Methods:
According to clinical features, assessment for the cause of cognitive decline and gait difficulty was performed. The brain CT scan showed significant ventriculomegaly (i.e. Evans index of 0.37) including third and fourth ventricles which was disproportionate to the amount of cortical atrophy (Figure 1). The other laboratory tests were in normal range including complete blood count, thyroid function tests, HIV antibody titer and vitamin B12 level. The clinical and imaging features were in favor of probable iNPH. Consequently, lumbar tap was performed two times that revealed significant change in gait after removal of approximately 30 ml of CSF. After the first trial of tap test, he can walk independently, which was more pronounced after the second trial. The speed and cadence of gait after first and second trial of tap test were noted in Table 1. The analyses of CSF markers were in normal range but the opening pressure was slightly elevated in two times of four lumbar puncture (Table 1).