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Tight filum terminale syndrome
Last revised by Dr Daniel J Bell ◉ on 08 May 2021
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Radswiki, T., Bell, D. Tight filum terminale syndrome. Reference article, Radiopaedia.org. (accessed on 19 Jan 2022) https://doi.org/10.53347/rID-15609
https://radiopaedia.org/articles/15609
Article created:
29 Oct 2011 by The Radswiki ◉
27 times by 5 users - see full revision history
Central Nervous System, Paediatrics, Spine
cases, neuroradiology
Cord-traction syndrome
Filum terminal syndrome
Occult tethered cord syndrome
Occult filum terminale syndrome
Tight filum syndrome
Tight filum
Tight filum terminale
URL of Article
Tight filum terminale syndrome, or tight filum syndrome, is a subtype of the tethered cord syndrome that is attributed to a thick, short, and/or otherwise inelastic filum terminale rather than other tethering agents.
Radiographic features
Treatment and prognosis
History and etymology
The term "tight filum terminale syndrome" is synonymous with "tethered cord syndrome" secondary to a "tight filum terminale." The emphasis on "syndrome" highlights a clinical diagnosis made by the synthesis of symptoms, neurologic exam signs, and laboratory tests such as urodynamics. In contrast, "tight filum terminale" is a pathoanatomic finding, which may or may not be visible radiologically or associated with the clinical syndrome.
When the clinical syndrome is present but imaging is normal (conus medullaris is normally positioned, filum terminale appears normal in size and signal, and other tethering agents are absent), the term occult filum terminale syndrome is used to imply that an inelastic but grossly normal-appearing filum terminale may be the culprit 2,4. This diagnosis remains controversial 7. The term occult tethered cord syndrome is synonymous because a histologic abnormality in the filum terminale is the implied diagnosis by exclusion 8.
Confusingly, "tethered cord syndrome" is sometimes used synonymously, as if to imply that a tight filum terminale is the main etiology of the tethered cord syndrome, even though in actuality there are many other etiologies. This ambiguity dates back to the first introduction of the term "tethered cord syndrome" by Hoffman and colleagues in 1976, who described a series of patients with spina bifida occulta and neurologic symptoms as well as a low conus and/or thick filum identified on iophenyldate myelography, i.e. the entity previously termed filum terminale syndrome 11. These authors claimed that this etiology "far outnumbers the more obvious forms of spinal dysraphism," even though patients with those disorders were excluded from the study 11. Since that time, the concept of tethered cord syndrome has been expanded to include that associated with the other spinal dysraphisms and other causes such as acquired adhesions.
In one surgical case series of children treated for tethered cord syndrome, tight filum terminale was the cause in 16% 3.
The condition is caused by incomplete involution of the distal spinal cord during development 1. Histologically, tight fila have increased/denser fibrous and adipose connective tissue 9. Tightness of the filum terminale results in stretching of the distal spinal cord with chronic ischemic changes 1.
Two major imaging findings characterize tight filum terminale syndrome 5:
short filum: low-lying conus medullaris terminating inferior to L2
thick filum: greater than 2 mm diameter, often fatty
Either, both, or neither finding can be seen in the syndrome i.e. in the latter case, an inelastic tight filum could have strictly normal imaging findings 6. Additional findings are noted below.
There may be reduced motion of the conus medullaris 1.
A fatty filum shows high signal on T1-weighted images.
A tight filum is usually dorsally positioned (in contact with the posterior dura rather than in between the cauda equina nerve roots), especially on prone imaging 6,8. There may be gradual tapering of the conus medullaris into the filum and the distal spinal cord appears straight (tense) rather than curved (relaxed), although these findings have unclear reliability 6.
The treatment is surgical sectioning of the lower end of the filum. The vast majority (90%) of children with tight filum terminale have stable to improved neurologic function following surgery 3.
American orthopedic surgeon George J Garceau (1896–1977) first described "the filum terminale syndrome" in 1953, hypothesizing that "a tight filum terminale may cause the cord-traction symptoms known as the Arnold-Chiari syndrome" 10.
1. Unsinn KM, Geley T, Freund MC, Gassner I. US of the spinal cord in newborns: spectrum of normal findings, variants, congenital anomalies, and acquired diseases. (2000) Radiographics : a review publication of the Radiological Society of North America, Inc. 20 (4): 923-38. doi:10.1148/radiographics.20.4.g00jl06923 - Pubmed
2. Van Calenbergh F. Introductory comment: Childhood tight filum syndrome. (2012) European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society. 16 (2): 101-2. doi:10.1016/j.ejpn.2011.07.017 - Pubmed
3. Shang AJ, Yang CH, Cheng C, Tao BZ, Zhang YZ, Gao HH, Bai SC. Microsurgical efficacy in 326 children with tethered cord syndrome: a retrospective analysis. (2019) Neural regeneration research. 14 (1): 149-155. doi:10.4103/1673-5374.243720 - Pubmed
4. Wehby MC, O'Hollaren PS, Abtin K, Hume JL, Richards BJ. Occult tight filum terminale syndrome: results of surgical untethering. (2004) Pediatric neurosurgery. 40 (2): 51-7; discussion 58. doi:10.1159/000078908 - Pubmed
5. Warder DE. Tethered cord syndrome and occult spinal dysraphism. (2001) Neurosurgical focus. 10 (1): e1. doi:10.3171/foc.2001.10.1.2 - Pubmed
6. Cornips EM, Vereijken IM, Beuls EA, Weber JW, Soudant DL, van Rhijn LW, Callewaert PR, Vles JS. Clinical characteristics and surgical outcome in 25 cases of childhood tight filum syndrome. (2012) European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society. 16 (2): 103-17. doi:10.1016/j.ejpn.2011.07.002 - Pubmed
7. Iskandar B.J., Amaefuna S.C. (2019) The Tethered Cord Syndrome and Its Occult Form. In: Tubbs R., Oskouian R., Blount J., Oakes W. (eds) Occult Spinal Dysraphism. Springer, Cham. doi:10.1007/978-3-030-10994-3_8
8. Nakanishi K, Tanaka N, Kamei N, Nakamae T, Izumi B, Ohta R, Fujioka Y, Ochi M. Use of prone position magnetic resonance imaging for detecting the terminal filum in patients with occult tethered cord syndrome. (2013) Journal of neurosurgery. Spine. 18 (1): 76-84. doi:10.3171/2012.10.SPINE12321 - Pubmed
9. Thompson EM, Strong MJ, Warren G, Woltjer RL, Selden NR. Clinical significance of imaging and histological characteristics of filum terminale in tethered cord syndrome. (2014) Journal of neurosurgery. Pediatrics. 13 (3): 255-9. doi:10.3171/2013.12.PEDS13370 - Pubmed
10. Garceau GJ. The filum terminale syndrome (the cord-traction syndrome). (1953) The Journal of bone and joint surgery. American volume. 35-A (3): 711-6. Pubmed
11. Hoffman HJ, Hendrick EB, Humphreys RP. The tethered spinal cord: its protean manifestations, diagnosis and surgical correction. (1976) Child's brain. 2 (3): 145-55. doi:10.1159/000119610 - Pubmed
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