 There are interval post-operative changes related to suboccipital craniectomy with resection of posterior arch of C1 for Chiari decompression. The cerebellar tonsils are less peg-like and more rounded in configuration compared to the prior study. The inferior margin of the tonsils extend below the widely patent neo-foramen magnum and are at the level of the upper margin of the arch of the anterior C1.The cerebral hemispheres, cerebellar hemispheres and brainstem have otherwise normal morphology and signal characteristics. There is no evidence of intracranial hemorrhage or mass effect. The ventricles and basal cisterns are normal in size and configuration. There is no midline shift or herniation. Incidentally noted are several small pineal cysts. The skull and extracranial soft tissues are unremarkable. The CSF flow sequence reveals biphasic flow ventral to the cervicomedullary junction, but it is difficult to detect biphasic flow dorsally. CSF identified through the cerebral aqueduct and fourth ventricle.
1. Postoperative findings related to interval posterior fossa decompression for Chiari malformation with a more rounded configuration of the cerebellar tonsils, which now only extend to the upper margin of C2. 2. Adequate biphasic flow ventral to the cervicomedullary junction, but is difficult to detect dorsally. Please correlate clinically.