Ida & Pingala (either side of the Sushumna)
 

I know that Sushumna runs up the center of the spine, and I know that Pingala terminates in the right nostril, while Ida terminates in the left. Here's my question: Does Ida also run up the left side of the back of the neck and into the base of the skull, while Pingala runs run up the right side of the back of the neck and into the base of the skull? Thanks.

this has an opinion. But personally I just experiment and don't worry about the opinions...

http://www.swamij.com/kundalini-awakening-3.htm