What is Normal Pressure Hydrocephalus?

February 28th, 2015

Normal pressure hydrocephalus (NPH) is a brain disorder that disproportionately affects seniors; it is one of the few treatable, and in many cases reversible, causes of dementia. However, because the symptoms of NPH may mimic Alzheimer’s disease, other dementias, or even the aging process, this disorder can be misdiagnosed without proper diagnostic testing. In fact, the Hydrocephalus Association estimates that more than 700,000 Americans have NPH, but that fewer than 20 percent receive an appropriate diagnosis.

Fortunately, NPH is a condition with highly successful surgical treatment options when caught early. Because its symptoms are typically progressive and the likelihood of successful treatment decreases the longer it goes undetected, it is important for seniors experiencing symptoms of NPH to promptly see their primary care physician, who can refer them to a neurologist. Educating caregivers on the signs of this disorder may facilitate early intervention for affected seniors.

Educating Caregivers on the Symptom Triad

NPH is characterized by excess cerebrospinal fluid (CSF) within the brain’s ventricles, or fluid-containing chambers, which eventually causes them to enlarge and then compress surrounding brain tissue. This increased pressure on the brain often causes the “NPH triad” of symptoms, which includes difficulty walking, cognitive decline, and urinary incontinence. This is likely because the parts of the brain most affected by increased fluid in the ventricles are the frontal lobes, which control the bladder, legs, and cognitive information processing. The disorder is called “normal pressure hydrocephalus” because a spinal tap will often show normal cerebrospinal fluid pressure even though excess fluid is in the brain.

Primary normal pressure hydrocephalus has no known cause, according to the Alzheimer’s Association and Hydrocephalus Association, but secondary NPH can result from a head injury or surgery, tumor, meningitis, or other brain infections.

Gait Disturbance

Up to 90 percent of seniors with NPH present with a change in gait, and it is often the most obvious first symptom. The gait in seniors with NPH is very distinct: wide, slow, and shuffling. These disturbances can range in severity from mild imbalance to a complete inability to walk, and they may lead to sudden falls. However, changes in gait, particularly a slow walking speed, may also indicate Alzheimer’s, other dementias, or Parkinson’s disease; it may be difficult for both physician and patient to distinguish the gait of early NPH from these disorders. Research presented at the 2012 Alzheimer’s Association’s International Conferencefound that slowed walking speed was associated with cognitive decline in senior participants, with Alzheimer’s patients showing the slowest walking speeds. And Parkinson’s disease presents with short stride length and slow gait, among other gait changes, which bears resemblance to NPH gait. In addition, seniors with arthritis, peripheral neuropathy, or cervical or lumbar stenosis may also experience gait difficulties.

NPH’s hallmark clinical feature that can distinguish it from other disorders is the wide-based gait with no feelings of unsteadiness or vertigo. Tell caregivers to keep an eye out for a wide stance as well as halting or “magnetic” steps, as if the senior’s feet are glued to the floor. As time progresses with undetected NPH, the base of the gait may continue to widen. Educate caregivers about the importance of alerting the senior’s physician the moment they notice any difficulty walking or changes in gait.

Urinary Incontinence

About 25 to 50 percent of patients with NPH experience urinary dysfunction, according to Johns Hopkins. This often begins with heightened urgency and frequency and progresses to complete loss of bladder control. These symptoms may be linked to a variety of other disorders affecting seniors, however, or even age-related changes in the bladder muscle. Remind caregivers, who may be inclined to view this symptom as innocuous because of its prevalence among seniors, to report any problems with urinary function. This issue could indicate a deeper underlying disorder, including NPH.

Cognitive Deficits

Some senior patients with NPH (or their caregivers) seek medical attention because of mental status changes, such as slowed processing, loss of interest in activities, apathy, or reduced problem-solving skills. The American Journal of Neuroradiology reports that NPH-induced dementia is subcortical in nature, meaning that it involves general reduced cognitive functioning rather than specific deficits in language or visual-spatial functioning, which helps distinguish it from Alzheimer’s disease. But because NPH-induced dementia is often less severe than other forms, it can be overlooked or mistakenly seen as a result of aging. When speaking with caregivers, stress the importance of reporting all recent changes in the senior’s thinking or problem-solving abilities to her doctor, who can conduct a thorough exam.

