Effect of neurostimulation on camptocormia in Parkinson's disease depends on symptom duration

Although some reports on neurostimulation are positive, no effective treatment method for camptocormia in Parkinson's disease (PD) is known to date. We aim to identify prognostic factors for a beneficial DBS effect on camptocormia. In an observational cohort study, we investigated 25 idiopathic PD patients, who suffered additionally from camptocormia, and underwent bilateral neurostimulation of the subthalamic nucleus (STN) to improve classical PD symptoms. Using an established questionnaire, we examined deep brain stimulation (DBS) effects on camptocormia in addition to general neurostimulation effects. A beneficial neurostimulation effect on camptocormia was defined as an improvement in the bending angle of a least 50%. In 13 patients, the bending angle of camptocormia improved, in 12 patients it did not. A multifactorial analysis revealed a short duration between onset of camptocormia and start of neurostimulation to be the relevant factor for outcome. All patients with duration of camptocormia up to 1.5 years showed a beneficial effect; patients between 1.5 and ∼3 years showed mixed results, but none with a duration of more than 40 months improved except for 1 patient whose camptocormia was levodopa responsive. The bending angle was not a prognostic factor. Our data indicate that the main prognostic factor for a beneficial DBS effect on camptocormia is its short duration. As an explanation, we suggest that neurostimulation may improve camptocormia only as long as muscle pathology is limited. Our findings may help to elucidate the mode of action of neurostimulation. A prospective study is necessary.