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What is hydrocephalus?
What is a CSF Shunt?

Why a Sophysa
Adjustable Valve?

My treatment with a
Sophysa Valve
     

 

I - What is Cerebro-Spinal Fluid?
The Central Nervous System is made of all the nervous tissues which form the encephalon and the spinal cord.  It is made of white and grey matter (nerves are excluded).

These noble tissues are essential to the human being functioning, as the encephalon ensures control over the whole body, but they are fragile and must be protected.

The Central Nervous System is protected, from the outside to the inside:
  • the cranium bones (for the encephalon) and the spinal canal (for the spinal cord) act like a “helmet”;
  • the meninges act like « a protective wrapping »;
      - the dura mater, which is the outside layer;
      - the arachnoid;
      - the pia mater which is directly in contact with the central nervous system;
  • the CSF, or Cerebro-Spinal Fluid, which plays the role of a shock absorber.
The brain consists of two cerebral hemispheres (one right and one left), which meet in their lower midline part to form the diencephalon, which extends into the brain stem.  The brain stem joins the spinal cord in its lower part.







Central Nervous System
Each cerebral hemisphere contains a cavity called the lateral ventricle.  The two lateral ventricles take the shape of a crescent which is open anteriorly and which consists of three horns (frontal, temporal and occipital).  They are connected in the midline to the underlying third ventricle through the foramen of Monro.
Lateral Ventricles
The diencephalon is the place where the two cerebral hemispheres meet, in which the 3rd ventricle lies.

The brainstem is located between the brain above and the spinal cord below.  It consists of 3 parts, the mesencephalon (or midbrain), the pons and the spinal bulb (or medulla).

The 4th ventricle is delineated anteriorly by the posterior surface of the pons and posteriorly by the cerebellum.  It communicates superiorly with the 3rd ventricle through the aqueduct of Sylvius and inferiorly with the ependymal canal and the sub-arachnoid spaces through the lateral foramina of Luschka and the median foramen of Magendie.
Anatomy of skull, brain and ventricles
Cerebro-spinal fluid is the transparent "gin clear" fluid that fills the cerebral ventricles.  It bathes the brain and the spinal cord.

In addition to its mechanical protective role, CSF takes part in metabolic exchanges between the nervous system and the rest of the body.

Roles of CSF are:
  • Nutrition;
  • Cleaning of waste due to cellular metabolism;
  • Absorption of shocks for the protection of the Central Nervous System.
CSF is produced in the ventricles by the choroid plexus at a rate of approximately 20 ml/h in adults (8 ml/h in infants).

The CSF circulates within the lateral ventricle, the 3rd ventricle and leave the 4th ventricle through the foramina, entering the sub-arachnoid spaces surrounding the brain and spinal cord.  These sub-arachnoid spaces are fibrous tissues situated between the pia mater and the arachnoid, which behave like a sponge. Ventricles and foramina are cavities that have a role of reservoir for the CSF.  There is permanently 125 ml to 150 ml of CSF in the ventricles.

CSF pathways
The fluid returns to the venous circulation by absorption through small formations, the arachnoid villi (Pacchioni granules), a type of outgrowth from the arachnoid, through the dura mater and spaces in contact with the sagittal sinus at the midline of the brain.
Meninges and CSF absorption in sagittal sinus
 
With this cycle of production, circulation and absorption, under normal conditions, a perfect equilibrium exists between secretion and absorption of CSF.
 

 
The average CSF pressure in adults when lying down is 120-180 mm H2O (~10 mm Hg). The pressure is almost zero or even negative when standing up. The reference measurement of CSF pressure is measured at the level of the cerebral ventricles: this is intraventricular pressure. It is often called intra-cranial pressure (ICP).
 
II - What is hydrocephalus?

The term hydrocephalus indicates excess of fluid within the cranium.  This is a pathological condition which occurs as a result of imbalance between the production and absorption of CSF.  The equilibrium described above is disrupted.

Hydrocephalus only forms if the CSF is unable to leave the ventricular cavities or if its absorption is disturbed.

