This condition is characterized by the "accumulation of" an excessive amount of CSF in the cerebral ventricles, secondary to an imbalance between production and reabsorption of the same fluid. Symptoms very similar to those of Alzheimer's disease ensue. Normotensive hydrocephalus presents, in fact, with a progressive impairment of cognitive functions, up to dementia. In addition to these manifestations, the disease can cause potentially disabling signs and symptoms, such as urinary incontinence and difficulty walking.
The exact causes of normal pressure hydrocephalus are still unknown. Sometimes, the disease appears to be secondary to severe head trauma, complications from neurosurgery, brain haemorrhages, or meningitis.
Normal pressure hydrocephalus is treatable as long as it is identified in time, with shunt implantation or periodic rachycentesis, to drain excess cerebrospinal fluid from the cerebral ventricles. Early intervention increases the chances of improvement in the clinical picture.
containing cerebrospinal fluid).
This situation arises when:
- Cerebrospinal fluid (or CSF) is unable to drain through the ventricular system;
- The amount of liquor absorbed into the circulation is less than that produced.
The result is the enlargement of the cerebral ventricles and the increase in intracranial pressure, which then tends to stabilize over time.
In the "normotensive hydrocephalus, a characteristic (but not specific) symptomatological triad is manifested, represented by:
- Disturbances of walking and balance: gait becomes slow and unstable, with considerable difficulty in lifting the feet from the ground;
- Cognitive disturbances (impaired memory, attention, initiative and mental programming);
- Urinary disorders (urinary urgency and incontinence).
What is the cerebrospinal fluid?
- Cephalorachidian fluid (also called CSF or cerebrospinal fluid) is the fluid that permeates and protects the central nervous system (brain, spinal cord, cranial nerves and spinal roots).
- The CSF is produced by the choroid plexus, located deep in the brain, inside cavities called cerebral ventricles. The latter are four in total and are connected to each other through openings (called foramina) and ducts. From the ventricles, the cerebrospinal fluid circulates to reach the surface of the brain and medulla, to then be reabsorbed by special structures, located at the level of the dura mater (membrane that covers the brain, medulla and spinal roots).
- Under normal conditions, there is a delicate balance between the production, circulation and absorption of CSF at the level of the cerebral ventricles.
- A disturbance in the production (in excess), in the reabsorption (in defect) or in the circulation (obstructions) of the cerebrospinal fluid can cause a condition of hydrocephalus, that is, a pathological swelling of one or more cerebral ventricles.
- In the case of normotensive hydrocephalus, there is dilation of all the cerebral ventricles (tetraventricular hydrocephalus) with alterations in the fluid dynamics of the CSF, without being able to identify any apparent cause that could justify its appearance.
;
- Frequent and sudden urge to urinate
- Inability to hold urine.
- Short-term memory impairment (amnesia);
- Reduced attention and concentration;
- Disorders of executive function (ie the set of schemes and processes of planning, control and coordination of the cognitive system);
- Reduced reaction time;
- Apathy;
- Mood swings.
The disorders that characterize normotensive hydrocephalus can have an evolutionary course over time, becoming irreversible. With the progression of the disease, in addition to the psycho-motor slowdown, various cognitive deficits appear. Memory tends to be compromised later and dementia can appear only in the most advanced stages.
To know
- The symptoms of normal pressure hydrocephalus are often similar to those of other diseases, such as Alzheimer's (short-term memory deficit), Parkinson's (walking disorders) or forms of senile dementia.
- Unlike these conditions, however, normotensive hydrocephalus is treatable, in most cases, with a surgical intervention that consists in the introduction of a valve (shunt) for the drainage of excess liquor.
- Since this is a progressive pathology, it should be emphasized that timeliness in diagnosis is important for successful therapy and better recovery of lost functions.
The first method aimed at ascertaining the pathology consists of lumbar puncture (or rachicentesis) which is followed, on the recommendation of the specialist, by CT and magnetic resonance imaging, with the aim of highlighting:
- A picture of ventricular dilation;
- Absence of neurodegenerative diseases (Parkinson's, Alzheimer's, etc.) or other conditions (tumors, bleeding, infections, etc.) that cause similar disorders.
Neuroradiological examinations
Usually, neuroradiological examinations show a disproportionate increase in ventricular volume compared to cortical atrophy; this finding is not specific, but may support the diagnosis of normal pressure hydrocephalus.
The investigations aimed at defining the condition include:
- CT scan of the skull and cerebral magnetic resonance: allow to highlight the increase in volume at the level of the ventricles and evaluate the presence of any structural causes that determine an obstruction (eg aneurysm, cerebral ischemia, etc.);
- PET (positron emission tomography): is a "survey that highlights the metabolic alterations of the brain.
Lumbar puncture (spinal tap)
As a diagnostic test, the patient undergoes a CSF subtraction test, through a lumbar puncture, with the removal of 30-50 ml of cerebrospinal fluid.
Temporary improvement of symptoms (i.e. walking, continence and cognitive function) after external lumbar drainage helps to confirm the diagnosis of normal pressure hydrocephalus. In addition, the procedure is used to evaluate a "possible positive response to the subsequent implantation of a shunt: the lumbar puncture, in fact, tends to mimic the effect of the implanted valve (CSF subtraction test).
