Cerebellar Tonsillar Cysts Associated with Chiari Malformation in Adults: A Short Series

Authors analyzed surgical patients with Chiari malformation (CM) associated with cerebellar tonsillar cyst. This association is quite rarely encountered in the literature.

We retrospectively reviewed 60 surgical adult patients with MRI evaluation who underwent posterior fossa decompression for treatment of CM type I. All surgeries were performed between January 1995 and July 2015. From 60 patients with CM, four cases presented cerebellar tonsillar cysts (male=2). Basilar invagination (BI) (n=4) and syringomyelia (n=1) were associated. There were pyramidal signs (n=4) and low cranial nerves dysfunction (n=1). Radiological evaluation showed T1-hypointense and T2-hyperintense image on the cystic tissue (n=4). The surgical technique was suboccipital craniectomy, C1-C2 laminectomy (if needed), y-shaped durotomy, total resection and coagulation/aspiration of tonsils.

In the present series, we were able to identify 7% of tonsillar cysts among 60 patients with CM. MRI with Flair and Diffusion sequences should be pre-operatively used for evaluation of tissue characteristics as differential diagnosis of cystic lesion and gliosis. The clinical presentation endorses surgical indication, with a good chance of clinical improvement. This was the first time that the frequency of tonsillar cysts has been evaluated in a series of adult patients.