[boytos]

http://www.sofamed.com/images/collier-cervical.jpg

It seem to "atrophy" neck muscle

[Jomar]

I think if someone has severe neck spasms this would help to relieve the weight of the head off of those muscles for awhile.

But you wouldn't want to use it for long term or become totally dependent on it.

You would also have to address the muscles, tightness & spasms and then carefully get those muscles back into shape.

If the head is properly aligned with the body is will be balanced better & create less strain on the neck.
Look for Alexander technique books, articles , videos that explain this.