Idiopathic Normal Pressure Hydrocephalus and Shunt Surgery

In 1965, normal pressure hydrocephalus was described as a treatable form of dementia presenting with gait disturbance, urinary incontinence and ventriculomegaly as well as normal cerebrospinal fluid pressure. Yet even now, over 50 years later, the cause of the most common type, idiopathic normal pressure hydrocephalus (iNPH), remains a mystery.

It is also difficult to predict which iNPH patients may derive the best clinical benefit from shunt surgery as outcomes vary greatly in literature. In order to find better guidance on treatment of this patient population, researchers at Yale recently sought to examine potential patient-level risk factors of 30- and upwards of 90-day hospital readmissions in elderly iNPH patients after VP shunt placement.

Readmission Rates After Shunt Surgery

Using data from the Healthcare Cost and Utilization Project Nationwide Readmission Database, Koo et al. studied 7,199 patients with iNPH aged 65 or older who had undergone VP shunt placement between 2013 and 2015. Of these patients:

• • 6% had a readmission overall
  • 3% of these readmissions occurred 30 days after discharge
  • 3% occurred within 31 to 90 days after discharge

Despite timing of readmission, primary diagnoses were similar. According to the study, which was recently published in World Neurosurgery, top diagnoses at readmission were:

• • Mechanical complication of nervous system device implant
  • Extracranial postoperative infection
  • Subdural hemorrhage
  • Infection and inflammatory reaction due to device implant

Koo et al. also found that predictors of 30-day readmission included age, diabetes and renal failure. Complications experienced during initial hospital stay were also associated with an increase in the likelihood for readmission at both 30 (30-R) and 31 to 90-days (90-R) compared to the non-readmission group (Non-R). The most common complications included:

• • Extracranial postoperative infection: 7% (30-R), 5.6% (90-R), 4.3% (Non-R)
  • Genitourinary complication: 4.6% (30-R), 2.7% (90-R), 2.1% (Non-R)
  • Intracranial hemorrhage: 2.8% (30-R), 1.6% (90-R), 0.6% (Non-R)

Female iNPH patients also showed less likelihood for readmission after the surgery.

“While our study shows the impact that some comorbidities have on unplanned readmission rates, the greatest risk factor associated for both 30- and 90-day readmissions is any inpatient complication,” the study authors write. “Therefore, creating potential perioperative interventions that may reduce postoperative complications, especially in the elderly, may have tremendous benefit in the care for these patients and reducing overall health care costs.”

iNPH Patients Want Shunt Surgery – Regardless of the Risks

Although Koo et al.’s research shines lights on which patients may experience better outcomes and less complications from VP shunt surgery, reported outcomes after shunt surgery vary widely. Despite this, iNPH patients typically opt for VP shunt surgery, according to a 2018 study by Subramanian et al. published in World Neurosurgery.

In their study, Subramanian et al. interviewed 31 iNPH patients who had undergone VP shunt surgery and had lived with their shunt for at least one year. Their aim was to examine the subjective experience iNPH patients have when deciding whether or not to undergo shunt surgery, and how the difficulties they may face can be used to improve outcomes and patient satisfaction.

The study revealed that the iNPH patients’ main motivation in choosing VP shunt surgery was the hope of improved mobility and independence. They no longer wanted to be seen as a burden to their caregivers. One patient in the study expressed this explicitly: “I wanted to be able to live my life without my daughter shuffling me all over the place.”

The study also found that most iNPH patients were willing to have the VP shunt surgery as soon as they were given the option—even if their neurosurgeon could not confirm that a good outcome would necessarily occur.

Subramanian et al. believe that these results indicate the need for effective communication between iNPH patients and their physicians as patients are often frustrated and desperate for any improvement in their condition. Patients also seem to be greatly influenced by their neurosurgeon’s recommendation so it is important to discuss iNPH patient’s goals before shunt surgery to lessen instances of disappointment postoperatively.

Additionally, Subramanian et al. believe that family and caregivers should be involved in the shunt surgery decision-making process, as their impact is thought to be another major factor in patients’ motivation to undergo the surgery.