AUTHOR=Kamo Masatsugu , Kajimoto Yoshinaga , Ohmura Tomohisa , Kameda Masahiro , Tucker Adam , Miyake Hiroji , Wanibuchi Masahiko 

TITLE=Weight and Abdominal Pressure-Induced Shunt Trouble in Patients With Shunted Normal Pressure Hydrocephalus: A Comprehensive Study on Pressure Environment of Shunt System

JOURNAL=Frontiers in Neurology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2022.882757

DOI=10.3389/fneur.2022.882757

ISSN=1664-2295

ABSTRACT=Objective.
We identified a new type of shunt malfunction (SM) in patients with normal pressure hydrocephalus (NPH). It is induced by weight change and can be treated with valve readjustment. There were two types of SM: underdrainage induced by weight gain and overdrainage induced by weight loss. This study aims to elucidate this mechanism by assessing the shunt pressure environment.
Methods
The total pressure environment of the shunt system was prospectively studied in shunted NPH patients at Osaka Medical College Hospital from 1999 to 2005. We measured the pressure environment during the initial pressure setting of the valve by the intracranial pressure (ICP) guide, after setting the valve, and when shunt malfunction was suspected. We evaluated ICP, intra-abdominal pressure (IAP), and hydrostatic and perfusion pressures of the shunt system in the sitting and supine positions. The target ICP for valve setting was empirically set at -8 to -13 mmHg in the sitting position, referring to the external auditory meatus. During the study period, we identified five cases of SM induced by weight change and assessed the changes in the pressure environment across pre-SM, SM, and post-SM.
Results
In four cases of underdrainage, gait disturbance worsened with an average weight gain of 6.8±1.2 kg. With weight gain, IAP and ICP increased by 8.8±1.6 mmHg and 4.8±1.0 mmHg, respectively. Consequently, ICP increased to -6.5±1.9 mmHg. One overdrainage patient developed an asymptomatic chronic subdural hematoma (CSDH) with a weight loss of 10 kg. With weight loss, both IAP and ICP decreased by five mmHg, and concomitantly, ICP decreased to -18 mmHg. In all patients, valve readjustment restored their ICP to the target pressure. After valve readjustment, gait disturbance improved immediately, and CSDH disappeared after one month.
Conclusion.
In shunted patients, weight change was linked to ICP via the IAP. Due to weight change, underdrainage occurred when ICP was above the target pressure, and overdrainage occurred when ICP was below it. We named this SM as weight and abdominal pressure-induced shunt trouble (WAIST). SM patients with weight changes should be the first to be tried for valve readjustment.