[Observational study on the coincidence of Alzheimer's disease and idiopathic normal pressure hydrocephalus: analysis of coincidence, the influence on response to cerebrospinal fluid drainage and cerebrovascular copathology].

Abstract

Objective: Analysis of the frequency of comorbid Alzheimer's disease in patients with suspected idiopathic normal pressure hydrocephalus (iNPH) and its effects on the response to cerebrospinal fluid (CSF) drainage as well as analysis of the frequency of a vascular copathology in patients with suspected iNPH.

Material and methods: This was a prospective observational analysis of patients with suspected iNPH who underwent guideline-conform NPH routine diagnostics including CSF drainage during clinical routine diagnostics between 1 July 2022 and 30 June 2023. Patients were recruited via the departments of neurology, neurosurgery and psychiatry of the University Hospital Carl Gustav Carus in Dresden. Typical NPH imaging results were acquired from available magnetic resonance imaging (MRI) and computed tomography (CT) sectional images. Relevant sociodemographic, clinical, cognitive and CSF diagnostic parameters were acquired via patient chart review. The patients were categorized with respect to the CSF results according to the amyloid-tau-neurodegeneration (ATN) classification.

Results: During the observational period 33 patients (14 female, 19 male, mean age 74.6 ± 8.1 years) with suspected iNPH were analyzed. Of the patients 19 (57.6%) had a complete and 14 (42.4%) an incomplete Hakim's triad. The difference between the MoCA scores before and after CSF drainage varied between patients with and without a response to CSF drainage (F(1;22) = 5.725; p = 0.026). There was a trend that patients with a pathological corpus callosum angle and conspicuous Evans index (p = 0.052) as well as patients with a pathological corpus callosum angle, Evans index and complete clinical Hakim's triad (p = 0.055) more frequently show a response. The mean Fazekas score was 1.7. There was no correlation between the Fazekas score and response to CSF drainage. In 25 patients (75.8%) biomarkers for dementia and neurodegeneration were detected. According to the ATN classification 20 patients (80%) were categorized as A⁺T^-, 3 (12.0%) as A⁺T⁺ and 2 (8.0%) as A^-T^-. Patients classified as A⁺T⁺ and A⁺T^- did not respond more often to CSF drainage (p = 0.600).

Conclusion: The combined determination of the corpus callosum angle and the Evans index as well es their contextualization with clinical characteristics can possibly improve the prognostic evaluation regarding response to CSF draínage. Especially a comorbid amyloid pathology and a cerebral microangiopathy represent frequent copathologies of iNPH but the influence on the response to CSF drainage remains to be elucidated.