Overdrainage shunt complications in idiopathic normal-pressure hydrocephalus and lumbar puncture opening pressure

Clinical article

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Management of idiopathic normal-pressure hydrocephalus (iNPH) is hard because the diagnosis is difficult and shunt surgery has high complication rates. An important complication is overdrainage, which often can be treated with adjustable–shunt valve manipulations but also may result in the need for subdural hematoma evacuation. The authors evaluated shunt surgery overdrainage complications in iNPH and their relationship to lumbar puncture opening pressure (LPOP).


The authors reviewed the charts of 164 consecutive patients with iNPH who underwent shunt surgery at their institution from 2005 to 2011. They noted age, sex, presenting symptoms, symptom duration, hypertension, body mass index (BMI), imaging findings of atrophy, white matter changes, entrapped sulci, LPOP, valve opening pressure (VOP) setting, number of valve adjustments, serious overdrainage (subdural hematoma requiring surgery), radiological overdrainage (subdural hematomas or hygroma seen on postoperative imaging), clinical overdrainage (sustained or postural headache), other complications, and improvements in gait, urine control, and memory.


Eight patients (5%) developed subdural hematomas requiring surgery. All had an LPOP of greater than 160 mm H2O and an LPOP-VOP of greater than 40 mm H2O. Radiological overdrainage was more common in those with an LPOP of greater than 160 mm H2O than in those with an LPOP of less than 160 mm H2O (38% vs 21%, respectively; p = 0.024). The BMI was also significantly higher in those with an LPOP of greater than 160 mm H2O (median 30.2 vs 27.0, respectively; p = 0.005).


Serious overdrainage that caused subdural hematomas and also required surgery after shunting was related to LPOP and LPOP-VOP, which in turn were related to BMI. If this can be replicated, individuals with a high LPOP should have their VOP set close to the LPOP, or even higher. In doing this, perhaps overdrainage complications can be reduced.

Abbreviations used in this paper:BMI = body mass index; iNPH = idiopathic normal-pressure hydrocephalus; IQR = interquartile range; LPOP = lumbar puncture opening pressure; VOP = valve opening pressure.

Article Information

Address correspondence to: Neill R. Graff-Radford, M.B.B.Ch., F.R.C.P., Department of Neurology, Mayo Clinic, 4500 San Pablo Rd., Jacksonville, FL 32224. email: graffradford.neill@mayo.edu.

Please include this information when citing this paper: published online August 9, 2013; DOI: 10.3171/2013.7.JNS13484.

© AANS, except where prohibited by US copyright law.



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    Scatterplot showing LPOPs according to the presence/absence of serious overdrainage complications.

  • View in gallery

    Scatterplot showing the difference between LPOP and the initial valve pressure setting according to presence/absence of radiological overdrainage complications. Those with serious overdrainage are in the group of patients with an LPOP-VOP of greater than 40 mm H2O.


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