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CASE REPORT
Year : 2020  |  Volume : 68  |  Issue : 5  |  Page : 1207-1210

Ligamentum Flavum Cyst: Rare Presentation Report and Literature Review


1 Department of Spine Services, Indian Spinal Injuries Centre, Sector-C, Vasant Kunj, New Delhi, India
2 Pathology Consultancy Services, Noida, Utter Pradesh, India

Date of Web Publication27-Oct-2020

Correspondence Address:
Dr. Vishwajeet Singh
Indian Spinal Injuries Centre, Vasant Kunj, Sector C, New Delhi - 110 070
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.299172

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 » Abstract 


Ligamentum flavum cysts (LFC) are uncommon and their differentiation from other Juxta-facetal cysts & epidural cystic lesions is difficult based on imaging techniques. We present one such rare case of ligamentum flavum cyst with relevant review of the literature. An eighty-eight years male presented with progressively worsening radicular symptom in the left lower limb. His neurological examination was unremarkable. Magnetic resonance imaging of lumbar spine revealed an epidural cystic lesion narrowing the left lateral recess. Intra-operatively, a mass was found originating from ventral surface of ligamentum flavum. Pathological examination was suggestive of fibro-collagenous tissue without synovial lining. The exact pathogenic mechanism for the formation of LFCs is not well understood. Association with segmental instability and degenerative conditions of spine is postulated. They are commonly seen at the mobile junctional levels of the spine. Persistent micro-traumatic events with abnormal movement maybe contributory to their origin. They present either with radiculopathy or neurogenic claudication symptoms owing to compressive effect on adjacent neural structure. LFC should be considered as a differential in patients with radicular pain or claudication symptoms with epidural cystic lesion seen on MRI. Complete excision of such lesion provides excellent pain relief in symptomatic individuals.


Keywords: Formainal stenosis, ligamentum flavus cyst, lumbar canal stenosis, neurogenic claudication
Key Message: Ligamentum flavum cysts (LFCs) are most common in junctional regions of spine and are indistinguishable from other juxta-facetal cysts based on imaging studies. LFCs represent the evolution of degenerative process in the vicinity of neural elements. Cystic degeneration can be one such variation in ligamentum flavum apart from hypertrophy and calcification, eventually narrowing the spinal canal. Cysts may become symptomatic if it compresses the neural structures and can have excellent resolution in symptomatology after surgical excision.


How to cite this article:
Singh V, Rustagi T, Mahajan R, Priyadarshini M, Das K. Ligamentum Flavum Cyst: Rare Presentation Report and Literature Review. Neurol India 2020;68:1207-10

How to cite this URL:
Singh V, Rustagi T, Mahajan R, Priyadarshini M, Das K. Ligamentum Flavum Cyst: Rare Presentation Report and Literature Review. Neurol India [serial online] 2020 [cited 2020 Dec 5];68:1207-10. Available from: https://www.neurologyindia.com/text.asp?2020/68/5/1207/299172




Ligamentum flavum cysts (LFC) are rarer entities, stirring a diagnostic dilemma on initial imaging studies. Pathological changes in ligamentum flavum, leading to cyst formation, are not completely understood.

We report a rare case of ligamentum flavum cyst in the lumbar spine, mimicking as epidural mass, presenting with neurogenic claudication and then discuss the origin of these cysts.


 » Case Report Top


An 88 years old Asian male presented with progressively increasing left leg pain for the last 1 year. The pain progressively limited his activities and walking was painful beyond fifty steps. Visual analog score (VAS) for leg pain was 8 and for backache was 2. Neurological examination revealed normal sensation and motor strength with preserved bowel and bladder function. Magnetic resonance imaging (MRI) of the lumbar spine demonstrated lumbar canal stenosis at the L4–L5 vertebral level [Figure 1]a. A cystic mass was appreciated in proximity to the left L4–5 facet joint in the epidural space [Figure 1]b. Mass was hyperintense on T2-weighted images and hypointense on T1-weighted images of the axial MRI, appearing as a synovial cyst arising from the facet joints.
Figure 1: (a) T2-weighted sagittal section of the Lumbar spine MRI shows a mass lesion with iso-intense to hyper-intense signal in the epidural space at L4-L5 vertebral level. (b) Axial image of the corresponding section shows the left sided location of the cyst compressing the thecal sac and displacing the roots laterally towards right

