Hydrocephalus normal pressure

GENERAL ASPECTS

What is normal pressure hydrocephalus?

It is an entity in which the cerebral ventricles are enlarged, but the pressure of the cerebrospinal fluid they contain is not elevated.

What are the cerebral ventricles?

They are four anatomical cavities located inside the brain, which communicate with each other. Inside them there is cerebrospinal fluid, which also surrounds the brain externally, providing mechanical protection.

What other names does it go by?

It has been called normal pressure hydrocephalus, normotensive hydrocephalus or chronic adult hydrocephalus.

Why does it occur?

There are two types of normal pressure hydrocephalus, depending on whether or not there is a directly identifiable cause. When a cause is not clearly identified, it is called idiopathic normal pressure hydrocephalus. On the other hand, when a cause is identified, we speak of secondary normal pressure hydrocephalus. In these cases, there is a failure in the reabsorption of cerebrospinal fluid, due to the existence of a previous cerebral hemorrhage or other inflammatory or infectious problems affecting the meninges (membranes that envelop the central nervous system).

Who is affected?

It affects both men and women with similar frequency. The probability of onset increases with age, being very rare in people under 60 years of age.

CLINIC

What problems can it cause?

Normal pressure hydrocephalus produces three main symptoms: walking problems, voiding problems and cognitive impairment. Sometimes all three symptoms are not present simultaneously. Headache, nausea and vomiting are usually not present.

What is the difficulty in walking like?

The gait disturbance usually consists of what is called “apraxic gait”. It consists of walking with short steps, with a tendency to drag the feet, as if they were “magnetized” and stuck to the ground. Sometimes the feet are separated to increase the base on which the body is supported. Changes of direction and turns are usually broken down into several steps. Sometimes there may be falls.

What are voiding problems?

There is usually what is called “urinary urgency”: the patient has a sudden urge to urinate and has difficulty reaching the bathroom, and may experience urinary incontinence.

What are the cognitive problems?

They usually appear months or years after the onset of gait problems. They usually consist of a global slowing, with attention and concentration problems. Executive function problems may appear, which refers to the ability to follow and adequately reason the correct steps to solve a specific problem.

How do the symptoms appear?

It is very common that the first symptoms are walking problems and these are usually the most responsive to treatment. Months or years later, urinary problems usually appear and, finally, cognitive problems. The course is progressive, i.e. a worsening of symptoms is usually observed over time.

DIAGNOSIS

How is it diagnosed?

It can sometimes be a difficult entity to diagnose, since the three problems (gait disturbance, voiding and cognitive problems) are often present for other causes, alone or in combination, in people over 65 years of age. Therefore, it is sometimes difficult to discern whether the symptoms are due to normal pressure hydrocephalus or, on the contrary, are justified by other problems (for example, spinal osteoarthritis that hinders gait, or prostate problems that alter urination).

What complementary tests can be performed?

The workup begins with a brain imaging test (MRI or cranial CT) that confirms the existence of enlarged brain ventricles (ventriculomegaly). However, there are many causes of ventriculomegaly, so it is necessary to assess whether the pattern of ventricular enlargement corresponds to that of normal pressure hydrocephalus.

Often, if the symptoms and imaging findings are compatible, a lumbar puncture is usually performed next. This allows measurement of cerebrospinal fluid pressure to confirm that it is normal, as well as hydrodynamic testing to support the diagnosis. It is often used to remove a high volume of cerebrospinal fluid (around 30-40 ml) and then assess whether there is improvement in symptoms. If there is improvement, it would support the diagnosis.

What other diseases can cause ventricular enlargement?

The existence of cerebral atrophy may cause the cerebral ventricles to increase in size. Therefore, it is important to consider the possibility of a neurodegenerative disease as an alternative diagnosis. Lewy body disease, progressive supranuclear palsy and Alzheimer’s disease are three of the most common entities that can produce similar symptoms and imaging abnormalities to those occurring in normotensive hydrocephalus.

TREATMENT

What is the treatment of normal pressure hydrocephalus?

It consists of performing a ventricular shunt. This is a surgical intervention in which excess cerebrospinal fluid is drained from the interior of the cerebral ventricles to other anatomical cavities in order to prevent its accumulation.

What types of ventricular shunts are there?

There are two main types. On the one hand, the ventriculo-peritoneal shunt, in which a catheter is placed to connect the cerebral ventricles with the abdominal cavity (peritoneum). On the other hand, the ventriculo-atrial shunt, in which the ventricles are joined to the atrial cavity of the heart.

What symptoms improve?

Usually, gait problems are the ones that improve the most after the correct treatment. Sometimes cognitive problems may also improve. However, these often have a lower response rate, especially if the patient is at least moderately demented or if they have been present for several years prior to treatment.

How long does the benefit last?

The long-term prognosis is uncertain. Although many patients maintain the benefit several years after surgery, in other cases a clinical worsening is identified before two years after the intervention was performed.