Introduction: Negative pressure hydrocephalus (NegPH) is a rare clinical ventriculomegaly syndrome in which patients require CSF diversion at a less-than-zero pressure. We present seven patients and a literature review, to characterize the natural history, management, and outcomes of this dangerous entity.

Methods: Institutional records were queried to identify patients who had undergone EVD drainage at less-than-zero pressure during the study period, 1995-2015. Chart review captured demographics, diagnoses, treatment modalities, morbidity, mortality, and disposition. Supportive systematic review of published cases and series reporting patient-specific findings in NegPH is further included.

Results: Seven NegPH patients were identified—three SAH, two IVH, one benign tumor, one TBI. One patient was pediatric; five were female. Maximum negative pressure required was -10mmHg. Mortality was 29%; in both patients, care was withdrawn due to severe neurologic disability. Major or minor permanent neurologic morbidity was 100%. Among survivors, 40% required out-of-home disposition. Complications included vasospasm (29%), seizures (43%), infection (43%), shunt revision (43%), and need for secondary neurosurgical intervention (71%). Permanent CSF diversion was required in 57%, with one patient each requiring valveless, antisiphon, Delta 0.5, and Delta 1.0 valves. Literature review identified seven preceding reports, documenting 26 patients.

Conclusions: NegPH is highly variable disease process. Extended clinical course, infection, surgical revision, and IVH predict poor outcome. Early recognition and prompt treatment as the most important factors influencing long-term survival. Patients with underlying CSF leak require surgical repair and titrated EVD wean using flow-directed goals. Pediatric or tumor patients may depend on multi-shunt systems draining ventricular and subdural spaces. SAH portends a grievous prognosis and severe NegPH that cannot be overcome by weaning or valveless shunts—thought attributable to permanent alterations in parenchymal compliance. Vanguard treatments using large-bore catheters or pumpable shunt systems offer approximations of negative pressure drainage, but have not been tested in larger series.

Patient Care: Our study characterizes a rare but dangerous and poorly understood neurosurgical entity, synthesizing our own experience in a complex case series with an overview of the preceding literature to provide clinicians with a summary of key points relevant to diagnosing and managing negative pressure hydrocephalus.

Learning Objectives: By the conclusion of this session, participants should be able to: 1.) Diagnose NegPH, and recognize clinical scenarios that are likely to precipitate its onset 2.) Discuss leading theories regarding the underlying mechanism of NegPH, and how they inform various approaches to clinical management 3.) Implement novel treatment plans for major etiologies of NegPH, including flow-directed drainage titration, multi-shunt complexes, large-bore catheters, and pumpable systems

References: Filippidas (2011) Negative-pressure and low-pressure hydrocephalus Lin (2014) A Rare Case of Low-pressure Hydrocephalus After Skull Base Surgery Yashar (2013) Treatment of refractory low-pressure hydrocephalus with an active pumping negative-pressure shunt system Galbarriatu (2013) Low-pressure hydrocephalus: indication for custom made catheters Akins (2011) The Genesis of Low Pressure Hydrocephalus Hunn (2014) Successful treatment of negative pressure hydrocephalus using timely titrated external ventricular drainage- a case series Lin (2014) A Rare Case of Low-pressure Hydrocephalus After Skull Base Surgery Clarke (2006) Very Low Pressure Hydrocephalus: Report of Two Cases