Symptoms of nGD usually develop first in childhood. The initial problems are usually enlargement of the liver and spleen, poor feeding and failure to gain weight adequately. These usually appear in the first year of life but may appear later.
One of the most common, and invariably one of the first, symptoms of nGD is abnormal eye movement. 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, flick your eyes quickly back and fix on another car, and so on. Your eyes would make a slow movement, followed by a quick movement 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’ analogy, the eyes follow the first car until 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.
To compensate for this, sufferers develop a habit of blinking in order to ‘unlock’ and then thrust their head sideways to look at the next object. There are many terms that have been used for this, such as ‘oculomotor apraxia’ and ‘saccade initiation failure.’ Horizontal eye movement is always affected first. In some children, vertical eye movements may be affected as well.
In spite of a normal hearing test, some people with nGD do not seem to hear very well. They can take a little longer to respond to questions, although eventually they will give a response. We now know that they have a problem with auditory processing. There also seems to be problems hearing what is said against a background noise. Normally, one is able to suppress such noise and ‘filter’ the important sounds. However, people with nGD have difficulty in doing this. This, together with auditory processing problems, may give the impression that he or she is very slow to respond to questions or instructions.
The nerve centres in the brain that control posture and movement are affected in nGD leading to problems including:
•Changes in tone (floppiness, rigidity)
•Abnormal movements (tics, tremor)
•Problems with balance (ataxia).
There is also a higher risk of seizures in nGD. Different types of seizures may be seen. Most can be controlled fairly easily, however, they do of course have implications for day-to-day activity, education, driving etc. One type of seizure is particularly important: myoclonic seizures which is when the muscles jerk. In nGD, myoclonic seizures are usually very difficult to treat and nearly always signify disease progression.
nGD sufferers may have quite severe impact on the chest and abdominal organs. Especially in small children, the abdominal distension caused by the enlarged liver and spleen may be so great that it may push upwards on the diaphragm. This can cause quite significant breathing difficulties and may also cause feeding problems in young children.
A generalized curvature of the spine (kyphosis) is seen in nearly all sufferers.
Lung disease is extremely common and may cause breathing problems, as well as troublesome cough and chest infections. Sufferers may also feel extremely tired.
More information can be found in our Type 3 Information Booklet which can be downloaded here.
