Repetitive Transcranial Magnetic Stimulation?

or Deep Brain Stimulation (DBS)?

Executive function and working memory are the foundation of a coherent and meaningful life. Before considering surgical brain stimulation for depression and Parkinson's Disease, remember that Magnetic Brain Stimulation increases executive function while Surgical (DBS) impairs executive function

Although there is a role for both methods, Surgical (DBS) is a last resort - after all other options have been tried. Outpatient brain stimulation is one option to try before surgery. 

for more information - see the following

Pham (2015) Self-Reported Executive Functioning in Everyday Life in Parkinson's Disease after Three Months of Subthalamic Deep Brain Stimulation.

Yamanaka (2012) Temporary deterioration of executive function after subthalamic deep brain stimulation inParkinson's disease.

Adam (2012) Executive control in Parkinson's disease: effects of dopaminergic medication and deep brain stimulation on anti-cue keypress performance.

Smeding (2011) Predictors of cognitive and psychosocial outcome after STN DBS in Parkinson's Disease. 

Daniels (2010) Risk factors for executive dysfunction after subthalamic nucleus stimulation in Parkinson's disease. 

Zahodne (2009) Cognitive Declines One Year After Unilateral Deep Brain Stimulation Surgery In Parkinson’s Disease: A Controlled Study Using Reliable Change (Part I)

Mikos Cognitive declines after unilateral deep brain stimulation surgery in Parkinson's disease: a controlled study using Reliable Change  (Part II)

Witt (2008) Neuropsychological and psychiatric changes after deep brain stimulation for Parkinson's disease: a randomised, multicentre study.

Jahanshahi (2000) The impact of deep brain stimulation on executive function in Parkinson's disease.