The meth addict walk...?

You can spot a meth head from 200 yards away simply by their specific gait. Why do they all have the same strange walk? Does the meth affect a specific part of the brain that causes that gait?

Meth increases dopamine availability...

probably alters inhibition/disinhibition in the basal ganglia?

NerveBlock -

You can always tell just by the face. Meth rots out the jaw and teeth. They all have the same “skeleton” look to them. 

Yep, tweaker jaw.  400 faces a minute.