Abstract
BACKGROUND: Bertolotti's syndrome (BS) is characterized by anomalous enlargement of the transverse process (TP) of the most caudal lumbar vertebra, which may articulate or fuse with the sacrum or ilium. OBSERVATIONS: A 69-year-old female presented to the hospital with a chief complaint of right low back pain (LBP) during rolling over, while crouching down, and with prolonged sitting. No obvious neurological abnormality was found. Radiography and CT findings revealed that the right TP of L5 articulated with the iliac bone. The patient's pain was resistant to conservative treatment with appropriate nonsteroidal anti-inflammatory drugs over a period of approximately 9 months. A local anesthetic injection into the articulated lesion under fluoroscopic guidance led to LBP improvement, but the effect was transient. Full endoscopic spine surgery (FESS) was performed to reduce the enlargement of the TP articulated with the ilium under fluoroscopy. Postoperative CT revealed the disconnection between the TP at L5 and the ilium. LBP dramatically resolved postoperatively, and the patient was discharged home without any perioperative complications. LESSONS: FESS may be an effective treatment for patients with LBP due to minimally invasive BS. https://thejns.org/doi/10.3171/CASE25188.