Generality
Normoteso hydrocephalus is a neurological pathology, which mainly affects older people.
This condition is characterized by the accumulation of an excessive quantity of cerebrospinal fluid in the cerebral ventricles, secondary to an imbalance between production and reabsorption of the same fluid. The result is symptoms very similar to those of Alzheimer's disease. Normoteso hydrocephalus presents itself, in fact, with a progressive impairment of cognitive functions, up to dementia . In addition to these manifestations, the disease can cause potentially debilitating signs and symptoms, such as urinary incontinence and difficulty walking .
The exact causes at the origin of normal pressure hydrocephalus are still unknown. Sometimes, the pathology appears to be secondary to severe head trauma, complications of neurosurgical interventions, cerebral haemorrhages or meningitis.
The normoteso hydrocephalus is treatable, provided it is identified in time, with the implantation of a shunt or the periodic rachicentesi, for the drainage of the cerebrospinal fluid in excess from the cerebral ventricles. Early intervention increases the chances of improving the clinical picture.
What's this
Normoteso hydrocephalus (or idiopathic chronic hydrocephalus) is a disease that mainly affects people over 60 years of age. This progressive disease is responsible for a highly debilitating symptomatology.
From a clinical point of view, normotensive hydrocephalus is defined by a disproportionate increase in volume of the cerebral ventricles (natural cavities of the brain that contain cerebrospinal fluid).
This situation arises when:
- Cerebrospinal fluid (or CSF) is unable to flow through the ventricular system;
- The quantity of liquor absorbed in the circulation is lower than that produced.
The result is the enlargement of the cerebral ventricles and the increase in intracranial pressure, which tends to stabilize, then, with the passage of time.
In normotensive hydrocephalus there is a characteristic (but not specific) symptomatic triad represented by:
- Disturbance of walking and balance : walking becomes slow and unstable, with considerable difficulty lifting the feet off the ground;
- Cognitive disorders (impairment of memory, attention, initiative and mental programming);
- Urinary disorders ( urinary urgency and incontinence).
What is the cerebrospinal fluid?
- The cerebrospinal fluid (also called liquor or cerebrospinal fluid ) is the fluid that permeates and protects the central nervous system (brain, spinal cord, cranial nerves and spinal roots).
- The liquor is produced by the choroid plexus, located in the depths of the brain, inside cavities called cerebral ventricles . The latter are in total four and are connected to each other through openings (called forams ) and ducts . From the ventricles, the cerebrospinal fluid circulates to reach the surface of the brain and marrow, to then be reabsorbed by special structures, located at the level of the dura mater (membrane that covers the brain, marrow and spinal roots).
- Under normal conditions, there is a delicate balance between production, circulation and absorption of CSF at the level of the cerebral ventricles.
- A disturbance of production (in excess), of reabsorption (in defect) or of circulation (obstruction) of the cerebrospinal fluid can cause a condition of hydrocephalus, that is of pathological swelling of one or more cerebral ventricles.
- In the case of normal pressure hydrocephalus, the dilation of all the cerebral ventricles (tetraventricular hydrocephalus) occurs with alterations of the liquor fluid dynamics, without being able to identify any apparent cause that may justify its appearance.
Causes
Normal pressure hydrocephalus involves an excessive accumulation of cerebrospinal fluid inside the cerebral ventricles. The latter undergo a dilatation that causes a distortion of the nerve connections between the brain and the spinal cord, causing the symptomatology associated with this condition (gait disturbances, urinary incontinence and dementia). Sometimes even direct blood flow to the brain tends to decrease.
In most cases, the exact cause of normal pressure hydrocephalus cannot be determined with certainty.
More rarely, the disease may be related to a previous cerebral haemorrhage (due, for example, to an aneurysm rupture), a severe head injury, a neurosurgical intervention or an episode of meningitis . However, it is still unclear how these conditions contribute to the normal pressure hydrocephalus.
Symptoms and Complications
Normoteso hydrocephalus is characterized by the gradual onset of the following symptom triad:
- Walking disorders (difficulty walking) with:
- Difficulty starting the march;
- Instability and disturbance of balance;
- Magnetic gait (inability to lift feet off the floor and shuffle);
- Tendency to fall;
- Sensation of heavy feet;
- Difficulty climbing and descending stairs;
- Bending the bust forward;
- Slow motion and / or reduced cadence.
