GLOSSARY

Aneurysm

A localised pathological dilatation of a blood vessel. An aneurysm may be congenital or may occur secondary to weakness of the blood vessel wall due to cardiovascular disease (atheroma etc.).

 

Arachnoid - Sub-arachnoid space

One of the meninges surrounding the brain leaving a space in which the CSF circulates.

 

Arachnoid cysts

Outgrowths of the arachnoid, forming pockets, which may be large or small in volume, and are filled with CSF. They may prevent the normal circulation of CSF.

 

Arnold-Chiari (Syndrome)

A rare malformation seen in neonates and characterised by the association of spina bifida (cf. above) with an abnormal arrangement of the posterior brain (brainstem and cerebellum), which is engaged in the upper part of the spinal canal, with hydrocephalus, producing severe brain damage.

 

Arterio-venous malformation

A congenital abnormality resulting from pathological communication between an artery and a vein through a vascular pocket (or lake).

 

Atrial

Relating to the right atrium of the heart.

 

Bradycardia

Slowing of the beating of the heart (< 60/min).

 

Catheter

A small silicone tube allowing the CSF to circulate. A constituent part of a shunt.

Cerebral compliance

Cerebral compliance (C) is the ability of the brain to adapt to changes in volume (dV) inside the cranium in order to reduce changes in pressure (dP), i.e. C = dV/dP. A brain is described as compliant, (i.e. it has good compliance) if a large change in ventricular volume results in a small change in ICP.

Coma - Comatose

The condition of a patient who does not react or reacts inappropriately to a stimulus.

Congenital

Relating to an event which has occurred during pregnancy or childbirth.

Craniosynostosis or Craniostenosis

Premature fusion of one or more of the cranial sutures (the lines uniting the flat bones of the vault of the cranium) causing development arrest and deformities of the cranium. It may cause raised intracranial pressure and visual disturbance.

Encephalon

The part of the central nervous system contained in the skull consisting of the brain, cerebellum and brain stem.

Ependyma

The membrane covering the surface of the ependymal canal.

Ependymal canal

The central canal in the spinal cord which communicates with the IVth ventricle.

Epidural

Cf. Peridural.

Extra-dural

External to the dura mater (on the cranial side).

 

Fontanelles

Spaces between the cranial bones, which are incompletely fused in infants.

Foramen

A passage or opening. An aperture which enables two cavities or organs to communicate.

Foreign body

An object introduced or implanted into the human body.

Hg

Signifies "Mercury" in the international nomenclature of chemical elements.

Lumbar puncture

Introduction of a fine trocart between two vertebral arches at the level of the lumbar spinal column, in order to remove CSF without aspiration. It may also be used to inject a drug or a contrast medium.

Meninges

Membranes which surround and protect the brain and spinal cord; anatomically there are 3 meninges: the pia mater, which adheres to the brain and the spinal cord, the dura mater, which adheres to the bone and the arachnoid between these two membranes.

Meningitis

Infection or inflammation of the meninges.

MRI

Magnetic Resonance Imaging. A non-invasive further investigation using a magnetic field analysed by computer, which allows the anatomical structures of the brain to be clearly visualised, in both physiological and pathological states. A complimentary investigation to the CT scan.

Overdrainage

Excessive drainage by the shunt.

Peridural

Localised internal or external to the dura mater, i.e. between the dura mater and the bone (cranium or vertebral body).

Peritoneum

The membrane which lines the inside of the abdominal cavity.

Raised intracranial pressure

A syndrome characterised by frontal or occipital headaches, vomiting and ocular manifestations. It may develop into coma. It is due to raised pressure in the cerebral blood vessels, oedema of the brain or accumulation of CSF, and may have a variety of causes: hydrocephalus, tumours, haematomas, abscesses, cerebrovascular accidents, meningitis.

Revision

A surgical operation designed to replace all or part of the shunt.

Sagittal

Through a vertical plane, orientated from front to back.

Silicone

An implantable plastic material used to manufacture catheters and many medical implants.

Slit Ventricle Syndrome

Ventricles which have a very thin radiological appearance, indicating excessive drainage.
The slit ventricle syndrome consists of an association of clinical signs:

• Headaches, occurring when standing up, and resolving when the patient lies down
• Vomiting, visual or auditory disturbance, drowsiness

and paraclinical signs:

• Near disappearance of the ventricles on a CT scan. The ventricles appear as only a slit, hence the name of the syndrome.

Spina bifida

A malformation consisting of a fissure in the spine due to a fusion defect of one or more vertebral arches, through which the meninges and, occasionally the spinal cord, herniate together with varying amounts of CSF.

Spinal cord

The part of the central nervous system located in the vertebral canal.

Sub-arachnoid (space)

The space located between the arachnoid and the pia mater.

Sub-dural

Located between the dura mater and the arachnoid.

Sub-dural haematoma

A collection of blood between the brain and the dura mater.

Tomodensitometry (Tomodensitometric)

Synonymous with CT scan. A specific radiological procedure allowing different tissues in the human body to be examined in vivo in sections.

Tunnellising

The creation of a conduit in the form of a tunnel, which is covered entirely by the tissues in which it is made. In this context, the tunnel is made in the subcutaneous tissue in order to pass a catheter from one part of the body to the other without exteriorising the catheter. For example, the cranial catheter (the place where the valve is positioned) is tunnellised to the umbilicus (the place where the distal catheter is positioned in the peritoneum) when a ventriculo-peritoneal shunt is formed.