Fig. 2.

Shunt testing results of proximal and distal obstruction. a Distal obstruction. Upper panel: distal obstruction detected after infusion of fluid. Initial baseline ICP appears normal (c. 12 mmHg); however, ICP increases to > 25 and towards the end to > 40 mmHg, completely out of range for a functioning distal catheter. Lowe panel: distal obstruction evident from initial monitoring of baseline ICP for 15 min. The opening ICP was > 20 mmHg, spontaneously increasing to > 30 mmHg after 5 min of monitoring, revealing sever intracranial hypertension caused by a patent ventricular, however blocked distal catheter. Infusion was not performed as it is unsafe in such high ICP. b Proximal (ventricular catheter) obstruction as evidenced by a lack of pulsation and therefore heart rate and amplitude detection from the pressure inside the shunt prechamber. This demonstrates lack of connection with the ventricles. Infusion can be started as normal, and an unobstructed distal run-off is detected through stabilisation of pressure at the expected critical level. All 3 patients had no or very mild changes in their ventricular size. Revision of the shunt confirmed obstruction at the sites indicated by infusion, and also confirmed patent opposite end. ICP intracranial pressure, HR heart rate, AMP amplitude of ICP, RAP compensatory reserve index