Delayed diagnosis of occult upper cervical ligamentous instability after initially negative CT and MRI following high-energy trauma: a case report

Background: Traumatic upper cervical ligamentous instability is an uncommon but potentially devastating consequence of high-energy trauma. Predominantly ligamentous injuries may remain occult despite initially reassuring computed tomography (CT) and magnetic resonance imaging (MRI) findings, particularly when pre-existing degenerative disease complicates interpretation. Case presentation: A 68-year-old man sustained a tractor rollover injury and was initially neurologically intact. CT showed no acute fracture or traumatic malalignment, and the craniocervical junction was interpreted as intact. MRI did not demonstrate definite ligamentous or spinal cord injury, but it showed C1–C2 degenerative disease, retro-odontoid pannus, and mild prevertebral and paraspinal edema. After imaging clearance, the cervical collar was removed. Six weeks later, progressive neck pain, Lhermitte’s sign, tinnitus, right-sided hyperesthesia, Hoffmann’s sign, and gait difficulty prompted repeat imaging. CT showed foramen magnum narrowing and increased dens-atlas distance, concerning for ligamentous injury. MRI demonstrated cervicomedullary compression and cord signal abnormality. He underwent closed reduction, occiput-to-C4 posterior fusion, C1 laminectomy, and foramen magnum decompression, with substantial improvement. Clinical discussion: Occult upper cervical ligamentous instability may occur despite normal or near-normal static craniometric findings. This case highlights the diagnostic challenge posed by ligamentous injury superimposed on advanced degenerative disease, with discordant imaging. Conclusion: Progressive occipitocervical pain or neurologic findings after high-energy trauma should prompt repeat imaging and urgent spinal evaluation for occult upper cervical instability, despite initially reassuring studies.