As the size of the cranium is fixed (except for children up to around 18 months of age in whom the fontanelles are still open), any increase in the volume of fluid within the ventricles affects the brain and leads to the development of neurological symptoms due to an increase in the Intracranial Pressure.

 
1 - Forms and types of hydrocephalus
Different forms of hydrocephalus may be distinguished:
  • Congenital, if it develops before or at birth;
  • Acquired, if it develops after birth, for example after a head injury, a meningitis, a cerebral haemorrhage or a neoplasic disease.
Hydrocephalus is commonly classified into two types:
  • Non-communicating or obstructive hydrocephalus;
  • Communicating or non-obstructive hydrocephalus.
Non-communicating hydrocephalus is caused by blockage of the circulation of CSF in the ventricular cavities.  This blockage usually occurs at the level of the aqueduct of Sylvius and may also be seen in the foramen of Monro and other foramina.  This type of hydrocephalus is commonly associated with clinical signs of raised intracranial pressure.

The major causes of non-communicating hydrocephalus are:
  • Congenital stenosis of the aqueduct of Sylvius;
  • Arnold Chiari Syndrome (Spina Bifida);
  • Tumours of the posterior fossa.
Communicating hydrocephalus occurs when the circulation of CSF around the brain is disturbed or if the absorption sites are non-functioning.

The major causes of communicating hydrocephalus may be grouped into two categories:

1 - Hydrocephalus due to excessive production of CSF: Choroid plexus papilloma (a very rare tumour);
2 - Hydrocephalus due to impaired re-absorption of CSF:
  • Idiopathic hydrocephalus, i.e. for which no cause can be found.  This is commonly known as Chronic Adult Hydrocephalus (CAH) or, alternatively, Normal Pressure Hydrocephalus (NPH), as in this instance the hydrocephalus is usually associated with near normal intraventricular pressure;
  • Post-meningitis hydrocephalus;
  • Post-haemorrhagic hydrocephalus (head injury, rupture of an aneurysm, or arterio-venous malformation, and so on…);
  • Hydrocephalus of the premature infant (following intraventricular haemorrhage, etc).
2 - Clinical signs of hydrocephalus
The clinical manifestations of hydrocephalus occur as a result of ventricular dilatation and of the increase in pressure within the cranium.

These manifestations may differ between patients and as a function of age.  The clinical signs for instance in infants and young children, whose cranial bones have not yet completely fused together, are different from those seen in adults.

The usual symptoms of hydrocephalus in infants include:
  • abnormal increase in head circumference;
  • bulging fontanelles;
  • dilatation of the veins on the surface of the cranium;
  • vomiting;
  • downward shift in gaze (sunset eyes), behavioural difficulties (irritability, drowsiness etc) or even seizures.
Depending on the cause, raised intracranial pressure may produce different signs in older children and adults. The major signs are:
  • headaches;
  • vomiting;
  • visual disturbance (blurred vision, double vision etc) with papilloedema, which is seen when the fundus of the eye is examined;
  • consciousness disorders: drowsiness, progressive lethargy or even coma.
Other signs may be found and are systematically looked for by doctors.  These include bradycardia or seizures.

The characteristic Hakim's Triad may be seen in normal pressure hydrocephalus, which is found mostly in adults:
  • psychiatric disorders, mimicking the appearances of dementia.  This involves mostly slow and poor quality ideation and activity, with apathy and indifference, serious memory and orientation disturbance, particularly in time, loss of attention and unawareness of reality.
  • gait disorders, with instability.  This is due to static abnormalities, which may develop into titubation.  The person moves around slowly and with care and may, occasionally, walk on the spot.  Turning around, or either starting or stopping suddenly leads to imbalance.
  • sphincter disturbance (incontinence++).  On occasions, the person is incontinent of urine and sometimes faeces.  It is not clear whether this is due to inattention, reduced awareness or urgency of micturition.  The patient may pass urine anywhere and soil his clothing.
 

 
     
 
 
 
 

 

Neurosurgical shunts
 

 

External CSF Drainage
 

 

ICP monitoring
 

 

Access ports
 
 
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