Juxtafacet cysts

Etiology and Pathogenesis

The formation of juxtafacet cysts is directly related to wear and tear of the spinal joints. Degenerative changes lead to excessive mobility and instability of the facet joints. As a result, the joint capsule is damaged, forming tears through which the synovial membrane (synovium) protrudes outward, forming a cystic cavity.

The appearance of such lesions is facilitated by concomitant pathologies:

• prior trauma;
• spondylolysis;
• chondrocalcinosis;
• Baastrup's disease (so-called "kissing spines").

Interestingly, in the cervical spine, half of such lesions originate from the cruciate ligament of the atlas (cruciate ligament of the atlas), although they are generally uncommon in the cervical and thoracic regions.

Symptoms and Localization Patterns

In most cases, the cyst grows from the posterior wall of the joint outward from the spinal canal. However, in approximately 20% of cases, it is directed anteriorly and grows into the spinal canal, which is fraught with compression of neural structures.

The clinical presentation largely depends on the level of the lesion:

• Lumbar spine: cysts are most common here. They compress the dural sac (thecal sac) or nerve roots in the lateral recesses (lateral recesses). This causes severe pain and radicular syndrome. Inflammation often develops around the lesion, provoking sciatica (sciatica). Large cysts can cause spinal stenosis and neurogenic intermittent claudication (neurogenic claudication).
• Cervical spine: radiculopathy develops extremely rarely.

These lesions almost never resolve on their own. One of the formidable complications is hemorrhage into the cyst cavity. This leads to its sharp enlargement and the progression of severe neurological symptoms literally within a few months.

Diagnostic radiology

Neuroimaging methods are the mainstay of diagnosis.

Magnetic resonance imaging (MRI) is the gold standard (the method of choice). An intraspinal cyst appears as a well-circumscribed epidural mass near the facet joint. Specific MRI signs:

• The rim surrounding the cyst demonstrates low signal intensity (hypointense, especially on long TR/TE sequences), but actively takes up contrast (gadolinium).
• The signal intensity of the contents on T1 and T2 is close to cerebrospinal fluid (CSF).
• If blood breakdown products are present inside the cyst (following hemorrhage), the signal on T1 and T2 will be high.

Computed tomography (CT) demonstrates a low attenuation mass (low attenuation) adjacent to the joint. Characteristic findings may include gas bubbles within the cavity and eggshell calcification of the wall (eggshell calcification).

If MRI or CT findings are inconclusive regarding whether the cyst communicates with the joint space, CT arthrography may be ordered.

Differential diagnosis

Juxtafacet cysts must be differentiated from other mass lesions located in the posterior and lateral compartments of the spinal canal. Similar signal characteristics on MRI can be seen in:

• discogenic cysts and sequestered disc herniations;
• cysts of the ligamentum flavum;
• arachnoid cysts and infectious processes;
• tumors (e.g., schwannomas or neurofibromas with signs of cystic degeneration).

Crucial diagnostic criterion: in juxtafacet cysts, degeneratively altered facet joints will always be visible on imaging.

Cysts of the Ligamentum Flavum

These lesions (Cysts of the Ligamentum Flavum) closely resemble juxtafacet cysts in imaging features and localization (frequently found at the L4-L5 level), but have a different origin.

They form within the ligamentum flavum itself (or are partially embedded in it) and are not directly connected to the facet joints. Their developmental mechanism involves ligamentous hypertrophy, myxoid degeneration or necrosis, and microhemorrhages. As a result, small cysts form, which can eventually merge into a single large one. This pathology is quite rare.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Indications for surgical excision of the cyst versus conservative therapy
• Features of the MRI appearance of blood breakdown products at various stages
• Baastrup's disease and its role in the formation of synovial cysts
• Technique for performing facet joint CT arthrography
• Mechanism of neurogenic intermittent claudication development in cysts

Other topics in the "Spine" section

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