When i have deep muscle tissue spasms and pain, the physio sometime start with dry needles to loosen those deep muscle fibres before starting work. Its so they dont damage the outside muslce fibers trying to reach the real problem.
For me they used to start at the bottom of the back of my head and then work their way down my spine. It helps with pain caused by muscle stifness some times.
Hope this helps.

I had friend who had dry needling it made her worse.

I had dry needling and I didn't find any relief. Sorry, but everyone is different 😕