Canis ISSN: 2398-2942

Spine: arachnoid cyst

Synonym(s): Meningeal cyst, Leptomeningeal cyst

Contributor(s): Laurent Garosi


  • Spinal arachnoid cysts have been reported with increasing frequency in dogs. A similar lesion is also seen in humans.
  • The term arachnoid cyst is misleading as there is extramedullary expansion and cord cavitation rather than cyst formation.
  • Additionally, there is no epithelial lining to the cyst.
  • Intradural arachnoid diverticulae is the preferred terminology.
  • Rare lesion most frequently at C1-C5 and T3-L3.
  • Cause: a congenital etiology for lesion is most likely, although trauma has been implicated in both humans and dogs. It is possible that abnormal cerebrospinal fluid dynamics contribute to cyst formation.
  • Signs: spinal cord lesion.
  • Diagnosis: myelography or MRI.
  • Treatment: usually responds to decompressive surgery.
  • Prognosis: potential for recurrence.



  • Most likely a congenital defect that expands during life.
  • CSF is forced into the cyst during normal CSF pulsations or during periods of increased CSF pressures such as occurs with abdominal straining, coughing.


  • Arise from developmental abnormality of the arachnoid architecture.
  • Duplicating or splitting of the arachnoid membrane is postulated during embryonic development which may allow for its expansion throughout life, progressively displacing spinal tissue.
  • Some propose a CSF-flow disturbance arising from a functional one-way valve at the cranial entrance to the lesion that opens periodically with fluctuations in CSF pressure.
  • Accumulation of cerebrospinal fluid (CSF) → pressure on meninges and local interference with spinal cord → signs referable to cord segment affected → progressive clinical deterioration as cyst enlarges further damaging cord.
  • The most common area of the spine affected is the cervical region, and the second most common area is the thoracic region.
  • The very large majority are in the dorsal or dorsolateral aspect of the spinal cord. Only a small minority are in a ventral or ventrolateral location.
  • Acquired arachnoid diverticulae have been suggested secondary to intervertebral disk disease Intervertebral disk: type 1 herniation Intervertebral disk: type 2 herniation , spinal cord trauma Spinal cord: concussion , and inflammatory spinal cord disease Spinal cord diseases: overview.


  • A slow progressive condition over several weeks.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Oxley W, Pink J (2012) Amelioration of caudal thoracic syringohydromyelia following surgical management of an adjacent arachnoid cyst. JSAP 53 (1), 67-72 PubMed.
  • Jurina K, Grevel V (2004) Spinal arachnoid pseudocysts in 10 rottweilers. JSAP 45 (1), 9-15 PubMed.
  • Gnirs K, Ruel Y, Blot S et al (2003) Spinal subarachnoid cysts in 13 dogs. Vet Radiol Ultrasound 44 (4), 402-408 PubMed.
  • Skeen T M, Polby N J, Muñana K R et al (2003) Spinal arachnoid cysts in 17 dogs. JAAHA 39 (3), 271-282 PubMed.
  • Rylander H, Lipsitz D, Berry W L et al (2002) Retrospective analysis of spinal-arachnoid cysts in 14 dogs. JVIM 16 (6), 690-696 PubMed.
  • Frykman F O (1999) Spinal arachnoid cyst in four dogs: diagnosis, surgical treatment and follow-up results. JSAP 40 (11), 544-549 PubMed.
  • Ness M G (1998) Spinal arachnoid cysts in two Shih Tzu littermates. Vet Rec 142 (19), 515-516 PubMed.
  • Cambridge A J et al (1997) Radiographic diagnosis - arachnoid cyst in a dog. Vet Radiol Ultrasound 38 (6), 434-436 PubMed.
  • Vernau K M et al (1997) Magnetic resonance imaging and computed tomography characteristics of intracranial intra-arachnoid cysts in 6 dogs. Vet Radiol Ultrasound 38 (3), 171-176 PubMed.
  • Hardie R J, Linn K A & Rendano V T (1996) Spinal meningeal cyst in a dog - a case report and literature review. JAAHA 32 (6), 477-480 PubMed.
  • McKee W M & Renwick P W (1994) Marsupialisation of an arachnoid cyst in a dog. JSAP 35 (2), 108-111 VetMedResource.
  • Bentley J F, Simpson S T & Hathcock J T (1991) Spinal arachnoid cyst in a dog. JAAHA 27 (5), 549-551 VetMedResource.
  • Dyce J, Herrtage M E, Houlton J E F & Palmer A C (1991) Canine spinal 'arachnoid cysts'. JSAP 32 (9), 433-437 VetMedResource.
  • Parker A J, Adams W M & Zachery J F (1983) Spinal arachnoid cysts in the dog. JAAHA 19 (6), 1001-1008 VetMedResource.
  • Parker A J & Smith C W (1974) Meningeal cysts in a dog. JAAHA 10, 595-597.
  • Gage E D, Hoerlein B F & Bartels J E (1968) Spinal cord compression resulting from a leptomeningeal cyst in a dog. JAVMA 152 (11), 1664-1670 PubMed.

Other sources of information

  • Le Couteur R & Child G (1989)diseases of the Spinal Cord.In:Textbook of Veterinary Internal Medicine.Ed S J Ettinger. Philadelphia: W B Saunders. pp 686-687.