Longitudinal improvement in postural instability is distinct from gait in treated adult hydrocephalus

Background: Ventriculoperitoneal shunting improves gait in patients with normal pressure hydrocephalus. Postural instability is a major concern, but mostly ignored in the evaluation and treatment of these patients. This study quantified postural instability using kinematics via a prospective cohort design. Methods: Seventeen patients with suspected normal pressure hydrocephalus and twenty age-matched, healthy controls underwent quantitative pull test and gait examinations while wearing inertial measurement units at baseline. Patients with suspected normal pressure hydrocephalus who were shunted (n=13) and not shunted (n=4) underwent further testing after a lumbar drain trial and at follow-up visits 6 and 12 months post-operatively. Results: While most gait improvement in patients who were shunted was seen immediately after the lumbar drain trial, measures of their postural response continued to improve after the lumbar drain trial through one year of follow-up. Patients who were not shunted showed no statistically significant changes in gait and postural instability measures. Conclusions: After shunting, postural instability improves continuously over one year. In contrast, a large improvement in gait is seen immediately with minimal change over the subsequent year. This difference in timing may implicate two distinct neurophysiological mechanisms of recovery and provides novel evidence that postural instability improves in response to long-term CSF diversion.