Ventriculus terminalis

Last revised by Ayla Al Kabbani on 23 Mar 2021

The ventriculus terminalis (or persistent terminal ventricle, or terminal ventricle of Krause, or 5th ventricle) is an ependymal-lined fusiform dilatation of the terminal central canal of the spinal cord, positioned at the transition from the tip of the conus medullaris to the origin of the filum terminale. This differs from a filar cyst which is located within the filum terminale.

It represents the canalization and retrogressive differentiation of the caudal end of the developing spinal cord and regresses in size during the first weeks after birth. 

Irrespective of the modality used to image the spine, a ventriculus terminalis in newborns appears as a cystic structure at the tip of the conus medullaris, extending over 8-10 mm with a transverse diameter of 2-4 mm. Later in childhood it often remains visible as a tiny cystic structure but is rarely identifiable in adults.

Typically show fluid signal characteristics

  • T1
    • typically hypointense
  • T2
    • typically hyperintense
  • T1 C+ (Gd): generally do not enhance

In 1859 the German anatomist Benedikt Stilling (1810-1879) 5, wrote that the ventriculus terminalis was an expanded CSF-space in the distal spinal cord with an ependymal lining; interestingly at that time it was called the seventh ventricle! Another German anatomist, Wilhelm Krause, determined that this was a true ventricle and named it the fifth ventricle 4.

Abnormal persistence of cystic dilatation of the ventriculus terminalis (cyst of the medullary conus) can occur and may present symptomatically in adulthood with bladder or bowel sphincter disturbance.

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Cases and figures

  • Case 1
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