Devoted to diagnostic and interventional spine imaging and therapeutics


Postoperative Annular Pseudocyst – Report Two Cases of an Unusual Complication Following Microdiscectomy, and Successful Treatment by Percutaneous Aspiration and Steroid Injection 2007

Interventional Spine

Phillip M Young, MD
Leo F Czervionke, MD, ASSR Member
Douglas S Fenton, MD, ASSR Member

Scientific Poster

Exhibit Panels: 1


Purpose: To describe two cases of patients presenting with recurrent symptoms following partial laminectomy and microdiscectomy for herniated disc material in which abnormal T2 signal and enhancement in the postoperative defect communicates with the disc space and conforms to the shape of the resected disc fragment and surgical bed. We have termed this "Postoperative Annular Pseudocyst" and performed successful percutaneous CT guided aspiration and injection in one case. These cases are described below.

Methods & Materials

Case 1:
A 60 year old male presented with worsening back pain and a right L4-L5 radiculopathy. MRI demonstrated a right L4-5 central/paracentral disc herniation with an inferiorly extruded fragment (Figure 1). Disc material caused moderate central canal stenosis and severe right lateral recess stenosis with compression of the right L5 and S1 nerve roots in the thecal sac. The patient subsequently underwent right L4-L5 hemilaminectomy with microdiscectomy.

MRI performed 13 months after surgery demonstrated T2 hyperintense scar and/or granulation tissue within the laminectomy defect extending into the posterolateral portion of the L4-5 intervertebral disc on the right (Figure 2). This tissue demonstrated contrast enhancement which extended into the posterior portion of the disc. In addition, enhancing tissue extended from the posterior disc margin into the epidural space and inferior to the disc on the right where it caused significant compression along the right ventral aspect of the thecal sac and posterior displacement of the right S1 nerve root. This tissue extending from the disc was heterogeneous in intensity. Disc biopsy was performed, and cultures were negative for aerobic, anaerobic, fungal, and mycobacterial organisms.

Case 2:
A 38 year old male presented with intractable left S1 radiculopathy. MRI of the lumbar spine demonstrated an extruded lumbar disc fragment in left L5-S1 lateral recess (Figure 3). The patient subsequently underwent successful partial L5 hemilaminectomy and discectomy at L5-S1. Initial relief of radiculopathy was excellent; however 17 months following surgery the patient presented with severe recurrence of symptoms.

MRI revealed a teardrop shaped fluid collection extending from the left posterolateral L5-S1 disc margin into the laminectomy defect (Figure 4). This collection conformed to the shape of the (removed) sequestered disc fragment seen previously. The fluid collection caused deformity of the left lateral aspect of the thecal sac and displaced the left S1 nerve root medially. The fluid collection also encroached on the medial aspect of the left L5-S1 neural foramen. Enhancing tissue was evidence along the margin of the fluid collection, likely representing scar and/or granulation tissue.


Treatment - Apiration and Therapeutic Injection:
Because of the patient's recurrent symptoms, therapeutic aspiration/injection was performed. The patient was placed prone on the table. A plastic grid was affixed to the patient's left lower back for localization purposes and initial axial CT scans were performed. Subsequently, the patient's left lower back was prepped and draped in sterile fashion. Subcutaneous and deep 1% lidocaine was instilled for local anesthesia. A small skin nick was performed. A 13.5 gauge styletted needle was advanced percutaneously
into the cystic lesion (Figure 5). The wall of this lesion was quite firm. Subsequently, approximately 1.25 mL of yellowish fluid was removed and sent for evaluation. Axial imaging was then performed which demonstrated decompression of the majority of the cyst. Subsequently, approximately 0.25 mL of Kenalog 40 mg/mL was instilled into the cyst. The needle was withdrawn outside the cyst wall and 0.5 mL Kenalog 40 mg/mL was instilled into the epidural space. No complications were observed during the procedure or immediately following. Followup interview with the patient indicates that he is doing very well following the procedure and feels brand new.


We hypothesize that these cases may represent the sequelae of granulation tissue and scar formation about extruded and sequestered disc fragments which is contiguous with the disc space. Following removal of the herniated disc material, if this scar tissue maintains communication with the disc, fluid may accumulate within this potential space, which can enlarge and cause symptoms from local mass-effect. We have termed this phenomenon "postoperative annular pseudocyst". We have successfully treated one case of this entity using CT guided percutaneous aspiration and injection.

Postoperative annular pseudocyst represents an unusual complication of herniated or sequestered disc pathology. Percutaneous aspiration and injection may be represent a potential therapy for this unusual entity.