Normal pressure hydrocephalus (NPH)

Normal pressure hydrocephalus (NPH)

What is normal pressure hydrocephalus (NPH)?

Normal pressure hydrocephalus (NPH), is a treatable brain condition and causes disequilibrium and a gait disturbance.disequilibrium and a gait disturbance. Also called communicating hydrocephalus or malresorptive hydrocephalus, it refers to the excess accumulation of cerebrospinal fluid (CSF) in the ventricles of the brain. However, when the CSF pressure is measured in these patients it is usually normal or only slightly raised.

Normal pressure lateral ventricles. White “butterfly”shape in the middle.
Normal pressure lateral ventricles. White “butterfly”shape in the middle.
Abnormal lateral ventricles. White “butterfly” shape in the middle.
Abnormal lateral ventricles. White “butterfly” shape in the middle.

Why is normal pressure hydrocephalus (NPH) important?

Normal pressure hydrocephalus (NPH) is a potential treatable cause of dementia and an important cause of disequilibrium, balance problems and gait disturbances. Normal pressure hydrocephalus is estimated to be responsible for up to 6% of all dementias. It is seen more commonly in elderly patients and can easily be mistaken for a vestibular disorder, leading to unnecessary investigations. By identifying and treating this condition the risk of falling and injury in the elderly may be reduced.

It should also be mentioned that it is often misdiagnosed as Alzheimer’s disease and Parkinson’s disease, which usually is more difficult to treat.

What is the cause of normal pressure hydrocephalus (NPH)?

In most cases the cause is unknown. It is then referred to as primary or ideopatic normal pressure hydrocephalus (NPH). This form is more common in the elderly and effects up to 3% of people. The mechanism of increased CSF accumelation is also unknown. It is speculated that a disturbance in the production, reabsorption, or circulation of the CSF in the ventricles may play a role. Males and females are equally effected.

Secondary normal pressure hydrocephalus (NPH) refers to the condition when the cause is known. Causes include brain bleeds, brain surgery, radiation, brain trauma and meningitis. This form is seen in all ages.

The symptoms and signs of normal pressure hydrocephalus (NPH).

The increase of CSF leads to enlargement of the ventricles and a build up of pressure in the brain. This compresses surrounding brain tissue and classically leads to the following three symptoms:

  • A gait disturbance (ataxia)
  • Dementia
  • Bladder problems

Gait disturbance is the earliest sign. It has a gradual onset. The gait is characterised by slow, short steps and walking on a broad base (ataxia). It is as if the patient is stuck to the ground. Turning is slow, and steplike. Sometimes patients may complain that it feels as if they are walking on a boat. Falls may occur. The disturbance can be so severe that it may not be possible for the patient to walk without a cane or a walker.

Dementia in the form of progressive cognitive impairment appears next and urinary incontinence usually later in the disease.

How is normal pressure hydrocephalus (NPH) diagnosed?

In patients with the clinical picture, brain imaging in the form of computed tomography (CT) or preferably magnetic resonance imaging (MRI) is the investigation of choice.  In some case a lumbar puncture with the removal of cerebrospinal fluid may improve the gait (Miller Fisher test). The pressure should however be normal or only slightly raised and the cerebrospinal fluid should be clear.

The treatment of normal pressure hydrocephalus (NPH).

Treatment entails the surgical placement of a ventriculoperitoneal (VP) shunt. The shunt drains some of the excess CSF to the abdomen where it is absorbed. The reduction in pressure on the brain leads to an improvement of symptoms. The gait typically improves in more than 85% of patients. The other symptoms also improve, especially when done early in the course of the disease. Although there may be some complications with a VP shunt, the benefits outway the risks and natural outcome.

Medication seems to be ineffective.

Who can help to diagnose normal pressure hydrocephalus (NPH)?

If this condition is suspected it is advised to consult a neurologist, neurosurgeon or neur-otologist who will assist in making the diagnosis.