Balance in idiopathic normal pressure hydrocephalus: microstructural brain correlates and relation to Alzheimer’s biomarkers.
Giulia Bommarito, Alessandra Griffa, Stéphane Armand, François Herrmann, Frederic Assal, Dimitri Van De Ville, Gilles Allali- Psychiatry and Mental health
- Cellular and Molecular Neuroscience
- Geriatrics and Gerontology
- Neurology (clinical)
- Developmental Neuroscience
- Health Policy
- Epidemiology
Abstract
Background
Patients with idiopathic normal pressure hydrocephalus (p‐iNPH) present with balance impairment, which contribute to falls and could improve after cerebrospinal fluid shunting procedure. Structural brain correlates of balance in iNPH have not been investigated yet. Moreover, as gait, balance changes after shunting could be affected by Alzheimer’s disease (AD) biomarkers. The aim was to assess the relationship between postural control and brain structural damage or AD biomarkers in p‐iNPH before and after CSF tap test (CSFTT), a prognostic test to predict response to shunting.
Method
thirty‐eight healthy controls (HC) and 23 p‐iNPH were consecutively recruited and underwent balance assessment, and MRI including diffusion weighted images before and after CSFTT (data after CSFTT available for 19 p‐iNPH). Center of pressure (COP) trajectories parameters and diffusion metrics were derived in both groups, during eyes open (EO) and eyes closed (EC) conditions. AD biomarkers were available for p‐iNPH. Repeated‐measures ANOVA (with one within‐subjects factor: EC/EO, and one between‐subjects factor: group) was used to compare posturographic measures. Non‐parametric correlation analysis was used to assess their relatioship with WM tracts diffusion metrics and AD biomarkers.
Result
COP speed in the antero‐posterior direction and sway area were worse in p‐iNPH compared to HC, and during EC compared to EO condition (group x factor interaction: F(1,59) = 5.02, p = .029 and F(1,59) = 4.95, p = 0.30, respectively), Fig.1. Orientation dispersion index and intracellular volume fraction of forceps minor and anterior thalamic radiation, tracts already related to balance in ageing, positively correlated to COP parameters during EC task in p‐iNPH (0.43<R<0.48, 0.02<p<0.046) and negatively in HC (‐0.44<R←0.21, 0.005<p<0.195). The relationship inverted after CSFTT in p‐iNPH, with a negative correlation found between sway area and forceps minor ODI (R = ‐0.47, p = .050), Fig.2. In p‐iNPH, no significant correlation was found between amyloid‐beta or phosphorylated‐tau and changes in posturography parameters after CSFTT (Fig.3).
Conclusion
postural control is impaired in p‐iNPH, especially during EC condition, suggesting an altered somatosensory function integration. Such impairment relates to microstructural damage of periventricular tracts, with a partial normalization of the relationship after CSFTT. Changes in balance after CSFTT do not seem to be affected by AD biomarkers.