Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is a brain disorder characterized by the accumulation of excess cerebrospinal fluid (CSF) in the brain’s ventricles. This condition leads to problems with thinking and reasoning, difficulty walking, and loss of bladder control.

About

Normal pressure hydrocephalus occurs when there is an abnormal buildup of CSF in the fluid-filled chambers of the brain called ventricles. Despite the excess fluid, the CSF pressure measured during a spinal tap is often within the normal range. As the ventricles enlarge due to the accumulation of CSF, nearby brain tissue can be disrupted and damaged, resulting in difficulties with walking, cognitive impairments, and loss of bladder control.

Prevalence

Normal pressure hydrocephalus primarily affects individuals 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. Only a small percentage of people with the condition receive an accurate diagnosis.

Causes and Risk Factors

While normal pressure hydrocephalus can be caused by other brain disorders such as tumors, head injuries, hemorrhages, infections, or inflammation, the exact cause of the fluid buildup is often unknown.

Symptoms

The hallmark symptoms of normal pressure hydrocephalus include:

– Difficulty walking, often described as a boat-like gait with the body leaning forward, wide leg stance, and feet appearing glued to the ground.
– Mild dementia characterized by a loss of interest in daily activities, forgetfulness, difficulty completing routine tasks, and short-term memory loss.
– Decline in thinking skills, including slower thought processes, apathy, impaired planning and decision-making, reduced concentration, and changes in personality and behavior.
– Loss of bladder control, which usually develops later in the disease compared to walking difficulties and cognitive decline.

 

Diagnosis

Normal pressure hydrocephalus is often overlooked or misdiagnosed because its symptoms resemble those of other conditions such as Alzheimer’s disease, Parkinson’s disease, and Creutzfeldt-Jakob disease. The “classic” clinical picture of normal pressure hydrocephalus involves experiencing all three hallmark symptoms, although not everyone with the condition exhibits all three. Diagnosis typically involves:

– Brain imaging to detect ventricle enlargement using techniques like magnetic resonance imaging (MRI) or CT scan. It helps distinguish normal pressure hydrocephalus from other brain disorders.
– Clinical examination by a neurologist with expertise in evaluating brain disorders that affect movement, thinking skills, and physical functions.
– Cerebrospinal fluid tests, including lumbar puncture, external lumbar drainage, measurement of CSF outflow resistance, intracranial pressure (ICP) monitoring, and isotopic cisternography to predict shunt responsiveness and determine shunt pressure.

Outcomes and Treatment

Limited studies have investigated the benefits of shunt insertion for normal pressure hydrocephalus, often with small sample sizes and short follow-up periods. The SINPHONI-2 trial suggested potential benefits of lumboperitoneal shunt surgery, but further research is necessary to validate these findings. Difficulty walking is the symptom most likely to improve, while the short-term benefits of shunt insertion tend to decline over time. Some studies have reported significant postsurgical complications.

Normal pressure hydrocephalus is one of the few causes of dementia that can be controlled or reversed with treatment. If symptoms and evaluation results indicate normal pressure hydrocephalus, a high-volume spinal tap may be performed to assess the potential benefits of shunt insertion. During this procedure, a large amount of spinal fluid is removed, and the individual is observed for improvements in walking, thinking, and reasoning. However, most people suspected of having normal pressure hydrocephalus do not experience improvements following the removal of cerebrospinal fluid. Currently, there are no effective nonsurgical treatments for normal pressure hydrocephalus, and diuretics, which remove excess fluid throughout the body, do not appear to alleviate symptoms. Further research is needed to better understand the condition’s prevalence, its effects on movement, thinking, and bodily functions, and the optimal targets and benefits of shunt insertion.