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Due to his unrelenting symptoms, surgical decompression was planned in the background of no obvious instability, as evidenced by dynamic radiographs [Figure 2]a and [Figure 2]b. Bilateral midline sparing L4 laminotomy and foraminotomy was done to expose the ligamentum flavum. The en-bloc excision of flavum was done on both sides. A cystic swelling was noticed arising from the ventral surface of flavum on the left side [Figure 3]. It was found non-adherent to the dura and compressing the thecal sac, displacing it to the right side. A tissue sample was sent for histopathological examination which demonstrated fibro-collagenous tissue consistent with connective tissue cyst [Figure 4]a and [Figure 4]b. The cyst wall was devoid of the synovial lining. The patient had immediate relief in leg symptoms after surgery.
Figure 2: (a and b) Flexion/ extension radiographs of lumbar spine does not demonstrate any obvious instability at L4-5 motion segment

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Figure 3: Post-operative sample of the excised cyst. It can be seen originating from the ventral surface of the ligamentum flavum, measuring roughly 1 cm in diameter

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Figure 4: Microscopic images obtained after histopathological examination of the cyst (a) Low magnification images showing cyst in ligamentum flavum. Cyst wall is fibro-collagenous in nature and shows proliferation of capillaries. (b). Higher magnification images show fibro-collagenous cyst wall. Cyst lining is devoid of epithelium and its lumen contain necrotic debris

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 » Discussion Top


We describe a rare case of LFC causing neurogenic claudication and discuss the pathogenesis and clinical implications in this report. LFC was first described by Moiel et al. in 1967, compressing the thecal sac and presenting as radicular leg pain.[1] Kao et al. in 1974 have first coined the term “Juxta-facetal cysts” to represent cysts arising from periarticular regions in the spine.[2] “Juxta-facetal” has been recently used to describe these entities owing to their common location around the facet joints, overlying the thecal sac and presenting as radicular or claudication leg pain.

The exact pathogenic mechanism in the formation of ligamentum flavum cyst is not well elucidated. It is believed that persistent micro-instability at motion segment with concomitant micro-trauma predisposes to cyst formation.[3] Nevertheless, abnormal micro-movement owing to motion-segment instability is challenging to demonstrate on imaging studies.

Ligamentum flavum is composed predominantly of elastic fibers and fewer collagen fibers. The predominance of elastic fibers distinguishes the ligamentum flavum from other spinal ligaments. Micro-traumatic events in ligament lead to regeneration with type-2 collagen formation with a reactive decrease in the elasticity.[4] The deposition of collagen results in further degeneration and ongoing myxoid changes culminates in cyst formation.[5]

Cysts appear on the ventral surface of the ligament without any connections to articular facets. This peculiarity is in contrast with the formation of a synovial cyst and ganglion cyst which arise from the articular synovial lining.

Other types of the cystic formation may include amyloid deposition in ligamentum flavum, in association with the normal aging process as well as with systemic amyloidosis.[6] At times, calcifications and ossifications are also seen within these cysts. Proteolytic enzyme released from neutrophils in the vicinity of calcium deposits has been seen.[7]

The most commonly reported location for LFCs is the lumbar spine [Table 1] There are few reported cases of cervical flavum cysts. It is interesting to note that no case of LFCs has been reported at thoracic locations, which further supports the theory of segmental instability in the genesis of LFCs. L4-L5 segment seemingly, is the most common level for the development of these cysts, as seen in our case. However, we did not observe appreciable instability on dynamic radiographs in our case. This observation supports the role of subtle micro-instability in the cyst formation. The cervicothoracic junction is the most commonly affected level in the cervical spine. There have been few reports of cysts at other locations in the sub-axial spine as well.
Table 1: Existing literature reporting the cases of ligamentum flavum cyst and their location

