Spontaneous regression of a subaxial cervical facet cyst

Abstract Subaxial cervical facet cyst is an extremely rare disorder. In previous reports, most cases were surgically treated. We describe a unique case involving the spontaneous regression of a subaxial cervical facet cyst. A 77-years-old man presented with gait disturbance, skilled finger movement disturbance, and numbness in the extremities. Magnetic resonance imaging (MRI) showed bilateral facet effusion and a facet cyst in the posterior epidural space at C4-5. He was diagnosed with myelopathy due to a subaxial cervical facet cyst. The Japanese Orthopaedic Association (JOA) score at the first visit was 8 points. Thereafter, the symptoms gradually improved with cervical orthosis and the JOA score improved to 13 points. The facet cyst observed in the first MRI scan disappeared on the second MRI scan. The JOA score was maintained at 2 years after discharge. The spontaneous regression of a subaxial cervical facet cyst on MRI with symptom relief observed in our case demonstrates the possibility of spontaneous regression of subaxial cervical facet cysts. Conservative treatment might be a treatment option for subaxial cervical facet cysts, especially in cases with radiculopathy in the middle cervical spine. However, the provision of early surgical treatment is important if the patient has acute myelopathy or if their neurological symptoms worsen over time.