Evaluation of coexistence of Alzheimer's disease in idiopathic normal pressure hydrocephalus using ELISA analyses for CSF biomarkers

Background: We investigated levels of the beta-amyloid 1-42 (A beta 42), total tau protein (T-tau) and tau phosphorylated at position threonine 181 (P-tau) in cerebrospinal fluid (CSF) of idiopathic normal pressure hydrocephalus (iNPH) patients and tried to find their clinical implications in the evaluation and treatment of iNPH. Method: Twenty-five possible iNPH patients were prospectively enrolled and their CSF was collected to analyze levels of A beta 42, T-tau and P-tau using ELISA method. Gait disturbance, urinary incontinence, and cognitive impairment were semi-quantified and detailed neuropsychological (NP) test was performed. Result: Eight iNPH patients were classified into the lower CSF A beta 42 group and 17 patients were classified into the higher CSF A beta 42 group. There was no difference in the iNPH grading score and its improvement after LP between the two groups. The lower CSF A beta 42 group showed more deficits in attention, visuospatial function and verbal memory in the baseline NP test and less improvement in phonemic categorical naming and frontal inhibitory function after LP. Conclusions: Our study suggested that concomitant AD in iNPH patients might contribute to lumbar puncture or shunt unresponsiveness, especially in the field of cognitive dysfunction.