Mitochondria are found in every tissue in the body and any of these can potentially be affected in mitochondrial disease. By no means all patients will develop complications of their disease and the fact that we sometimes ask for tests does not mean that we think that you have a particular problem. Nevertheless, we feel it is prudent to look for complications that we know can happen because a lot of them can be effectively treated if caught early enough.

Blood tests

We tend to perform a routine screen of blood tests every time you come to clinic. These are for a wide variety of problems, for example a low blood count, liver or kidney problems. One particular thing that we look carefully for is the development of diabetes as this is a common problem in our patients. We can sometimes detect this on a blood test before any symptoms are apparent, and as with most things it is easier to treat if caught early.

Heart tests

We know that the heart can be involved in mitochondrial disease, particularly in the MELAS mutation. We can pick up changes in the heart using simple tests before they cause symptoms. The main one that we use is an electrocardiogram (ECG). This involves placing sticky electrodes on the chest wall and recording the electrical activity of the heart. The procedure is painless and usually takes only a few minutes. In patients with MELAS we would want to do this once a year, however in other mutations we feel that every other year may be enough.

In patients with abnormalities on the ECG, or with other symptoms such as chest pain, we would normally also perform an echocardiogram (“ECHO”). This involves putting cold jelly on the chest and using an ultrasound probe to take pictures of the heart. As with an ECG it is painless, but it usually takes longer (about half an hour).

The point of both these tests is that we can often pick up treatable problems before they cause symptoms.


EEG : You might be asked to attend for an electroencephalogram (EEG). This measures your brain’s electrical activity. To do this we stick twenty small electrodes on to your scalp. This is painless and the adhesive gel washes out completely. All you then have to do is to sit in a comfortable chair and relax. We might ask you to overbreathe for a couple of minutes which can make you feel a bit light headed and we might also flash a strobe light in the room. Both of these make the test more accurate but have no long-term effects. The reason that we record the EEG is that it gives us information on how the brain is working. For example, some patients have seizures and the EEG can tell us which parts of the brain are involved. Similarly it can give us information on how well the brain is able to use food energy to make ATP.

Nerve conduction studies: Some patients complain of tingling in their hands and feet. If this is the case we may ask you to have Nerve conduction studies, which can tell us if the nerves supplying these areas are healthy. To do these we give small electric shocks to the nerves and measure the response. We might also put a small needle in different muscles to measure the activity. This all sounds a bit brutal, and it does hurt a bit. However, the doctors doing the tests are experts at making things as painless as possible and we can gain valuable information from them. For example, tingling hands can be caused by a trapped nerve in the wrist and a small operation can cure this completely. Unfortunately, if the nerves are damaged as part of the mitochondrial disease it is not possible to reverse this, but nevertheless there are effective treatments we can use to reduce the symptoms.

Respiratory function

The muscles that move the chest wall and allow us to breathe can be affected in mitochondrial disease. This can cause breathlessness, but sometimes the only symptoms can be headaches in the morning or excessive sleepiness. One of the best ways to check for respiratory muscle weakness is with a simple breathing test that we can do in the clinic. We will ask you to blow as hard and as long as you can into a tube and from this we can measure your lung capacity and strength. The test is quick and has no long term effects. Sometimes we need more accurate information and you might be asked to attend the respiratory function laboratory for more detailed tests. Similarly, if we suspect that your breathing is affected during sleep, we might admit you overnight on to the ward so that we can put a small sensor on to your finger tip and measure the oxygen level in your blood over the whole night.

Eye tests

The eyes can be affected in several ways in mitochondrial diseases and we regularly perform eye tests in the clinic. Firstly the muscles around the eyes can be involved; this causes drooping of the eyelids (ptosis) and a reduced ability to move the eyes around (ophthalmoplegia). Secondly, the eyes themselves can be affected leading to blurred vision. It is often possible to improve patients’ vision with for example special glasses or minor surgery to lift the eyelids and for this reason we often ask one of our ‘eye doctor’ colleagues Mr Griffiths, (he has a special interest in this area), to review our patients.


Many patients develop hearing problems as part of their illness. Usually this can be helped with hearing aids. We often ask patients to attend the audiology department for detailed hearing tests and to be fitted with suitable hearing aids.


Mitochondrial disease can affect the muscles of the tongue and throat leading to problems with speech and swallowing. We often ask our dieticians and speech and language therapists for their advice on measures that can be used to improve matters. Sometimes this can be achieved with a change in diet or the use of dietary supplements. When swallowing becomes more problematic we may request a test of swallowing called a videofluoroscopy which provides a moving image of the swallowing process. Some patients develop such severe problems that they are no longer able to swallow safely without food going the wrong way into the lungs and in these patients we often ask the surgeons to pass a fine tube directly through the abdominal wall into the stomach. This is called a PEG tube and allows liquid food to be dripped slowly into the stomach over several hours. Where assessed safe to do so patients may still eat small amounts of food by mouth, but this alone would be insufficient to meet the body’s nutrient and energy demands. PEG feeding may also be used to supplement an inadequate diet due to severe loss of appetite or where calorie intake is insufficient to sustain appropriate growth.