Aim:Idiopathic normal pressure hydrocephalus (iNPH) is characterized by ostural instability, often with a forward leaning posture. However, the presence of concomitant spinal sagittal plane deformity and spinopelvic alignment and have not been studied in this population. The objective of this study was to measure the baseline spinopelvic parameters and characterize the sagittal, and coronal plane deformities in patients with iNPH.Material and Methods:We analyzed a series of patients at one academic institution who underwent ventriculoperitoneal shunting for iNPH with pre-shunt standing full length x-rays. The series of patients was enrolled consecutively to minimize selection bias. We quantified comorbid sagittal plane spinal deformity based on the Scoliosis Research Society-Schwab classification system by assessing pelvic incidence and lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sagittal vertical axis (SVA).Results:Seventeen patients (59% male) were included in this study. Mean (± standard deviation) age was 74 ± 5.3 years with a body mass index (BMI) of 30 ± 4.5 kg/m2. Six patients (35%) had marked sagittal plane spinal deformity by at least one parameter: five (29%) had greater than 20˚ PI-LL mismatch, three (18%) had >9.5 cm SVA, and one (6%) had PT greater than30˚. Additionally, the thoracic kyphosis exceeded the lumbar lordosis in nine patients (53%).Conclusion:Positive sagittal balance, with thoracic kyphosis exceeding lumbar lordosis, is common in iNPH patients. This may lead to postural instability, especially in patients whose gait does not improve following shunting. These patients may warrant further investigation and workup, including full length standing x-rays. Future studies should assess for improvement in the sagittal plane parameters following shunt placement.