4-year-old status post Chiari decompression. Evaluate Chiari and syrinx. There has been evolution of postoperative changes of Chiari decompression which included suboccipital craniectomy, C1 laminectomy, and reduction of cerebellar tonsillar tissue. There has also been evolution of the previously seen diffusion abnormality involving the inferior cerebellum. The cerebellar tonsils and cervicomedullary junction remain caudally displaced with persistent crowding at the foramen magnum at the C1-C2 level; retroflexed dens also contributes to the crowding. Cerebellar tonsils extend to the mid to lower C2 level on the right, previously at the C2-C3 level on preoperative study. There is interval decrease in T2/FLAIR signal abnormality involving the inferior cerebellum. No new parenchymal signal abnormality is seen. No suspicious intracranial mass, midline shift, or herniation. Ventricles remain normal in size. Subcentimeter pineal cyst is unchanged. Cystic arachnoid space extension superiorly along the anterior superior surface of the tentorium cerebell is also unchanged. Extradural suboccipital fluid collection is again seen and compatible with a pseudomeningocele. There is mild to moderate mucosal thickening in the right maxillary sinus which is increased in the interval. There is also mild additional scattered paranasal sinus opacification.CSF flow imaging again demonstrates focally attenuated biphasic flow through the anterior aspect of the foramen magnum, similar to prior. Flow through the posterior aspect of the foramen magnum is similar to recent prior but improved since preoperative MRI from 5/25/2016. There appears to be preserved flow into the fourth ventricle.MRI CERVICAL SPINE
1. Postoperative changes of Chiari decompression have evolved in the interval. The residual cerebellar tonsils and cervicomedullary junction remain caudally displaced with persistent crowding at the foramen magnum at the C1-C2 level, although improved compared to preoperative study. 2. There has been interval progression of cervical and partially imaged thoracic syringohydromyelia.