Confirming a diagnosis of dementia can be difficult, particularly when the condition is in its early stages. This is because many of the symptoms of dementia can be caused by other conditions.
It can be helpful if you and a close relative are seen together, as they can help you remember what is happening.
In order for dementia to be diagnosed correctly, you will have a number of different tests and assessments including:
- a review of your personal history including education and employment
- a review of your medical history
- a full assessment of your mental abilities
- a range of tests, including blood tests to rule out other possible causes of your symptoms, such as a vitamin B deficiency
- imaging scans, such as a CT scan or magnetic resonance imaging (MRI) scan, which can provide information about the physical state and structure of your brain
- a review of any medication you may be taking, in case these are contributing to your symptoms
Some of these tests can be carried out by your GP. Others will be carried out by other specialists, such as a neurologist (an expert in treating conditions that affect the brain and nervous system) or a psychiatrist with experience in treating dementia.
Assessing your mental abilities
There are some questionnaires that can be used to help test your mental abilities and how severe your symptoms are. One widely used questionnaire is the Mini Mental State Examination (MMSE).
The MMSE can be used to assess a number of different mental abilities including:
- short- and long-term memory
- attention span
- concentration
- language and communication skills
- ability to plan
- ability to understand instructions
The MMSE is a series of questions, each carrying a score that can give a maximum result of 30 points. Example questions include:
- memorising a short list of objects and then repeat the list back
- writing a short sentence that is grammatically correct, such as ‘the dog sat on the floor’
- correctly identifying the current day of the week, followed by the date, the month, the season and the year
The MMSE cannot diagnose dementia by itself but it is useful for assessing the level of mental impairment that a person with dementia may have.
- a score of 25 or above is considered normal
- a score of 18 to 24 indicates mild to moderate impairment
- a score of 17 or below indicates serious impairment
These scores are affected by education. Some people who cannot read or write well may always score less than 25, but they may not have dementia. Other people with a higher level of education, may have a higher score but still have dementia.
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Further tests
There are blood tests that can be used to rule out other conditions that may be responsible for the patient's symptoms.
A full blood count
A full blood count can be used to assess your general health and check for a range of disorders, including anaemia and infection. A blood sample will usually be taken from a vein in your arm using a needle and syringe. The test will also check for other illnesses.
Blood glucose test
A blood glucose test can be used to find out whether your blood glucose level is normal, and can also determine whether you have diabetes. A blood sample is taken to rule out whether your symptoms might be caused by undiagnosed diabetes.
Urine analysis
Urine analysis is used to diagnose diabetes or problems with your kidneys. During the test, you will be asked to pass a small sample of urine into a sterile container.
Measurement of thyroid hormones
A measurement of your thyroid hormones may be taken in order to screen for thyroid disorders, including an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism).
Measurement of vitamin B12 levels
You may also have a test to check whether your symptoms are caused by a lack of vitamin B12. However, if you do have a B12 deficiency, it is still possible that you may also have dementia.
Imaging scans
Imaging scans can check if there are any underlying problems with your brain, such as a brain tumour, that could help explain your symptoms.
Imaging scans can also identify changes in the appearance of the brain that may indicate dementia. Several types of imaging scans can be used in the diagnosis of dementia.
Computerised tomography
A computerised tomography (CT) scan can take a series of X-ray images of your brain. The images are fed into a computer to build up a detailed 3D image of the inside of your brain.
Magnetic resonance imaging
A magnetic resonance imaging (MRI) scan may be used as an alternatve to a CT scan.
MRI scans help doctors determine whether:
- there is any shrinkage to the outer layer of the brain
- there is any evidence of changes to the blood vessels
- there are any blood clots that might have resulted in vascular dementia
The test will also show whether other conditions, such as a brain tumour, are causing your symptoms.
Single photon-emission computed tomography
A single photon-emission computed tomography (SPECT) scan may be recommended if doctors are unsure whether you have Alzheimer's disease, frontot-emporal dementia or vascular dementia.
A SPECT scan is similar to a CT scan, but the scanner used for a SPECT scan is able to take moving pictures of the blood flow in your brain. The results show if the blood flow in your brain is abnormal, which can often be used to help diagnose the type of dementia.
