Does the shunt opening pressure influence the effect of shunt surgery in normal pressure hydrocephalus?

Abstract

Thirteen patients with normal pressure hydrocephalus were operated upon with an externally maneuverable shunt system (Sophy SU8) in order to investigate its influence on clinical outcome, intracranial pressure and cranial CT parameters. The opening pressure was set at high at surgery and lowered stepwise at intervals of three months to medium and low. The clinical condition, intracranial pressure and cranial CT parameters were examined at the end of the 3 months interval on each pressure level. The patients improved within the first 3 months inspite of an unchanged mean intracranial pressure and remained in a stable clinical condition during the rest of the study period. The intracranial pressure was significantly reduced at 9 months. The ventricular index, Evans index, temporal horn and third ventricle width were reduced 3 months post-operatively and did not change significantly during the rest of the study. The pre-operative third ventricle width was correlated to high psychometric test results after shunt surgery. Reduction in ventricular index, Evans index and third ventricle width after surgery correlated to improvement in psychometric scoring. The clinical improvement after shunt surgery for normal pressure hydrocephalus is seen within 3 months and is independent of the adjusted valve pressure.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus: Second Edition

“…Although rare, sibling cases of NPH have been reported, in which the individuals had clinical features indistinguishable from iNPH. 8,26) More recently, a large family with NPH patients in three generations who had clinical and MRI features that were indistinguishable from iNPH has been reported. 29) It has also been suggested that a copy number variation in a certain region of the genome may play a role as a genetic risk factor for iNPH.…”

“…In recent studies that were strictly aimed at iNPH patients, the measurement of proteins and neuropeptides in the CSF has been conducted. Neurofilament light chain, 2,136) transforming growth factor (TGF)-b1, TGF-b type II receptor, and a2-leucine-rich glycoprotein (LRG) 84,85) are significantly increased in the CSF of iNPH patients, whereas acetylcholine esterase activity, lactic acid, 87) b-amyloid-42, 60,112) b trace, 26) a secreted form of b-amyloid precursor protein (APP), and a secreted form of APPa 112) were significantly decreased in the CSF of iNPH patients. Since the levels of total tau (t-tau), but not phosphorylated tau (p-tau), were increased in the CSF of iNPH patients, they were reported to be useful in the differential diagnosis of Alzheimer's disease.…”

“…There is no established method for determining the initial postoperative valve pressure setting. The generally accepted method is to start with a high pressure setting and gradually lower the setting according to the clinical condition in order to prevent CSF overdrainage complications 7,8,18,26,51) (Recommendation grade B).…”

“…44) This method uses a higher initial pressure setting in order to compensate for the excessive decrease of ICP in the upright position. Other evidence in support of this algorithm include a study that showed symptomatic improvement in all subjects after setting a Sophy Valve } (Sophysa, Crown Point, Indiana, USA) at a high pressure, 26) and another study found that the final setting in more than 80% of patients using a 51) These studies, however, employed methods that are relatively invasive and difficult to use. In recent years, however, a quick and easy algorithm based on the patient's height and weight has been developed ( Table 7).…”

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus Guidelines From the Guidelines Committee of Idiopathic Normal Pressure Hydrocephalus, the Japanese Society of Normal Pressure Hydrocephalus

“…According to this method, the initial pressure setting is determined based on the pressure environment of the upright condition in which shunt flow is expected to be a maximum and, therefore, the resultant pressure setting becomes relatively higher than previously considered. Evidence supporting this approach is available in several studies: One study showed improvement in symptoms in all subjects after setting the Sophy valve  (SV; Sophysa, U.S.A.) at a high pressure, 58) another study found that the final setting in more than 80% of patients with CHPV was approximately 150 mmH 2 O. 98B) If symptoms due to overdrainage develop in patients treated with conventional fixed-type valves, patients are advised to maintain a recumbent position and then allowed a gradual transition to the upright position.…”