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BACKGROUND: Idiopathic normal pressure hydrocephalus (iNPH) is typically manifested in people over 65 years. The condition of gait disturbances, incontinence, and cognitive dysfunction can be reversed in up to 80% of the cases by ventricular shunting. Neuropsychological testing and standardized brain imaging of signs of iNPH are essential to detect and define the progression. The aims of this thesis were to develop a radiological iNPH scale, examine how morphological features relate to symptoms of iNPH, investigate if dual-task testing (e.g., walking and talking) is helpful in detecting iNPH, and monitor developing symptoms over two years.

METHOD: The studies include 168 participants (median [range] age 73 [66–92]) at baseline (2014/2015) and 104 participants (age 75 [68–91]) at follow-up (2016/2017) from the general population. Neuropsychological tests of executive functions, memory, and motor performance, and computed tomography (CT) for brain imaging were used.

RESULTS: Seven morphological features were combined into a scoring scale for iNPH. The total score correlated with clinical symptoms (r = -0.40, p <.001). All core symptoms were associated to wider temporal horns (TH) (p <.01). Participants with iNPH stopped walking to talk more frequently (p = .044). Participants who developed iNPH during the study worsened more on declarative memory (ES -0.37).

DISCUSSION: The Radscale was related to symptoms of iNPH and the TH to all main clinical features. Difficulties walking while recalling a previous event, worsened declarative memory, and expanding ventricular space surrounding the hippocampus were noticeable signs of iNPH. Memory functions are important to recognize in iNPH.