Ligamentum flavum cyst of lumbar spine: a case report and literature review

Abstract

Ligamentum flavum cysts have rarely been reported and known to be the uncommon cause of spinal compression and radiculopathy. A 63-year-old man presented right sciatica lasting for 1 month. Lumbar computerized tomography and magnetic resonance imaging demonstrated an extradural cystic mass adjacent to the L5-S1 facet joints. Partial hemilaminectomy and flavectomy at the L5-S1 space were performed, and then the cystic mass was excised. Histopathology confirmed a connective tissue cyst, which is consistent with the ligamentum flavum. Microscopic examination of the cyst wall revealed that it is closely packed collagen fibril. The symptom of patient was improved after surgery. Because of rarity of ligamentum flavum cysts and nonspecific clinical and radiologic findings, the preoperative diagnosis is not easy. The histologic features of ligamentum flavum cysts are distinct from other cystic lesion of lumbar spine. This study presents a case and literature review of ligamentum flavum cyst. We summarize the pathophysiology, occurrence, differential diagnosis of rare ligamentum flavum cyst, especially on lumbar spine.

Keywords: Cyst; Ligamentum flavum; Lumbar vertebrae.

Fig. 1

Lumbar axial computerized tomography (CT) on L5/S1 level showing the ruptured disc-like material, but is unsual isodensity mass within air density (A). CT after myelogram showing the extradural mass, locating ventrolateral area of right S1 root (B).

Fig. 2

T2-weighted sagittal magnetic resonance imaging (MRI) showing that the 1.2 cm sized cystic mass was disconnected the L5-S1 intervertebral disc and seemed to originate from facet or ligament flavum(A). T2-weighted axial MRI demonstrating the isointense mass. In addition, it compressing the thecal sac and right S1 nerve root (B).

Fig. 3

Intraoperative finding. The mass was originated from ligament flavum and contained cystic fluid. The mass was compressing the thecal sac and tightly adherent to dura.

Fig. 4

Photomicrograph of the surgical specimen showing cyst formation. The cyst wall (arrows) consists of fibrotic connective tissue without synovial lining (×200, H&E)