A new scale for assessment of severity and outcome in iNPH.

OBJECTIVE: To present a new, continuous, calibrated and norm-based scale for the grading of severity and assessment of treatment outcome in idiopathic normal pressure hydrocephalus (iNPH).

PATIENTS AND METHODS: A scale designed for the assessment of the four domains, gait, neuropsychology, balance and continence, using ordinal ratings and continuous measures, was developed. Data from a series of 181 consecutive iNPH patients were used to calibrate the continuous parts of the scale and to describe the distributional properties of the ordinal ratings. Data from normative studies were used to determine the limits for normal scores.

RESULTS: The construction of the scale made it well equipped to separate iNPH patients at baseline, and the total scores assumed a bell-shaped, approximately normal distribution. All four domain scores correlated significantly with each other, underscoring the well-known syndromatic nature of iNPH, and justifying the use of a total score to describe the patients. Reliability [Cronbach's α for the total score = 0.74, and for the domains of gait and neuropsychology, 0.86 and 0.89, respectively) and validity estimates (convergent validity evaluated by Spearman rank correlations for the scale and the modified Rankin scale (ρ = -0.61) and the mini mental state examination (ρ = 0.57)] are satisfying.

CONCLUSION: The iNPH scale covers the four most important symptom domains and the full range of severity of the iNPH syndrome. The scale is sensitive, reliable, valid and feasible. We recommend that it should be used in future iNPH research.