Ventriculus Terminalis

The ventriculus terminalis (also known as the terminal ventricle and the fifth ventricle) is a rarely identified cerebrospinal fluid cavity within the conus medullaris. The ventriculus terminalis does not communicate with the subarachnoid space or the central canal of the spinal cord, and may actually be an embryonal remnant of the primitive central canal, leading some to refer to it a sinus terminalis instead.

They are occasionally associated with caudal regression of the spinal cord, Chiari type I malformation, lipomyelomeningoceles, and lumbosacral "lipomas." Some authors believe that all of us have some sort of cystic CSF space at the conus medullaris, but that it's simply larger [and detectable on imaging] in some people and tends to regress (but not completely resolve) over time.

The characteristic imaging features are more commonly seen in children: Cystic lesion of the conus medullaris without spinal cord signal abnormality. In adults, ventriculus terminalis is more likely to have septations and be associated with spinal cord edema, kyphotic deformity and spinal arteriovenous malformations.

Rarely, ventriculus terminalis can enlarge in the presence of meningeal hemorrhage or deformities of the vertebral canal. An enlarged or symptomatic ventriculus terminalis can be treated by cyst fenestration with or without shunting to the subarachnoid space, pleural cavity, or peritoneal cavity.

References

• Kernohan JW. The ventriculus terminalis: its growth and development. J Comp Neurol 1924;38:107–125.
• Suh SH, Chung TS, Lee SK, Cho YE, Kim KS. Ventriculus terminalis in adults: unusual magnetic resonance imaging features and review of the literature. Korean J Radiol. 2012 Sep-Oct;13(5):557-63.
• Woodley-Cook J, Konieczny M, Spears J. The Slowly Enlarging Ventriculus Terminalis. Pol J Radiol. 2016 Nov 7;81:529-531.