Spinal hydatid disease is an uncommon manifestion of hydatid disease, caused by the larval stage of Echinococcus granulosus, or less commonly E. alveolaris or E. multilocularis, and describes a spectrum of disease involving the spinal cord, the spine, or both.
Hydatid disease is endemic in numerous regions of the world, including the Mediterranean region, the Middle East, Africa, the eastern part of Turkey, Australia and parts of South America 1,2. Spinal hydatid disease is uncommon and most commonly affects the thoracic spine, although any part of the spine can be affected 1,2.
Although often asymptomatic, clinical signs and symptoms often include 1-3:
- back pain
The most significant complication and presentation of spinal hydatid disease is spinal cord compression 1-3. Furthermore, rupture of a spinal hydatid cyst can result in a type 1 hypersensitivity reaction such as anaphylaxis 2.
Hydatid disease is acquired via contaminated food with eggs of the Echinococcus spp tapeworm 1,2. The oncospheres released from the eggs in the bowel enters the portal circulation, thus usually affecting the liver, but also affecting other sites via haematogenous spread 1,2.
Spinal hydatid disease is thought to occur via three possible mechanisms 1:
- haematogenous spread directly to spinal structures (most common)
- direct invasion from extraspinal structures
- infection secondary to cerebrospinal fluid seeding due to ruptured cysts of cerebral hydatid disease
Spinal hydatid disease can be anatomically classified according to the Dew/Braithwaite & Lees classification 1,4:
- type 1: intramedullary
- type 2: intradural, extramedullary
- type 3: extradural, intraspinal
- type 4: vertebral
- type 5: paravertebral
Under this classification, types 1 and 2 are very rare, with 90% of cases being instead confined to the bone and extradural space 1. However, multiple types can also co-exist 1.
Bony disease has very similar features to vertebral osteomyelitis, however, tend to not demonstrate any osteoporosis and sclerosis, and have an absence of damage to the vertebral discs 1,2,5. The cysts themselves have a similar density to cerebrospinal fluid and very rarely demonstrate calcification 6. CT may also reveal the underlying aetiology if spinal hydatid disease is secondary to direct invasion from extraspinal structures 1,2.
MRI is a more sensitive tool for diagnosing spinal hydatid disease 1,2. Generally, spinal hydatid cysts tend to have a tube-like shape, rather than the classic spherical-shaped cysts that are seen elsewhere in the body and do not have associated perilesional oedema 1,2. They also demonstrate similar signal characteristics to cerebrospinal fluid in all pulse sequences 1,2:
- T1: hypointense cyst with an iso- or hypointense cystic wall
- T1 C+: shows wall enhancement, although this may be subtle
T2: hyperintense cyst with a hypointense cystic wall
- Upon inactivation, it has been reported that cysts tend to lose their hyperintensity and their walls lose their hypointensity
Treatment and prognosis
The cornerstone of spinal hydatid disease management is surgery, the most common procedure being simple decompression with laminectomy 2,7. Surgery is often an emergency due to spinal cord compression either being the presenting feature of being an impending complication 2,7. Due to high rates of bone involvement in spinal hydatid disease, cyst rupture is often common during surgery which would allow for further seeding of the disease, and thus the spinal hydatid disease tends to be recurrent in nature 2. Pharmacotherapy, with agents such as albendazole, may have a role in reducing the risk of recurrence postoperatively 2.
Considerations include 1,2,5:
- 1. Neumayr A, Tamarozzi F, Goblirsch S, Blum J, Brunetti E. Spinal cystic echinococcosis--a systematic analysis and review of the literature: part 1. Epidemiology and anatomy. PLoS neglected tropical diseases. 7 (9): e2450. doi:10.1371/journal.pntd.0002450 - Pubmed
- 2. Pamir NM, Ozduman K, Elmaci I. Spinal hydatid disease. Spinal Cord. 40(4):153-60. doi:10.1038/sj/sc/3101214
- 3. Bhake A, Agrawal A. Hydatid disease of the spine. Journal of neurosciences in rural practice. 1 (2): 61-2. doi:10.4103/0976-3147.71715 - Pubmed
- 4. Braithwaite PA, Lees RF. Vertebral hydatid disease: radiological assessment. Radiology. 140 (3): 763-6. doi:10.1148/radiology.140.3.7280247 - Pubmed
- 5. Pedrosa I, Saíz A, Arrazola J, Ferreirós J, Pedrosa CS. Hydatid disease: radiologic and pathologic features and complications. Radiographics : a review publication of the Radiological Society of North America, Inc. 20 (3): 795-817. doi:10.1148/radiographics.20.3.g00ma06795 - Pubmed
- 6. Polat P, Kantarci M, Alper F, Suma S, Koruyucu MB, Okur A. Hydatid disease from head to toe. Radiographics : a review publication of the Radiological Society of North America, Inc. 23 (2): 475-94; quiz 536-7. doi:10.1148/rg.232025704 - Pubmed
- 7. Neumayr A, Tamarozzi F, Goblirsch S, Blum J, Brunetti E. Spinal cystic echinococcosis--a systematic analysis and review of the literature: part 2. Treatment, follow-up and outcome. PLoS neglected tropical diseases. 7 (9): e2458. doi:10.1371/journal.pntd.0002458 - Pubmed