 There is redemonstration of postoperative findings related to suboccipital craniectomy for Chiari malformation, as well as resection of posterior arch of C1. Mild platybasia and retroflexion of the dens are again noted. The cerebellar tonsils are unchanged in appearance and positioning. There is stable posterior tenting of the cervicomedullary junction suggestive of adhesions. There remains moderate crowding at the level of the neoforamen magnum. Allowing for differences in technique, there is questioned interval diminished visualization of CSF signal dorsal to the cerebellar tonsils associated to the right of midline as seen on 301/30 compared to prior 401/26.There remains diminished CSF flow anteriorly at the craniocervical junction and slightly turbulent/asynchronous bidirectional flow just inferiorly at the level of the dens, appearing similar to prior exam. There is adequate CSF space posteriorly at the craniocervical junction, with stable to slightly improved biphasic flow visualized. The ventricles and sulci are stable. The basal cisterns remain patent. There is no midline shift or mass effect. There are no areas of abnormal signal. There is no diffusion abnormality. No extra-axial fluid collection is identified. Normal flow-voids are demonstrated in the major intracranial vascular structures. The midline structures are within normal limits. CERVICAL SPINE
1. No significant interval change in MR appearance of postoperative findings relating to prior suboccipital craniectomy with suggestion of possible adhesions along the cervicomedullary junction.2. Questioned slight decreased delineation of CSF signal dorsal to the cerebellar tonsils just to the right of midline, which could suggest additional adhesions.Stable configuration of retroflexed dens and mild platybasia resulting in diminished and minimally turbulent CSF flow ventrally with stable to slightly improved visualization of dorsal biphasic flow at this level. 