Hello and welcome to health care magic,
You need to know that I do understand that you are concerned but your anxiety
and worry will only cause increased problems and symptoms.
Chiari though can run in the family is a rare condition and it is unfortunate that your brother died because of improper post op care. In any case it is treatable and you have nothing to worry about.
Meanwhile to put your mind at peace I would advice you to take a CT Brain and Ct Temporal bone
and get back to me or any ENT with the reports
Dr Sriram nathan