Social Adjustment and Executive Function after STN Surgery; Caudal Zona Incerta Stimulation

Subject: Social Adjustment and Executive Function after STN Surgery; Caudal Zona Incerta Stimulation

Date: 7/5/2006

1. Neurosurgery in Parkinson’s disease: A distressed mind in a repaired body?
M Schupbach, M Gargiulo, ML Welter; L Mallett, C Behar, JL Houeto, D Maltete, V Mesnage, Y Agid
Neurology 2006;66:1811-1816

Despite excellent motor and ADL improvement, social adjustment after STN-DBS surgery may worsen in some patients, according to this study.

Twenty-nine patients undergoing STN-DBS were evaluated pre-operatively and at 18 to 24 months post-operatively. UPDRS motor and ADL scores each improved significantly, and neuropsychological status remained unchanged. Repeated open, unstructured interviews were conducted by psychologists, neurologists, and a psychiatrist, and patients were evaluated on the Social Adjustment Scale, whose six subdomains include income, work, social life, family, couple, and children. As a group, there were no significant changes in the SAS as a whole or for any subdomain. However, this lack of mean change reflected a combination of worsening in some patients and improvement in others in several subdomains, including work and couple. Overall, 8 patients improved, 10 did not change, and 11 worsened in their overall social adjustment.

Individual patient experiences discussed in the report included:
--3 patients who had difficulty accepting the presence of an electronic device in their brain.
--19 patients who experienced a feeling of strangeness (“I haven’t found myself after the operation”).
--12 patients who experienced a loss of vitality, including 5 who became frankly apathetic. Ten patients had increased vitality.
--Increased awareness of the impact of PD disease progression.
--Reluctance to resume former activities, despite improved physical ability.
--Loss of aim in life.

Effects on the couple were profound in some cases, with 3 divorces within the follow-up period, and significant marital stress in 17 cases (12 of 24 couples were already in crisis before surgery). More than half the spouses were disappointed by the results of the surgery, and were disconcerted by the patient’s post-operative struggle to adjust. Effects on attitudes toward work were also significant, with 5 patients choosing not to return to work, and 5 feeling unable to return to work.

The authors conclude, “in spite of the excellent motor outcome, it is clear that the operation can result in poor adjustment of the patient to his or her personal, family, and socio-professional life. Whether this is a purely reactive response to a new situation or whether it is caused by an effect of the STN stimulation on behavior, or both, remains to be elucidated.”

2. Neuropsychological effects of bilateral STN stimulation in Parkinson disease: A controlled study
HMM Smeding, JD Speelman, M Konig-Haanstra, PR Schuurman, P Nijssen, T van Laar, B Schmand
Neurology 2006;66:1830-1836

Bilateral STN-DBS may worsen executive function, according to this study.

Ninety-nine patients undergoing bilateral surgery were evaluated before and 6 months after electrode implantation, with a battery of neuropsychological tests, and compared to a group of 36 patients not undergoing surgery. Compared to the control group, the STN-DBS group had a greater decline in verbal fluency, color naming, selective attention, and verbal memory. They displayed a decrease in positive affect, and an increase in emotional lability and cognitive complaints. Nonetheless, surgical patients had an improved quality of life, and a slight decrease in depressive symptoms.

“The most parsimonious explanation for the decrease in verbal fluency and selective attention, and to a lesser extent for the decrease in verbal recall and color-naming speed, seems to be executive dysfunction,” the authors conclude. Regarding the costs and benefits of the operation, they state: “Cognitive decline, if apparent, was of concern to the patients, but the advantages in daily life resulting from the improved motor functioning usually made up for it. Conversely, in some of our patients cognitive of emotional changes led to an evident step backwards in daily life. If they had known this beforehand, they would not have decided positively for surgery. This was more often expressed by relatives than by the patients themselves.”

3. Stimulation of the caudal zona incerta is superior to stimulation of the subthalamic nucleus in improving contralateral parkinsonism
P Plaha, Y Ben-Shlomo, NK Patel, SS Gill
Brain 2006;129:1732-1747

Stimulation of the caudal zona incerta improves motor scores more than stimulation of the STN, according to this study. The cZI is the motor component of the zona incerta nucleus, and lies posterior to the STN.

Comparison of contralateral motor scores was performed after implantation of 64 leads in 35 patients: 17 in the STN (group 1), 20 dorsomedial to the STN (group 2), and 27 in the cZI (group 3). Results showed:
--Motor score reductions were 55%, 61%, and 76% respectively (p<0.001).
--Tremor reduction was 61%, 86%, and 93% (p=0.01).
--Rigidity reduction was 50%, 52%, and 76% (p=0.002).
--Bradykinesia reduction was 59%, 56%, and 65% (p=0.17).
--There were no significant differences in dyskinesia scores, levodopa reduction, or stimulation parameters.