Billy, that is the rule of thumb, EXCEPT for tremor dominant type Parkinson's. If you are truly tremor dominant (tremor was your first & worst symptom), then DBS will probably work to improve symptoms, whether or not your tremor improved with Sinemet (C/L). According to my neurologist, the tremor of most tremor dominants does not respond to Sinemet. Mine, for example, never did & I am not alone. Just another reason to respect the fact that PD comes in different flavors for different people. We are not all the same.