Filar cysts in rare cases may progress in size, particularly when associated with filar lipoma

  • Kyoichi Seo
  • Hirofumi Oguma
  • Rieko Furukawa
  • Akira GomiEmail author
Original Article



Filar cysts (FCs) are detected incidentally on ultrasonography (US) of the neonatal spine. Their clinical significance has not been widely discussed in the literature because FCs are usually asymptomatic. This study aimed to investigate the clinical features of FCs and distinguish FCs that warrant attention.


We retrospectively analyzed 396 patients with lumbosacral skin stigmata. Patients who were younger than 1 month old at reference underwent US initially, and those older than 1 month of age underwent magnetic resonance imaging (MRI) at the age of 5–12 months. Patients with an FC in the US underwent subsequent MRI at the age of 5–12 months. Patients with an FC were followed clinically for at least 3 years.


FCs were identified in 56 (14.1%) patients. Of the 195 children who underwent US initially, FCs were detected in 49 (25.1%) children. FCs were detected in seven children who underwent MRI initially. Of the 50 children with FCs who underwent MRI at the age of 5–12 months, FCs in 20 patients (40%) showed natural regression and FCs in 30 patients (60%) remained. Two of these 30 patients showed progression in size of the FC, and in both cases, the FCs were associated with a filar lipoma; however, the resected cysts were not neoplastic and did not have obvious clinical significance.


Our study characterizes clinical features of filar cysts. Two-thirds of FCs remained in late infancy. The best sequence of MRI to follow-up FCs is heavily T2-weighted images.


Filar cyst Ventriculus terminalis Ultrasonography Natural history CISS image 



We thank Lesley McCollum, PhD, from Edanz Group ( for editing a draft of this manuscript.

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there are no conflicts of interest.

Ethical approval

This study was approved by the Office of Research Integrity Review Board of Jichi Medical University.


  1. 1.
    Brian DC, Marilyn JS (2011) Spinal ultrasonography. In: Siegel MJ (ed) Pediatric sonography, 4th edn. Lippincott Williams & Wilkins, Philadelphia, pp 647–674Google Scholar
  2. 2.
    Choi JH, Lee T, Kwon HH, You SK, Kang WK (2018) Outcome of ultrasonographic imaging in infants with sacral dimple. Korean J Pediatr 61:194–199CrossRefGoogle Scholar
  3. 3.
    Irani N, Goud AR, Lowe LH (2006) Isolated filar cyst on lumbar spine sonography in infants: a case-control study. Pediatr Radiol 36:1283–1288CrossRefGoogle Scholar
  4. 4.
    Kriss VM, Kriss TC, Babcock DS (1995) The ventriculus terminalis of the spinal cord in the neonate: a normal variant on sonography. AJR 165:1491–1493CrossRefGoogle Scholar
  5. 5.
    Lowe LH, Johanek AJ, Moore CW (2007) Sonography of the neonatal spine: part I, normal anatomy imaging pitfalls, and variations that may simulate disorders. AJR 188:733–738CrossRefGoogle Scholar
  6. 6.
    Ponger P, Ben-Sira L, Ben-Adani L, Steinbok P, Constantini S (2010) International survey on the management of skin stigmata and suspected tethered cord. Childs Nerv Syst 26:1719–1725CrossRefGoogle Scholar
  7. 7.
    Schwartz ES, Barkovich AJ (2019) Congenital anomalies of the spine. In: Barkovich AJ, Raybaud C (eds) Pediatric neuroimaging, 6th edn. Wolters Kluwer, Philadelphia, pp 973–1042Google Scholar
  8. 8.
    Severino R, Severino P (2017) Surgery or not? A case of ventriculus terminalis in an adult patient. J Spine Surg 3:475–480CrossRefGoogle Scholar
  9. 9.
    Suh SH, Chung TS, Lee SK, Cho YE, Kim KS (2012) Ventriculus terminalis in adults: unusual magnetic resonance imaging features and review of the literature. Korean J Radiol 13:557–563CrossRefGoogle Scholar
  10. 10.
    Unsinn KM, Geley T, Freund MC, Gassner I (2000) US of the spinal cord in newborns: spectrum of normal findings, variants, congenital anomalies, and acquired diseases. RadioGraphics 20:923–938CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of NeurosurgeryJichi Medical UniversityShimotsukeJapan
  2. 2.Department of Pediatric Medical Imaging, Jichi Children’s Medical Center TochigiJichi Medical UniversityShimotsukeJapan
  3. 3.Department of Pediatric Neurosurgery, Jichi Children’s Medical Center TochigiJichi Medical UniversityShimotsukeJapan

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