A Treatable Brain Disorder That’s Often Mistaken for Alzheimer’s

If you’re over age 65, it’s common to feel that you’re slowing down a bit. Simply walking to your mailbox could take longer than it used to, and you may have even started shuffling as you walk. Getting out of a chair could be getting harder, too.

On top of that, your bladder might not be cooperating, so you have started to wear pads for incontinence. Your thinking isn’t quite as clear as it used to be, and you are now having trouble keeping your checkbook.

Don’t make this mistake: While these changes all may seem to point to the fact that you’re simply growing older, having all three of these symptoms could actually be a red flag for a treatable brain disorder.

As many as 700,000 people in the US are believed to have idiopathic (with no known cause) normal pressure hydrocephalus (iNPH), an often-misdiagnosed brain condition. Of the 5.2 million individuals diagnosed with dementia, estimates show that 10% to 15% actually have this treatable condition.

WHEN IT’S NOT NORMAL AGING

A shuffling gait, incontinence and memory problems may prompt a person to see his/her doctor, but these symptoms are also among the most common in older adults. For that reason, your doctor may chalk up these problems to “normal aging”—when, in fact, they are not normal.

If the patient is savvy and doesn’t accept that answer, he/she will find another doctor and get a more extensive workup.

The turning point comes when the doctor orders a CT scan or an MRI—a test usually included in a dementia evaluation. If the imaging test shows that the brain’s ventricles—normal cavities within the brain that contain cerebrospinal fluid (CSF)—are enlarged, that should trigger consideration of iNPH.

What’s gone wrong: Hydrocephalus results from a defect in circulation of the CSF, which surrounds and cushions the brain. Normally, the choroid plexus (vascular tissue in the ventricles) produces up to 2.5 cups of CSF daily, which bathes the brain and is absorbed back into circulation, maintaining a constant volume of fluid inside the skull. If absorption slows down, then CSF accumulates, the ventricles enlarge and eventually symptoms (such as those described earlier) may appear.

GETTING DIAGNOSED

If the brain scan shows enlarged ventricles, indicating possible iNPH, the next step is to see a neurologist for a clinical exam. The first symptom a neurologist will probably look for is a gait disturbance, including difficulty getting in or out of a seat, trouble initiating gait, shuffling gait and instability on turns. The presence of a shuffling gait along with cognitive slowing and memory impairment and/or urinary incontinence raises the diagnosis to “probable iNPH.”

Important: Because cognitive defects caused by iNPH are frequently mistaken for Alzheimer’s disease, a neurologist is best qualified to distinguish between the two types of memory loss.

Unlike Alzheimer’s, iNPH usually does not reach the stage where the individual fails to recognize family or close friends. In addition, those with early Alzheimer’s rarely display the distinctive gait impairment characteristic of iNPH, such as difficulty standing or turning, as mentioned above.

Unlike arthritis, the gait disturbance caused by iNPH is due to a neurologic impairment rather than pain or stiffness. Normal walking should be effortless, but individuals with iNPH must concentrate to walk and often complain that their feet won’t do what they want them to do.

The slowness and shuffling of iNPH may cause it to be mistaken for Parkinson’s disease, but the tremor that is typical of Parkinson’s is not a key feature of iNPH. Patients with iNPH may even be prescribed medications for Alzheimer’s, Parkinson’s or incontinence, but these rarely help.

Another disorder that iNPH may resemble is vascular dementia, which is caused by the cumulative effects of various risk factors, such as high blood pressure, a history of small strokes, elevated cholesterol and diabetes. Because vascular dementia and iNPH often affect the same areas of the brain, the conditions can produce similar symptoms and sometimes even occur at the same time.

GETTING THE RIGHT TREATMENT

It’s important for iNPH to be treated. While there are no drugs for iNPH, the good news is that most cases can be treated by surgically implanting a shunt. The shunt consists of three components—a narrow tube that is placed in the ventricles…a valve mechanism to control the flow, which is usually placed beneath the scalp…and a narrow tube that transports excess CSF somewhere else in the body, usually to the abdominal cavity, where it’s easily absorbed into the bloodstream.

To determine whether shunt surgery will help, tests of the patient’s response to CSF removal are recommended. A spinal tap (also known as lumbar puncture) may be performed on an outpatient basis. With this procedure, approximately 30 milliliters (ml) to 40 ml, or nearly 1.5 ounces, will be removed. The patient’s gait should be evaluated before the lumbar puncture and several hours afterward. If the gait improves significantly, then a shunt is very likely to help the patient.

If there’s no improvement after the spinal tap, a more extensive test called external lumbar drainage (ELD) may be performed in the hospital. In this case, the doctor will insert a temporary tube into the spinal fluid to drain it for about four days, for an approximate total of 400 ml to 600 ml, or 13.5 ounces to 20 ounces, of CSF.

ELD is like a test-drive of shuntlike conditions for the brain, without actually having the shunt operation. If the patient shows improvement following prolonged drainage, he will then be referred for shunt surgery. If the patient does not respond to prolonged drainage, then the odds of a shunt helping are small—below 5%.

iNPH CARE LASTS A LIFETIME

Following shunt surgery, recovery rates for iNPH patients range from 60% to 90%, according to the medical literature. All symptoms can improve, but the extent of improvement may be limited if patients have other disorders that contribute to their symptoms.

It’s important for people with shunts to visit the neurologist or neurosurgeon regularly following shunt surgery, initially to find the optimal setting for the shunt valve that controls drainage and on an ongoing basis to ensure that it’s still operating correctly.

Too much drainage can increase the risk of bleeding within the skull, known as a subdural hematoma, and can cause symptoms such as headaches and nausea. Sometimes, therapy is useful to help patients regain balance and cognitive function.

FINDING THE BEST DOCTOR

To find a neurologist or neurosurgeon who has experience diagnosing and treating iNPH, consult the website of the Hydrocephalus Association, which provides a directory of neurologists and neurosurgeons throughout the US.