Bifrontal-Parietal Ratio: A Novel Risk Factor for Cerebrospinal Fluid Overdrainage after Ventriculoperitoneal Shunting.

 This study aimed to examine potential risk factors associated with cerebrospinal fluid overdrainage after ventriculoperitoneal (VP) shunting.  We retrospectively examined the medical records of hydrocephalus patients who underwent VP shunting at a single institution between January 2011 and December 2017 and had a minimum 3-year follow-up. Variables studied included age, gender, hydrocephalus etiology, symptoms, shunt valve, ventricular catheter entry point, and neurosurgical history, including history of external ventricular drainage. Radiographic variables included Evans index, bicaudate index, callosal angle, measurements of frontal lobe thickness, and bifrontal-parietal ratio.  Among the 182 study patients, 11 experienced overdrainage. Age, gender, etiology, symptoms, and surgical history did not significantly differ between patients who experienced overdrainage and those who did not. Evans index, bicaudate index, and callosal angle did not significantly differ between the groups. Measurements of frontal lobe thickness and bifrontal--parietal ratio were significantly lower in the overdrainage group.  Bifrontal-parietal ratio may be useful to predict overdrainage after VP shunt surgery.