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Most of the LFCs are located in close vicinity to the facet joint. Few authors suggested the origin of these cysts from fluid migration through the defect into the ligament. Others refute this observation, stating no connection exists between facet joints and ligamentum flavum.[8]

There are no specific symptoms pertaining to LFCs and presentation depends on location, size and growth rate of the cyst. Asymmetric compression may present with unilateral radicular pain and mimic foraminal stenosis. The central location of cyst occluding the spinal canal may present with symptoms of canal stenosis and claudication type leg pain. Shah et al. reported the case of midline cyst embedded in ligamentum flavum without connections to facet joints and presenting with bilateral claudicant leg pain.[9] The most common presentations are radicular pain (97%), motor deficit (39%), sensory changes (55%), abnormal reflexes (18%), and positive Lasegue's test (33%). Surgical emergencies arising from cysts are rare. There are few reports of Cauda equina syndrome with concomitant LFCs complicated by infection and hemorrhage within the cyst.[10]

Differential diagnosis of these intraspinal epidural mass is ligamentum flavum cyst, juxta-articular cysts, perineural cyst, dermoid cyst, schwannoma, neurofibroma, ependymal cyst or infected cyst. MRI may help to differentiate LFCs from the synovial cysts, however at times, differentiation is possible only during surgery.

Conservative treatment can achieve a varying degree of success. Percutaneous steroid injection of synovial and juxta-facetal cyst has reportedly not achieved good results. Surgical excision is a reasonable choice when conservative measures fail. The goal of surgical excision is decompression and complete removal of cyst along with ligamentum flavum. Most of the cyst are non-adherent to the dura and only require careful dissection before excision. LFCs represent a rare cause of nerve compression and radicular or claudication pain and it should be considered in the differentials along with synovial and ganglionic cysts, in the setting of neurogenic leg pain and imaging studies suggestive of the epidural cystic lesion.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

1.
Moiel RH, Ehni G, Anderson MS. Nodule of the ligamentum flavum as a cause of nerve root compression. Case report. J Neurosurg 1967;27:456-8.  Back to cited text no. 1
    
2.
Kao CC, Winkler SS, Turner JH. Synovial cyst of spinal facet. Case report. J Neurosurg 1974;41:372-6.  Back to cited text no. 2
    
3.
Chan LF, Lui CC, Cheng MH, Lin JW. Ganglion cyst in the ligamentum flavum of the cervicothoracic junction. J Formos Med Assos 1996;95:490-2.  Back to cited text no. 3
    
4.
Viejo-Fuertes D, Liguoro D, Rivel J, Midy D, Guerin J. Morphologic and histologic study of the ligamentum flavum in the thoraco-lumbar region. Surg Radiol Anat 1998;20:171-6.  Back to cited text no. 4
    
5.
Yoshida M, Shima K, Taniguchi Y, Tamaki T, Tanaka T. Hypertrophied ligamentum flavum in lumbar spinal canal stenosis. Pathogenesis and morphologic and immunohistochemical observation. Spine 1992;17:1353-60.  Back to cited text no. 5
    
6.
Savitz MH, Sachdev VP. Cyst of the ligamentum flavum: Report of six cases. Neurosurgery 1992;30:461-2.  Back to cited text no. 6
    
7.
DiMario S, Marmor E, Albrecht S, Mohr G. Ligamentum flavum cysts causing incapacitating lumbar spinal stenosis. Can J Neurol Sci 2005;32:237-42.  Back to cited text no. 7
    
8.
Spinner RJ, Hebert-Blouin MN, Maus TP, Atkinson JL. Evidence that atypical juxtafacet cysts are joint derived. J Neurosurg Spine 2010;12:96-102.  Back to cited text no. 8
    
9.
Shah K, Segui D, Gonzalez-Arias S. Midline ligamentum flavum cyst of lumbar spine. World Neurosurg 2018;110:284-7.  Back to cited text no. 9
    
10.
Pindrik J, Macki M, Bydon M, Maleki Z, Bydon A. Midline synovial and ganglion cysts causing neurogenic claudication. World J Clin Cases 2013;1:285-9.  Back to cited text no. 10
    


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