Thank you for posting your query at DoctorSpring.com.
I have noted your symptoms and CT scan findings.
Normally, the cerebellum (smaller brain located at the back of bigger brain) remains within the skull. In your case, a small part of cerebellum is coming down through the foramen magnum (opening in the skull bone). As a result, there is a risk of compression of lower brain (brainstem) and upper cervical spinal cord (cervical region). This condition is also called as Chiari malformation.
This can be confirmed by MRI brain and upper cervical spine.
If there is compression of brainstem or cervical cord, then a decompressive surgery may be needed. Otherwise, there is no need for surgery.
I hope it helps. Please get back if you have any more queries.
Dr. Sudhir Kumar MD (Medicine), DM (Neurology)
Senior Consultant Neurologist