[Pallidal and subthalamic stimulation in Parkinson's disease: lessons from the unsatisfactory results]

Deep brain stimulation is being widely used in advanced Parkinson's disease (PD). Outcome determinants are not known.

Some relevant data about outcome may be obtained from the study of patients with unsatisfactory results.

We have retrospectively analyzed the number and causes of unsatisfactory results (insufficient improvement 6 months after the intervention) in 211 patients.

Forty patients (18.9%) experienced an unsatisfactory result. Inadequate clinical selection by advanced age, abnormal MRI and levodopa unresponsive symptoms was the main cause in 28 cases. In 11 patients a misplacement of the electrode was reported. In 2 cases no cause was identified. Thirty-four out of the 40 patients corresponded to the early experience of the teams involved in the study.

We conclude that the main factors responsible for a negative outcome are related to the inadequate clinical selection of the patients and the incorrect placement of the electrode. The experience of the team may also be a key factor.