Acetabular paralabral cysts demonstrating perineural propagation

Abstract

Objective: Acetabular paralabral cysts are common and are almost always associated with labral tears. Uncommonly, they extend into the periacetabular soft tissues or may propagate along peripheral nerves causing pain and hip dysfunction. The aim was to evaluate the clinical and MRI presentations of such cases including perineural propagation.

Methods: Retrospective cross-sectional study with a search of electronic health records for cases of acetabular paralabral cysts demonstrating perineural propagation was performed. Clinical and MR imaging features were tabulated after re-review by experienced musculoskeletal radiologists, and available outcomes were recorded. Descriptive statistics were performed.

Results: 14 cases were recorded. The mean age was 56.9 years (range = 30-79 years) and female:male ratio was 1:2.6. The commonest presenting complaint was hip pain (10/14, 71.4%). Other complaints included groin pain, perineal pain and hip dysfunction. No symptoms were attributed to the acetabular paralabral cyst in 3/14 patients (21.4%). None had foot drop. The cysts were multilocular in all cases and were homogenously T2 hyperintense in 13/14 (92.9%). Labral tears were identified in 11/14 cases (78.6%). The sciatic nerve was most commonly involved in 5/14 cases (35.7%) with the obturator, medial femoral cutaneous nerve, femoral nerve, superior and inferior gluteal nerves also affected.No intervention was undertaken in 9/14 cases (64.3%). 5/14 (35.7%) underwent image guided aspiration and corticosteroid injection. 4/5 such patients reported reduced pain following the procedure.

Conclusion: Paralabral cysts demonstrating perineural propagation are uncommon and exhibit varied presentations. Most patients who underwent image-guided or surgical interventions reported an improvement in symptoms.

Advances in knowledge.: This is the first description of a series of patients with acetabular paralabral cysts demonstrating perineural propagation in the literature. A comprehensive description of their clinical and imaging characteristics and interventions/outcomes where relevant is provided.

Figure 1.

40-year-old male. Axial fsPDW demonstrates a paralabral cyst arising from the labrocapsular junction of the right hip (small arrow) with medial extension and compression of the right sciatic nerve (long arrow). fsPDW, fat saturated proton density-weighted.

Figure 2.

46-year-old female. Figure 2A: Axial fsPDW image demonstrating a paralabral cyst (long arrow) arising from a posterior labral tear (small arrows) with posterolateral extension adjacent to the sciatic nerve (arrowheads).Figure 2B: CT image in prone position during cyst fenestration and attempted aspiration with 16G needle. Figure 2C. Follow-up axial fsPDW MR of left hip 2 years later shows resolution of the cyst with residual labral tear still present (small arrow). fsPDW, fat saturated proton density-weighted.

Figure 3.

56-year-old male. Figure 3A (axial) and Figure 3B (coronal) T ₂W images demonstrating a paralabral cyst (long arrows) arising posteriorly from the left hip joint extending towards the sciatic nerve (short arrows). T ₂W, T ₂ weighted.

Figure 4.

72-year-old male. Figure 4A (axial) and Figure 4B: (coronal) T ₂W images show a paralabral cyst arising medially from the left hip and extending alongside the obturator nerve (long arrow). The normal contralateral obturator nerve is identified for comparison (short arrow). T ₂W, T ₂ weighted.

Figure 5.

62-year-old male with right hip FAI and fibrocystic change at the femoral head-neck junction. Axial fsPDW image shows an anterior labral tear (small arrow) with a paralabral cyst propagating alongside right femoral nerve (long arrow). FAI, femeroacetabular impingement; fsPDW, fat saturated proton density-weighted.

Figure 6.

31-year-old female with left hip pain. Axial STIR image demonstrates a lobulated paralabral cyst arising anteriorly from the left hip joint and displacing the femoral neurovascular bundle. STIR, short tau inversion recovery

Figure 7.

Schematic diagram demonstrating the relationship between the (left) hip joint and major nerves in the vicinity.