Neuronal correlates of movement disorders in normal pressure hydrocephalus (NPH)-before and after therapeutic lumbar puncture

Introduction: Normal pressure hydrocephalus (NPH) affects predominantly elderly people possing major impact gait problems which improve upon guidance.

Objective and Hypothesis: It has been hypothesised that reduced resorption of CSF leads to penetration into the frontal reducing the cerebral blood flow (CBF). We document blood-oxygen level dependend (BOLD)-signal changes with functional magnetic resonance imaging (fMRI) before and after lumbar puncture (LP). In order to explore the neuronal correlates, subjects were asked to perform imaginary foot movement and walking tasks. We expected a changed brain activity pattern after therapeutic LP procedure.

Methods: MR scans were performed at a 3T headscanner (Siemens Allegra, Germany) before and 3 days after LP. Before scanning, subjects were asked to walk with closed eyes (i) freely and (ii) guided. During scanning, patients performed the following tasks: (a) moving the right foot; (b) imagine moving the right foot; (c) imagine walking freely and (d) imagine guided walking. BOLD-MRI data were acquired with a standard EPI-sequence covering the whole brain prior and after LP analysed with SPM Ô.

Results: After LP, brain activation during imaginary tasks was observed in larger areas with a widespread and more pronounced interindividual pattern. We found activations in the hippocampal/parahippocampal region to be primarily associated with improvements in gait as well as in cognitive functions. Striatal activation was found in imaginary tasks (C and D) only after therapeutic LP.

Conclusion: Contrasting with hypothese of frontal lobe disturbances in our present data we indicate changed activation pattern in the hippocampal/parahippocampal region to correlate with improvements of gait function.