The Impact of Alzheimer’s and Vascular Dementia on Shunt Outcomes in Idiopathic Normal Pressure Hydrocephalus: A Comparative Study

Introduction: Idiopathic normal pressure hydrocephalus (iNPH) is characterized by gait disturbance, urinary incontinence, cognitive decline, and ventricular enlargement with normal cerebrospinal fluid (CSF) opening pressure, with a prevalence of around 0.2% in individuals aged 70–79, rising with age. This study examines the impact of comorbidities on shunt outcomes and complications in iNPH

Methods: We conducted a systematic search of PubMed, Web of Science, Embase, and the Cochrane Library (up to October 2024) for studies reporting comorbidities associated with iNPH

Results: A total of twenty-one studies involving 1,394 elderly individuals with iNPH were included. Eleven studies addressed Alzheimer's disease (AD), while five focused on vascular dementia (VD). Although AD and VD pathology do not significantly affect initial responses to shunt surgery, patients with these comorbidities show poorer long-term outcomes and reduced cognitive improvements, particularly in executive functions. A high risk of dementia development is often linked to concurrent AD. Cortical biopsies indicated a 24% prevalence of AD-related neuropsychological findings, correlating with shunt outcomes. Despite these challenges, shunt surgery remains effective, significantly improving gait and urinary function. Key predictors of cognitive enhancement include baseline cognitive scores and age. Neuropsychological assessments, especially the EU-iNPH scale, help identify comorbidities and refine prognoses after CSF shunting. Noninvasive screening methods may improve evaluations, while cortical biopsies as a research tool provide insights correlating with clinical outcomes.

Conclusion : These findings underscore the impact of AD and VD on iNPH treatment outcomes. The high prevalence of AD contributes to variable shunt surgery success rates, with gait improvement at 64% in iNPH-only patients versus 41% in those with AD. Cognitive improvement was 40% in the iNPH group compared to 27% in the AD + iNPH cohort, highlighting the need for accurate diagnosis and targeted management of AD and VD in iNPH patients.