MRI-Volumetry in the Evaluation of Shunt Treatment for Hydrocephalus

MRI-Volumetry in the Evaluation of Shunt Treatment for Hydrocephalus, a Randomised, Double-blind Study.

This randomized, double-blinded, cross-over study aim to evaluate the effects of shunt treatment in idiopathic normal pressure hydrocephalus (iNPH) by measuring cerebral ventricular volume and clinical symptoms at different shunt opening pressures. Further, proteins in the cerebrospinal fluid (CSF) will be compared before and after shunt surgery.

The participants are evaluated before surgery and one month, two months, three months and three months plus one day after surgery. At each evaluation point a MRI of the brain with volumetric sequences is performed and clinical data is collected (Walking speed and steps for Time up and go, 10m walking and 3m walking backwards. Mini Mental State Examination, balance, gait, self rating of incontinence, Epworth Sleepiness Scale).

At surgery, all patients are given a ventriculoperitoneal (VP) shunt (Strata ® ) with an opening pressure setting of 1.5. After the first evaluation, one month postoperatively, participants are randomized to either a higher (2.5) or a lower (1.0) opening pressure, ratio 1:1. The opening pressure setting is blinded both for patients and the clinician during the subsequent clinical evaluations. At two months, the opening pressure is crossed over to the alternative setting (2.5 or 1.0). At three months, all participants receive the lowest shunt opening pressure (0.5) with the final evaluation the next day.

Semiautomatic measurement of the lateral as well as the third cerebral ventricles will be performed using the MRI scans and volumetric software: SyMRI (SyntheticMR AB, Linköping, Sweden)

CSF is collected at three times for each participant, from the lumbar spine pre- and 3 months postoperatively and intracranially during surgery. Further, intracranial CSF is taken through the Rickham Reservoir at the 3 months postoperative evaluation. After CSF from the participants has been collected, a single batch mass spectrometry will be performed with all the samples simultaneously.

Sample size was determined to achieve 80% power for a two tailed paired t-test for a mean change in ventricular volume of 8ml, estimated from postoperative change in ventricular volume in a previous study.

Hypotheses:

• The volume of the ventricular system in the brain decreases significantly after shunt-surgery.
• The ventricular volume is larger at high opening pressures compared to low opening pressures of the shunt.
• The decrease in ventricular volume is related to clinical outcome.

Inclusion Criteria:

• Diagnosis of idiopathic normal pressure hydrocephalus and planned treatment with shunt surgery.

Exclusion Criteria:

• Ongoing anticoagulation treatment
• Ongoing Clopidogrel treatment
• Mini mental state examination results of 15 or lower.
• Contraindications to magnetic resonance imaging.