A friend has been diagnosed with Dandy-Walker syndrome.
What are the details of this condition?
I would like to talk to him about it, but need some information first.
In order to discuss Dandy-Walker syndrome, one needs first to say something of the anatomy and physiology of the brain.
The brain and spinal cord are covered by three membranes, collectively known as the meninges and it is these that become inflamed in meningitis.
There is a space between the first membrane covering the nervous tissue and the second that is called the subarachnoid space. It is filled with a fluid known as cerebrospinal fluid or CSF.
The same fluid is found in hollow cavities or ventricles within each side of the brain and the part of the brain that joins the base to the spinal cord, known as the brain stem.
There are four ventricles. The two (one on either side) in the cerebral hemispheres are termed the lateral ventricles, while the two in the mid brain, extending down through the brain stem into the central channel running through the middle of the spinal cord are termed the third and fourth ventricles.
CSF is secreted by cells in the lateral ventricles and third and fourth ventricles. All four ventricles are in physical communication with one another and also communicate with the subarachnoid space via passageways out of the fourth ventricle.
CSF produced by the cells in the ventricles is reabsorbed by frond-like cells or villi associated with the spinal cord. CSF acts as a support structure for the brain and spinal cord, and normally allows a uniform pressure to be maintained on the nervous tissue structure.
The skull may be considered to be a watertight box containing the brain, blood and CSF.
The normal volume of circulating CSF within the system of ventricles described above is around 125ml. Any increase in circulating blood within the brain must therefore be associated with a decrease in CSF volume, otherwise brain tissue will be compressed.
Excessive production of CSF, or failure of reabsorption due to obstruction of the passageways out of the fourth ventricle, leads to an accumulation of fluid in the brain ventricles leading to hydrocephalus.
The latter occurs when there is a mechanical blockage sometimes relating to a defect of development, when the condition becomes apparent during infancy.
Dandy-Walker syndrome is a cyst in the balance control part of the brain (cerebellum) that is involved with the fourth ventricle. This may interfere with the body's ability to drain CSF from the brain, resulting in hydrocephalus.
Dandy-Walker cysts are formed during early embryonic development while the brain forms. The cyst in the cerebellum typically has several blood vessels running through it connecting to the brain, therefore surgical removal is not possible.
In the majority of cases of Dandy-Walker the cause is not known, though there are a few known cases resulting from autosomal recessive genes. Dandy Walker is generally discovered before birth by ultrasound.
Symptoms in the newborn may include a bulge or lump on the back of the head.
The syndrome may include a variety of other symptoms, including congenital heart problems; malformations of the face, fingers, or toes; other structural anomalies of the brain; abnormal breathing patterns; mental retardation and delay in physical development; high pain threshold; fits and imbalance.
The classical clinical signs of hydrocephalus in infancy result from an increase in the pressure within the skull.
The child's head increases in circumference and becomes larger than normal for its age - with an abnormal shape, prominent veins on the forehead and a wide soft spot or fontanelle on top.
The face becomes relatively smaller by comparison and the child's eyes can appear like 'the setting sun' owing to distortion of the surrounding bones.
Clinical examination of the nervous system can also produce a variety of abnormal signs, depending on where the excess pressure is exerting its effect on the brain.
Treatment of hydrocephalus varies with the cause and therefore the prognosis of the condition. When surgery is indicated, there are procedures that can be performed to bypass the obstruction and thus relieve the increased CSF pressure.
As a result, the fluid is either diverted internally within the CSF circulation system or externally by a tube into the abdominal (peritoneal) cavity or via the major veins in the neck and eventually therefore on into the right side of the heart.
The NetDoctor Medical Team