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Take Parkinson’s disease. Although this disorder is largely treated with medication by our neurologist colleagues, a select number of neurosurgeons specialize in performing surgery for medically refractory Parkinson’s cases. The surgery involves stereotactic insertion of one or two electrodes deep into the brain through a very small hole. It’s necessary to monitor the brain’s electrophysiology, and millimeter or submillimeter precision is key. At some centers, the neurosurgeons who perform this particular operation also gravitate toward brain biopsy cases, which are technologically similar: they use precise stereotactic equipment and involve maneuvering a biopsy needle through a tiny hole. Some neurosurgeons love this sort of work. It’s neat and clean. There’s very little blood.

On the other hand, other neurosurgeons hate this sort of work. They prefer the bigger cases that involve wider exposure of the brain and more hands-on manipulation of the anatomy. They might even call their differently minded colleagues “needle jockeys.”

But there’s one thing most neurosurgeons agree on, and that is the seemingly simple operation we call the VP shunt. “VP” stands for ventriculoperitoneal. In essence, the shunt is a long, thin tube that runs from the fluid-filled cavities in the brain (the ventricles) to the belly; it’s designed to drain the excess cerebrospinal fluid that characterizes hydrocephalus. Pediatric neurosurgeons can’t get away from this operation, because it’s their bread and butter. Childhood hydrocephalus is one of the most common disorders they treat, and the VP shunt is a lifesaver.

Many neurosurgeons, however, shy away from the adult-onset form of hydrocephalus called normal-pressure hydrocephalus (NPH), which is often misdiagnosed as Alzheimer’s disease. As is often the case in medicine, we don’t understand much about this disease, but we know how to treat it. Placement of a shunt can relieve its symptoms, which include poor balance and a shuffling gait, memory loss, and incontinence.

You might think that NPH would be a favorite among neuro­surgeons. After all, treating it has the potential to be quite rewarding. I have seen some patients improve so dramati­cally that their families say a miracle must have occurred.

Still, surgeons often joke that shunt work is akin to plumbing. But I can’t imagine that plumbers encounter quite as much trouble. One strike against the operation is economic: ­Medicare reimburses the surgeon less than $1,000, a fee that covers all follow-up in the hospital and three months’ worth of office visits. Financial considerations aside, what irks so many neurosurgeons about the VP shunt is its fiddle factor.

NPH can be unpredictable. In some patients, one or two symptoms improve when the shunt is installed but another doesn’t. What’s more, the symptoms have a way of creeping back for no apparent reason, even after an initially successful operation. This is frustrating for the patient, the family, and the surgeon. It leads to a series of questions: Did the shunt stop working? Is the tubing clogged? Are we dealing with more than one disease? To answer these questions, how much of a workup are we going to do? Should we get x-rays of the shunt and a CT scan of the head? What about tapping the shunt by putting a needle into it to see whether fluid can be withdrawn (which reveals whether the tubing is blocked but risks introducing an infection)? Then there are the other vague symptoms that tend to crop up in older patients: dizziness, fatigue, headache, abdominal discomfort. When such symptoms arise, the shunt is inevitably called into question.

These frustrations are here to stay, but surgeons continue to hope that the newest iteration of the VP shunt will at least ease the technological hassles. In my experience, though, what often happens is that new ones replace the old.

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Credits: Steve Moors

Tagged: Biomedicine, imaging, neuroscience, image analysis, neurotechnology, brain surgery

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