Predicting dementia severity changes after shunt surgery for idiopathic normal-pressure hydrocephalus: Role of the tap test and cognitive assessments.

OBJECTIVE

To determine the most appropriate assessment scale and timing of the tap test for predicting improvements in dementia severity after shunt surgery in patients with idiopathic normal-pressure hydrocephalus (iNPH).

METHODS

Data were extracted from an observational study that followed patients with iNPH as follows: Patients diagnosed with possible iNPH and scheduled for a tap test were enrolled. Patients diagnosed with probable iNPH by the tap test underwent shunting and followed up for 3 months after shunting. Patients with missing data in the tap test assessment items (gait speed: 3 consecutive days before tapping and 3 consecutive days after tapping; cognition: before tapping, 1 day after tapping and 1 week after tapping; and urinary dysfunction: before tapping and 1 week after tapping) or in the Clinical Dementia Rating (CDR) assessed before tapping and 3 months after shunting were excluded from this study.

RESULTS

54 patients were included in the analysis. The change in CDR-Sum of Boxes (CDR-SoB) score after shunt surgery was significantly correlated with the change in Mini-Mental State Examination (MMSE) score (β = -0.417, p < 0.001) and Frontal Assessment Battery (FAB) score (β = -0.379, p = 0.002) 3 months after shunt surgery after adjusting for age and sex. The change in MMSE score after shunt surgery was correlated with the change in MMSE score 1 day after tapping (β = 0.411, p = 0.001), the change in the minimum Timed Up and Go test score across repeated tests after tapping (β = -0.376, p = 0.004) and attention/concentration in Wechsler Memory Scale-Revised 1 day after tapping (β = -0.289, p = 0.024). The change in FAB score after shunt surgery was correlated with the change in the maximum FAB score across repeated tests after tapping (β = 0.523, p < 0.001).

CONCLUSION

Combining MMSE and FAB assessments during the tap test may yield more useful information in assessing cognitive impairment than using either MMSE or FAB alone.