Comparing subjective measurements to objective kinematics after Deep Brain Stimulation and Ventriculoperitoneal shunting in patients with Parkinson’s disease and normal pressure hydrocephalus

Introduction: Patients with normal pressure hydrocephalus (NPH) and Parkinson’s Disease (PD) are treated surgically with ventriculoperitoneal shunt (VPS) and Deep Brain Stimulation (DBS), respectively. We sought to compare objective kinematic measurements of postural instability to subjective patient balance ratings using the Activities-specific Balance Confidence (ABC) scale after treatment.

Methods: 16 patients with PD, 5 patients with NPH, and 52 age-matched healthy controls underwent quantitative pull test examinations while wearing inertial measurement units at baseline. PD and NPH patients repeated testing 12 months post-operatively. ABC scales were administered at each appointment. Center of mass and foot position data were used to compare pull test step length and reaction times between groups. Mean ABC scores were compared.

Results: At baseline, PD patients had significantly slower reaction times than controls. At follow-up, they reacted significantly faster, no longer significantly different than controls. Pull test step lengths did not significantly change in PD patients and did not differ from controls at baseline or follow-up. NPH patients did not significantly differ in reaction time compared to controls at baseline or follow-up. They had significantly shorter step lengths than controls at baseline and significantly improved their step lengths from baseline to follow-up, where the follow-up step length was not significantly different from controls. ABC scores for PD patients were significantly lower than controls and did not significantly change from baseline to follow-up. NPH patients scored significantly lower on the ABC scale than both controls and PD patients but demonstrated a significant increase between baseline and follow-up.

Conclusion : NPH patients demonstrated both significant improvements in their step lengths and subjective balance scores. PD patients demonstrated a significant improvement in reaction time but did not improve subjective balance scores. This may indicate that step length, and not reaction time, is a key element of subjective balance rating.