NRP/511 Week 7: Neurological Pathophysiology Case, sample paper

Feet Stuck to the Floor, a Bladder That Cannot Wait and a Checkbook Left Unbalanced: The Pathophysiology of Normal Pressure Hydrocephalus in a 76-Year-Old Retired Accountant

[Student Name]

University of Phoenix

NRP/511: Advanced Pathophysiology

Week 7 Assignment

[Instructor Name]

[Date]

The patient is a composite written for a model paper.

Mr. F., a 76-year-old retired accountant, was brought to our clinic by his daughter. Over the past year he has begun walking with short, shuffling steps, his feet seeming stuck to the floor when he starts to walk or turns. He has fallen twice. He now needs to rush to the bathroom and has had several accidents. His daughter noticed he stopped balancing his checkbook, something he did for 50 years, and he seems slower and less interested in things. His Montreal Cognitive Assessment score is 22 out of 30. This paper explains the condition that likely links these problems.

The Triad

In 1965, Adams et al. described patients with dementia, gait disturbance and urinary incontinence who had enlarged ventricles but normal cerebrospinal fluid pressure on lumbar puncture and who improved after shunting. They called the condition symptomatic occult hydrocephalus with normal cerebrospinal fluid pressure. The triad they described remains the clinical picture of what is now called idiopathic normal pressure hydrocephalus (Adams et al., 1965).

Cerebrospinal Fluid in Balance

Cerebrospinal fluid is produced mainly by the choroid plexus in the ventricles, about 500 mL a day, flows through the ventricles into the subarachnoid space and is absorbed into the venous system, traditionally through the arachnoid granulations, with other routes also contributing. Normally, production and absorption are balanced, and the ventricles stay small.

What Goes Wrong

In normal pressure hydrocephalus, absorption is impaired, so resistance to outflow rises. Williams and Malm (2016) describe several proposed contributors, including reduced compliance of aging blood vessels, which changes the pulsations that move cerebrospinal fluid, and impaired absorption pathways. The ventricles enlarge. Pressure measured by lumbar puncture is normal or only slightly elevated, but it is thought to fluctuate, with intermittent pressure waves, and the enlarged ventricles exert stretching force on surrounding tissue even at normal average pressure.

The name says normal pressure, but the brain around the ventricles is under constant strain from a fluid space that has quietly grown too large.

Why Gait Suffers First

The corticospinal fibers that control the legs descend close to the lateral ventricles, while fibers to the arms and face lie farther out. As the ventricles expand, the fibers nearest them, those controlling the legs, are stretched and compressed first. Reduced blood flow to the periventricular white matter adds ischemic injury (Williams & Malm, 2016). The result is a gait that is wide-based, slow and shuffling, with difficulty initiating steps, often described as magnetic, while arm movements are relatively preserved. This distinguishes it from Parkinson disease, in which arm swing and hand movements are usually affected and rest tremor is common.

Why the Bladder Cannot Wait

Frontal lobe pathways that inhibit bladder contraction also pass near the ventricles. When they are stretched, bladder inhibition weakens, producing urgency and urge incontinence. Early in the disease, patients often notice urgency before incontinence; later, frontal involvement may lead to reduced awareness of incontinence.

Why Thinking Slows

Stretching of frontal and subcortical white matter pathways disrupts networks for attention, processing speed and executive function. The cognitive pattern in normal pressure hydrocephalus is typically subcortical: slowed thinking, apathy, poor planning and reduced attention, with relatively preserved language and recognition. Mr. F.'s difficulty with his checkbook, a task requiring planning and sustained attention, and his apathy fit this pattern. In Alzheimer disease, early memory loss and word-finding problems are more prominent.

Imaging

Brain imaging shows enlarged ventricles out of proportion to the degree of cortical atrophy, commonly measured by the Evans index, the ratio of the maximal width of the frontal horns to the maximal inner width of the skull, with values above 0.3 suggesting ventriculomegaly (Relkin et al., 2005). Other supportive features include narrowing of the high convexity sulci and a sharp callosal angle.

Testing the Mechanism

If enlarged ventricles are causing symptoms, removing fluid should help. A large-volume lumbar tap removes 30 to 50 mL of cerebrospinal fluid, and gait is measured before and after. Improvement supports the diagnosis and predicts benefit from a shunt; a negative tap does not exclude it, because its sensitivity is limited (Relkin et al., 2005). Extended lumbar drainage over several days is a more sensitive test used in some centers.

Treatment

A ventriculoperitoneal shunt diverts cerebrospinal fluid from the ventricles to the abdomen, relieving the strain. Gait is the symptom most likely to improve, with cognitive and urinary symptoms improving less consistently. Williams and Malm (2016) note that outcomes are better when symptoms are shorter in duration and gait is the dominant problem. Shunts carry risks, including infection, overdrainage and subdural hematoma, and require careful selection of patients.

Conditions That Coexist

Normal pressure hydrocephalus often occurs alongside other conditions of aging. Many patients also have small vessel disease in the white matter from hypertension, which can cause a similar gait and cognitive pattern, and some have early Alzheimer pathology. When these coexist, shunting may help less, because not all of the symptoms come from the enlarged ventricles (Williams & Malm, 2016). Mr. F. has hypertension, so his MRI will be read for white matter disease as well as ventricular size, and the neurologist will weigh both in deciding whether he is a good candidate for a shunt.

What His Examination Shows

On examination, Mr. F. walks with short steps and a wide base, turns in several small steps and hesitates at the doorway. His arms swing normally, he has no rest tremor and his muscle tone in the arms is normal, findings that argue against Parkinson disease. His reflexes are brisk in the legs. He recalls three of five words after a delay but improves with cues, a pattern more typical of slowed retrieval than of the storage failure seen in Alzheimer disease.

Why Diagnosis Matters

Normal pressure hydrocephalus is one of the few treatable causes of dementia and gait decline in older adults, yet its symptoms are easily attributed to aging, Parkinson disease or Alzheimer disease. Mr. F.'s daughter had assumed his changes were normal aging. I order an MRI of the brain and refer him to neurology for evaluation, including a tap test if imaging supports the diagnosis.

Safety in the Meantime

His two falls are a warning. I arrange a physical therapy evaluation and home safety review, and recommend a bedside commode at night to reduce rushing to the bathroom in the dark.

Conclusion

In normal pressure hydrocephalus, impaired cerebrospinal fluid absorption enlarges the ventricles while measured pressure stays normal, stretching and reducing blood flow to periventricular white matter. Because leg fibers lie closest to the ventricles, gait fails first; frontal bladder pathways and frontal-subcortical networks explain urgency and slowed thinking. The same mechanism explains the imaging findings, the value of the tap test and why diverting fluid can improve a condition that looks like irreversible decline.

References

Adams, R. D., Fisher, C. M., Hakim, S., Ojemann, R. G., & Sweet, W. H. (1965). Symptomatic occult hydrocephalus with normal cerebrospinal-fluid pressure: A treatable syndrome. New England Journal of Medicine, 273(3), 117-126. https://doi.org/10.1056/NEJM196507152730301

Relkin, N., Marmarou, A., Klinge, P., Bergsneider, M., & Black, P. M. (2005). Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery, 57(3 Suppl.), S4-S16. https://doi.org/10.1227/01.NEU.0000168185.29659.C5

Williams, M. A., & Malm, J. (2016). Diagnosis and treatment of idiopathic normal pressure hydrocephalus. Continuum: Lifelong Learning in Neurology, 22(2), 579-599. https://doi.org/10.1212/CON.0000000000000305