The applause sign in elderly patients with idiopathic normal pressure hydrocephalus.

Applause sign (AS) was shown to be an indicator of frontal subcortical dysfunction in many neurodegenerative diseases. Idiopathic normal pressure hydrocephalus (INPH) is one of those in which frontosubcortical disconnection can be displayed. We aimed to examine the presence of AS in the elderly patients with INPH and its possible diagnostic role in the frontal dysfunction commonly seen in the disease. Sixty-six patients diagnosed with probable INPH, 32 with behavioral variant of frontotemporal dementia (bvFTD) and 325 healthy elderly subjects were included in this cross-sectional and retrospective study. AS was evaluated with the clapping test. Patients with INPH were further assessed with frontal assessment battery (FAB), Stroop test, verbal fluency test and clock drawing test (CDT). The concentration of total amyloid-β 42 (Aβ42), Aβ40, total (t) tau and phosphorylated (p)-tau proteins were also measured in the cerebrospinal fluid (CSF). AS was observed in all groups (40% in bvFTD, 28.8% in INPH, 1.2% in controls, respectively). It was significantly more frequent in patients with bvFTD and INPH as compared to the controls (p < 0.001, for each). The frequency was similar in the patients with bvFTD and INPH (p = 0.802). Significant differences were found between the AS(+) and (-) INPH patients with regards to FAB, Stroop test-errors and verbal fluency test, except for the CSF proteins. AS can be used as a simple, useful and rapid clinical test that investigates executive dysfunction in elderly patients with INPH in both inpatient and outpatient settings.