Avoiding overdrainage with M.blue valve in pediatric hydrocephalus: efficiency, complications and valve survival

Overdrainage (OD) is a significant long-term complication in shunted pediatric patients and remains difficult to prevent consistently. The M.blue valve is an adjustable gravity-assisted (GA) device designed to address this issue. This study aims to add experience about the use of M.blue in pediatric hydrocephalus.

A retrospective review was conducted on children under 15 years who received M.blue valves between April 2019 and October 2023 at La Fe University and Polytechnic Hospital. Data collected included demographics, hydrocephalus etiology, indications for M.blue implantation, changes of pressure settings over time, valve efficacy in OD control, associated complications, and valve survival.

A total of 100 M.blue valves were implanted in 77 children (mean age: 5.77 ± 4.7 years; 44 males, 33 females). Mean follow-up was 36.92 months (range: 12-66). The most frequent etiology of hydrocephalus was posthemorrhagic hydrocephalus in preterm infants (29.9%), followed by tumor-related hydrocephalus (10.4%). M.blue was used for prevention in 32 cases (41.5%) and for treatment in 45 (58.5%). There were 197 pressure readjustments, with an overall trend toward increasing pressure settings over time; six cases required a setting of 40 cmH₂O. OD was prevented in 81.2% and successfully treated in 84.4% of cases. Complications included blockage of the adjustability mechanism in 38 of 78 tested valves (48.7%), with clinical impact in 20 cases (25.6%) and requiring surgical replacement in 12 (15.4%). Age under 2 years was the only factor associated with blockage (p < 0.005). Spontaneous pressure changes occurred in nine valves, six of which were simultaneously linked to adjustability failure, four of them requiring surgical replacement. Seven additional cases showed valvular obstruction with clinical deterioration. Only three cases developed ventricular catheter obstruction. Shunt survival rates at 1 and 3 years were 82% and 62%, respectively. Younger age at implantation was associated with higher rates of blockages of the adjustability mechanism and revisions.

The M.blue valve is effective in preventing and treating OD in children, with good shunt survival and low incidence of catheter obstruction. Progressive pressure increases are often required to control OD, reflecting dynamic CSF physiology and the unpredictability of optimal settings. The main limitation is the frequent blockage of the adjustability mechanism, followed by spontaneous pressure changes and valve obstruction.