High Yield Overview

Lumbar Synovial Cysts

Facet Joint Pathology | Cause of Radiculopathy | Indicator of Instability

L4/5Most Common Level

65yoPeak Age

40%Associated Spondylolisthesis

50%Recurrence (Aspiration)

Classification (Pathological)

Synovial Cyst

PatternLined by synovial cells. Communicates with the facet joint. Associated with instability.

TreatmentResection +/- Fusion

Ganglion Cyst

PatternNo synovial lining. Degenerative mucinous degeneration. Less common communication.

TreatmentResection

Ligamentum Flavum Cyst

PatternDegenerative cyst within the ligamentum flavum. Can mimic synovial cyst.

TreatmentResection

Critical Must-Knows

Synovial cysts are a marker of underlying FACET JOINT INSTABILITY.
They most commonly occur at L4/5 (the most mobile segment).
Spontaneous resolution is rare but possible (cyst rupture).
Aspiration/Injection has a high failure/recurrence rate (~50%).
Surgical excision is curative, but may require FUSION if frank instability (spondylolisthesis) is present.

Examiner's Pearls

"
Pain is often postural (worse standing/walking) - mimicking Neurogenic Claudication.
"
Unilateral Radiculopathy is the most common presentation.
"
Look for 'Fluid Sign' on MRI (Hyperintense T2) - confirms fluid content.
"
Calcified cysts (Hypointense T2) are adherent and difficult to resect.

Surgical Risks

At a Glance

Synovial Cyst vs Disc Herniation

Feature	Synovial Cyst	Disc Herniation
Location	Posterolateral (Dorsal to nerve)	Anterior (Ventral to nerve)
Origin	Facet Joint	Intervertebral Disc
Signal (T2)	Bright (Fluid) or Dark (Calcified)	Dark (Dessicated nucleus)
Association	Spondylolisthesis (Instability)	Degenerative Disc Disease

Mnemonics

Mnemonic

CYSTCyst Characteristics

Communicate

Connects with facet joint

Yields

Yields to pressure (fluctuant) or Calcified

Spondylolisthesis

Associated with instability

T2 Bright

High signal on MRI

Memory Hook:Key imaging features.

Mnemonic

SIPTreatment Hierarchy

Steroid

Injection (Diagnostic/Therapeutic)

Intervention

Aspiration / Rupture

Procedure

Surgical Decompression (+/- Fusion)

Memory Hook:Stepwise management.

Mnemonic

FACETSynovial Features

Fluid

T2 Bright

Adherent

Stuck to dura

Communication

With joint

Extradural

Location

Thecal

Compression

Memory Hook:Pathological features.

Overview and Epidemiology

Pathophysiology and Mechanisms

The Facet Joint

Synovial joint heavily innervated by medial branch nerves.
The cyst typically arises from the medial aspect of the joint.
Occupies the Posterolateral epidural space.

Relationship to Nerve Root

Compresses the nerve root from Posterior to Anterior.
(Contrast with Disc Herniation which compresses Anterior to Posterior).
Clinical Note: This makes the nerve root very superficial during surgery - Risk of injury mainly during initial exposure.

Instability Link

L4/5 is the most mobile lumbar segment.
Degenerative Spondylolisthesis is present in up to 40-50% of cases.
The cyst is the body's attempt to stabilize the joint ("Hydraulic Splint").

Classification Systems

Pathological Classification There is no widely used clinical classification (e.g. AO Spine) specifically for synovial cysts. They are classified based on Pathology or Location.

True Synovial Cyst:
- Lined by synovium (cuboidal or pseudo-stratified epithelium).
- Clear communication with the joint space.
- Often reducible with positioning.
Ganglion / Pseudocyst:
- No synovial lining but fibrous connective tissue capsule.
- Contains mucinous fluid.
- Often due to myxoid degeneration of the collagen in the joint capsule or Ligamentum Flavum.
- Less likely to reduce.

Clinical Assessment

History

Radiculopathy: Unilateral leg pain (Sciatica).
Neurogenic Claudication: Pain worse with walking/standing (Stenosis).
Postural: Often relieved by sitting (flexion opens the canal).
Acuity: Can be acute (bleeding into cyst) or subacute/chronic.

Examination

Lasegue's Sign: Straight leg raise may be positive.
Motor/Sensory: Deficit corresponding to the level (e.g. L5 EHL weakness).
Kemp's Test: Extension/Rotation often exacerbates facet pain.

Imaging and Investigations

Diagnostic Protocol

X-RayStability Check

AP/Lateral.
Flexion/Extension Views: CRITICAL to rule out dynamic instability (Spondylolisthesis).
Look for: Facet hypertrophy, vacuum phenomenon.

MRIGold Standard

T2 Weighted: Hyperintense (Bright) = Fluid.
T1 Weighted: Hypointense. High signal may indicate hemorrhage (subacute).
Gadolinium: Rim enhancement is typical (inflammation).

