Ventriculus terminalis cyst in an infant: a case report

Abstract

Background: Filar cysts are frequently found on neonatal ultrasound and are physiologically involuting structures with natural resolution. Hence, there has been no previous histologic correlation. Ventriculus terminalis is a focal central canal dilation in the conus medullaris and usually not clinically significant. Extra-axial cyst at the conus-filum junction connected to ventriculus terminalis is extremely rare, especially when associated with tethered lipomatous filum terminale and with progressive cyst enlargement.

Case presentation: A Caucasian female neonate with abnormal gluteal cleft had ventriculus terminalis cyst with an extra-axial cyst at the conus-filar junction and taut lipomatous filum on ultrasound examination and magnetic resonance imaging. This persisted at 6-month follow up imaging. In light of the nonresolving extra-axial mass and thick taut lipomatous filum, the child underwent L1-L3 osteoplastic laminectomies. The extra-axial cyst expanded after bony decompression and furthermore on dural opening; visualized on ultrasound. It communicated with the central canal and was documented with intraoperative photomicrographs. It was excised and filum sectioned. Histological immunostaining of the cyst wall showed neuroglial and axonal elements. The child did well without deficits at 4-year follow up with normal urodynamics.

Conclusion: Progression dilation of ventriculus terminalis and extra-axial conofilar cyst with tethered lipomatous filum will likely progress to clinical significance and require surgical intervention. The embryologic basis for this pathology is discussed, with literature review.

Keywords: Case report; Extra-axial cauda equina cyst; Filar cyst; Lipomatous filum; Tethered cord; Ventriculus terminalis.

Fig. 1

Sagittal ultrasound of lumbar spine at 1 day of age. The conus ends at L2. Note the oblong anechoic cyst at the conofilar junction dorsal to the conus medullaris

Fig. 2

A Midsagittal and axial T2-W magnetic resonance image of lumbar spine at 6 months of age visualizes the persistent conofilar cyst. B Midsagittal T1-W magnetic resonance image at 6 months of age demonstrates a thick filum with fibrolipoma (arrow)

Fig. 3

Sagittal (A) and axial (B) intraoperative ultrasound after L1–L3 laminectomies with intact dura. The cyst (arrow) appears to be larger compared with the size demonstrated on magnetic resonance imaging

Fig. 4

A Intraoperative photograph through the microscope. Upon opening the dura, the cyst further expanded and “mushroomed out” into the operative field. B The cyst is opened and communicates with the central canal of the conus (arrow). The thick lipomatous filum is seen (*)

Fig. 5

A Vacuolization of the equinal cord; B canalization with “forking”; C ventriculus terminalis; D filar cyst; E normally developed cord; F ventriculus terminalis cyst; G ventriculus terminalis cyst with “forking”