Challenges in Neuropsychological Improvement After Shunt Surgery for Idiopathic Normal Pressure Hydrocephalus

Objectives We sought to analyze cognitive performance and depressive symptoms of Idiopathic Normal Pressure Hydrocephalus (iNPH) patients three months after the shunt surgery. We assembled different neuropsychological tests into specific cognitive domains: Verbal Memory, Non-Verbal Memory, Executive Functions, Visuo-spatial Abilities, Language and Psychomotor Pace. Methods INPH patients underwent a complex neuropsychological assessment prior to the shunt surgery and three months after. We compared the results of cognitive performance before and after the shunt surgery in order to assess the effect of the surgery on cognition and depressive symptoms. Additionally, we compared the post-surgical cognitive performance of iNPH patients to age, sex- and education-matched group of healthy controls to see whether the iNPH patients reached the performance level of the normal population. Results Out of the 126 patients for suspected iNPH 33 patients met all the inclusion criteria. Additionally, we used 71 healthy controls. For the analysis of cognitive performance change after shunt surgery we found significant improvement in tests covering Verbal Memory ( p  = 0.033, p  = 0.043 and p  = 0.007) and Psychomotor Pace ( p  = 0.003). We found mixed results for tests covering Executive functions ( p  = 0.890, p  = 0.070, p  = 0.002). We found no improvement for the tests covering Non-Verbal Memory ( p  = 0.100, p  = 0.297), Language ( p  = 0.916, p  = 0.498) and Visuo-spatial Abilities ( p  = 0.483). We also found improvement in depressive symptoms ( p  = 0.020). For the analysis of the 3 months after surgery iNPH patients cognitive performance and control group cognitive performance we found all neuropsychological tests to significantly differ ( p  < 0.001). Conclusion Shunt surgery appears to have a positive effect on the neuropsychological performance of patients with iNPH. However, the improvement is limited. First, the effect does not appear to be comprehensive but rather restricted to certain neuropsychological domains. We observed improvements in the Verbal Memory and Psychomotor Pace domains, while results for Executive Functions were mixed—suggesting a positive effect on patients' ability to plan but no effect on their ability to shift. No effects were found for Visuospatial Abilities or Language. Second, the improvement appears to be limited in magnitude. Although overall performance improves three months after surgery, it still does not reach the level of healthy individuals. Nevertheless, the absence of worsening might also be seen as a positive effect. Interestingly, depressive symptoms followed a similar pattern to cognitive functioning before and after surgery. We found that shunt surgery significantly alleviated depressive symptoms.