Assess the utility of Delphi as an alternative for CSF tap test in prediction of response to ventriculoperitoneal shunt (VPS) in normal pressure hydrocephalus (NPH).

NPH is a condition of disturbed CSF dynamics, defined by a clinical triad of gait disturbance, urinary complaints, and cognitive decline, in the presence of hydrocephalus. Current treatment is implantation of a VPS, which is indicated followed an improvement on a CSF tap test (removal of 30-50 ml of CSF while measuring change in "Timed Up and Go (TUG)"). This in an invasive test with several drawbacks. There is an ongoing need for a safer, objective procedure to allow clinicians more precise prediction of treatment response.

Twenty "probable NPH" patients and 20 age matched healthy controls underwent a neurological exam, cognitive evaluation and brain MRI scans.  

All subjects performed Delphi, a non-invasive measure that probes brain network response, through induction of focused magnetic stimulation over selected brain networks, while simultaneously measuring the brain electrophysiological response. A subset of subjects which underwent VPS were evaluated for their symptoms 1-3 months following the operation.

Significant differences were measured in Delphi Waveform Adherence (WFA) between NPH patients from age matched HC (p<0.01) in response to primary motor cortex stimulation and lower motor threshold (p<0.01). Delphi WFA and the Interhemispheric Coherence (IHC) of Delphi waveform in response to M1 stimulation at baseline, was highly correlated to the change in symptoms post VPS (r=-0.84, p=0.02 and r=-0.92 p=0.0007 respectively) as opposed to CSF Tap test (r=-0.58, p=0.18) which did not show significant correlation.

These results demonstrate Delphi’s potential superiority in the prediction of VPS effect in NPH. If verified in a larger sample this might pose Delphi as a substitute diagnostic test for NPH and an enhanced predictive tool for the response to VPS thus enabling better patient management.