Radiological features of gait phenotypes in patients with idiopathic normal pressure hydrocephalus

Silvia Nicolosi^1,2Massimiliano Todisco²Matteo Paoletti^2*Eduardo Caverzasi^1,2Francesco Tarantino³Elena Ballante^1,2Francesca Valentino²Roberta Zangaglia²Silvia Figini¹Giuseppe Cosentino²Claudio Pacchetti²Anna Pichiecchio^1,2

• ¹University of Pavia, Pavia, Lombardy, Italy
• ²Neurological Institute Foundation Casimiro Mondino (IRCCS), Pavia, Italy
• ³Azienda Sanitaria Locale di Brindisi, Brindisi, Italy

According to the higher-level gait disorder (HLGD) pattern, patients with idiopathic normal pressure hydrocephalus (iNPH) can be divided into two motor phenotypes, namely a disequilibrium (wide-based gait) subtype or a locomotor (parkinsonian) (locomotor) subtype. We aimed to understand the neuroimaging correlates of iNPH phenotyping into different gait patterns, by assessing specific radiological features and their correlations with clinical scores.We enrolled 86 probable iNPH patients (53 males; age range: 69-88 years), who underwent a comprehensive clinical assessment, including neuropsychological tests, and a conventional MRI scan. Cohort was subdivided into disequilibrium subtype (29 subjects) and locomotor parkinsonian subtype of HLGD (57 patients) based on gait evaluation. We compared the iNPH subtypes assessing differences in eight linear radiological indexes and their clinical correlates.The Height of the Third Ventricle was the only radiological feature that differed between the two motor phenotypes (p < 0.05), being higher in the locomotor parkinsonian subtype and showing a trend of correlation with the motor score of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale and with the continence score of the iNPH Rating Scale. Among several clinical-radiological correlations, a reduced callosal angle correlated with the severity of motor and urinary symptoms (p < 0.05).Discussion: A greater height of the third ventricle possibly leading to a top-down compressive effect on the midbrain could be a neuroimaging marker of the locomotor parkinsonian phenotype of iNPH.The extensive correlations between linear radiological indices and clinical scales suggest a possible role for radiological features in clinical monitoring.Larger cohorts are needed to confirm our data.