Spinal Cysts

Spinal cysts are benign, fluid-filled lesions that can develop at any level of the spine. They can often be asymptomatic for many years and its normal for them to vary in size and type. They can occur at any age, though are more common in over 50s  and overall there is no gender difference when it comes to who is affected.

What causes spinal cysts?

Some spinal cysts are congenital and arise from embryonic malformations while the foetus is still developing; others can manifest due to increasing instability of the spine. The cause of this instability can vary – conditions such as arthritis and disc disease are both known to frequently occur alongside spinal cysts.

Trauma can also cause cysts to form: this may be in the form of an infection, such as meningitis, injury – including trauma, haemorrhage – inflammation and surgery. The latter can be due to incidental damage from a tumour, a lumbar puncture, or the administration of spinal anaesthesia or contrasting dye into the subarachnoid space

What types of spinal cysts are there? A lot – but don’t worry, we’ll break it down!

We can classify spinal cysts in a number of different ways. For example, if we do this based  on their neighbouring anatomical relationships, we can divide them into:

• Discal cysts – these are uncommon and frequently resemble herniated discs
• Synovial cysts – also sometimes called a ganglion cyst – these arise at the facet joints of the spine and are most common in the lumbar region
• Perineural cysts – also known as Tarlov cysts – these form around the myelin sheaths of the spinal nerve roots and are the only cysts that form in the sacrum
• Extradural cysts – these form outside the dura that surrounds the spinal cord
• Intradural cysts – found inside the dura of the spinal cord
• Intramedullary cysts – developing in the medulla (innermost part) of the spinal cord

While clear, anatomy is not the only way in which we can categorise spinal cysts – we can also use the location of the cyst itself (bear in mind there is going to be some overlap here):

• Arachnoid cysts – found forming from the arachnoid membrane of the spinal cord
• Meninx cysts – arising from one of the meninges that surround the spinal cord
• Peripheral nerve cysts – these form around peripheral nerves exiting/entering the spinal cord
• Juxtafacet cysts – also known as synovial cysts, which we’ve just covered.
• Discal cysts – which we’ve also looked at previously
• Neuroenteric cysts – these are rare and arise from embryonic malformations that result in mucus secreting tissues (such as is found in the respiratory and gastrointestinal systems) developing in the central nervous system.
• Ependymal cysts – these develop from the ependyma; the epithelial tissue that lines the CSF drainage system of the central nervous system

Of all cysts we’ve just covered, arachnoid cysts are the most common, so we’ll focus on those for the rest of this read.

A little more on arachnoid cysts particularly

They are more common in men than women and are lesions filled with cerebro-spinal fluid (CSF). They can be congenital or trauma-related in origin and themselves can be split into five types, based on their relationship to the spinal cord and dura:

1. Intramedullary/syrinx
2. Subdural-extramedullary
3. Subdural-epidural
4. Intraspinal-epidural
5. Intraspinal-extraspinal

Of the arachnoid cysts, intraspinal-extraspinal cysts are the ones we see most often

Key Clinical Features of Spinal Cysts

Although there are a lot of different ways we can understand spinal cysts as we’ve just seen, thankfully their symptoms are all the same! They include:

• Gait ataxia (unsteady, staggered walking)
• Difficulty moving
• Scoliosis (abnormal curvature of the spinal column)
• Changes in bladder/bowel function
• Backache
• Radicular pain (from a pinched nerve) on one side
• Numbness/tingling
• Pain that worsens with posture and weight bearing
• Paralysis (though this is extremely rare)

Diagnosis of Spinal Cysts

Spinal cysts are frequently incidental findings – appearing on scans requested as part of a different investigation. These scans can be either Computed Tomography (CT) or Magnetic Resonance Images (MRI). On the image we will see a bubble-like growth, most clearly at the points where the vertebrae join.

Treatment of Spinal Cysts

Sometimes a cyst is asymptomatic, in which case it is left alone. In other instances, they can be managed conservatively, with medications such as anti-inflammatories or pain relief, as well as through routine drainage. Alternatively, surgical interventions may also be carried out; which procedure we choose will be based on the type, size and location of the cyst.

In the case of subarachnoid cysts, surgical management may include excision: where the entire cyst and its contents are removed via either a laminectomy or laminoplasty is done in order to permanently remove the pressure caused by the cyst on the spinal cord. In other instances, fenestration, where the cyst is opened so the fluid  may flow out (but the cyst itself remains in place), might also be an option. Additionally, we can also use shunting – with a cystoperitoneal shunt being inserted to relieve the pressure caused by the cyst via permanent drainage into the abdominal cavity.

Prognosis of Spinal Cysts

The outcome of both conservative and surgical treatment of symptomatic cysts are positive and patients usually make a full recovery. However, if untreated, the cyst will continue to expand and symptoms will worsen – with added potential of bleeding into the cyst itself, which will further  damage the spinal cord

Summary

Spinal cysts are non-malignant lesions and  have many different subtypes – the most common of which are arachnoid, intraspinal-extraspinal cysts. All cysts can be asymptomatic; those that are not we can managed either medically or surgically with a good outcome.

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References

Fam, M., Woodroffe, R., Helland, L., Noeller, J., Dahdaleh, N., Menezes, A. and Hitchon, P., 2018. Spinal arachnoid cysts in adults: diagnosis and management. A single-center experience. Journal of Neurosurgery: Spine, 29(6), pp.711-719.

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Healthline. 2021. Arachnoid Cysts | Definition and Patient Education. [online] Available at: https://www.healthline.com/health/arachnoid-cysts#outlook [Accessed 19 March 2021].

****Healthline. 2021. Perineural Cysts. [online] Available at: https://www.healthline.com/health/perineural-cysts#symptoms [Accessed 19 March 2021].

****Ninds.nih.gov. 2021. Arachnoid Cysts Information Page | National Institute of Neurological Disorders and Stroke. [online] Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Arachnoid-Cysts-Information-Page [Accessed 19 March 2021].

1. Spinal Cysts. [online] Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/spinal-cysts [Accessed 19 March 2021].

Spine, A., Lim, J. and Nguyen, B., 2021. Spinal Cysts: Symptoms, Causes and Treatment. [online] Atlantic Brain and Spine (en-US). Available at: https://www.brainspinesurgery.com/spinal-cysts/ [Accessed 19 March 2021].

Sun, J., 2016. Classification, mechanism and surgical treatments for spinal canal cysts. Chinese Neurosurgical Journal, 2(1).

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