- Urinary incontinence (bladder control problems) with:
- Frequent and sudden need to urinate;
- Inability to retain urine.
- Dementia (cognitive deficits) with:
- 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 normal pressure hydrocephalus, may have an evolutionary course over time, becoming irreversible. With the progression of the disease, in addition to the psycho-motor slowing down, various cognitive deficits appear. Memory tends to be compromised later and dementia can only appear in the more advanced stages.
To know
- The symptoms of normoteso hydrocephalus are often similar to those of other pathologies, such as Alzheimer (short-term memory deficit), Parkinson (gait disorders) or forms of senile dementia.
- Unlike these conditions, however, normoteso hydrocephalus is treatable, in most cases, with a surgical intervention which consists in the introduction of a valve (shunt) for the drainage of excess liquor.
- Since this is a progressive disease, it must be emphasized that timeliness in diagnosis is important for successful therapy and better recovery of lost functions.
Diagnosis
Diagnosis is based on clinical and neurological assessment.
The symptoms that most commonly occur in normal pressure hydrocephalus (gait disorders, urinary incontinence and dementia) are not specific to this condition, especially in older people. Other pathologies - such as some forms of vascular dementia and Alzheimer's - can cause, in fact, similar disorders. Therefore, making the diagnosis of normal pressure hydrocephalus can be particularly difficult.
The first method to ascertain the pathology consists in the lumbar puncture (or rachicentesi) followed by a CT scan and magnetic resonance imaging, in order to highlight:
- A picture of ventricular dilation;
- Absence of neurodegenerative diseases (Parkinson's, Alzheimer's, etc.) or other conditions (tumors, hemorrhages, infections, etc.) that cause similar disorders.
Neuroradiological examinations
Usually, neuroradiological examinations show a disproportionate increase in ventricular volume compared to cortical atrophy; this is not specific, but may support the diagnosis of normal pressure hydrocephalus.
The investigations aimed at defining the condition include:
- TAC on the skull and brain Magnetic Resonance : allow to highlight the increase in volume at the level of the ventricles and evaluate the presence of any structural causes that cause an obstruction (eg aneurysm, cerebral ischemia, etc.);
- PET (positron emission tomography) : is a survey that highlights the metabolic alterations of the brain.
Lumbar puncture (rachicentesi)
As a diagnostic test, the patient is subjected to a liquor subtraction test, through a lumbar puncture, with removal of 30-50 ml of cerebrospinal fluid.
Temporary improvement in symptomatology (ie walking, continence and cognitive function) after external lumbar drainage helps confirm the diagnosis of normal pressure hydrocephalus. Furthermore, the procedure serves to evaluate a possible positive response to the subsequent implantation of a shunt: lumbar puncture, in fact, tends to mimic the effect of the implanted valve (liquor subtraction test).
Treatment
The treatment of normal pressure hydrocephalus consists of a neurosurgical intervention. If correctly framed, the pathology can be managed with excellent results.
Shunt implant
In patients deemed suitable - that is, who have demonstrated a positive response to the liquor subtraction test - a device called a "shunt" (valve) can be implanted, which allows the elimination of excess cephalorachidian fluid from the cerebral ventricles.
This intervention allows the reduction of the dimensions of the dilated ventricles and can help alleviate the symptoms of normal pressure hydrocephalus, especially with regard to gait, continence and the ability to perform daily activities; less often, an improvement in cognitive functions is observed.
The most widely used technique is based on the positioning of a ventricolo-peritoneal shunt (from the cerebral ventricles to the peritoneum).
What is a shunt?
Shunts are plastic and silicone devices, generally consisting of two catheters (for example: one ventricular and one peritoneal) and a programmable one-way valve. These can be implanted to redirect excess cerebrospinal fluid from the brain to other areas of the body (in the ventricolo-peritoneal shunt, for example, the CSF is transported to the abdomen, where it is reabsorbed).
The risks associated with shunt implantation for the treatment of normal pressure hydrocephalus are rare, but possible. These include intraparenchymal cerebral hemorrhage and infections. On the other hand, late complications include the obstruction of a catheter or the disconnection of one of the two catheters from the valve.
Lumbar puncture
For patients who do not want or cannot undergo a shunt implantation, it is possible to achieve a clinical improvement for a long time, repeating the rachicentesi (or external lumbar drainage) with evacuations of large amounts of liquor, at intervals of a few weeks or months.
