====== Filum terminale lipoma ======

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Type of [[Lipomyeloschisis]].

[[Filum terminale]] lipomas (FTL) represent a sub-type of [[spinal lipoma]]s, where there is fatty infiltration of the [[filum]]. 

Findings provide further evidence for the idea that entities, such as filar lipoma, TFT, and RMC, can be considered consequences of a continuum of regression failure occurring during late secondary [[neurulation]]
((Morioka T, Murakami N, Suzuki SO, Mukae N, Shimogawa T, Kurogi A, Shono T, Mizoguchi M. Surgical histopathology of a filar anomaly as an additional tethering element associated with closed spinal dysraphism of primary neurulation failure. Surg Neurol Int. 2021 Jul 27;12:373. doi: 10.25259/SNI_340_2021. PMID: 34513140; PMCID: PMC8422463.)).

===== Natural history =====

Filum terminale lipomas (FTLs) are being identified with increasing frequency due to the increasing utilization of MRI. Although an FTL may be associated with [[tethered cord syndrome]] (TCS), in many cases FTLs are diagnosed incidentally in patients without any symptoms of TCS. The [[natural history]] of FTLs is not well defined.

Filum terminale lipomas are a common incidental finding on spinal MRI, and most patients present without associated symptoms. The untreated natural history is generally benign for asymptomatic patients
((Cools MJ, Al-Holou WN, Stetler WR Jr, Wilson TJ, Muraszko KM, Ibrahim M, La Marca F, Garton HJ, Maher CO. Filum terminale lipomas: imaging prevalence, natural history, and conus position. J Neurosurg Pediatr. 2014 May;13(5):559-67. doi: 10.3171/2014.2.PEDS13528. Epub 2014 Mar 14. PMID: 24628511.)).

===== Clinical features =====
In most cases, a fatty filum is an [[incidental]] and [[asymptomatic]] finding. However, in some individuals, it is associated with [[spinal dysraphism]] and [[tethered cord syndrome]].


Asymptomatic [[lipoma]]s of the [[filum terminale]] occur in 0.2–4%
((Uchino A, Mori T, Ohno M. Thickened fatty filum
terminale: MR imaging. Neuroradiology. 1991; 33:
331–333))
((Brown E, Matthes JC, Bazan C,3rd, et al. Prevalence
of incidental intraspinal lipoma of the lumbosacral
spine as determined by MRI. Spine. 1994; 19:833–
836))
of [[MRI]]s.

===== Pathology =====

Lipoma of the filum terminale is formed as a result of a developmental error in mesodermal cell migration
((Thompson EM, Clinical significance of imaging and histological characteristics of filum terminale in tethered cord syndrome, Journal of Neurosurgery: Pediatrics, Mar 2014 / Vol. 13 / No. 3 / p. 255-259.)).

===== Radiographic features =====

A thin filum (<2 mm in diameter at the L5/S1 level) is rarely symptomatic. When the [[filum]] is thickened (with or without fat) it is much more likely to be associated with a low lying cord (tip of the conus at or below the mid point of L2) and cord tethering. As such careful assessment of the position of the conus is essential 
((Boos N. Spinal disorders, fundamentals of diagnosis and treatment. Springer Verlag. (2008) ISBN:3540405119. Read it at Google Books - Find it at Amazon)).

==== CT ====

If large enough, then fat density (-90 to -30 HU) can be seen below the level of the conus. If small, and depending on the quality of the CT scanner, the size of the patient, and the amount of quantum mottle, it may be difficult to identify. 

==== MRI ====

The abnormality typically is linear and extends over some distance. Signal follows that of fat on all sequences and can demonstrate chemical shift artifact on T2* / gradient weighted sequences. 

T1: hyperintense 
T2: hyperintense
fat saturated sequences: signal loss demonstrated 
T1 C+ (Gd): no enhancement 

===== Differential diagnosis =====

There is little or no differential when the presence of fat is confirmed, however other filum terminale lesions can be considered only to be eliminated.

paraganglioma of the filum terminale
rare
iso- to hyperintense on T2 but hypointense on T1
intense enhancement post contrast
myxopapillary ependymoma
iso- to hyperintense on T2, but hypointense on T1
enhancement post contrast

===== Treatment =====

[[Filum terminale lipoma treatment]].

===== Case series =====

A total of 436 patients with FTL were identified. There were 217 males and 219 females. Of these patients, 282 (65%) were adults and 154 (35%) were children. Symptoms of TCS were present in 22 patients (5%). Fifty-two patients underwent surgery for FTL (12%). Sixty-four patients (15%) had a low-lying conus and 21 (5%) had a syrinx. The natural history analysis included 249 patients with a mean follow-up time of 3.5 years. In the follow-up period, only 1 patient developed new symptoms
((Cools MJ, Al-Holou WN, Stetler WR Jr, Wilson TJ, Muraszko KM, Ibrahim M, La Marca F, Garton HJ, Maher CO. Filum terminale lipomas: imaging prevalence, natural history, and conus position. J Neurosurg Pediatr. 2014 May;13(5):559-67. doi: 10.3171/2014.2.PEDS13528. Epub 2014 Mar 14. PMID: 24628511.)).