gms | German Medical Science

Objective: Adjustable valves (AV) were introduced by Bush/Matson about 1951, Kuffer 1969, Portnoy 1973 (On-Off), Sophysa & Medos-P 1984 (in clinics 90), followed by STRATA-, ProGAV- and ProSA-valves. Major AV-series are rare and long-term results completely missing.

Methods: Since 1988 we prospectively registered 1091 patients with 1336 AVs; 671 had Medos-P, 359 Miethke-ProGAV, 18 Heyer-Schulte-ON-OFF, 18 Sophy-SU3/8, 4 Sophysa-Polaris, 19 Miethke-ProSA and 1 STRATA. In vitro 197 AVs (11 types) were tested, 28 new, 169 explanted.

Results: Except of early Sophies the accuracy of new valves was acceptable. The flow through AVs alone (without additional ASDs, gravitational or SiphonGuard) were similar compared to ball-valves with the same resistance: With 30 cm hydrostatic pressure we found 1500–2200 ml/h in low and ca. 700 ml/h in high adjustments. Over-drainage is unavoidable even in highest settings. In vivo: Follow-up 1 day to 20 years. 27% of Medos-P- vs. 10% of ProGAV-valves required 1–3 replacements, mainly due to infections, blockade and adjustment problems, especially in Medos-P (9.8%, n = 64). In ICP-measurements patients with AVs alone showed mostly, but not always unphysiological low ICPs in upright. Children developed in >50% slit ventricles ± clinical symptoms, often microcephaly and acquired isolated forth ventricles (34 cases); in contrast, no AV-patient with a gravitational valve developed a trapped 4^th ventricle. Similar to literature AVs alone showed 5–23% subdural haematoms dependent on subgroup (maximum risk in NPH) and risk factors (anticoagulation, brain trauma); 30–60% required drainages. Our own AV-patients developed hygromas requiring surgery in 10% without gravitational units, with g-valves in 2.5%.

Conclusions: On one hand the "titration" of ICP is helpful and sometimes sufficient for mild over-drainage (e.g. small subdural haematomas); in most over-drainage problems such as avoidance of slit- or trapped ventricles AVs fail. On the other hand the lack of robustness, unsolved safety-, adjustment- and handling problems counterbalance the advantages. Clinical studies of simple vs. AV-valves (alone) showed no superiority. In contrast AVs combined with gravitational valves seem to be the recently best solution. However, improvements of robustness and handling are necessary in all existing AV-products.