Postoperative annular pseudocyst: report of two cases with an unusual complication after microdiscectomy, and successful treatment by percutaneous aspiration and steroid injection

BACKGROUND CONTEXT: After microdiscectomy for extruded disc fragments, patients may develop recurrent symptoms from numerous causes. Postoperative annular pseudocysts represent a unique entity not previously described in the medical literature. PURPOSE: To report unique imaging findings in two patients who presented with recurrent radiculopathic symptoms after microdiscectomy. To report successful percutaneous aspiration and steroid injection in one of these cases. STUDY DESIGN/SETTING: Report of two cases. METHODS: Two patients underwent preoperative imaging with noncontrast magnetic resonance imaging (MRI) and postoperative imaging with pre- and postcontrast MRI. One of these patients underwent therapeutic computed tomography (CT)-guided aspiration and injection. RESULTS: MRI demonstrated T2 hyperintense and enhancing collections, which conformed to the shape of the resected disc fragment and communicated with the disc annulus. One of these cases demonstrated enlargement over several months with worsening of symptoms. Aspiration of the lesion produced thick fluid. The patient experienced marked relief of symptoms after the aspiration and injection of steroid into the lesion. CONCLUSIONS: The unique imaging findings in these patients represent a previously undescribed complication of microdiscectomy, which we have termed "postoperative annular pseudocyst." We have successfully treated one case with CT-guided percutaneous aspiration and injection.