Solving a complex, rare, and challenging scenario in a normal pressure hydrocephalus with recurrent shunt dysfunction and multiple revisions - The opposing role of evolving low-pressure hydrocephalus and idiopathic raised intra-abdominal pressure.

BACKGROUND: Maintenance of pressure gradient within the intracranial chamber, shunt hardware, and the abdominal cavity plays a significant role in the optimal functioning of the ventriculo peritoneal shunt. We report a rare and a complex scenario in a patient with normal pressure hydrocephalus (NPH) who had recurrent and refractory ventricular peritoneal shunt dysfunction. Following a meticulous analysis, this was attributed to a very rare, and, first to be documented in the literature, a combination of an evolved very low pressure hydrocephalus (VLPH) system and asymptomatic raised intra-abdominal pressure (IAP).

CASE DESCRIPTION: A 72-year-old male presented with NPH syndrome, associated with recurrent shunt dysfunction. A thorough systematic evaluation, which included intracranial pressure monitoring and IAP monitoring, revealed the presence of VLPH and a concomitant elevated IAP that was asymptomatic. This unique situation required changes in surgical strategy, which included correction of VLPH state, insertion of the anti-siphon device, and the placement of the distal end of the shunt into the pleural cavity. This led to solving the "mystery" of recurrent shunt dysfunction in this complex scenario.

CONCLUSION: It is imperative to perform the pressure analysis of the intracranial chamber, shunt hardware, and even the abdominal cavity, especially, in every case of refractory shunt revisions. Possibilities of a rare cause such as VLPH or an asymptomatic raised IAP acting alone or in combination must be considered. Only then, the final cerebrospinal fluid diversion strategy should be decided.