Symptomatic posterior fossa and supratentorial subdural hygromas as a rare complication following transarticular screw fixation with posterior wiring for atlantoaxial instability: A case report Rationale: Atlantoaxial transarticular screw fixation has been an effective and appealing method for inducing fusion of the C1-C2 complex. This technique is usually performed with Gallie fusion. In performing Gallie fusion using sublaminar wiring, a major concern is the risk of dural tear associated with passing sublaminar wires through the epidural space. We present the first report on symptomatic symptomatic subdural hygroma (SDH) due to transarticular screw fixation with posterior wiring. Patients concerns: A 50-year-old man had sustained dens fracture 20 years ago and presented with severe neck pain following a recent traffic accident. The images showed atlantoaxial instability due to nonunion of the dens fracture and the patient underwent transarticular screw fixation with posterior sublaminar wiring using Gallie technique. When the U-shaped wire was passed under the arch of C1 from inferior to superior, a dural tear and cerebrospinal fluid (CSF) leak occurred. The site of dural tear was repaired by direct application of sutures. The patient was discharged in good condition. Fifteen day after surgery, the patient was readmitted with a history of a progressive headache associated with vomiting and vertigo. Diagnonsis: Brain CT and MRI showed bilateral posterior fossa and a right-sided supratentorial SDH. Interventions: The patient underwent right occipital burr hole and evacuation of posterior fossa SDH due to deteriorating neurological status. Outcomes: The patient's condition gradually improved after the operation and became asymptomatic at 3-year follow-up. Lessons: Posterior fossa and supratentorial SDH could occur resulting from any intraoperative dural tear and CSF leakage during posterior cervical spinal surgery. Symptomatic SDH after posterior cervical spinal surgery should be cautiously assessed and treated. Level of Evidence: 5