Withdrawal of shunt systems – clinical use of the programmable shunt system and its effect on hydrocephalus in children

Abstract.

Objects: The most important function of the programmable valve (PV) is to limit the shunt-dependent flow of the cerebrospinal fluid by upgrading valve pressure. This activates the regular circulation of cerebrospinal fluid, which may make successful removal of the shunt possible once sufficient cerebral development has been achieved. The purpose of this paper is to indicate the possibility of shunt removal using the programmable Medos and Sophy valves (one programmable Sophy valve was specially designed for this situation). Methods: Prior to regular use of the PV, removal of existing shunt systems was attempted in 57 children, since some systems malfunctioned and others had abdominal tubes that were meanwhile too short as the children had grown as they became older. Shunt removal was successfully achieved in only 18 patients (32%). However, in patients in whom PV valves were used, shunt removal was successful in 68 out of 114 patients (57%). This shows that the success rate of shunt removal becomes significantly higher when PV valves are used. The 68 cases in which PV valves were used and shunt removal was successful were divided into three groups: A, B, and C. In group A (36 cases, 53%), the Medos valve was used for the initial PV shunt implantation and the pressure was gradually increased up to 200 mmH₂O. The shunt systems were then withdrawn. Group B (29 cases, 43%) includes patients who experienced both the minor symptoms and ventricular enlargement attributable to increased valve pressure. The pressure was gradually upgraded by pumping several times and was maintained at close to 200 mmH₂O. After 6–24 months' observation shunt removal was performed, and in 21 out of 29 cases the outcome was good. However, the remaining 8 patients (12%) still had symptoms and required shunt reinsertion. The specially designed Sophy valves were then used, which allowed the pressure to be set at above 200 mmH₂O. The pressure was increased by degrees up to 400 mmH₂O and kept at the same level for 6–24 months. The shunt systems were then removed successfully. Although a high pressure setting was required over a sustained period, a total of 29 patients (43%) were able to have their shunts removed. In group C (3 cases, 4%), which included patients with aqueduct stenosis, the pressure was raised and thus allowed ventricle enlargement. Third ventriculostomy was performed under neuroendoscopy with the shunt pressure maintained at a high level. Shunt systems were removed successfully. Conclusions: This study showed that it is possible to remove the shunt systems in 50% or more of pediatric hydrocephalus cases in which PV valves are used. This is achieved through careful control of the valve pressure. Close observation is essential during the period when the PV pressure is maintained at a high level, as well as 6–12 months after shunt removal.