Hyperacute onset of adjacent segment disease with dorsally migrated herniated nucleus pulposus causing cauda equina syndrome: a case report.

Purpose: To report the first case of hyperacute onset of adjacent segmental disease (ASD) with dorsally migrated herniated nucleus pulposus (HNP) causing cauda equina syndrome.
Methods: A 55-year-old female complained of lower back pain with radiating pain in both lower extremities that had not responded to conservative treatment over the previous six months. Plain radiographs and magnetic resonance imaging (MRI) findings revealed degenerative spondylolisthesis with spinal stenosis at L3-4, L4-5, and a slight bulging disc at L2-3. The patient underwent decompressive total laminectomy and posterior fusion at L3-4 and L4-5. The stenotic symptoms improved significantly after surgery, and she was then discharged on postoperative day 7.
Results: However, the patient visited the emergency department four days after discharge (postoperative day 11) complaining of sudden onset of bilateral lower extremity weakness and voiding and defecation difficulties. The follow-up MRI showed dorsally migrated huge HNP and a detached posterior longitudinal ligament (PLL) at L2-3, which was diagnosed as hyperacute onset of ASD causing cauda equina syndrome. The patient underwent an emergency second operation consisting of partial laminectomy at L2-3 with removal of the dorsally migrated huge HNP. After the second operation, the symptoms of cauda equina syndrome improved. One year after the second operation, the patient is doing well without recurrence of symptoms.
Conclusions: Our case showed that hyperacute onset of ASD with dorsally migrated huge HNP can cause cauda equina syndrome, even within 2 weeks after lumbar fusion surgery. Therefore, a high index of suspicion, timely diagnosis, and surgical treatment are needed to avoid the catastrophic neurologic complications in similar extremely rare cases.