typically located at the lumbar or lumbosacral area.
• CSDs are a more diverse group of malformations, often less visible at birth, but may present complications later on. Although the skin remains whole in a CSD, the appearance of stigmata or subcutaneous masses could suggest an underlying dysraphism.

Neurenteric Cysts and Other Developmental Abnormalities

• Neurenteric cysts represent a variant of CSD resulting from the persistence of the accessory neurenteric canal between the yolk sac and amniotic cavity. The continued existence of part or whole of this canal during the development of the notochord and neural plate may lead to a variety of developmental abnormalities being collectively referred to as ‘split notochord syndrome’.
• The abnormal fusion of vertebrae, causing developmental abnormalities such as ‘butterfly’, ‘block’ or ‘hemivertebrae’, can also be a result of the persistence of the neurenteric canal. Furthermore, there could be splitting of the spinal cord (diastematomyelia).