CT MyeloAlternative

Used if MRI contraindicated.
Shows "filling defect" in the dye column.
Good for visualizing calcification of the cyst wall.

Management Algorithm

Clinical Algorithm— Cyst Management

Loading flowchart...

Surgical Technique

Micro-decompression / Cyst Resection

Indication: Stable joint (No slip), Leg pain dominant.
Technique:
1. Midline approach or Tubular.
2. Laminectomy / Medial Facetectomy.
3. Identify cyst (often purple/blue color).
4. Dissect plane between Dura and Cyst. CAUTION: Often very adherent.
5. Excision.
Cons: Risk of recurrence or iatrogenic instability.

Complications

Complication	Risk	Note
Dural Tear	High (5-10%)	Higher than disc herniation due to inflammatory adhesions.
Recurrence	10-20%	If decompressed alone without fusion.
Instability	Variable	Post-facetectomy slip progression.
Incomplete Relief	5%	Especially if calcified cyst wall left behind.

Postoperative Rehab

Hospital Stay

Decompression: Day Case or Overnight (23hr stay).
Fusion: 2-3 Days.

Restrictions

Decompression: No heavy lifting (over 10kg) for 6 weeks (Risk of recurrent herniation/cyst through annulotomy if done).
Fusion: Brace optional (surgeon preference). No bending/twisting/lifting (BLT) for 6-12 weeks until fusion mass forms.

Red Flags in Recovery

Positional Headache: Potential CSF leak/pseudomeningocele.
Return of Radiculopathy: Early recurrence or hematoma.
Fever/Wound Ooze: Infection (Discitis).

Outcomes and Prognosis

Conservative: Spontaneous regression is rare.
Injection: Temporary relief in 50%. High recurrence. Good for temporary pain control or poor surgical candidates.
Surgery:
- Over 90% satisfaction for leg pain relief.
- Fusion provides lower recurrence rates than decompression alone (Xu et al).

Evidence Base

Fusion vs Decompression

Xu et al • Spine (2010)

Key Findings:

Compared decompression alone vs decompression + fusion.
Fusion group had significantly lower recurrence rate (0% vs 1.8%).
Fusion group had significantly lower re-operation rate.
Back pain relief was superior in the Fusion group.

Clinical Implication: Fusion is favored if ANY element of instability exists.

Cyst Rupture Outcomes

Martha et al • Spine J (2009)

Key Findings:

Review of percutaneous cyst rupture.
50% of patients needed surgery within 6 months.
Repeat injections provided diminishing returns.
Concluded it is a temporizing measure only.

Clinical Implication: Counsel patients that injections are likely temporary.

Cyst vs Disc

Bydon et al • Neurosurgery (2013)

Key Findings:

Synovial cysts are more likely to present with back pain than disc herniations.
Re-operation rates were higher in the cyst group (unless fused).
Dural tear rates were significantly higher (9.6% vs 2.1%).

Clinical Implication: Pre-operative warning about Dural Tear is mandatory.

Natural History of Synovial Cysts

Khan AM et al • J Spinal Disord Tech (2006)

Key Findings:

Spontaneous regression rare (under 5%)
Most cysts enlarge or remain stable over time
Progressive neurological deficit occurs in 15% without treatment
Mean time to surgery from diagnosis is 8 months

Clinical Implication: Expectant management rarely succeeds - plan intervention if symptomatic

Minimally Invasive vs Open Decompression

Shen J et al • Spine J (2015)

Key Findings:

MIS tubular decompression with similar outcomes to open
Shorter hospital stay (1.2 vs 2.8 days)
Less blood loss and muscle damage
Similar recurrence rates when facet preserved

Clinical Implication: MIS approach is safe alternative when fusion not planned

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

The 'Stable' Cyst

EXAMINER

"65M, L4/5 Synovial Cyst causing L5 radiculopathy. Flexion/Extension X-rays show NO slip. What surgery do you offer?"

EXCEPTIONAL ANSWER

This is a controversial area. 1. **Option A (Decompression Alone)**: Micro-decompression and cyst excision. - *Pros*: Minimally invasive, quick recovery, outpatient. - *Cons*: 10% risk of recurrence, 5% risk of slip progression. 2. **Option B (Fusion)**: TLIF. - *Pros*: Definitive. - *Cons*: Overkill for a 'stable' spine? **My Approach**: In a 65M with no instability, I would offer **Micro-decompression** first, with counseling about the 10% re-do rate. Fusion is reserved for recurrence or overt instability.

KEY POINTS TO SCORE

Define Stability (Dynamic X-rays)

Balance morbidity vs durability

Consent for Dural Tear (Adhesions)

COMMON TRAPS

✗Fusing everyone (Overtreatment)

✗Missing the dynamic slip on X-ray

VIVA SCENARIOStandard

Intra-op Dural Tear

EXAMINER

"During resection of an L4/5 cyst, you encounter a dural tear. The cyst wall was adherent. What is your management algorithm?"

