DIAGNOSIS OF THE CONDITIONS THAT CAUSE DEMENTIA: DIAGNOSING TREATABLE CONDITIONS
The doctor’s first and most important task is to make sure that there isn’t a treatable cause for the dementia. This may be found in about one person in twenty who develops a dementing illness when he or she is over the age of seventy, and about one person in ten under this age. Discovering a treatable condition does not always cure the dementia; in some circumstances it merely stops it getting worse. For this reason it is important that the treatable causes are looked for as early in the course of the disease as possible. The types of illness that one finds vary from simple things like vitamin deficiencies, infections that have been quietly rumbling on for many years, malfunctioning of the thyroid gland, and abnormalities of the levels of different salts in the blood to more complicated things such as blood clots in the head that can be removed. It is often possible for the doctor to get some clue as to whether or not one of these conditions is present, but not infrequently there may be no outward sign that the person who is being investigated has anything abnormal wrong with him or her. The most important vitamin deficiencies are probably those of the B group, including too little vitamin B12 or B1. Folic acid is a related substance, a deficiency of which can also cause a reversible dementia although this particular problem isn’t encountered very often.
A very important condition not to miss is normal pressure hydrocephalus. This is in some ways similar to the problem that affects the brain in some children with spina bifida and results from an increased build-up of CSF in the hollow spaces (ventricles) within the brain. It may occur in people who have previously had a cerebral haemorrhage, a severe head injury sufficient to knock them out, or meningitis, but in many people there is no obvious predisposing cause. It can often be seen easily on a brain scan.
Normal pressure hydrocephalus has certain distinguishing features that will be apparent even to a lay person. Although many sufferers with dementia, whatever the underlying cause, become incontinent and have difficulty in walking, this is usually a feature later on towards the middle or later stages of their illness. In normal pressure hydrocephalus the incontinence and walking difficulties occur much earlier. To begin with the abnormal mental function often appears to be at least partly manifested by a slowness of thinking rather than an inability to do so. The situation is not always clear-cut, however, and sometimes other causes of dementia can mimic normal pressure hydrocephalus; but if a person’s symptoms are as described it is essential that the possibility of this diagnosis is investigated and a brain scan should be organized. The raised pressure can be treated by a small operation in which a fine tube has one of its ends placed within one of the hollow spaces, and the other into the chest or somewhere else into which the excess fluid can drain away, thus reducing the pressure within the brain.
In some people in whom dementia is suspected, the real cause of their illness is a different psychiatric condition, most commonly depression. It can often be very difficult to distinguish between depression and dementia, especially in older people. Sometimes the two conditions co-exist and then it can be very difficult to sort out the situation. For this reason many patients need to be seen by a psychiatrist. In some parts of the country psychiatrists are in any case responsible for assessing a person with dementia; in many places, however, this job is undertaken by other experts, either specialists in the care of the elderly or neurologists.
Another important condition that is to a certain extent treatable is the dementia associated with a high alcohol intake. This can occur for a number of reasons. On the one hand the alcohol itself can cause brain damage and on the other many people who are alcoholic have an inadequate diet and are therefore subject to vitamin and other dietary deficiencies. It has been shown that if a heavy drinker can change his or her habits, much of the damage that has occurred can be remedied.
It is fairly obvious from the range of treatable underlying conditions that may be present that a variety of tests will be needed. These are usually blood tests, which cause little if any upset to the person being investigated, collection of a sample of urine for investigation in some circumstances – and this can be a little more tricky – and sometimes a chest X-ray and an electrocardiograph (ECG), or heart tracing. In some cases it is necessary to arrange a lumbar puncture. This involves inserting a needle into the spinal canal through a gap between two of the bones that make up the spinal column. This procedure sometimes causes concern to a carer but with modern techniques a lumbar puncture is usually not very traumatic, although it may be uncomfortable. The person suffering from dementia will usually not remember having undergone any of the tests, so if he or she has experienced some discomfort, it is soon forgotten. Testing can be important as sometimes it is the only way of being certain whether or not a treatable condition is present.
Lumbar punctures are not undertaken in very many cases; in situations where some years ago they would often have been necessary, a brain scan, often called a CT or CAT scan, will be arranged instead. The scanners are only available in major centres and can only be used for a limited number of scans each day. It is not therefore possible for everybody with dementia to have a scan and the doctor has to use his common sense to decide which people most need one. There are even newer types of scanner available — the MRI and the PET scan — but these are highly specialized investigations that have no part in the routine assessment of a person with dementia. Their application is discussed in a later chapter.
There are many treatable illnesses that can cause dementia although only a few people actually suffer from one or other of them. It is nevertheless extremely important to diagnose them when they are present and for this reason it is essential that any one with dementia, or possible dementia, is investigated as early in the course of the disease as possible. Treatment may range from very simple measures such as replacing a vitamin deficiency, giving a tablet to replace a hormone that a failed thyroid gland can no longer produce, or treating a grumbling infection with appropriate antibiotics to more complicated procedures that involve an operation, albeit a relatively minor one. Below are two case histories that are fairly typical.
Sister Mary
Dr Johnson was called to see a nun who lived in a convent. It was apparent that she had been becoming more and more confused over a considerable period of time and although her fellow nuns wanted to carry on looking after her for as long as they could, they were beginning to find it very difficult. After carefully inquiring into the history of her illness and other relevant medical matters, Dr Johnson examined his new patient very carefully. He discovered some abnormalities when examining sensation in her legs and wondered whether she had a treatable cause for her dementia. He therefore arranged the appropriate tests and also those for the other conditions that might be present even though he could find no sign of them.
The results of the investigations showed that the dementia was probably the result of a deficiency of vitamin B12. Dr Johnson arranged for the district nurse to administer some B12 injections and a month later he returned to the convent to see whether this had resulted in any recovery. Although Sister Mary was still confused, her condition was much improved. He continued to see her regularly over a period of several months during which she improved further, although only to a limited extent. Nevertheless there was now no question of her having to leave the convent as the other nuns found her once more a pleasant and easy person to manage.
Mr Allan
Mr Allan, though in his late fifties, was a well-built and muscular ex-professional wrestler. He lived with his wife who for some time had been increasingly worried about his progressive forgetfulness and behaviour which was sometimes rather odd. For this reason he had been investigated by his general practitioner who thought that he was suffering from Alzheimer’s disease. All the usual treatable conditions that could be excluded by arranging blood tests had been proved to be absent; Mrs Allan was resigned to the future and had joined the support group of her local branch of the Alzheimer’s Disease Society. About nine months after the diagnosis of Alzheimer’s disease had been made she noticed that her husband was having episodes of incontinence which she put down to the difficulty that he had begun to experience with walking, especially trying to get up and down the stairs.
Talking to her new friends in the support group she discovered that this wasn’t similar to the experience of others and so she went to her doctor to ask him why it was that her husband had developed difficulty with walking, and apparently also incontinence, at such an early stage in his condition. The general practitioner referred her husband for a second opinion and a brain scan was organized which showed that he had normal pressure hydrocephalus. A shunt (a fine tube) was inserted into the hollow space within his right hemisphere and the excess fluid allowed to drain off into his chest. Six weeks later he was considerably improved, no longer incontinent, able to walk normally, and with a considerable degree of improvement in his mental function. The latter continued to progress, but he never quite regained the intellectual ability that he had enjoyed before his illness began.
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