| It can be surprising to realize that an organ as | | | | made in the skull (but inside the skin of the scalp) |
| high-powered and sophisticated as the brain also | | | | and redirects the excess CSF through another |
| has a plumbing system. And, as the case with a | | | | tube into either a jugular vein in the neck or into |
| house's plumbing, the drainage side of the system | | | | the abdominal cavity (peritoneum). Thus, the |
| can get gummed up. But the symptoms are | | | | patient can receive either a "VJ" shunt or a "VP" |
| different. When a home's drainage backs up, well...I | | | | shunt, with the letters designating the locations of |
| won't go there. When the brain's drainage system | | | | the two ends of the shunt. |
| backs up, the brain's owner can become | | | | The success or failure of shunting depends not |
| confused, incontinent of urine and unsteady on his | | | | just on the skill of the surgeon, but also on the |
| or her feet. | | | | selection of appropriate patients. Sometimes |
| The plumbing system in question is that which | | | | hydrocephalus turns up unexpectedly on scans |
| produces and drains the cerebrospinal fluid (CSF). | | | | when doctors are looking for something else |
| Normal CSF looks the same as water from a | | | | entirely. Although an unexpected finding like this |
| faucet, but is created from the bloodstream in | | | | should always cause the doctors to re-think the |
| the choroid plexus tissue within three of the | | | | case, the point is that hydrocephalus doesn't |
| brain's four inner chambers -- the right and left | | | | always cause problems. Sometimes the |
| "lateral" ventricles and the midline "fourth" | | | | hydrocephalus has been there for years and the |
| ventricle, but not the interposed, midline "third" | | | | brain has adjusted to it in a way that produces no |
| ventricle. The CSF percolates through | | | | symptoms. This is an example of a case that |
| passageways from one ventricle to another, | | | | should not be shunted, though it would still be |
| finally emerging through openings at the base of | | | | appropriate to monitor the patient and his or her |
| the brain to bathe the outer surfaces of the brain | | | | scans over subsequent months and years. |
| and spinal cord before getting reabsorbed into the | | | | Who, then, should receive a shunt? The answer, |
| bloodstream again. This re-absorption occurs in | | | | in short, is people for whom the benefits of the |
| special collection-nodes in the membranes | | | | operation exceed its risks. Identifying them, |
| surrounding the brain. The entire CSF volume of | | | | however, is the tough part. And the task is made |
| about 150 milliliters or five ounces (about as much | | | | even more difficult by the lack of randomized, |
| as a glass of wine) is produced and reabsorbed | | | | controlled trials in which a group of patients |
| four times a day, so the fluid is constantly turning | | | | receiving treatment is compared to an equivalent |
| over. | | | | group of patients not receiving treatment. |
| But blockages along the way can interfere with | | | | Although similar reasoning applies to adults thought |
| the normal flow of the CSF. For example, when | | | | to have internal (high-pressure) hydrocephalus, I'll |
| the passageway between the third and fourth | | | | lay out the decision-tree as it applies to external |
| ventricles becomes narrowed or choked with | | | | (normal-pressure) hydrocephalus. Published |
| sludge, the CSF backs into the lateral and third | | | | observations imply that shunts are most likely to |
| ventricles. Those ventricles react to the increased | | | | help NPH patients who have the following |
| pressure by becoming physically dilated or | | | | features: |
| enlarged. In this case, a CT or MRI scan could | | | | - substantial enlargement of all four ventricles |
| reveal the location of the blockage by showing | | | | - a full "triad" of symptoms, including confusion, |
| expansion of the two lateral and the single third | | | | urinary incontinence and altered walking |
| ventricles, but a normal-sized fourth ventricle. | | | | - poor walking as the first of the three |
| Another example of a blockage and its | | | | symptoms |
| consequences is when the collection-nodes | | | | - temporary improvement of symptoms after |
| responsible for CSF re-absorption in the brain's | | | | drainage of 50-60 milliliters (2 ounces) of CSF by |
| overlying membranes (meninges) become clogged. | | | | lumbar puncture (spinal tap) The elderly patients |
| In this case, all four ventricles are upstream from | | | | most at risk for NPH are also at increased risk for |
| the blockage, and all four of them expand. This, | | | | other diseases, and the shunting operation doesn't |
| too, is visible on brain scans. | | | | help symptoms produced by other causes. For |
| Both cases are examples of hydrocephalus, or | | | | example, confusion can be caused by Alzheimer's |
| water on the brain. The first case is one of | | | | disease and strokes. Urinary incontinence can be |
| "internal" or high-pressure hydrocephalus. The | | | | due to prostate disease in men and sagging pelvic |
| second is called "external" or normal-pressure | | | | tissue in women. Walking can be disrupted by |
| hydrocephalus (NPH). In NPH the pressure is | | | | arthritis, fractured bones, low vision, inner-ear |
| inexplicably normal much of the time, but the | | | | disease, Parkinson's disease and many other |
| term is somewhat misleading because prolonged | | | | unrelated processes. |
| recordings with pressure-monitors do show | | | | So it's important for the doctor to determine if |
| intermittent periods of increased pressure. | | | | other diseases might be to blame for the very |
| Hydrocephalus of one kind or another is especially | | | | symptoms that seem, at first glance, to be from |
| prevalent at the two extremes of the life cycle -- | | | | NPH. Assuming that NPH still seems likely, the next |
| in the very young and the very old -- but can | | | | round of decision-making concerns the possibility |
| occur at any age. In infancy, hydrocephalus can | | | | that an operation will cause harm. Even a patient |
| be caused by malformed brain-tissue. In contrast, | | | | whose brain scan and symptoms are classic for |
| adults with hydrocephalus were usually born with | | | | NPH can develop serious complications from the |
| normal brain anatomy, but acquired a blockage | | | | operation. A particularly feared complication is |
| due to a tumor, injury, bleed or infection. | | | | bleeding into the space outside the brain, called a |
| However, many cases of hydrocephalus in adults | | | | subdural hematoma. Older patients are also more |
| occur without a history of these preceding | | | | likely to have other medical conditions that could |
| illnesses. | | | | compromise the safety of an operation, like |
| CT and MRI scans are sensitive tools in detecting | | | | coronary artery disease or emphysema. |
| hydrocephalus, particularly when it's striking | | | | Cases in which expected benefits of the operation |
| enough not be confused with ventricular | | | | are much greater than risks, or in which the risks |
| enlargement due to gradual loss of surrounding | | | | are much greater than the expected benefits, are |
| brain tissue from aging. The main treatment of | | | | easy to make decisions about. But many other |
| hydrocephalus is for a surgeon to insert a tube | | | | cases are in the gray zone in which potential |
| (shunt) into one of the swollen lateral ventricles | | | | benefits and risks are more evenly matched and |
| and provide an alternative pathway for the | | | | the chances of doing harm with an operation |
| backed-up CSF to drain. Once the shunt | | | | come close to canceling out the chances of doing |
| equipment is in place, a piece of hardware about | | | | good. |
| the size of a large button sits outside the hole | | | | |