gms | German Medical Science

Objective: Hydrocephalus shunt malfunction can – especially in children - occur insidiously without obvious signs and symptoms of raised ICP. It therefore imposes a diagnostic challenge. Imaging-based shunt-tests are, if at all, qualitative and carry risks of radiation exposure. Computerized shunt-infusion-studies, however, enable a quantitated shunt function assessment without radiation exposure. We report on feasibility and results of this technique, which is our routine procedure for shunt assessment.

Methods: To perform SIS we insert two butterfly needles into the pre-chamber, one for computerized ICP recording, one for mock CSF infusion. After baseline ICP recording, infusion is started at 1.5 ml/min until a new ICP plateau is reached. Dedicated software (ICM+), containing the shunt’s resistance characteristics, calculates baseline and plateau ICP, ICP-amplitudes, outflow resistance and critical shunt pressure (CSP = maximum pressure for plateau provided normal shunt resistance).

Results: 39 SIS were performed in 35 children. Functional shunts were defined by ICPplateau >1mmHg below CSP, non-functional as >1mmHg above CSP and borderline in between. 17(43,6%) of shunts were obstructed, 3(7,7%) borderline and 19(48,7%) functional. Baseline ICP in obstructed shunts was significantly above shunt working pressure (n=0.003). CSF outflow resistance and ICP plateau were significantly elevated (n=0.001) in obstructed shunts, cut-off thresholds were 5.9 mmHg/ml/min and 8.5 mmHg, respectively. All obstructed shunts were revised. In all either ventricular size decreased, external CSF spaces enlarged, head circumference stopped growing or parents reported clinical improvements. No shunt infections were observed.

Conclusion: SIS is a simple and elegant radiation free technique for quantitated shunt function-tests and answers reliably all questions regarding suspected shunt malfunction. Dedicated software containing shunt hydrodynamic characteristics is necessary and small children will need short-term sedation. SIS should become routine in neurosurgery units.