Significant Association of Slow Vasogenic ICP Waves with Normal Pressure Hydrocephalus Diagnosis

We aimed to test whether there is an association of slow vasogenic wave (SVW) occurrence with positive response to external lumbar drainage (ELD) and ventriculoperitoneal shunting and to design a method for the recognition and quantification of SVWs in the intracranial pressure (ICP) signal.

We constructed SVW templates using normalized sine waves. We calculated the cross-correlation between the respective SVW template and the ICP signal. This was followed by shifting the templates forward and performing the cross-correlation analysis again until the end of the recording. Cross-correlation values above a threshold were considered to be indicative of SVWs. This threshold was previously determined and validated on a sample of ICP records of six patients. We calculated the root mean square of the recognized SVW periods as a measure of signal strength. Time-averaged signal strength was calculated over the full recording time (ICP_Smean) and over the wave periods (ICP_S).

We determined ICP_S and ICP_Smean in recordings of 2 groups of patients presenting with Hakim's triad: 26 normal pressure hydrocephalus (NPH) patients and 20 non-NPH patients. We then tested whether there was an association between ICP_S or ICP_Smean and the respective diagnosis using a Mann-Whitney test. We found significant association between ICP_S (p = 0.014) and ICP_Smean (p = 0.022) and the diagnoses.

The described method based on pattern recognition in the time domain is suitable for the detection and quantification of SVWs in ICP signals. We found a significant association between the occurrence of SVWs and independent NPH diagnosis.