Relationships between intracranial compartment volumes and clinical symptoms in patients with idiopathic normal pressure hydrocephalus before and after cerebrospinal fluid shunt surgery

Objective To investigate the relationships of intracranial compartment volumes with the severity of clinical symptoms before surgery, and the degree of symptom improvement one year after cerebrospinal fluid(CSF)shunt surgery in patients with idiopathic normal pressure hydrocephalus(iNPH). Methods Twenty-one patients meeting the diagnosis criteria of international guidelines of iNPH and undergoing CSF shunt surgery in Department of Neurosurgery in our hospital from 2016 to 2017 were included.All patients underwent brain MRI measurement before surgery, and were evaluated by using 3-meter timed up and go test(TUG), minimum mental state examination(MMSE), idiopathic normal pressure hydrocephalus grading scale(iNPHGS)and modified Rankin scale(mRS)before and one year after CSF shunt procedures.The ventricular volume, brain volume, pericerebral CSF volume, total intracranial volume and Evans' index were measured in the pre-operative imaging of the brain.The following four pre-operative intracranial compartment volumes were calculated: the relative ventricular volume, brain volume ratio, pericerebral CSF volume ratio and the ratio of ventricular volume to pericerebral CSF volume. Results The scores of gait, cognitive function and urinary function were improved after surgery in iNPH patients(all P 0.05). There was no significant difference in intracranial compartment volumes between patients having improvement in mRS, TUG, MMSE and iNPHGS and patients having no improvement one year after surgery in iNPH patients(all P>0.05). Conclusions Patients with iNPH can benefit from CSF shunt surgery and have improvements of clinical symptoms including gait, cognitive function and urinary function.Preoperative intracranial compartment volumes(the relative ventricular volume, brain volume ratio, pericerebral CSF volume ratio and the ratio of ventricular volume to pericerebral CSF volume)and Evans' index have no correlations with the severity of clinical symptoms before surgery, and have no correlations with the degree of symptom improvement one year after surgery in iNPH patients.For this reason, preoperative intracranial compartment volumes and Evans' index cannot be used to predict whether or not CSF shunt surgery can improve specific clinical symptoms. Key words: Hydrocephalus, normal pressure; Cerebral ventricles; Cerebrospinal fluid shunts