Intracranial pressure parameters in idiopathic normal pressure hydrocephalus patients with or without improvement of cognitive function after shunt treatment.

BACKGROUND/AIMS: Previous research has shown improvements in the clinical triad (gait, incontinence and cognitive dysfunction) after shunt surgery in idiopathic normal pressure hydrocephalus (iNPH) patients with intracranial pulse pressure amplitudes >4-5 mm Hg, the pulse amplitudes being <4 mm Hg in the nonresponders. However, it is unknown whether similar differences exist regarding change in cognitive functioning after shunt surgery. The aim of this study was to compare preoperative intracranial pressure (ICP) parameters between iNPH that either improved or not improved in cognitive function after shunt treatment.

METHODS

Neuropsychological testing was performed before and after surgery in 27 consecutive iNPH patients treated with ventriculoperitoneal shunts. The ICP recordings were performed as part of routine preoperative assessment, stored as raw data files, and analyzed retrospectively. The mean ICP as well as single ICP wave amplitudes were computed and analyzed in consecutive 6-second time windows.

RESULTS

Significant improvement in neuropsychological tests, defined as a 4-point improvement in Folstein Mini-Mental State Examination or improvement by one standard deviation in 50% of subtests of Dementia Rating Scale, was found in 12 patients (44%; shunt responders). In these patients, mean ICP was similar though the mean ICP wave amplitude was significantly higher than in the shunt nonresponders.

CONCLUSIONS

While preoperative mean ICP was similar, the mean ICP wave amplitudes were considerably higher in iNPH patients with significant change in cognitive function following shunt surgery.