Case of the Week: Preoperative MR/CT Diagnosis of Left L2-L3 Disc Surgically Documented As Massive Synovial Cyst

BACKGROUND: The diagnosis of a lumbar herniated disc, stenosis, and other degenerative findings are typically established preoperatively with MR scans, supplemented with non-contrast CT studies. Here, a 77-year-old female, diagnosed as having L2-S1 stenosis and a large left-sided L2-L3 herniated disc was found at surgery to have a massive left-sided L2-L3 synovial cyst. CASE DESCRIPTION: A 77-year-old female was followed by pain management for 6-months with proximal left lower extremity weakness. The lumbar MR at that time was read as demonstrating a large left L2-L3 disc herniation with inferior migration to the L3 mid pedicle level, accompanied by L2-S1 lumbar stenosis. When she finally consulted neurosurgery, she exhibited severe left iliopsoas and quadriceps weakness (2/5), absent lower extremity reflexes, and profound decreased pin appreciation in the left L2-L3 distributions. The repeat MR and new CT studies confimred a large left L2-L3 disc accompanied by moderate/marked L2-S1 stenosis. However, at surgery, consisting of a laminectomy L2-S1, the supposed left L2-L3 disc proved to be a massive synovial cyst. Postoperatively, the patient regained normal function, and remained neurologically intact 6 months later. CONCLUSION: In this 77 year-old female, the preoperative MR and CT scans were interpreted as showing a “typical” large left L2-L3 herniated disc. This proved at surgery to be a massive left L2-L3 synovial cyst. As demonstrated in this case, older patients with degenerative lumbar disease/stenosis, may have synovial cysts that mimic disc herniations both clinically and on preoperative diagnostic studies.