Archives for March 2009

I came across this website this morning, and the information was so easy to understand, that I thought I would share it.  They also have a pamphlet which is great to print out and send to people.

The key symptoms of Type 3 NGD:

Eye Movements
Imagine you are standing at the side of a road, watching the cars go past. Normally you would fix on a car, follow it until it moved out of your field of vision, then your eyes would flick quickly back and fix on another car, and so on. So your eyes would make a slow movement, followed by a quick movement. You would be able to do this without moving your head. The movements of the eyes are called saccades, and the combination of the quick and slow movements is called nystagmus. 

In NGD, the ability to initiate the quick movements is lost. Slow movements are unaffected. So, to use the cars-on-the-road parallel, the eyes follow the first car till it moves out of the field of vision, then stay ‘locked’ in that position. The ability to flick quickly back to fix on the next car is lost.  This is what Hannah has developed so far in terms of symptoms.

To compensate for this, sufferers develop a habit of blinking in order to ‘unlock’ and then thrusting their head sideways to look at the next object. This is not seen in young children, who have not developed the habit. Older children and adults become quite expert at this, and as a result, the eye movement problem may be much less obvious. This may give the impression that the eye movements get better as the child gets older. However, there is no evidence that they do actually improve.

There are many terms that have been used for this, such as ‘oculomotor apraxia’, ‘saccade initiation failure’ etc. It is invariably the first visible sign of type 3 NGD. It is therefore very important not to miss it, since the diagnosis of NGD often hinges on it. Sometimes it can appear when a child is as young as six months.

It is usually possible for someone with experience of NGD to pick this up on clinical examination alone, although it can be difficult in certain circumstances. For example:

* In young children, who may not be very co-operative
* Soon after the initial diagnosis of Gaucher Disease is made, when the child may be too ill to co-operate
* In patients with very mild disease, regardless of their age.
* In such situations the use of special equipment may be necessary in order to make the diagnosis. However, such equipment is not widely available.

Horizontal eye movement is always affected first. For some children, vertical eye movements may be affected as well. It is not clear why horizontal movement should be affected before vertical movement.

How does this affect my child’s day-to-day activities?
There are several practical problems that may arise as a result of these abnormal eye movements.

Your child will be unable to look from side to side quickly, and so is particularly vulnerable in a crowd. This is especially relevant in a crowded playground. He or she may get inadvertently knocked over.

Your child’s ability to cross the road may be severely affected, as he or she will be unable to look quickly from side to side for approaching vehicles.

There are also significant educational issues. These are discussed more fully in the companion booklet to this one; Neuronopathic Gaucher Disease; Special Educational Needs.

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Audiology
It is important that your child’s hearing is carefully checked. Most children appear to have normal hearing. However, many parents have noticed that in spite of a normal hearing test, their child does not seem to hear very well. Some children take a little longer to respond to questions, although eventually they give the right answer. In other words, they seem to have a problem with processing. They also seem to have problems hearing what is said to them against a background noise. This is known as cocktail party syndrome.

Research is under way to find out exactly why this should be the case. One area that is being investigated is the brainstem. The test used is the brainstem auditory evoked response (BAER). There are standardised ways of doing this. Usually, a series of clicks is emitted through headphones placed over the child’s ears, and the response is read through special electrodes placed over the scalp. Normally, a trace is obtained showing several waves. These waves have a distinctive shape and occur at certain intervals. Although people initially believed that each step in the hearing pathway is represented by a wave, the real situation is probably far more complex, so interpreting the result can be quite difficult.

What is clear is that these waveforms are more severely affected in Type 2 than Type 3. However, within each group the pattern is not so clear. Also it is not yet clear how useful the test is in monitoring disease progression. Although there is evidence that the waveform may get less distinct as the child grows older, there is no clear evidence that this means that the disease is progressing.

It should be emphasized that the BAER is not a hearing test. Its function is to test the pathways within the brain. A proper hearing test should always be performed. In fact, if there are any abnormalities in the BAER, they can be interpreted accurately only if a hearing test has been performed.

How does this affect my child’s day-to-day activities?
Even if the peripheral hearing is normal, there may be problems. If your child suffers from cocktail party syndrome, his or her ability to understand what is being said, particularly against a noisy background – for example, in the playground or a noisy classroom – may be affected. This, together with the processing problem mentioned above, may give the impression that he or she is very slow to respond to questions or instructions.

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Movement Disorders
Problems with posture and movement can be seen in Gaucher Disease. The most common of these is Parkinson’s disease. It has been thought for some time that Parkinsonian symptoms are more common in people with Gaucher Disease. They are different from those seen in otherwise normal people in that they occur at a younger age, are more severe and are more resistant to therapy. Initially it was thought that they might be part of NGD. However, these symptoms occur in type I sufferers as well. Most people now believe that these symptoms are not true manifestations of NGD, but that Gaucher disease sufferers are more likely to develop Parkinsonian symptoms.

Other movement disorders have been observed as well. Because of this, there has been a lot of recent interest in the basal ganglia. These are the nerve centres in the brain that control posture and movement. If they are affected, potential problems include:

Changes in tone (floppiness, rigidity)
Abnormal movements (tics, tremor)
Problems with balance (ataxia).
Further research is needed to clarify these issues.

How does this affect my child’s day-to-day activities?
This will vary depending on the nature and degree of the movement disorder.

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Other Problems
NGD sufferers may have quite severe visceral disease (visceral refers to involvement of the viscera or the chest and abdominal organs). Especially in small children, the abdominal distension caused by the enlarged liver and spleen may be so great as to push upwards on the diaphragm. This can cause quite significant breathing difficulties, and may also cause feeding problems.

The spine is invariably involved. A generalized curvature (kyphosis) is seen in nearly all sufferers. The reason for this is not quite clear.

Lung disease is extremely common and may cause breathing problems, a troublesome cough and chest infections. These are thought to be due to the presence of Gaucher cells in the lungs.

Sufferers may feel extremely tired. There may be more than one reason for this, such as lung involvement or spinal involvement. However, in many cases there is no obvious cause. There is no doubt though that it can be quite significant.