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Key points
- Normal pressure hydrocephalus (NPH) can mimic other types of dementia and is reversible.
- Symptoms that are typical of dementia can mean a variety of diagnostic possibilities.
- Physicians should consider all alternatives prior to arriving at a diagnosis of dementia.
As a medical student learning differential diagnosis, I was taught, “If you hear hoofbeats, think horses, not zebras.” In general, this makes sense. Practitioners generally consider the likely causes of a patient’s symptoms rather than the “exotics.” However, sometimes, you do indeed need to think about zebras instead of horses. A recent patient encounter illustrates this point.
Geoffrey is a 75-year-old man who called my office about a month ago. He told me his primary care physician had referred him because he suspected Geoffrey was depressed due to a recent decline in his health.
When I opened the door to my waiting room, I saw an older man who was strongly built but struggled to get off the couch, even with his cane. He moved slowly, but what caught my attention was his unusual gait. Instead of walking with his legs in tandem, one after the other, he was almost bowlegged. His facial expression was flat, although he was very pleasant about introducing himself.
As he lowered himself onto the couch in my office, I began, “What can I do for you today?”
“I don’t know. All I know is life is not worth living. I can’t go on like this.”
“Tell me more," I said.
Geoffrey saw a psychiatrist 20 years ago because he was experiencing depression and anxiety. He has been taking the same combination of medication for twenty years without a dose adjustment.
In 2020, he had surgery on his knees that replaced both joints. Shortly thereafter, he fell and hit his head. I asked whether he thought that event was linked to his present feelings.
“No, not just that,“ he said.
In October of last year, he experienced severe pain in his sciatic nerve (which runs from your buttock along the back of your leg). This was so severe Geoffrey required hospitalization for pain control. After discharge, he was admitted to a rehabilitation center. At the time of this meeting, he was receiving physical therapy at home twice weekly but mostly stayed in bed.
When I inquired about other symptoms, I learned that Geoffrey had sleep apnea but had trouble using the prescribed CPAP machine, so his sleep was disturbed.
What alarmed Geoffrey the most was the decline in his cognitive function. He worked in communication for high-level government organizations for years and regularly released press reports that were read by millions of people. He had been promoted frequently and was an award-winning journalist. Currently, he was having word-finding difficulty, poor memory even for recent events, and embarrassingly, he had become incontinent for urine.
His physical and mental decline had taken a toll on him to the point that he could not see a future for himself or his wife. He appeared severely depressed.
Having seen a neurologist, he was in the process of a workup for early dementia. He was adopted at birth, so we did not know his family's medical history. The neurologist considered Parkinson’s, among other possibilities, as the cause of his cognitive decline.
Suddenly, I heard hoofbeats. The triad of wide-based gait, apparent dementia, and urinary incontinence reminded me of a diagnosis I had seen before. I wondered if Geoffrey had a condition called normal pressure hydrocephalus. An MRI of his brain had been ordered, but the results were not yet available.
What is normal pressure hydrocephalus? (NPH)
Normal pressure hydrocephalus (NPH) is a brain disorder in which excess cerebrospinal fluid (CSF) accumulates in the brain's ventricles (hollow spaces), causing thinking and reasoning problems, difficulty walking, and loss of bladder control. In healthy individuals, cerebrospinal fluid flows in and around the brain and spinal cord to help cushion them from injury and provide nutrients. In individuals with normal pressure hydrocephalus, excess cerebrospinal fluid accumulates in the brain’s ventricles, which are fluid-filled chambers.
Normal pressure hydrocephalus is called "normal pressure" because CSF pressure, measured during a spinal tap, is often normal despite the excess fluid. As brain ventricles enlarge with the excess CSF, they can disrupt and damage nearby brain tissue, leading to difficulty walking, problems with thinking and reasoning, and loss of bladder control.
Normal pressure hydrocephalus primarily affects people in their 60s and 70s. The Hydrocephalus Association estimates that nearly 700,000 adults have normal pressure hydrocephalus, but it is often misdiagnosed as Alzheimer’s or Parkinson’s disease. In fact, less than 20 percent of people with the disease are properly diagnosed. That means half a million people are potentially walking around with a diagnosis they think is progressive. The good news: NPH can be reversed.
Geoffrey’s MRI confirmed enlarged ventricles. With his triad of symptoms, he was referred to a neurosurgeon who hospitalized him and performed sequential removals of small amounts of CSF under local anesthesia. After each procedure, Geoffrey’s gait and cognitive abilities were tested to see if the diagnosis was correct and to judge whether a more significant procedure (placement of a shunt) would help him long term. The good news was he improved significantly even after this minor decrease in his CSF pressure.
What is a cerebral shunt?
A shunt is a hollow tube surgically placed in the brain (or occasionally in the spine) to help drain cerebrospinal fluid and redirect it to another location in the body where it can be reabsorbed. The procedure is done in the hospital under general anesthesia and takes about an hour. The newer shunts are programmable, allowing the surgeon to adjust the strength of the shunt based on the patient's response. Some patients improve within days, but full recovery generally takes longer.
I saw Geoffrey again today. When I opened the waiting room door, I saw someone who looked ten years younger. Better than that, he was smiling. He did not use a cane, stood up from the couch without assistance, and has an almost normal, narrow gait. He told me he was grateful, but more than that, he was hopeful that he could resume his previously active life with his wife. His surgical procedure is planned for the end of April.
If you or someone you love is contemplating suicide, seek help immediately. For help 24/7, dial 988 for the National Suicide Prevention Lifeline, or reach out to the Crisis Text Line by texting TALK to 741741. To find a therapist, visit the Psychology Today Therapy Directory.
References
Madoka Nakajima, Kaito Kawamura, Chihiro Akiba, Koichiro Sakamoto, Hambing Xu, Chihiro Kamohara, Ikuko Ogino, Kostadin Karagiozov, Yuichi Tange, Kazuaki Shimoji, Shinya Yamada, Akihide Kondo, Hajime Arai, Masakazu Miyajima.
(2021) Differentiating comorbidities and predicting prognosis in idiopathic normal pressure hydrocephalus using cerebrospinal fluid biomarkers: a review. Croat Med J. 2021;62:387-98.