EXCEPTIONAL ANSWER

**Recognition**: Identify the CSF leak. **Management**: 1. **Exposure**: Ensure adequate bony exposure to see the edges of the tear. 2. **Primary Repair**: 4-0 Nurolon/Prolene running locking suture. 3. **Adjuncts**: Patch (Duragen), Glue (Tisseel). 4. **Valsalva**: Check repair under pressure. 5. **Post-op**: Flat bed rest (24-48hrs). Drain management (off suction or no drain).

KEY POINTS TO SCORE

Adherent cysts = High risk

Adequate exposure is key to repair

Don't ignore it

COMMON TRAPS

✗Stuffing gelfoam and hoping (Will form pseudomeningocele)

✗Leaving suction drain on full, sucking nerve roots out

MCQ Practice Points

Diagnosis

Q: What MRI finding distinguishes a synovial cyst from a ganglion cyst? A: Communication with the facet joint. (Though clinically managed similarly).

Level

Q: Which spinal level accounts for over 75% of synovial cysts? A: L4/5. It is the level of maximal mobility/instability.

Location

Q: Where are these cysts typically located relative to the thecal sac? A: Posterolateral. Compressing the traversing nerve root in the lateral recess.

Outcome

Q: What is the recurrence rate after percutaneous aspiration? A: ~50%. It is high.

Pathology

Q: What does the presence of a synovial cyst imply about the facet joint? A: Instability. It is a marker of hypermobility.

Australian Context

Epidemiology

Increasing prevalence with ageing population.
Common referral to public hospital outpatients, often managed with steroid injections initially to delay surgery.

Exam Day Cheat Sheet

Cyst Summary

High-Yield Exam Summary

Key Facts

•L4/5 Most Common
•Marker of Instability
•Adherent to Dura
•High recurrence with aspiration

Imaging

•T2 Hyperintense (Fluid)
•T1 Hypointense
•Posterolateral location
•Facet OA

Treatment

•Conservative (rarely works)
•Injection (Temorizing)
•Decompression (Stable)
•Fusion (Unstable)

Risks

•Dural Tear (High)
•Recurrence (10%)
•Iatrogenic Instability
•Infection (Discitis)

Image Manifest

[4-magnetic-resonance-imaging-revealed-a-15-cm-intras.png]: Intrasacral Cyst showing compression
- [5-sagittal-t2-weighted-mri-images-showing-sequential.png]: Axial T2 MRI showing lateral recess compression

Feature

Synovial Cyst

Disc Herniation

Location

Posterolateral (Dorsal to nerve)

Anterior (Ventral to nerve)

Origin

Facet Joint

Intervertebral Disc

Signal (T2)

Bright (Fluid) or Dark (Calcified)

Dark (Dessicated nucleus)

Association

Spondylolisthesis (Instability)

Degenerative Disc Disease

Complication

Risk

Note

Dural Tear

High (5-10%)

Higher than disc herniation due to inflammatory adhesions.

Recurrence

10-20%

If decompressed alone without fusion.

Instability

Variable

Post-facetectomy slip progression.

Incomplete Relief

Especially if calcified cyst wall left behind.

Fusion vs Decompression

Xu et al • Spine (2010)

Key Findings:

Compared decompression alone vs decompression + fusion.
Fusion group had significantly lower recurrence rate (0% vs 1.8%).
Fusion group had significantly lower re-operation rate.
Back pain relief was superior in the Fusion group.

Clinical Implication: Fusion is favored if ANY element of instability exists.

Cyst Rupture Outcomes

Martha et al • Spine J (2009)

Key Findings:

Review of percutaneous cyst rupture.
50% of patients needed surgery within 6 months.
Repeat injections provided diminishing returns.
Concluded it is a temporizing measure only.

Clinical Implication: Counsel patients that injections are likely temporary.

Cyst vs Disc

Bydon et al • Neurosurgery (2013)

Key Findings:

Synovial cysts are more likely to present with back pain than disc herniations.
Re-operation rates were higher in the cyst group (unless fused).
Dural tear rates were significantly higher (9.6% vs 2.1%).

Clinical Implication: Pre-operative warning about Dural Tear is mandatory.

Natural History of Synovial Cysts

Khan AM et al • J Spinal Disord Tech (2006)

Key Findings:

Spontaneous regression rare (under 5%)
Most cysts enlarge or remain stable over time
Progressive neurological deficit occurs in 15% without treatment
Mean time to surgery from diagnosis is 8 months

Clinical Implication: Expectant management rarely succeeds - plan intervention if symptomatic

Minimally Invasive vs Open Decompression

Shen J et al • Spine J (2015)

Key Findings:

MIS tubular decompression with similar outcomes to open
Shorter hospital stay (1.2 vs 2.8 days)
Less blood loss and muscle damage
Similar recurrence rates when facet preserved

Clinical Implication: MIS approach is safe alternative when fusion not planned