Key clinical milestones 15 years and onwards after DBS-STN surgery-A retrospective analysis of patients that underwent surgery between 1993 and 2001.

Objective: Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for motor fluctuations in Parkinson's disease (PD), but does not halt disease progression. The long-term deterioration of key functions such as cognition, speech, ability to swallow, gait, urinary bladder control, orientation and reality perception is decisive for patients' independency in daily life. In this paper we investigated patients with advanced PD operated at our center with STN-DBS for at least 15 years ago, in respect to key clinical milestones reflecting their overall function in daily living.

Patients And Methods: Retrospective analysis of clinical data concerning key clinical milestones including death in PD-patients, 15 years or more after they underwent STN-DBS surgery. All PD-patients implanted with STN-DBS at Sahlgrenska Hospital before January 1, 2001, were regularly assessed until death, drop-out, or January 11, 2016.

Results: Sixteen men and seven women with a median (range) disease duration of 18 (10-28) years were operated with STN-DBS. The median (range) follow-up time post-surgery was 12 (2-18) years and 692 person-years of disease duration were observed. In January 2016, nine PD-patients (39%) were still alive (eight with active STN-DBS). Initially, motor symptoms improved in all patients. Sustained benefit (implying active stimulation at the last follow up) was maintained in 19 of them (83%) but STN-DBS was inactivated in four (17%) due to inefficacy. Over time, all patients deteriorated slowly, and a majority developed severe non-motor and axial symptoms such as dementia, inability to talk, swallow and walk, urinary incontinence, psychosis, and need for nursing home care. At the last follow up, 16/23 (70%) patients were treated with antidepressants.

Conclusion: A majority of PD-patients experience sustained motor benefit with continuous STN-DBS. However, over time, non-motor and axial symptoms slowly and severely restrict PD-patients' function in their daily living.