Differential Diagnosis of Normal Pressure Hydrocephalus

While physicians will be alerted to the possibility of NPH if the triad of symptoms present, it is important to share with caregivers that all three are not necessary for diagnosis. Diagnosis requires a combination of clinical features, examination, and brain imaging, which often shows ventricular enlargement. If a senior does not receive this extensive workup from his doctor, urge him and his caregiver to seek out a second opinion. Suggest that they look for a neurologist who specializes in NPH and other dementias, or one familiar with current diagnostic protocols.

NPH and Alzheimer’s may appear similar on brain scans, which is another reason that differentiation can be difficult. Other dementias, including Alzheimer’s, may cause atrophy or shrinkage of the brain, resulting in MRI and CAT scans that show enlarged ventricles in the same way that NPH appears on scans. A spinal tap will often be used to determine whether the removal of CSF fluid relieves the senior’s symptoms, pointing to the presence of NPH.

The Hydrocephalus Association notes that some physicians opt to order more involved cerebrospinal fluid tests as well, such as the placement of a lumbar drain or catheter (sometimes called continuous lumbar drainage), to allow continuous removal of CSF fluid over several days. This test requires hospitalization and comes with associated risks, so it may not be recommended for all patients. Still, it allows for more accurate recording of CSF pressure and indicates how well the senior will do with the surgical implantation of a shunt, which is currently the only widely accepted treatment for NPH.

Bright Outlook for Patients With NPH

Once the diagnosis of normal pressure hydrocephalus has been confirmed, with other dementias ruled out by a neurologist or neurosurgeon, a shunt, a device that “shunts” the CSF fluid from the brain to another part of the body, will likely be recommended if the senior is a candidate for surgery. It is important to share with seniors and caregivers that the surgical treatment for this disorder is advanced, so they should stay optimistic about improvement.

It is also worth noting to caregivers that for some patients, both NPH and another form of dementia may be present, each requiring their own differential diagnosis and treatment. In fact, Alzheimer’s disease with comorbidity in NPH is not uncommon. However, Alzheimer’s is not surgically treatable like NPH. Alzheimer’s and other forms of dementia cannot be cured, but current drug treatments can mask symptoms and help seniors better function while in mild to moderate stages.

Research has found that staying cognitively active may reduce the risk of Alzheimer’s; one study found that seniors who reported the most frequent participation in intellectually stimulating activities were 47 percent less likely to develop Alzheimer’s than those who had the least frequent participation.

Shunt Surgery

During shunt surgery, the proximal end of the catheter is placed into a ventricle in the brain, and the distal end is either placed into the peritoneal (or abdominal) cavity, called a ventriculoperitoneal shunt, or into a vein that leads to the heart, called a ventriculoatrial shunt. The shunt has a flow-regulated valve that opens when fluid pressure in the brain rises and closes when it is normal, designed to prevent overdrainage. Newer shunts have programmable valves that can be easily readjusted from outside the patient’s body using a magnetic tool. This helps prevent the need for repeated surgeries.

Surgical implantation of a shunt into the brain often provides substantial symptom improvement in NPH patients, and in some cases works within days or weeks of surgery. A 2012 article in the US National Library of Medicine reports that 70 to 90 percent of treated patients have clinical improvement with surgical treatment. Shunt surgery may sound concerning to your senior patient or her caregiver since it requires hospital admission, so it is important to stress this procedure’s high success rate in resolving or improving NPH symptoms. It may also reduce the senior’s level of disability and dependence on others due to symptoms of the disorder.

Shunts do not come without risk — ranging from malfunction to obstruction — but the majority of these complications can be managed successfully with prompt medical attention. Refer your senior patient and her caregiver to the Hydrocephalus Association’s shunt systems fact sheet for more information.

For seniors with dementia symptoms who are prone to sudden falls, a a medical alert device can improve safety and quality of life. Learn more about Lifeline medical alert systems.