No abstract

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.

Peripheral artery disease (PAD) results from atherosclerotic plaque deposition on arterial walls causing reduced blood flow to affected tissue and can result in pain, tissue loss, poor wound healing, limb loss, and death. Diagnosis of PAD and clinical assessment of these patients requires the use of a vascular Doppler device. By emitting an ultrasound signal when placed over an artery and measuring the Doppler shift of the signal reflected from moving blood cells, this device produces an audio output descriptive of several blood flow parameters. As shown through multiple rounds of clinician interviews, current vascular Dopplers are expensive, bulky, and lack objective signal analysis. An improved vascular Doppler offering solutions to these problems was designed and prototyped. This prototype demonstrated a reduction in cost and comparable signal quality compared to Doppler devices currently available, and offered an opportunity for future development of automated signal analysis capabilities.

Background: Quantitative biomarkers are needed for the diagnosis, monitoring and therapeutic assessment of postural instability. Objective: Create a practical and objective measure of postural instability using kinematic measurement of the pull test to incorporate into clinical practice. Methods: Twenty patients evaluated and treated for normal pressure hydrocephalus were tested over a number of sessions. Patients were fitted with 15 inertial measurement units during each session. At each session, the patient underwent 10-20 pull tests performed by a trained clinician. The clinician purposefully induced a range of perturbations during each session to assess the patient's step response. Kinematic data was extracted for each pull test and aggregated. Results: Patients participated in 57 sessions for a total of 860 trials and were separated into groups by pull test score. The center of mass velocity profile easily distinguished between groups such that score increases correlated with decreases in peak velocity and later peak velocity onset. All patients except those scored as "3" demonstrated an increase in step length and decrease in reaction time with increasing pull intensity. Groups were distinguished by differences in overall step length or reaction time regardless of pull intensity (y-intercept). A logistic regression model including only kinematic variables identified three kinematic factors that could be used to identify trials in which patients needed to be caught (i.e. "fell"). Conclusion: An instrumented, purposefully varied pull test produces kinematic metrics useful for distinguishing clinically meaningful differences between and within NPH patients. These metrics should be followed prospectively to examine fall risk.