Discal cysts (also known as a disk cyst or disc cyst) are uncommon lesions of the spine, representing an extrathecal cyst which communicates with the adjacent intervertebral disc through an annular fissure.
The vast majority of discal cysts, as rare as they are, have been reported in males (M:F 9:1), typically of Asian ethnicity 1,2. They are usually found in young adults 1,2.
Clinical presentation is indistinguishable from disc herniation with sciatica and back pain the most common presenting symptoms 2.
The aetiology of these discal cysts remains uncertain, but they are believed to occur due to traumatic disruption of the annulus with subsequent accumulation of fluid, which forms a surrounding pseudocapsule 1,2. In support of this theory is the fact that they are primarily encountered in young men, and are often haemorrhagic at surgery 1.
Disc cysts have been most commonly reported at the L4/5 level 1. MRI is required for assessment of these lesions.
Disc cysts appear as sharply circumscribed lobulated cystic lesions in the anterior epidural space communicating with the disc space via a stalk through an annular fissure.
Typical signal intensity is as follows 1:
- variable signal intensity
- usually hypointense
- usually hyperintense
- low signal rim
- occasionally a fluid/fluid or blood/fluid level is seen
- peripheral enhancement
If performed, contrast injected into the disc space passes into the cyst 1,2.
Treatment and prognosis
Treatment is not always required and discal cysts have been reported to spontaneously regress 1. Epidural steroid / local anaesthetic may be useful temporising measures.
CT guided aspiration has been reported 1. Microsurgical resection is the more common alternative if symptomatically required 1,2.
Imaging differential considerations include 1:
- synovial cyst: arises from facet joint, usually degenerate
- disc extrusion: contains nuclear material
- cystic neurofibroma
- Tarlov cyst: usually along nerve root, CSF intensity
- subacute epidural haematoma
- spinal anatomy
- congential abnormalities of the spine
- spinal infection / inflammation / degeneration
- intervertebral disc
- intervertebral disc disease nomenclature
- lumbar disc disease
- acute calcific discitis
- acute disseminated encephalomyelitis (ADEM)
- Charcot-Marie-Tooth disease
- HIV vacuolar myelopathy
- HTLV-1 associated myelopathy (tropical spastic paraparesis)
- multiple sclerosis
- neuromyelitis optica (NMO) - (Devic's disease)
- transverse myelitis
- SCA3 (Machado-Joseph disease)
- subacute combined degeneration of the cord
- subacute necrotizing myelopathy
- tabes dorsalis
- spinal ischaemia
- spinal trauma
- spinal tumours and cysts
- spinal vascular malformations
- 1. Diehn FE, Maus TP, Morris JM et-al. Uncommon Manifestations of Intervertebral Disk Pathologic Conditions. Radiographics. 2016;36 (3): 801-23. doi:10.1148/rg.2016150223 - Pubmed citation
- 2. Aydin S, Abuzayed B, Yildirim H et-al. Discal cysts of the lumbar spine: report of five cases and review of the literature. Eur Spine J. 2010;19 (10): 1621-6. doi:10.1007/s00586-010-1395-9 - Free text at pubmed - Pubmed citation