Hi and welcome to the Chiari forum.
May I ask what testing you have had ..obviously an MRI...was it cervical spine or brain ? And have you had the thoracic and lumbar spine MRI or a CINE MRI?
We all need to have many tests to see just how our Chiari is affecting us and our over all health....breathing issues is one that should raise a red flag....so be aware of your symptoms and any changes contact your Dr right away so he/she can determine what course of action is needed in your case. Drop attacks are another symptom to be aware of and contact the Dr if these should start.....
Our symptoms are due to the obstruction to CSF flow, and this obstruction can lead to the formation of a syrinx or Syringomyelia...which can compress the brain stem or spinal cord depending on location of the syrinx.
Again, more testing, and having the right Dr is key, you want a true Chiari specialist to help guide you through this.
Educate yourself on Chiari and ALL related conditions this will help you choose the right Dr for you.