Overview
Normal pressure hydrocephalus is characterised by too much cerebrospinal fluid in the brain’s ventricles. It typically affects adults in their 60s and 70s, who may forget a friend’s name or no longer enjoy a walk around the block. Implanting one of our shunts may help relieve symptoms.
Definition
Hydrocephalus refers to an excessive amount of cerebrospinal fluid within the brain’s ventricles. Normal pressure hydrocephalus is a type of hydrocephalus that affects older adults, typically those in their 60s and 70s.
Under normal conditions, a delicate balance exists between the production, circulation, and absorption levels of cerebrospinal fluid in the cavities of the brain known as “ventricles.” Hydrocephalus develops when cerebrospinal fluid can’t flow through the ventricular system, or when absorption into the bloodstream isn’t the same as the amount of cerebrospinal fluid produced.
Symptoms
Normal pressure hydrocephalus is characterised by the gradual onset of three symptoms, usually in this order:
- Gait disturbance (difficulty walking) in the form of small shuffling steps, a tendency to fall, a feeling of heavy feet, or difficulty using stairs
- Urinary incontinence (impaired bladder control) in the form of a frequent or urgent need to urinate, or the loss of control to hold back urine
- Mild dementia (cognitive impairments) in the form of forgetfulness, short-term memory loss, loss of interest in activities, or mood changes
Causes
Like other types of hydrocephalus, the defining characteristic of normal pressure hydrocephalus is the enlargement of the ventricles in the brain. The expanded ventricles seem to distort the nerve pathways between the brain and the spinal cord, thus causing the symptoms. In some cases, blood flow to the brain decreases as well.
For more than 50% of people with normal pressure hydrocephalus, the cause of the hydrocephalus cannot be determined. In the other cases, the individual has a history of brain haemorrhage (for example, from an aneurysm rupture or brain trauma) or meningitis. However, it’s not clear why or how these conditions lead to normal pressure hydrocephalus.
Diagnosis
Normal pressure hydrocephalus can be difficult to diagnose, since not all of the symptoms may arise at the same time. Furthermore, these symptoms are often associated with other conditions that are common in an ageing population (such as Parkinson’s disease, osteoarthritis, and Alzheimer’s disease).
One or more of the following diagnostic tests are typically used to check for normal pressure hydrocephalus:
- Brain imaging exams identify enlarged ventricles
- CT scans use x-rays to produce cross-sectional images that allow doctors to look at many different parts of the brain
- Magnetic resonance imaging provides important detail of the ventricular system and helps to rule out other disorders like subdural haematoma, tumour, infection, or a structural abnormality
- Neuropsychological testing is the most accurate means of determining and documenting cognitive strengths and problems
- Lumbar cerebrospinal fluid drainage is used to predict the likelihood of a positive response by the individual to a shunting procedure
- Lumbar puncture or spinal tap is an invasive diagnostic test that removes cerebrospinal fluid from the spinal column
- Extended lumbar drainage is an option if an individual does not respond to a simple lumbar puncture
- Cerebrospinal fluid outflow resistance is a more involved test that determines the capacity of the body to absorb excess cerebrospinal fluid