A Trial of High and Low Pressure Level Settings on a Programmable Ventriculoperitoneal Shunt Valve for Idiopathic Normal Pressure Hydrocephalus
A Trial of High and Low Pressure Level Settings on a Programmable Ventriculoperitoneal Shunt Valve for Idiopathic Normal Pressure Hydrocephalus
In treating idiopathic normal pressure hydrocephalus with a shunt there is always a risk of
 underdrainage or overdrainage. The hypothesis is tested whether treatment of patients with an
 adjustable valve preset at the highest opening pressure (OPV), leads to comparable clinical
 results with less subdural effusions than in a control group with an opening pressure preset
 and kept fixed at a low pressure level.
Idiopathic normal pressure hydrocephalus (INPH) is characterized by a clinical triad of
 symptoms: gait disturbance, urinary incontinence and cognitive impairment. INPH typically
 develops among the elderly and shares some symptoms with other neurological disorders. In
 general, 60-70% of patients with the complete clinical triad and signs of hydrocephalus on
 CT/MRI will improve after cerebrospinal fluid (CSF) shunting. Implantation of a shunt,
 however, carries complications such as infection, obstruction, underdrainage, and
 overdrainage. The cumulative complication rate and revision rate is estimated to be 35-80%
 among adults. The England shunt registry described an overall incidence of underdrainage of
 52%, and studies have resulted in incidences of overdrainage between 2 and 21%. Børgesen
 claims that 80% of complications of shunting for INPH are related to overdrainage.
 Overdrainage may lead to low intracranial pressure syndrome and subdural effusions (SDE). Low
 intracranial pressure syndrome is characterized by orthostatic headaches and sometimes
 nausea, vomiting, drowsiness, diplopia, upward gaze palsy and visual defects. As INPH
 patients are often elderly patients with concomitant brain atrophy and normal CSF pressure
 they are especially at risk for developing signs and symptoms of overdrainage.

 Overdrainage can be prevented or treated by implanting an anti-siphon device (ASD) or
 changing the opening pressure of the valve (OPV). Different ASDs have been developed since
 the first publication in 1973. They have in common that the lumen of the catheter is closed
 under influence of a negative hydrostatic pressure at the level of the ASD. The optimal valve
 setting for treating INPH is still the subject of controversy. The dilemma in INPH patients
 is that a low OPV might lead to overdrainage-related symptoms. A high valve setting might
 lead to underdrainage and the patient misses the chance of maximum improvement.

 Studies examining whether to use a low or high OPV have been contradictory so far.

 After randomization, baseline primary and secondary outcome measure assessments are conducted
 preoperatively. Within 24 hours of shunting, skull, thoracic, and abdominal X-rays are done
 to verify device connections and position. Follow-up visits at 1, 3, and 9 months include all
 primary and secondary outcome assessments. All measurements are done by a research assistant
 who visits the participating hospitals to prevent inter-observer variation. Study end for
 each patient is defined as completing the 9 month visit or death, detection of SDE on CT, or
 shunt removal or revision due to infection or dysfunction.

 The PL in Group 1 (control group) is allowed to be increased to a higher setting when an SDE
 is detected. The patient thereby reaches study end, and the treating physician is free to
 decide how to manage the PL. The 9-month follow-up is still obtained. The PL in Group 2 is
 preset at the highest PL and eventually lowered 1 step at each follow-up visit when the
 modified mini mental state (3MS) or Gait score is not increased ≥ 15% provided that no SDE is
 visible on a new CT scan. The 15% is considered the minimum percentage to reliably determine
 improvement.
Inclusion Criteria:

 -  At least two out of three of the typical signs of normal pressure hydrocephalus:

 -  gait disturbance,

 -  cognitive impairment and

 -  urinary incontinence.

 -  Radiological verification of a communicating hydrocephalus.

 -  Cerebrospinal fluid pressure at lumbar puncture < 150 mm H2O.

 Exclusion Criteria:

 -  Aqueduct stenosis.

 -  Severe comorbidity.

 -  Age > 85 years.

 -  Possibly confounding neurological diseases.

 -  Recent meningitis or subarachnoid hemorrhage.